Cortical circuits supporting the integration of contextual and sensoryinformation
Robin Dard
Laboratoire de traitement sensoriel – LSENS
Ecole polytechnique fédérale de Lausanne – EPFL

Résumé : In nature, humans and animals need to contextualize sensory information theyreceive to elicit appropriate motor sequences through a process known assensorimotor transformation. While we begin to understand how sensoryinformation is transformed into motor action, it is still unclear in what way contextualinformation can modify a given sensorimotor plan. We investigate this phenomenonby training water-restricted mice in a context-dependent multisensory detectiontask. The first stimulus (a single whisker deflection) is rewarded upon licking in acontext-dependent manner, while the second stimulus (auditory pure tone) isalways rewarded upon licking, irrespective of context. In this task, the context isprovided by two different auditory background textures that change every block of20 trials. Upon learning, mice were able to switch their behavior according to thecontextual auditory textures at the first whisker trial of the block and perform onaverage 10 switches per session. This context dependent behavioral switch wasfurther supported by our observation that mouse performance collapsed in theabsence of the auditory contextual cues.To investigate the cortical regions required for task execution, we carried out arandom-access optogenetic inactivation screen of the dorsal cortex and targetedpharmacological inactivation. We established the necessity of the whiskersomatosensory and secondary motor associated cortices (wS1/wS2, wM1/wM2) intask execution and observed that inhibition of the retrosplenial cortex (RSC)increases lick probability to the whisker stimuli in the non-rewarded context.We used widefield calcium imaging in mice expressing GCaMP6f selectively inL2/3 excitatory neurons to investigate how contextual and sensory informationintegrate to guide behavior in a flexible manner. We observed that spontaneousactivity prior to the whisker or auditory stimuli reflected the current context in mostcortical areas. Right after the whisker stimulus, the sensory-evoked activity washighly similar in the two contexts in sensory areas but it differed in frontal premotorregions before the onset of the motor response.We hypothesize a key role of frontal premotor cortex in integrating contextualinformation with sensory-evoked activity, which might be transmitted directly fromsensory cortex.

Invité par Michel Picardo