Perception, decision making, and movement deeply involve cortical circuitry, which has a stereotyped architecture repeated across the entire surface of the brain. In this talk, I will discuss our investigations of how the different cortical layers contribute to behavior. I will show how modern optogenetic and traditional lesion manipulations can lead to opposing conclusions about the necessity of a brain structure, layer, or cell type. We have developed novel cortex-dependent tasks for the rodent whisker system in which we manipulate and record the layers to test their functions. By combining array recordings and modeling in these tasks, we are additionally able to disentangle the contributions of sensory, motor, choice, and reward signals to the activity of individual neurons. We find that task context can reweight this mixture so dramatically that the most fundamental features of cortex, such as topographic representations disappear. On-going experiments using two-photon microscopy of apical tuft dendrites during animal training suggest that cortical layer 1 may be a key substrate by which learning reconfigures sensory cortex according to task context.
In all mammals including humans, the cerebral cortex mediates the highest levels of cognition, from sensing our world, applying learned knowledge, making decisions, to executing movements. The long-term goal of my research program is to understand how this cognitive machinery is assembled from unique cortical cell types arranged in circuits with specific architectures. Many mental disorders are diseases of these cortical circuits. Evolution’s solutions to cognition are also adaptable to produce intelligent machines in research and medicine. I am working to uncover principles of cortical microcircuitry and computation by exploiting electrophysiology, cellular imaging, cellular manipulation, and computational modeling – all in the context of behaviour. We use the rodent whisker-barrel system for our experiments because mice – one of the world’s most heavily used model organisms – rely predominantly on whisker-mediated touch to explore the world. My lab’s current focus is to understand the computational and behavioural roles of the different cortical layers.