Independent representations of self-motion and object location in barrel cortex output

Abstract

During active tactile exploration, the dynamic patterns of touch are transduced to electrical signals and transformed by the brain into a mental representation of the object under investigation. This transformation from sensation to perception is thought to be a major function of the mammalian cortex. In primary somatosensory cortex (S1) of mice, layer 5 (L5) pyramidal neurons are major outputs to downstream areas that influence perception, decision-making, and motor control. We investigated self-motion and touch representations in L5 of S1 with juxtacellular loose-seal patch recordings of optogenetically identified excitatory neurons. We found that during rhythmic whisker movement, 54 of 115 active neurons (47%) represented self-motion. This population was significantly more modulated by whisker angle than by phase. Upon active touch, a distinct pattern of activity was evoked across L5, which represented the whisker angle at the time of touch. Object location was decodable with submillimeter precision from the touch-evoked spike counts of a randomly sampled handful of these neurons. These representations of whisker angle during self-motion and touch were independent, both in the selection of which neurons were active and in the angle-tuning preference of coactive neurons. Thus, the output of S1 transiently shifts from a representation of self-motion to an independent representation of explored object location during active touch.

High-frequency burst spiking in layer 5 thick-tufted pyramids of rat primary somatosensory cortex encodes exploratory touch

“…It remains to be determined how the information pathways on whisker motion and whisker touch are merged to form a comprehensive sensory percept 62 . The integration could occur in S1 since silencing of S1 leads to a dramatic drop in behavioral performance of mice that learned to report the position of an object 63 .…”

Cortex-independent open-loop control of a voluntary orofacial motor action

“…Vibrissa sensory feedback is neither required before nor after learning the task Do rats require sensory feedback to finely move their vibrissae? This is physiologically plausible since reafferent signals, encoded by mechanoreceptor afferents 19,21,33 , are present in the rodent brainstem 16,33,34 , thalamus 16,23,35 , neocortex 5,36,37 , and cerebellum 22,38 . To test the requirement of sensory feedback, we deafferented two "expert" rats, taking advantage of the separation of the vibrissa sensory and motor nerves (figure 2A and supplementary figure 2A).…”

Internal monitoring of whisking and locomotion in the superior colliculus

“…Moreover, the tactile 2 features encoded by movement-related SC neurons are unknown. Given the established role of the SC in visuomotor processing (41)(42)(43)(44)(45), we hypothesized that neurons in the mouse SC combine an internal representation of whisker movement with tactile information to enable active tactile localization (10,12,46).…”