Stored-Trace Reactivation in Rat Prefrontal Cortex Is Correlated with Down-to-Up State Fluctuation Density

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During light slow-wave sleep, the thalamo-cortical network oscillates in waxing-and-waning patterns at about 7 to 14 Hz and lasting for 500 ms to 3 s, called spindles, with the thalamus rhythmically sending strong excitatory volleys to the cortex. Concurrently, the hippocampal activity is characterized by transient and strong excitatory events, Sharp-Waves-Ripples (SPWRs), directly affecting neocortical activity-in particular the medial prefrontal cortex (mPFC)-which receives monosynaptic fibers from the ventral hippocampus and subiculum. Both spindles and SPWRs have been shown to be strongly involved in memory consolidation. However, the dynamics of the cortical network during natural sleep spindles and how prefrontal circuits simultaneously process hippocampal and thalamo-cortical activity remain largely undetermined. Using multisite neuronal recordings in rat mPFC, we show that during sleep spindles, oscillatory responses of cortical cells are different for different cell types and cortical layers. Superficial neurons are more phase-locked and tonically recruited during spindle episodes. Moreover, in a given layer, interneurons were always more modulated than pyramidal cells, both in firing rate and phase, suggesting that the dynamics are dominated by inhibition. In the deep layers, where most of the hippocampal fibers make contacts, pyramidal cells respond phasically to SPWRs, but not during spindles. Similar observations were obtained when analyzing γ-oscillation modulation in the mPFC. These results demonstrate that during sleep spindles, the cortex is functionnaly "deafferented" from its hippocampal inputs, based on processes of cortical origin, and presumably mediated by the strong recruitment of inhibitory interneurons. The interplay between hippocampal and thalamic inputs may underlie a global mechanism involved in the consolidation of recently formed memory traces.cortical deafferentation | fast spiking neurons | regular spiking neurons | memory reprocessing | Up and Down states

Section: Interaction Between Thalamic and Hippocampal Inputs At Multiplementioning

confidence: 61%

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confidence: 99%

Inhibition recruitment in prefrontal cortex during sleep spindles and gating of hippocampal inputs

Peyrache

Battaglia

Destexhe

2011

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“…Cortical sleep spindles are correlated with hippocampal sharp waves (8, 9) and stored-trace reactivation (10), and are therefore frequently associated with declarative memory processes. Other studies have shown that spindles increase in response to other kinds of learning as well (5,7,8,17,29), and this is confirmed by our results, which focus on what is essentially a motor task.…”

Section: Resultsmentioning

confidence: 99%

“…For example, increases in spindle density have been correlated with learning a declarative memory task (5), with retention of verbal memories (6), and with relevant recall of a remote memory (7). Additionally, spindles are correlated with sharp-wave complexes in the hippocampus (8,9) and are associated with storedtrace reactivation in the neocortex (10). It has been hypothesized that sleep spindles actually facilitate learning by establishing a cortical state that is conducive to synaptic plasticity, and therefore, to sleep-dependent memory consolidation (11,12).…”

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confidence: 99%

Sleep spindles are locally modulated by training on a brain–computer interface

Johnson

Blakely

Hermes

et al. 2012

The learning of a motor task is known to be improved by sleep, and sleep spindles are thought to facilitate this learning by enabling synaptic plasticity. In this study subjects implanted with electrocorticography (ECoG) arrays for long-term epilepsy monitoring were trained to control a cursor on a computer screen by modulating either the high-gamma or mu/beta power at a single electrode located over the motor or premotor area. In all trained subjects, spindle density in posttraining sleep was increased with respect to pretraining sleep in a remarkably spatially specific manner. The pattern of increased spindle activity reflects the functionally specific regions that were involved in learning of a highly novel and salient task during wakefulness, supporting the idea that sleep spindles are involved in learning to use a motorbased brain-computer interface device.

“…Although reactivation had originally been reported in the hippocampus as a mechanism of memory consolidation (12)(13)(14), it may constitute a fundamental property of neural ensembles in many brain areas. Indeed, in addition to hippocampus, reactivation has been reported in rat prefrontal cortex (15)(16)(17), motor and somatosensory cortex during quiescent awake states (18), rat primary visual cortex (V1) during slow-wave sleep (19), and rat and cat V1 immediately after stimulus presentation during anesthesia (20)(21)(22).…”

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confidence: 99%

Image sequence reactivation in awake V4 networks

Eagleman

Dragoi

2012

In the absence of sensory input, neuronal networks are far from being silent. Whether spontaneous changes in ongoing activity reflect previous sensory experience or stochastic fluctuations in brain activity is not well understood. Here we describe reactivation of stimulusevoked activity in awake visual cortical networks. We found that continuous exposure to randomly flashed image sequences induces reactivation in macaque V4 cortical networks in the absence of visual stimulation. This reactivation of previously evoked activity is stimulusspecific, occurs only in the same temporal order as the original response, and strengthens with increased stimulus exposures. Importantly, cells exhibiting significant reactivation carry more information about the stimulus than cells that do not reactivate. These results demonstrate a surprising degree of experience-dependent plasticity in visual cortical networks as a result of repeated exposure to unattended information. We suggest that awake reactivation in visual cortex may underlie perceptual learning by passive stimulus exposure.electrophysiology | monkey