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Scopolamine and medial frontal stimulus-processing during interval timing
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Scopolamine and medial frontal stimulus-processing during interval timing

Qiang Zhang, Dennis Jung, Travis Larson, Youngcho Kim and Nandakumar S Narayanan
bioRxiv: the preprint server for biology
Cold Spring Harbor Laboratory
04/05/2019
DOI: 10.1101/598862
url
https://doi.org/10.1016/j.neuroscience.2019.07.004View
Published (Version of record)This article has now been published in a journal and has been peer-reviewed by subject experts. This version may differ significantly from the preprint version. Open Access
url
https://doi.org/10.1101/598862View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

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Abstract

Neurodegenerative diseases such as Parkinson’s disease (PD), dementia with Lewy Bodies (DLB), and Alzheimer’s disease (AD) involve loss of cholinergic neurons in the basal forebrain. Here, we investigate how cholinergic dysfunction impacts the frontal cortex during interval timing, a process that can be impaired in PD and AD patients. Interval timing requires participants to estimate an interval of several seconds by making a motor response, and depends on the medial frontal cortex (MFC), which is richly innervated by basal forebrain cholinergic projections. Past work has shown that scopolamine, a muscarinic cholinergic receptor antagonist, reliably impairs interval timing. We tested the hypothesis that scopolamine would attenuate time-related ramping, a key form of temporal processing in the MFC. We recorded neuronal ensembles from 8 mice during performance of a 12-s fixed-interval timing task, which was impaired by the administration of scopolamine. Consistent with past work, scopolamine impaired timing. To our surprise, we found that time-related ramping was unchanged, but stimulus-related activity was enhanced in the MFC. Principal component analyses revealed no consistent changes in time-related ramping components, but did reveal changes in higher components. Taken together, these data indicate that scopolamine changes stimulus-processing rather than temporal processing in the MFC. These data could help understand how cholinergic dysfunction affects cortical circuits in diseases such as PD, DLB, and AD. Highlights The cholinergic muscarinic inhibitor scopolamine impairs interval timing behavior. Scopolamine does not change time-related ramping activity in the medial frontal cortex. Medial prefrontal stimulus-related modulation increased

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