Stephen Leigh Cowen

Interests

Research

I am interested in the question of how the activities of ensembles of neurons drive our capacity to decide, remember, and navigate. In particular, I am interested in the role of the prefrontal cortex in cost-benefit decision making and in the role of the hippocampus in navigation and memory consolidation. I investigate these topics through large-scale extracellular recording of the activities of networks of neurons and dopamine release in rats as the animals perform decision-making and navigation behaviors. A number of interesting observations have emerged from these experiments. For example, we found that the neurons believed to be critical for working memory also were exquisitely sensitive to small body movements, suggesting a link between working memory systems in the brain and physical movement. This observation that has since motivated the development of novel tools for the analysis and measurement of movement. Our investigation of cost-benefit decision making has revealed that neurons in the anterior cingulate cortex, a region within the frontal cortex, may also be important for the capacity to persevere through physically strenuous sequences of movements (e.g. lifting weights or finishing a marathon) as these neurons respond to specific actions and the effort that must be maintained over time to acquire a goal. Finally, our work in spatial navigation indicates that neurons in the hippocampus, a region that is a critical component of the brain’s navigation system, can rapidly switch between visual and egocentric (body centered) reference frames when the location of a goal demands such switching. Our ultimate goal is to connect our investigations of the frontal cortex and hippocampus in order to determine how communication between these regions guides decision making and memory formation.

Teaching

Teaching undergraduate and graduate courses has been a deeply meaningful component of my work at the University of Arizona. A principal reason for my passion for teaching is that it serves as an outlet for me to communicate the excitement involved in scientific discovery. I have been fortunate to have a course load that mirrors my own interests. For example, I teach undergraduate and graduate level courses in cognitive neuroscience, systems neuroscience, neuroanatomy, the neural basis of decision making, and statistics (courses listed below). I also have considerable background in data analysis, computational theories of the brain, and computer programming. This background has informed my lectures in statistics and will serve as a foundation for planned future courses in computational neuroscience and data analysis.NRSC/PSYC 596e/496: Neural Mechanisms of Decision MakingPSYC 313: Drugs and the BrainPSYC 230: Measurement and StatisticsPSYC 402: Brain and CognitionPSYC 413: Drugs and the Brain Advanced (offered in Fall 2021)PSYC 506a: Neural Systems, Neural Encoding, and ComputationPSYC 510: Graduate Statistics in RCourse Section: NRSC 560: Systems Neuroscience. 3 Lectures: Memory, Cortex, and HippocampusGuest lecturer in Human Neuroanatomy.

Courses

Scholarly Contributions

Journals/Publications

• Chou, Y., Cowen, S., Sundman, M. H., Liu, Y., Lim, K., Ugonna, C., & Ton That, V. (2022). Association Between Responsiveness to Transcranial Magnetic Stimulation and Interhemispheric Functional Connectivity of Sensorimotor Cortex in Older Adults. Brain Connectivity. doi:10.1089/brain.2021.0180
• Cowen, S. L., Falk, T., Sherman, S. J., Bartlett, M. J., & Ye, T. (2021). Spectral signatures of L-DOPA-induced dyskinesia depend on L-DOPA dose and are suppressed by ketamine.. Experimental neurology, 340, 113670. doi:10.1016/j.expneurol.2021.113670
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  L-DOPA-induced dyskinesias (LID) are debilitating motor symptoms of dopamine-replacement therapy for Parkinson's disease (PD) that emerge after years of L-DOPA treatment. While there is an abundance of research into the cellular and synaptic origins of LID, less is known about how LID impacts systems-level circuits and neural synchrony, how synchrony is affected by the dose and duration of L-DOPA exposure, or how potential novel treatments for LID, such as sub-anesthetic ketamine, alter this activity. Sub-anesthetic ketamine treatments have recently been shown to reduce LID, and ketamine is known to affect neural synchrony. To investigate these questions, we measured movement and local-field potential (LFP) activity from the motor cortex (M1) and the striatum of preclinical rodent models of PD and LID. In the first experiment, we investigated the effect of the LID priming procedures and L-DOPA dose on neural signatures of LID. Two common priming procedures were compared: a high-dose procedure that exposed unilateral 6-hydroxydopamine-lesioned rats to 12 mg/kg L-DOPA for 7 days, and a low-dose procedure that exposed rats to 7 mg/kg L-DOPA for 21 days. Consistent with reports from other groups, 12 mg/kg L-DOPA triggered LID and 80-Hz oscillations; however, these 80-Hz oscillations were not observed after 7 mg/kg administration despite clear evidence of LID, indicating that 80-Hz oscillations are not an exclusive signature of LID. We also found that weeks-long low-dose priming resulted in the emergence of non-oscillatory broadband gamma activity (> 30 Hz) in the striatum and theta-to-high-gamma cross-frequency coupling (CFC) in M1. In a second set of experiments, we investigated how ketamine exposure affects spectral signatures of low-dose L-DOPA priming. During each neural recording session, ketamine was delivered through 5 injections (20 mg/kg, i.p.) administered every 2 h. We found that ketamine exposure suppressed striatal broadband gamma associated with LID but enhanced M1 broadband activity. We also found that M1 theta-to-high-gamma CFC associated with the LID on-state was suppressed by ketamine. These results suggest that ketamine's therapeutic effects are region specific. Our findings also have clinical implications, as we are the first to report novel oscillatory signatures of the common low-dose LID priming procedure that more closely models dopamine replacement therapy in individuals with PD. We also identify neural correlates of the anti-dyskinetic activity of sub-anesthetic ketamine treatment.
• Bartlett, M. J., Flores, A. J., Ye, T., Smidt, S. I., Dollish, H. K., Stancati, J. A., Farrell, D. C., Parent, K. L., Besselsen, D. G., Doyle, K., Heien, M. L., Cowen, S. L., Steece-Collier, K., Sherman, S. J., & Falk, T. (2020). Preclinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia.. Experimental Neurology, 333, 113413. doi:https://doi.org/10.1016/j.expneurol.2020.113413
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  Parkinson's disease (PD) is the second most common neurodegenerative disease. Pharmacotherapy with L-DOPA remains the gold-standard therapy for PD, but is often limited by the development of the common side effect of L-DOPA-induced dyskinesia (LID), which can become debilitating. The only effective treatment for disabling dyskinesia is surgical therapy (neuromodulation or lesioning), therefore effective pharmacological treatment of LID is a critical unmet need. Here, we show that sub-anesthetic doses of ketamine attenuate the development of LID in a rodent model, while also having acute anti-parkinsonian activity. The long-term anti-dyskinetic effect is mediated by brain-derived neurotrophic factor-release in the striatum, followed by activation of ERK1/2 and mTOR pathway signaling. This ultimately leads to morphological changes in dendritic spines on striatal medium spiny neurons that correlate with the behavioral effects, specifically a reduction in the density of mushroom spines, a dendritic spine phenotype that shows a high correlation with LID. These molecular and cellular changes match those occurring in hippocampus and cortex after effective sub-anesthetic ketamine treatment in preclinical models of depression, and point to common mechanisms underlying the therapeutic efficacy of ketamine for these two disorders. These preclinical mechanistic studies complement current ongoing clinical testing of sub-anesthetic ketamine for the treatment of LID by our group, and provide further evidence in support of repurposing ketamine to treat individuals with PD. Given its clinically proven therapeutic benefit for both treatment-resistant depression and several pain states, very common co-morbidities in PD, sub-anesthetic ketamine could provide multiple therapeutic benefits for PD in the future.
• Cowen, S. L., Falk, T., Fell, M. J., Wohlford, L. A., Gies, K. F., Monroe, E. J., Eby, A. J., Wiegand, J. L., Bartlett, M. J., & Crown, L. M. (2020). Sleep Spindles and Fragmented Sleep as Prodromal Markers in a Preclinical Model of LRRK2-G2019S Parkinson's Disease.. Frontiers in neurology, 11, 324. doi:10.3389/fneur.2020.00324
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  Sleep disturbances co-occur with and precede the onset of motor symptoms in Parkinson's disease (PD). We evaluated sleep fragmentation and thalamocortical sleep spindles in mice expressing the p.G2019S mutation of the leucine-rich repeat kinase 2 (LRRK2) gene, one of the most common genetic forms of PD. Thalamocortical sleep spindles are oscillatory events that occur during slow-wave sleep that are involved in memory consolidation. We acquired data from electrocorticography, sleep behavioral measures, and a rotarod-based motor enrichment task in 28 LRRK2-G2019S knock-in mice and 27 wild-type controls (8-10 month-old males). Sleep was more fragmented in LRRK2-G2019S mice; sleep bouts were shorter and more numerous, even though total sleep time was similar to controls. LRRK2-G2019S animals expressed more sleep spindles, and individual spindles were longer in duration than in controls. We then chronically administered the LRRK2-inhibitor MLi-2 in-diet to n = 12 LRRK2-G2019S and n = 15 wild-type mice for a within-subject analysis of the effects of kinase inhibition on sleep behavior and physiology. Treatment with MLi-2 did not impact these measures. The data indicate that the LRRK2-G2019S mutation could lead to reduced sleep quality and altered sleep spindle physiology. This suggests that sleep spindles in LRRK2-G2019S animals could serve as biomarkers for underlying alterations in sleep networks resulting from the LRRK2-G2019S mutation, and further evaluation in human LRRK2-G2019S carriers is therefore warranted.
• Crown, L. M., Bartlett, M. J., Wiegand, J. L., Eby, A. J., Monroe, E. J., Gies, K., Wohlford, L., Fell, M. J., Falk, T., & Cowen, S. L. (2020). Sleep Spindles and Fragmented Sleep as Prodromal Markers in a Preclinical Model of LRRK2-G2019S Parkinson's Disease. Frontiers in neurology, 11, 324.
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  Sleep disturbances co-occur with and precede the onset of motor symptoms in Parkinson's disease (PD). We evaluated sleep fragmentation and thalamocortical sleep spindles in mice expressing the p.G2019S mutation of the leucine-rich repeat kinase 2 () gene, one of the most common genetic forms of PD. Thalamocortical sleep spindles are oscillatory events that occur during slow-wave sleep that are involved in memory consolidation. We acquired data from electrocorticography, sleep behavioral measures, and a rotarod-based motor enrichment task in 28 -G2019S knock-in mice and 27 wild-type controls (8-10 month-old males). Sleep was more fragmented in -G2019S mice; sleep bouts were shorter and more numerous, even though total sleep time was similar to controls. -G2019S animals expressed more sleep spindles, and individual spindles were longer in duration than in controls. We then chronically administered the LRRK2-inhibitor MLi-2 in-diet to = 12 -G2019S and = 15 wild-type mice for a within-subject analysis of the effects of kinase inhibition on sleep behavior and physiology. Treatment with MLi-2 did not impact these measures. The data indicate that the -G2019S mutation could lead to reduced sleep quality and altered sleep spindle physiology. This suggests that sleep spindles in -G2019S animals could serve as biomarkers for underlying alterations in sleep networks resulting from the -G2019S mutation, and further evaluation in human -G2019S carriers is therefore warranted.
• Eby, A. J., Crown, L., & Cowen, S. L. (2020). INVESTIGATING MOTOR LEARNING IN A LRRK2 MOUSE MODEL OF PARKINSON’S DISEASE. The FASEB Journal, 34(S1), 1-1. doi:10.1096/fasebj.2020.34.s1.04831
• Falk, T., Sherman, S. J., Steece-Collier, K., Cowen, S. L., Heien, M. L., Doyle, K., Besselsen, D. G., Parent, K. L., Farrell, D. C., Stancati, J. A., Dollish, H. K., Smidt, S. I., Ye, T., Flores, A. J., & Bartlett, M. J. (2020). Preclinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia.. Experimental Neurology.
• Ondek, K., Pevzner, A., Tercovich, K., Schedlbauer, A. M., Izadi, A., Ekstrom, A. D., Cowen, S. L., Shahlaie, K., & Gurkoff, G. G. (2020). Recovery of Theta Frequency Oscillations in Rats Following Lateral Fluid Percussion Corresponds With a Mild Cognitive Phenotype. Frontiers in neurology, 11, 600171.
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  Whether from a fall, sports concussion, or even combat injury, there is a critical need to identify when an individual is able to return to play or work following traumatic brain injury (TBI). Electroencephalogram (EEG) and local field potentials (LFP) represent potential tools to monitor circuit-level abnormalities related to learning and memory: specifically, theta oscillations can be readily observed and play a critical role in cognition. Following moderate traumatic brain injury in the rat, lasting changes in theta oscillations coincide with deficits in spatial learning. We hypothesized, therefore, that theta oscillations can be used as an objective biomarker of recovery, with a return of oscillatory activity corresponding with improved spatial learning. In the current study, LFP were recorded from dorsal hippocampus and anterior cingulate in awake, behaving adult Sprague Dawley rats in both a novel environment on post-injury days 3 and 7, and Barnes maze spatial navigation on post-injury days 8-11. Theta oscillations, as measured by power, theta-delta ratio, peak theta frequency, and phase coherence, were significantly altered on day 3, but had largely recovered by day 7 post-injury. Injured rats had a mild behavioral phenotype and were not different from shams on the Barnes maze, as measured by escape latency. Injured rats did use suboptimal search strategies. Combined with our previous findings that demonstrated a correlation between persistent alterations in theta oscillations and spatial learning deficits, these new data suggest that neural oscillations, and particularly theta oscillations, have potential as a biomarker to monitor recovery of brain function following TBI. Specifically, we now demonstrate that oscillations are depressed following injury, but as oscillations recover, so does behavior.
• Seaton, B. T., Hill, D. F., Cowen, S. L., & Heien, M. L. (2020). Mitigating the Effects of Electrode Biofouling-Induced Impedance for Improved Long-Term Electrochemical Measurements In Vivo. Analytical chemistry, 92(9), 6334-6340.
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  Biofouling is a prevalent issue in studies that involve prolonged implantation of electrochemical probes in the brain. In long-term fast-scan cyclic voltammetry (FSCV) studies, biofouling manifests as a shift in the peak oxidative potential of the background signal that worsens over days to weeks, diminishing sensitivity and selectivity to neurotransmitters such as dopamine. Using open circuit potential (OCP) measurements, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and electrochemical impedance spectroscopy (EIS), we examined the biofouling-induced events that occur due to electrode implantation. We determined that the FSCV background signal shift results from cathodic polarization of the Ag/AgCl-wire reference electrode and increased electrochemical impedance of both the Ag/AgCl-wire reference electrode and carbon-fiber working electrode. These events are likely caused collectively by immune response-induced electrode encapsulation. A headstage utilizing a three-electrode configuration, designed to compensate for the impedance component of biofouling, reduced the FSCV background signal shift in vivo and preserved dopamine sensitivity at artificially increased impedance levels in vitro. In conjunction with a stable reference electrode, this three-electrode configuration will be critical in achieving reliable neurotransmitter detection for the duration of long-term FSCV studies.
• Siegenthaler, J. R., Gushiken, B. C., Hill, D. F., Cowen, S. L., & Heien, M. L. (2020). Moving Fast-Scan Cyclic Voltammetry toward FDA Compliance with Capacitive Decoupling Patient Protection. ACS sensors, 5(7), 1890-1899.
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  Carbon-fiber microelectrodes allow for high spatial and temporal measurements of electroactive neurotransmitter measurements using fast-scan cyclic voltammetry (FSCV). However, common instrumentation for such measurements systems lack patient safety precautions. To add safety precautions as well as to overcome chemical and electrical noise, a two-electrode FSCV headstage was modified to introduce an active bandpass filter on the electrode side of the measurement amplifier. This modification reduced the measured noise and ac-coupled the voltammetric measurement and moved it from a classical direct current response measurement. ac-coupling not only reduces the measured noise, but also moves FSCV toward compliance with IEC-60601-1, enabling future human trials. Here, we develop a novel ac-coupled voltammetric measurement method of electroactive neurotransmitters. Our method allows for the modeling of a system to then calculate a waveform to compensate for added impedance and capacitance for the system. We describe how first by measuring the frequency response of the system and modeling the analogue response as a digital filter we can then calculate a predicted waveform. The predicted waveform, when applied to the bandpass filter, is modulated to create a desired voltage sweep at the electrode interface. Further, we describe how this modified FSCV waveform is stable, allowing for the measurement of electroactive neurotransmitters. We later describe a 32.7% sensitivity enhancement for dopamine with this new measurement as well as maintaining a calibration curve for dopamine, 3,4-dihydroxyphenylacetic acid, ascorbic acid, and serotonin . We then validate dopamine with stimulated release. Our developed measurement method overcame the added capacitance that would traditionally make a voltammetric measurement impossible, and it has wider applications in electrode sensor development, allowing for measurement with capacitive systems, which previously would not have been possible.
• Hill, D. F., Parent, K. L., Atcherley, C. W., Cowen, S. L., & Heien, M. L. (2018). Differential release of dopamine in the nucleus accumbens evoked by low-versus high-frequency medial prefrontal cortex stimulation. Brain stimulation, 11(2), 426-434.
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  The medial prefrontal cortex (mPFC) coordinates goal-directed behaviors, which may be mediated through mPFC regulation of dopamine release in the nucleus accumbens (NAc). Furthermore, frequency-specific oscillatory activity between the frontal cortex and downstream structures may facilitate inter-region communication. Although high-frequency (e.g., 60 Hz) mPFC stimulation is known to increase basal dopamine levels in the NAc, little is known about how phasic dopamine release is affected by mPFC stimulation. Understanding the frequency-specific control of phasic dopamine release by mPFC stimulation could elucidate mechanisms by which the mPFC modulates other regions. It could also inform optimization of deep brain stimulation for treatment of neurological disorders.
• Barnes, C. A., Barnes, C. A., Cowen, S. L., Cowen, S. L., Gray, D. T., Gray, D. T., Wiegand, J. L., Wiegand, J. L., Schimanski, L. A., & Schimanski, L. A. (2018). Age‐associated changes in waking hippocampal sharp‐wave ripples. Hippocampus, 30(1), 28-38. doi:10.1002/hipo.23005
• Cowen, S. L., Cowen, S. L., Falk, T., Falk, T., Sherman, S. J., Sherman, S. J., Schmitt, M. B., Schmitt, M. B., Bartlett, M. J., Bartlett, M. J., Ye, T., & Ye, T. (2018). Ten-Hour Exposure to Ketamine Enhances Corticostriatal Cross-Frequency Coupling and Broad-Band Gamma Oscillations in the Hippocampus.. Frontiers in Neural Circuits, 12:61. doi:doi: 10.3389/fncir.2018.00061.
• Cowen, S. L., Gray, D. T., Wiegand, J. L., Schimanski, L. A., & Barnes, C. A. (2018). Age-associated changes in waking hippocampal sharp-wave ripples. Hippocampus.
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  Hippocampal sharp-wave ripples are brief high-frequency (120-250 Hz) oscillatory events that support mnemonic processes during sleep and awake behavior. Although ripples occurring during sleep are believed to facilitate memory consolidation, waking ripples may also be involved in planning and memory retrieval. Recent work from our group determined that normal aging results in a significant reduction in the peak oscillatory frequency and rate-of-occurrence of ripples during sleep that may contribute to age-associated memory decline. It is unknown, however, how aging alters waking ripples. We investigated whether characteristics of waking ripples undergo age-dependent changes. Sharp-wave ripple events were recorded from the CA1 region of the hippocampus in old (n = 5) and young (n = 6) F344 male rats as they performed a place-dependent eyeblink conditioning task. Several novel observations emerged from this analysis. First, although aged rats expressed more waking ripples than young rats during track running and reward consumption, this effect was eliminated, and, in the case of track-running, reversed when time spent in each location was accounted for. Thus, aged rats emit more ripples, but young rats express a higher ripple rate. This likely results from reduced locomotor activity in aged animals. Furthermore, although ripple rates increased as young rats approached rewards, rates did not increase in aged rats, and rates in aged and young animals were not affected by eyeblink conditioning. Finally, although the oscillatory frequency of ripples was lower in aged animals during rest, frequencies in aged rats increased during behavior to levels indistinguishable from young rats. Given the involvement of waking ripples in memory retrieval, a possible consequence of slower movement speeds of aged animals is to provide more opportunity to replay task-relevant information and compensate for age-related declines in ripple rate during task performance.
• Edgin, J. O., Cowen, S. L., Spanò, G., Gómez, R. L., Demara, B. I., & Alt, M. (2018). REM sleep in naps differentially relates to memory consolidation in typical preschoolers and children with Down syndrome. Proceedings of the National Academy of Sciences, 115(46), 11844-11849. doi:10.1073/pnas.1811488115
• Porreca, F., & Cowen, S. L. (2018). Chronic pain impairs cognitive flexibility and engages novel learning strategies in rats. Pain, 159, 1403-1412.
• Spanò, G., Gómez, R. L., Demara, B. I., Alt, M., Cowen, S. L., & Edgin, J. O. (2018). REM sleep in naps differentially relates to memory consolidation in typical preschoolers and children with Down syndrome. Proceedings of the National Academy of Sciences of the United States of America, 115(46), 11844-11849.
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  Sleep is recognized as a physiological state associated with learning, with studies showing that knowledge acquisition improves with naps. Little work has examined sleep-dependent learning in people with developmental disorders, for whom sleep quality is often impaired. We examined the effect of natural, in-home naps on word learning in typical young children and children with Down syndrome (DS). Despite similar immediate memory retention, naps benefitted memory performance in typical children but hindered performance in children with DS, who retained less when tested after a nap, but were more accurate after a wake interval. These effects of napping persisted 24 h later in both groups, even after an intervening overnight period of sleep. During naps in typical children, memory retention for object-label associations correlated positively with percent of time in rapid eye movement (REM) sleep. However, in children with DS, a population with reduced REM, learning was impaired, but only after the nap. This finding shows that a nap can increase memory loss in a subpopulation, highlighting that naps are not universally beneficial. Further, in healthy preschooler's naps, processes in REM sleep may benefit learning.
• Hill, D. F., Parent, K. L., Atcherley, C. W., Cowen, S. L., & Heien, M. L. (2017). Nucleus accumbens dopamine release evoked by stimulation of the medial prefrontal cortex peaks at 20 Hz at long stimulation durations. Brain Stimulation, 11(2), 426-434. doi:10.1016/j.brs.2017.11.010
• Lewis, S., Negelspach, D., Kaladchibachi, S., Cowen, S. L., & Fernandez, F. (2017). Spontaneous Alternation: A Gateway to Spatial Working Memory in Drosophila? Learning and Memory. Learning and Memory.
• Parent, K. L., Hill, D. F., Crown, L. M., Wiegand, J. P., Gies, K. F., Miller, M. A., Atcherley, C. W., Heien, M. L., & Cowen, S. L. (2017). Platform to Enable Combined Measurement of Dopamine and Neural Activity. Analytical chemistry, 89(5), 2790-2799. doi:10.1021/acs.analchem.6b03642
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  Complex behaviors depend on the coordination of the activities of ensembles of neurons and the release of neuromodulators such as dopamine. The mechanisms underlying such coordination are not well-understood due to a lack of instrumentation for combined and real-time monitoring of neuromodulator release and the activities of large ensembles of neurons. Here we describe a measurement platform that allows for the combined monitoring of electrophysiology from a high-density electrode array and dopamine dynamics from a carbon-fiber microelectrode. Integration of these two measurement systems was achieved through modification of the existing instrumentation. A shared grounded reference electrode was used in both systems to minimize electrical interference. Further, an optional solid-state-relay array positioned between the electrophysiological electrode array and amplifiers was added to provide additional electrical isolation. The capacity of the integrated measurement platform, termed DANA (Dopamine And Neural Activity), to measure action potentials (high frequency) and local-field oscillations (low frequency) was characterized in vitro using an artificial cerebral spinal fluid gelatin. In vivo recordings from the DANA platform in anesthetized rats demonstrated the ability of the system for near-simultaneous measurement of dopamine release and activity from multiple neurons both in distant brain regions (striatum and hippocampus) and within the same brain region (striatum). Furthermore, this system was shown to be sufficiently compact to measure activity in freely moving animals through recording of single-neuron activity, high-frequency local-field oscillations, and dopamine release.
• Spano, G., Gomez, R. L., Edgin, J. O., Demara, B. I., & Cowen, S. L. (2017). 0205 TO NAP OR NOT TO NAP? SLEEP-DEPENDENT MEMORY CONSOLIDATION IN TYPICALLY AND ATYPICALLY DEVELOPING PRESCHOOLERS. Sleep, 40(suppl_1), A76-A76. doi:10.1093/sleepj/zsx050.204
• Okun, A., McKinzie, D. L., Witkin, J. M., Remeniuk, B., Husein, O., Gleason, S. D., Oyarzo, J., Navratilova, E., McElroy, B., Cowen, S., Kennedy, J. D., & Porreca, F. (2016). Hedonic and motivational responses to food reward are unchanged in rats with neuropathic pain. Pain, 157(12), 2731-2738. doi:10.1097/j.pain.0000000000000695
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  Rewards influence responses to acute painful stimuli, but the relationship of chronic pain to hedonic or motivational aspects of reward is not well understood. We independently evaluated hedonic qualities of sweet or bitter tastants and motivation to seek food reward in rats with experimental neuropathic pain induced by L5/6 spinal nerve ligation. Hedonic response was measured by implantation of intraoral catheters to allow passive delivery of liquid solutions, and "liking/disliking" responses were scored according to a facial reactivity scale. Spinal nerve ligation rats did not differ from controls in either "liking" or "disliking" reactions to intraoral sucrose or quinine, respectively, at postsurgery day 21, suggesting no differences in perceived hedonic value of sweet or bitter tastants. To assess possible motivational deficits during acute and chronic pain, we used fixed- and progressive-ratio response paradigms of sucrose pellet presentation in rats with transient inflammatory or chronic neuropathic pain. Assessment of response acquisition and break points under the progressive ratio schedule revealed no differences between sham and spinal nerve ligation rats for up to 120 days after injury. However, rats with inflammation showed decrements in lever pressing and break points on days 1 and 2 after complete Freund adjuvant injection that normalized by day 4, consistent with transient ongoing pain. Thus, although acute ongoing inflammatory pain may transiently reduce reward motivation, we did not detect influences of chronic neuropathic pain on hedonic or motivational responses to food rewards. Adaptations that allow normal reward responding to food regardless of chronic pain may be of evolutionary benefit to promote survival.
• Wiegand, J. P., Gray, D. T., Schimanski, L. A., Lipa, P., Barnes, C. A., & Cowen, S. L. (2016). Age Is Associated with Reduced Sharp-Wave Ripple Frequency and Altered Patterns of Neuronal Variability. The Journal of Neuroscience, 36(20), 5650-60. doi:10.1523/JNEUROSCI.3069-15.2016
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  Spatial and episodic memory performance declines with age, and the neural basis for this decline is not well understood. Sharp-wave ripples are brief (∼70 ms) high-frequency oscillatory events generated in the hippocampus and are associated with the consolidation of spatial memories. Given the connection between ripple oscillations and memory consolidation, we investigated whether the structure of ripple oscillations and ripple-triggered patterns of single-unit activity are altered in aged rats. Local field and single-unit activity surrounding sharp-wave ripple events were examined in the CA1 region of the hippocampus of old (n = 5) and young (n = 6) F344 rats during periods of rest preceding and following performance on a place-dependent eyeblink-conditioning task. Neural responses in aged rats differed from responses in young rats in several ways. First, compared with young rats, the rate of ripple occurrence (ripple density) is reduced in aged rats during postbehavior rest. Second, mean ripple frequency during prebehavior and postbehavior rest is lower in aged animals (aged: 132 Hz; young: 146 Hz). Third, single neurons in aged animals responded more consistently from ripple to ripple. Fourth, variability in interspike intervals was greater in aged rats. Finally, neurons were tuned to a narrower range of phases of the ripple oscillation relative to young animals. Together, these results suggest that the CA1 network in aged animals has a reduced "vocabulary" of available representational states.
• Cowen, S. L., Falk, T., Fell, M. J., Wohlford, L., Wiegand, J., Giess, K., Morrision, E. J., Eby, A. J., Bartlett, M. J., & Crown, L. M. (2017). Sleep spindles and fragmented sleep as prodromal markers in LRRK2 G2019S Parkinson’s disease. Frontiers in Neurology.
• Cowen, S. L., & Nitz, D. A. (2014). Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity. The Journal of neuroscience : the official journal of the Society for Neuroscience, 34(1), 232-41.
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  Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.
• Miller, M. A., Thomé, A., & Cowen, S. L. (2013). Intersection of effort and risk: Ethological and neurobiological perspectives. Frontiers in Neuroscience.
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  Abstract: The physical effort required to seek out and extract a resource is an important consideration for a foraging animal. A second consideration is the variability or risk associated with resource delivery. An intriguing observation from ethological studies is that animals shift their preference from stable to variable food sources under conditions of increased physical effort or falling energetic reserves. Although theoretical models for this effect exist, no exploration into its biological basis has been pursued. Recent advances in understanding the neural basis of effort-and risk-guided decision making suggest that opportunities exist for determining how effort influences risk preference. In this review, we describe the intersection between the neural systems involved in effort-and risk-guided decision making and outline two mechanisms by which effort-induced changes in dopamine release may increase the preference for variable rewards. © 2013 Miller, Thomé and Cowen.
• Miller, M. A., Thomé, A., & Cowen, S. L. (2013). Intersection of effort and risk: ethological and neurobiological perspectives. Frontiers in neuroscience, 7, 208.
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  The physical effort required to seek out and extract a resource is an important consideration for a foraging animal. A second consideration is the variability or risk associated with resource delivery. An intriguing observation from ethological studies is that animals shift their preference from stable to variable food sources under conditions of increased physical effort or falling energetic reserves. Although theoretical models for this effect exist, no exploration into its biological basis has been pursued. Recent advances in understanding the neural basis of effort- and risk-guided decision making suggest that opportunities exist for determining how effort influences risk preference. In this review, we describe the intersection between the neural systems involved in effort- and risk-guided decision making and outline two mechanisms by which effort-induced changes in dopamine release may increase the preference for variable rewards.
• Cowen, S. L., Davis, G. A., & Nitz, D. A. (2012). Anterior cingulate neurons in the rat map anticipated effort and reward to their associated action sequences. Journal of neurophysiology, 107(9), 2393-407.
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  Goal-directed behaviors require the consideration and expenditure of physical effort. The anterior cingulate cortex (ACC) appears to play an important role in evaluating effort and reward and in organizing goal-directed actions. Despite agreement regarding the involvement of the ACC in these processes, the way in which effort-, reward-, and motor-related information is registered by networks of ACC neurons is poorly understood. To contrast ACC responses to effort, reward, and motor behaviors, we trained rats on a reversal task in which the selected paths on a track determined the level of effort or reward. Effort was presented in the form of an obstacle that was climbed to obtain reward. We used single-unit recordings to identify neural correlates of effort- and reward-guided behaviors. During periods of outcome anticipation, 52% of recorded ACC neurons responded to the specific route taken to the reward while 21% responded prospectively to effort and 12% responded prospectively to reward. In addition, effort- and reward-selective neurons typically responded to the route, suggesting that these cells integrated motor-related activity with expectations of future outcomes. Furthermore, the activity of ACC neurons did not discriminate between choice and forced trials or respond to a more generalized measure of outcome value. Nearly all neural responses to effort and reward occurred after path selection and were restricted to discrete temporal/spatial stages of the task. Together, these findings support a role for the ACC in integrating route-specific actions, effort, and reward in the service of sustaining discrete movements through an effortful series of goal-directed actions.
• Nitz, D., & Cowen, S. (2008). Crossing borders: sleep reactivation as a window on cell assembly formation. Nature neuroscience, 11(2), 126-8.
• Cowen, S. L., & McNaughton, B. L. (2007). Selective delay activity in the medial prefrontal cortex of the rat: contribution of sensorimotor information and contingency. Journal of neurophysiology, 98(1), 303-16.
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  The medial prefrontal cortex (mPFC) plays a critical role in the organization of goal-directed behaviors and in the learning of reinforcement contingencies. Given these observations, it was hypothesized that mPFC neurons may store associations between sequentially paired stimuli when both stimuli contribute to the prediction of reward. To test this hypothesis, neural-ensemble spiking activity was recorded as rats performed a paired-associate discrimination task. Rats were trained to associate sequentially presented stimuli with probabilistic reward. In one condition, both elements of the stimulus sequence provided information about reward delivery. In another condition, only the first stimulus contributed to the prediction. As hypothesized, stimulus-selective, prospective delay activity was observed during sequences in which both elements contributed to the prediction of reward. Unexpectedly, selective delay responses were associated with slight variations in head position and thus not necessarily generated by intrinsic mnemonic processes. Interestingly, the sensitivity of neurons to head position was greatest during intervals when reward delivery was certain. These results suggest that a significant portion of delay activity in the rat mPFC reflects task-relevant sensorimotor activity, possibly related to enhancing stimulus detection, rather than stimulus-stimulus associations. These observations agree with recent evidence that suggests that prefrontal neurons are particularly responsive during the performance of action sequences related to the acquisition of reward. These results also indicate that considerable attention must be given to the monitoring and analysis of sensorimotor variables during delay tasks because slight changes in position can produce activity in the mPFC that erroneously appears to be driven by intrinsic mechanisms.
• Maurer, A. P., Cowen, S. L., Burke, S. N., Barnes, C. A., & McNaughton, B. L. (2006). Organization of hippocampal cell assemblies based on theta phase precession. Hippocampus, 16(9), 785-94.
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  The factors that control the spatial tuning of hippocampal neurons are incompletely understood, and there is no generally agreed upon definition of what constitutes a "place field". One factor that must be considered is the phenomenon of "phase precession". As a rat passes through the place field of a particular hippocampal neuron, its spikes shift to earlier phases of the theta rhythm. Except for the special cases discussed herein, the phase shift never exceeds 360 degrees. Moreover, under conditions in which place field sizes change dynamically, precession rate is tightly coupled with the place field size, suggesting that a single cycle of theta phase precession could be used to define unitary place field boundaries. Theta phase precession implies that the "cell assembly" of active hippocampal neurons changes systematically over the course of a single theta cycle. A given cell can exhibit more than one place field in a given environment, each field showing the same pattern of 360 degrees of phase precession. The existence of multiple fields implies that one cell can participate in multiple cell assemblies within the same environment. We show here that place fields, defined as a single cycle of phase precession, can overlap spatially, with the result that the cell fires with spikes clustered at two different phases over the theta cycles in which the fields overlap. Thus, the same neuron can participate in different cell assemblies within a single theta cycle.
• Maurer, A. P., Cowen, S. L., Burke, S. N., Barnes, C. A., & McNaughton, B. L. (2006). Phase precession in hippocampal interneurons showing strong functional coupling to individual pyramidal cells. The Journal of neuroscience : the official journal of the Society for Neuroscience, 26(52), 13485-92.
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  Although hippocampal interneurons typically do not show discrete regions of elevated firing in an environment, such as seen in pyramidal cell place fields, they do exhibit significant spatial modulation (McNaughton et al., 1983a). Strong monosynaptic coupling between pyramidal neurons and nearby interneurons in the CA1 stratum pyramidale has been strongly implicated on the basis of significant, short-latency peaks in cross-correlogram plots (Csicsvari et al., 1998). Furthermore, interneurons receiving a putative monosynaptic connection from a simultaneously recorded pyramidal cell appear to inherit the spatial modulation of the latter (Marshall et al., 2002). Buzsaki and colleagues hypothesize that interneurons may also adopt the firing phase dynamics of their afferent place cells, which show a phase shift relative to the hippocampal theta rhythm as a rat passes through the place field ("phase precession"). This study confirms and extends the previous reports by showing that interneurons in the dorsal and middle hippocampus with putative monosynaptic connections with place cells recorded on the same tetrode share other properties with their pyramidal cell afferents, including the spatial scale of the place field of pyramidal cell, a characteristic of the septotemporal level of the hippocampus from which the cells are recorded, and the rate of phase precession, which is slower in middle regions. Furthermore, variations in pyramidal cell place field scale within each septotemporal level attributable to task variations are similarly associated with variations in interneuron place field scale. The available data strongly suggest that spatial selectivity of CA1 stratum pyramidale interneurons is inherited from a small cluster of local pyramidal cells and is not a consequence of spatially selective synaptic input from CA3 or other sources.
• Battaglia, F. P., Sutherland, G. R., Cowen, S. L., L., B., & Harris, K. D. (2005). Firing rate modulation: A simple statistical view of memory trace reactivation. Neural Networks, 18(9), 1280-1291.
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  PMID: 16257176;Abstract: Memory trace reactivation in hippocampal ensembles during sleep has been suggested as a coordinating mechanism for consolidation of new memories. Here we propose a simple statistical scheme allowing analysis of the reactivation of firing rate modulations, with a well-defined null hypothesis. This method allowed reliable detection of ensemble reactivation across three experimental settings. Reactivation of firing rate modulations mirrors several properties of commonly studied reactivation measures: it is stronger during hippocampal sharp waves, and decays over a period of 10-20 min. Moreover, in some conditions, firing rate reactivation covaries with reactivation of cell pair cross-correlations, suggesting the two phenomena reflect similar processes. We propose an attractor network model, with pre-wired attractors, in which experience selects and primes some attractors. Priming occurs by either experience dependent synaptic plasticity or changes in neuronal excitability. Primed attractors are more likely to activate in the following sleep, inducing reactivation of both rates and cross-correlations.

Presentations

• Cowen, S. L. (2017, January). Brains, oscillations, aging, and memory. Arizona Neuroscience DataBlitz. Tucson, AZ.
• Cowen, S. L. (2017, March). Integrated Measurement of Dopamine Release and Large-Scale Ensemble Activity in Behaving Animals. Mayo Clinic Brain Initiative Symposium. Rochester, MN: Mayo Clinic.
• Cowen, S. L., & Majumdar, A. (2017, October). Tools for Measuring Neural Activity. IBM Cloud University Conference. Berlin, Germany.
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  This was a video-presentation of me describing our measurement technologies. It was presented within a larger session in Germany (I was not physically present - only virtually). Session: Neuro-Electro-Chemical Transmitter Analytics Research
• Richard, C., Crown, L. M., Wiegand, J. P., Bartlett, M. J., Falk, T., Heien, M. L., & Cowen, S. L. (2017, August). Altered Sleep Spindles in a LRRK2 Mouse Model of Parkinson's Disease. UROC Minority Health Disparities Summer Research Program Poster Session. Tucson, AZ.
• Alt, M., Edgin, J. O., Gomez, R. L., Cowen, S. L., Bianca, D., Goffredina, S., Bianca, D., Alt, M., Cowen, S. L., Gomez, R. L., Goffredina, S., & Edgin, J. O. (2016, Summer). Sleep and Memory Consolidation in Toddlers with Down syndrome:. The 6th International Conference on Memory, ICOM-6. Budapest, Hungary.
• Cowen, S. L. (2016, June). Ketamine and its impact on corticostriatal-limbic interactions. Pain Mechanisms and Therapeutics Conference. Taormina, Italy.
• Cowen, S. L. (2016, March). Effort-reward decision making: Neural systems and neuromodulation. Invited talk at Emory University. Atlanta, GA.
• Cowen, S. L. (2016, October). Identification of network and oscillatory signatures of the LRRK2 mutation. Michael J. Fox Foundation LRRK2 Consortium teleconference. Skype: Michael J. Fox Foundation.
• Cowen, S. L., & Heien, M. L. (2016, March). Simultaneous Detection of Dopamine Release and Multiple Single-Unit Activity in Awake and Behaving Rats. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy National Convention. Atlanta, GA: PITTCON.
• Cowen, S. L. (2015, May). The Influence of Aging on the Variability of Neuronal Activity. McKnight Brain Institute Meeting. Miami, FL: McKnight Brain Institute.
• Cowen, S. L. (2014, April). Neural System, Networks, and the Impact of Aging. Invited speaker: Rising Stars in Neuroscience lecture. Gainesville, Florida: Evelyn F. McKnight Brain Institute.
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  April 24,2014
• Cowen, S. L. (2014, April). Rising Stars in Neuroscience lecture: Neural System, Networks, and the Impact of Aging. Evelyn F. McKnight Brain Institute Annual Meeting. Gainesville, FL: Evelyn F. McKnight Brain Institute.
• Cowen, S. L. (2014, September). Effort and the Anterior Cingulate. Workshop on the Computational Properties of the Prefrontal Cortex. Whistler, Canada.

Poster Presentations

• Brian, D. R., Gabriel, H., Reed, B., Miller, J. E., & Cowen, S. L. (2023, November). Alpha-synuclein overexpression in the basal ganglia vocal nucleus Area X alters waveform patterns in a zebra finch model of Parkinsonian vocal deficits. . Society for Neuroscience.
• Cowen, S. L., Falk, T., Keener, A., Bartlett, M. J., & Vishwanath, A. (2023, Fall). In a hemi-lesioned model of L-DOPA-induced dyskinesia neuronal firing was reduced in the un-lesioned striatum and ketamine reduced burst-like firing in striatal neurons bilaterally. . Society for Neuroscience. Washington DC.
• Stopera, C., Bartlett, M. J., Cowen, S. L., Sherman, S. J., & Falk, T. (2023, Fall). Pravastatin sensitizes parkinsonian rats to L-DOPA and blocks the long-term anti-dyskinetic activity of sub-anesthetic ketamine. Society for Neuroscience Meeting. Washington DC.
• Vishwanath, A., Bartlett, M. J., Falk, T., & Cowen, S. L. (2022, Spring). Ketamine disrupts 80-Hz gamma oscillations and reduces burst firing in naïve and parkinsonian rats with levodopa-induced dyskinesia.. 16th International Conference on Alzheimer’s and Parkinson’s Diseases and related neurological disorders, AD/PD™.
• Cowen, S. L., Falk, T., Sherman, S. J., Jordan, G. A., Bartlett, M. J., & Vishwanath, A. (2021, January). Ketamine disrupts 80-Hz gamma oscillations in parkinsonian rats with L-DOPA-induced dyskinesia.. Society for Neuroscience Global Connectome Conference.
• Falk, T., Cowen, S. L., Jordan, G. A., Vishwanath, A., Sexauer, M. R., Stopera, C., & Bartlett, M. J. (2021, January). The string-pulling task as a novel and simple behavior to test for parkinsonian deficits in unilaterally 6-OHDA-lesioned rodents.. Society for Neuroscience Global Connectome Conference.
• Sherman, S. J., Cowen, S. L., Heien, M. L., Liu, C., Ye, T., Stopera, C., Bartlett, M. J., & Falk, T. (2021, Spring). Update on preclinical and clinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia. 6th Annual ABRC-Flinn Research Conference. Phoenix, AZ.
• Sherman, S. J., Cowen, S. L., Heien, M. L., Farrell, D. C., Ye, T., Bartlett, M. J., & Falk, T. (2020, Spring). Preclinical and clinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia.. 5th Annual ABRC-Flinn Research Conference, Phoenix, AZ.
• Sherman, S. J., Cowen, S. L., Steece-Collier, K., Heien, M. L., Farrell, D. C., Ye, T., Bartlett, M. J., & Falk, T. (2020, Summer). Preclinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia.. European Neuroscience Virtual Forum Abstracts, 2020..
• Sherman, S. J., Cowen, S. L., Steece-Collier, K., Heien, M. L., Farrell, D. C., Ye, T., Bartlett, M. J., & Falk, T. (2020, Summer). Preclinical evidence in support of repurposing sub-anesthetic ketamine as a treatment for L-DOPA-induced dyskinesia.. European Neuroscience Virtual Forum Abstracts.
• Cowen, S. L., Falk, T., Bartlett, M. J., & Ye, T. (2018, Fall). L-DOPA-induced striatal gamma oscillations split into low- and high-frequency components following ketamine exposure in an animal model of L-DOPA-induced dyskinesia. Society for Neuroscience Meeting.
• Cowen, S. L., Falk, T., Bartlett, M. J., & Ye, T. (2018, Fall). L-DOPA-induced striatal gamma oscillations split into low- and high-frequency components following ketamine exposure in an animal model of L-DOPA-induced dyskinesia. Society for Neuroscience.
• Cowen, S. L., Falk, T., Gies, K., Wiegand, J., Eby, A., Bartlett, M. J., Wohlford, L., & Crown, L. M. (2018, Fall). Six month-old LRRK2 G2019S knock-in mice do not express motor learning deficits on the rotarod task. Society for Neuroscience Meeting.
• Cowen, S. L., Falk, T., Gies, K., Wiegand, J., Eby, A., Bartlett, M. J., Wohlford, L., & Crown, L. M. (2018, Fall). Six month-old LRRK2 G2019S knock-in mice do not express motor learning deficits on the rotarod task. Society for Neuroscience.
• Cowen, S. L., Falk, T., Wohlford, L., Monroe, E., Eby, A., Bartlett, M. J., Wiegand, J., & Crown, L. M. (2018, Fall). The frequency of sleep spindle oscillations is increased in the G2019S LRRK2 mouse model of Parkinson’s disease. New Mexico EEG and Behavior Conference.
• Bartlett, M. J., Flores, A. J., Ye, T., Dollish, H. K., Doyle, K., Cowen, S. L., Sherman, S. J., & Falk, T. (2017, Summer). Mechanisms of sub-anesthetic ketamine infusions to reduce levodopa-induced dyskinesia: effects on striatal mTOR signaling and beta band oscillations in striatum and motor cortex.. International Parkinson and Movement Disorders Society Abstracts.
• Cowen, S. L., Bartlett, M. J., Ye, T., & Falk, T. (2017, Novermber). Oscillatory Signatures of L-DOPA-induced Dyskinesia Are Not Reduced by Ketamine. Society for Neuroscience Annual Meeting. Washington DC.
• Cowen, S. L., Crown, L. M., & Nitz, D. (2017, November). Local-field potential activity in the medial prefrontal cortex does not respond to anticipation of effort or reward. Society for Neuroscience Annual Meeting. Washington DC.
• Cowen, S. L., Falk, T., Bartlett, M. J., & Ye, T. (2017, November). Oscillatory signatures of L-DOPA-induced dyskinesia are not reduced by ketamine.. Society for Neuroscience Abstracts.
• Cowen, S. L., Falk, T., Bartlett, M. J., Gies, K., & Wiegand, J. P. (2017, November). Altered sleep physiology in a LRRK2 mouse model in Parkinson's Disease. Society for Neuroscience Meeting. Washington DC.
• Cowen, S. L., Falk, T., Giess, K., Bartlett, M. J., & Wiegand, J. (2017, November). Altered slow-wave sleep in the LRRK2 mouse model of Parkinson’s disease.. Society for Neuroscience Abstracts.
• Cowen, S. L., Wiegand, J. P., Falk, T., & Bartlett, M. J. (2017, November). Altered sleep physiology in a LRRK2 mouse model in Parkinson's Disease. Society for Neuroscience. Washington DC.
• Cowen, S. L., Witte, R. S., Wilhite, C. A., Hill, D. F., Burton, A., Bera, T., & Ingram, P. (2017, November). Acoustoelectric brain imaging: preliminary results in anesthetized rats. UA COM Founder's Day Junior Investigator Poster Forum.
• Demara, B., Gomez, R. L., Cowen, S. L., Spano, G., & Edgin, J. O. (2017, October). To Nap or Not to Nap?: Sleep-dependent Memory Consolidation in Typically and Atypically Developing Preschoolers. World Sleep 2017. Prague: World Sleep Congress.
• Falk, T., Sherman, S. J., Cowen, S. L., Doyle, K., Dollish, H. K., Ye, T., Flores, A. J., & Bartlett, M. J. (2017, Summer). Mechanisms of sub-anesthetic ketamine infusions to reduce levodopa-induced dyskinesia: effects on striatal mTOR signaling and beta band oscillations in striatum and motor cortex.. International Parkinson and Movement Disorders Society Abstracts.
• Falk, T., Ye, T., Bartlett, M. J., & Cowen, S. L. (2017, Novermber). Oscillatory Signatures of L-DOPA-induced Dyskinesia Are Not Reduced by Ketamine. Society for Neuroscience Meeting. Washington DC.
• Heien, M. L., Heien, M. L., Heien, M. L., Cowen, S. L., Cowen, S. L., Cowen, S. L., Falk, T., Falk, T., Falk, T., Miller, M., Miller, M., Miller, M., Giess, K. F., Giess, K. F., Giess, K. F., Crown, L. M., Crown, L. M., Crown, L. M., Bartlett, M. J., , Bartlett, M. J., et al. (2017, Spring). Longitudinal studies of tonic dopamine for investigation of neural disorders. PittCon Conference Abstracts.
• Cowen, S. L., & Heien, M. L. (2016, December). A system for the combined measurement of dopamine and neural activity (DANA). NSF/NIH Brain Initiative Investigators Meeting. Bethesda, MD: NIH.
• Schmit, M. D., Cowen, S. L., Dollish, H. K., Falk, T., Dollish, H. K., Falk, T., Schmit, M. D., & Cowen, S. L. (2016, Fall). BRIAN: The Brains of Neuroscience Outreach. BRAIN AWARENESS CAMPAIGN EVENT at Society for Neuroscience Meeting.
• Schmit, M. D., Ye, T., Bartlett, M. J., Falk, T., & Cowen, S. L. (2016, Fall). Directional Propagation of Ketamine-induced High-Frequency Oscillations between the Striatum, Hippocampus, and Motor Cortex.. Society for Neuroscience Abstracts.
• Wiegand, J., Giess, K. F., Bartlett, M. J., Falk, T., & Cowen, S. L. (2016, Fall). Stronger cortical spindles and less power variability in hippocampal ripples in a LRRK2 mouse model of Parkinson’s disease. Society for Neuroscience Abstracts.
• Wiegand, J., Giess, K., Bartlett, M. J., Falk, T., & Cowen, S. L. (2016, Fall). Increased power of sleep spindle oscillations in the LRRK2 mouse model of Parkinson’s disease.. 4th World Parkinson Congress Abstracts.
• Witte, R. S., Qin, Y., Ingram, P., Burton, A., Tseng, H., Hill, D. F., Wilhite, C. A., Falk, T., Xu, Z., O'Donell, M., & Cowen, S. L. (2016, Fall). Acoustoelectric Brain Imaging of Deep Dipole Sources in a Human Head Phantom. 3rd Annual BRAIN Initiative® Investigators Meeting.
• Ye, T., Bartlett, M. J., Schmit, M. B., Sherman, S. J., Falk, T., & Cowen, S. L. (2016, Fall). Alterations of oscillatory activity in the striatal-cortical circuit following repeated sub-anesthetic ketamine administration in 6-OHDA-lesioned rats.. Society for Neuroscience Abstracts.
• Ye, T., Cowen, S. L., Bartlett, M. J., Falk, T., Schmit, M., Sherman, S. J., Schmit, M., Sherman, S. J., Bartlett, M. J., Falk, T., Ye, T., & Cowen, S. L. (2016, Fall). Gamma-band oscillatory activity in the motor cortex is progressively enhanced following repeated ketamine administration in 6-OHDA-lesioned rats.. 4th World Parkinson Congress Abstracts.
• Parent, K. L., Bartlett, M. J., Crown, L. M., Giess, K. F., Miller, M., Falk, T., Cowen, S. L., & Heien, M. L. (2017, Spring). Longitudinal studies of tonic dopamine for investigation of neural disorders. PittCon Conference Abstracts.