SSA: Memories of touch: The role of higher order cortical areas in processing and remembering tactile textures.

Humans mainly use the visual system to understand and interpret the world, making it difficult for us to imagine the
world of touch in any detail or understand its importance. Yet if we were unable to recognise objects from the way
they feel, we would then most likely realise the wealth of information yielded up by this vital sense. This studentship
project is aimed at understanding how texture information is processed in the brain and how the brain adapts and
learns to attribute meaning to particular textures. To do this we will study texture processing in the rodent brain.
Rodents are nocturnal animals and are therefore highly reliant on tactile information for identifying objects in their
environment. Rodents are experts at touch. In laboratory tasks, we have found that they preferentially use their
whiskers to identify different textures. Remarkably, they are able to distinguish between surfaces that differ in particle
size by just 18um, a distance that is orders of magnitude smaller than the spacing between whiskers on the face.
Building on the findings of an earlier BBSRC PhD studentship (Pacchiarin et al. 2017; 2020), we propose to extend our
investigation of how higher order somatosensory processing occurs in the cerebral cortex. We have established that
primary somatosensory cortex (SI) is necessary for texture discrimination in freely moving mice by using chemo-
genetic methods to inactivate temporarily SI during a whisker-dependent discrimination. Furthermore, using in vivo
2-photon microscopy of dendritic spines, we have found that SI neurones undergo structural synaptic plasticity during
texture discrimination, if and only if the mice learn the discrimination. The next step is to determine how texture
information processing proceeds from SI to the hippocampus via the hypothesised ventral stream pathway. We will
initially study SII, which is strongly connected to SI, projects ventrally to Perirhinal cortex, and responds to tactile
textures. We will inactivate SII during the learning task using DREADDs and measure whether the mice still learn the
texture discrimination. These studies will lead to an understanding of how tactile sensory experience can be stored as
memories that are used to direct future choices.