Microstimulation of sensory cortex engages natural sensory representations

Abstract

Cortical activity patterns occupy a small subset of possible network states. If this is due to intrinsic network properties, microstimulation of cortex should evoke activity patterns resembling those observed during natural sensory input. Here, we use optical microstimulation of virally transfected layer 2/3 pyramidal neurons in mouse primary vibrissal somatosensory cortex to compare artificially evoked activity with natural activity evoked by whisker touch and movement ('whisking'). We find that photostimulation engages touch but not whisking responsive neurons more than expected by chance. Neurons that respond to photostimulation and touch or to touch alone exhibit higher spontaneous pairwise correlations than purely photoresponsive neurons. Exposure to several days of simultaneous touch and optogenetic stimulation raises both overlap and spontaneous activity correlations among touch and photoresponsive neurons. We thus find that cortical microstimulation engages existing cortical representations and that repeated co-presentation of natural and artificial stimulation enhances this effect.

Sparse and distributed cortical populations mediate sensorimotor integration

“…Touch-whisking interactions are likely more complex: whisking activity decorrelates vS1 activity 59 and likely increases sensitivity to external input. By directly activating touch-whisking neurons, whisking network activity may predispose the touch network towards stronger touch responses via pattern completion 34,35 (Figure 7H). The converse may also be true: touch activity could influence whisking networks via touch-whisking neurons, potentially driving movement adjustments as object contacts are made 49 .…”

“…What is the source of this increasing activity? Cortical excitatory circuitry is organized into assemblies 29 that exhibit high levels of recurrence 30 , with neurons that represent the same sensory input [31][32][33] exhibiting elevated connectivity, enabling pattern completion [34][35][36] and amplification 37 . Consequently, even small additions of spikes can bias ongoing activity 38 , movement 39 , and perception 40,41 .…”

Representational drift in barrel cortex is receptive field dependent

“…Correlated spontaneous L2/3 calcium activity predicts connectivity 28,51,52 . In vS1, declines in touch responsiveness following touch neuron ablation 53 and channeling of activity towards natural touch responsive populations 54 point to elevated connectivity among touch neurons. Physically, then, a subset of neurons exhibiting elevated connectivity and greater long-term stability may act as a scaffold for less stable neural activity.…”

Brain-machine interface learning is facilitated by specific patterning of distributed cortical feedback

“…Several recent studies have used twophoton imaging to measure the activity of neurons in primary sensory areas during detection of a spot-like optogenetic photostimulation. One study showed that over the course of training sessions, an optogenetic spot stimulation in S1 increasingly engaged the touch-related neuronal assemblies in this area, disproportionally more than the whisking-related neurons (45). In another study focusing on the primary visual cortex (46), neurons recorded in the cortical area below the stimulation spot developed a specific tuning for the single spot compared to other stimulation patterns.…”