Biology subjects

McAfee, S. S.

Publications and source records attributed to McAfee, S. S..

3 recordsLinked to original sources

bioRxiv2020

Cerebellar modulation of gamma coherence between prefrontal cortex and hippocampus during spatial working memory decision making

Spatial working memory (SWM) is a cognitive skill supporting survival-relevant behaviors, such as optimizing foraging behavior by remembering recent routes and visited sites. It is known that SWM decision-making in rodents requires the medial prefrontal cortex (mPFC) and dorsal hippocampus. The decision process in SWM tasks carries a specific electrophysiological signature of a brief, decision-related increase in neuronal communication in the form of an increase in the coherence of neuronal theta oscillations (4-12 Hz) between the mPFC and dorsal hippocampus, a finding we replicated here during spontaneous exploration of a plus maze in freely moving mice. We further evaluated SWM decision-related coherence changes within frequency bands above theta. Decision-related coherence increases occurred in seven frequency bands between 4 and 200 Hz and decision-outcome related differences in coherence modulation occurred within the beta and gamma frequency bands and in higher frequency oscillations up to 130 Hz. With recent evidence that Purkinje cells in the cerebellar lobulus simplex (LS) represent information about the phase and phase differences of gamma oscillations in the mPFC and dorsal hippocampus, we hypothesized that LS might be involved in the modulation of mPFC-hippocampal gamma coherence. We show that optical stimulation of LS significantly impairs SWM performance and decision-related mPFC-dCA1 coherence modulation, providing causal evidence for an involvement of cerebellar LS in SWM decision making at the behavioral and neuronal level. Our findings suggest that the cerebellum might contribute to SWM decision-making by optimizing the decision-related modulation of mPFC-dCA1 coherence.

neuroscience↗

bioRxiv2017

Cerebellar Purkinje cell simple spike activity in awake mice represents phase differences between oscillations in medial prefrontal cortex and hippocampus

The cerebellum has long been recognized for its role in tasks involving precise timing, particularly the temporal coordination of movements. Here we asked whether cerebellar might be involved in the temporal coordination of the phases of neuronal oscillations in the medial prefrontal cortex (mPFC) and dorsal hippocampus CA1 region (CA1). These two structures and the cerebellum are jointly involved in spatial working memory. The phases of oscillations in the mPFC and CA1 have been shown to reach a stable alignment (coherence) during the decision making process in a spatial working memory task. Here we report that PC simple spike activity in the cerebellar lobulus simplex in awake, head-fixed mice represents specific phase differences between oscillations in the mPFC and CA1. Most PCs represented phase differences in more than one the conventional frequency bands (delta, theta, beta and gamma). Between the 32 PCs analyzed here, phase differences in all frequency bands were represented. PCs representing phase differences in the theta and low gamma bands showed significant population preference for mPFC phase leading CA1 phase. These findings support the possibility of a cerebellar involvement in the temporal coordination of phase relationships between oscillations in the mPFC and CA1.

neuroscience↗

bioRxiv2017

Thalamocortical transmission of visual information in awake mice involves phase synchronization and spike synchrony at high gamma frequencies

AbstractSynchronization of neuronal spike activity is thought to play a key role in the transmission of information for sensory processing in the brain, and this synchronization is influenced by oscillatory population activity occurring in multiple frequency ranges at multiple stages of sensory pathways. In the neocortex, gamma frequency oscillations appear to play an important role in synchronizing neuronal ensembles and allowing for selective communication between regions, yet relatively little is known about whether gamma oscillations facilitate transmission of sensory information from thalamus to cortex. Here, we investigate the role of gamma oscillations in promoting synchronous spike activity between the visual thalamus (dLGN) and primary visual cortex (V1) in awake mice, a model sensory system with prominent gamma oscillations that are modulated by visual input. We demonstrate that transmission of visual information to cortex involves phase-synchronized oscillations in the high gamma range (50-90Hz), with concomitant millisecond-scale synchronization of thalamic and cortical spike activity. Transition from a full-field gray image to a high-contrast checkerboard image caused gamma activity to rapidly increase in amplitude, frequency, and bandwidth, yet the gamma oscillations in dLGN and V1 maintained a consistent phase relationship. High contrast stimulation also caused an increase in amplitude of oscillations in the beta and low gamma range, but those were not associated with synchronous thalamic activity. These results indicate a role for high gamma oscillations in mediating the functional connectivity between thalamic and cortical neurons in the visual pathway, a similar role to beta oscillations in primates.\n\nSignificance statementThe mechanisms by which neurons selectively communicate are essential to our understanding of how the brain processes information. Abundant evidence suggests that cortical sensory processing involves the synchronization of high frequency electric field oscillations known as gamma oscillations, which allow groups of neurons to synchronize their spike activity in order to collaboratively process sensory input. Here, we show that oscillations and spikes in the visual thalamocortical pathway of the mouse exhibit synchrony across a broad high gamma frequency range (50-90Hz), suggesting these oscillations play an important role in the relay of visual information to the cortex. This is substantially different from oscillations observed in monkeys, in which gamma is absent in thalamus and beta oscillations support thalamocortical relay.

neuroscience↗