WhiskerSchema · Understanding the integration of body schema in the cortical representations of space during tool use

When walking with a cane, a blind person can localize the objects they touch. Tool-based sensing requires the brain to combine sensory signals at the hand and proprioceptive information together with knowledge of the physical properties of the tool. To correctly interpret the signals sensed with a tool, the brain incorporates the tool in its internal representation of the body in space, known as the body schema. However, the neuronal basis for integrating somatosensory with the body schema information is largely unknown. I hypothesize that feedback projections from higher cortical areas involved in body schema shape cortical somatosensory processing to create a spatial representation of touch. I propose to tackle this question at the cellular and circuit levels by introducing the mouse as a model organism. Mice use their whiskers to effectively localize objects in space, yet the whiskers themselves lack mechanoreceptors. Here, I will record neuronal activity in the somatosensory cortex (S1) using two-photon imaging while presenting mice with objects at different locations in a two-dimensional horizontal plane. From my preliminary experiments, I found that individual layer 2/3 neurons in S1 have preferences for different spatial positions. Using optogenetics, I will test the impact of feedback projections from the body schema network on the spatial representation in S1. Finally, I will employ a prosthetic whisker designed in the host lab to vary the physical parameters of the mouse whisker. This experimental design will allow exploring the consequences of a mismatch between the body schema and the actual physical properties of the tool used in the cortical representation of space. Through the development of a prosthetic whisker, this proposal aims to leverage the mouse model to shed light on a major open question in cognitive neuroscience.