Cortical recruitment determines learning dynamics and strategy

Abstract

Abstract. Salience is a broad and widely used concept in neuroscience whose neuronal correlates, however, remain elusive. In behavioral conditioning, salience is used to explain various effects, such as stimulus overshadowing, and refers to how fast and strongly a stimulus is associated to a conditioned event. Here, we show that sounds of diverse quality, but equally intense and perceptually detectable, recruit surprisingly different levels of population activity in mouse auditory cortex. When using these sounds as cues in a Go/NoGo discrimination task, the degree of cortical recruitment matches the salience parameter of a reinforcement learning model used to analyze learning speed. Moreover, we confirm a generic prediction of the model by training mice to discriminate light-sculpted optogenetic activity patterns in auditory cortex verifying that cortical recruitment causally determines association or overshadowing of the stimulus components. This demonstrates that cortical recruitment captures major aspects of stimulus salience during reinforcement learning.peer-reviewed)

Deep imaging in the brainstem reveals functional heterogeneity in V2a neurons controlling locomotion

“…Raw calcium data were preprocessed using a Gaussian filter (MATLAB) with a 150-ms half-width. We also deconvolved the calcium signal to show an estimate of the time course of the firing rate using the equation S d = dS/dt + S (32)(33)(34), where S d is the deconvolved signal, S is the raw signal, and  = 0.5 s is our estimate of GCaMP6s decay time in V2a neurons, directly measured on traces obtained after PCA/ICA. GCaMP6s transients have a long exponential decay, whose time constant depends on cell type.…”

Continuity within somatosensory cortical map shapes the integration of optogenetic input

“…Photostimulation was done at high power (measured, 10-15 mW per mm 2 ). Spiking activity resulting from such photostimulation was demonstrated previously (10,40). Using a photodetector, we ensured that the edge of the photostimulation was sharp: intensity 5 % at 20 microns.…”

“…To what extent direct activation of cortical ensembles in these maps may be necessary and sufficient for eliciting sensory percepts is an area of active research (8)(9)(10). Animals can be trained to report direct cortical stimulation of primary sensory areas for all modalities (9)(10)(11)(12)(13)(14).…”

“…To what extent direct activation of cortical ensembles in these maps may be necessary and sufficient for eliciting sensory percepts is an area of active research (8)(9)(10). Animals can be trained to report direct cortical stimulation of primary sensory areas for all modalities (9)(10)(11)(12)(13)(14). Interestingly, several studies have shown that animals trained in a sensory perception task could rapidly generalize when the peripheral stimuli were replaced by cortical microstimulations (9,(14)(15)(16)(17)(18)(19)(20).…”

“…Throughout these experiments, stimulation of distinct cortical zones in a topographic sensory map elicited distinct percepts matching the expected peripheral locations on the sensory organ ( 9 , 10 , 21 – 23 ). This consistency has been interpreted as additional evidence that the topographical organization of sensory areas serves a fundamental function for sensory processing ( 24 ).…”