Deconstructing action planning and action observation in parietal circuits in rats (RAT MIRROR CELL)

Framework: FP7 — Ideas
Programme: European Research Council
Theme: European research council
Destination: Starting grants
Action type: Support for frontier research (ERC)
Panel: Neurosciences and neural disorders
Countries involved: Norway
Call:  (ERC-2013-StG, 2013)
Start date: 2014-01-01
End date: 2018-12-31
Duration (months): 60.0
Total project cost (EUR): 1500000.0
EU funding (EUR): 1500000.0
Participants: 1
Project status: CLOSED

More than a century of research on the motor system in primates and humans has revealed that motor behavior is computed across several regions of cortex, with the earliest stages of movement planning occur in posterior parietal cortex (PPC). In addition to playing a key role in planning movement, PPC, along with pre-motor cortex, contain subsets of cells exhibiting sensory-motor ‘mirror’ coding, where neurons fire when an animal performs an action and when it observes the same action performed by a cohort. Mirror neurons may provide a physiological mechanism for the unification of action perception and action execution, potentially underlying observational learning and empathy. The tuning properties of PPC cells result from converging sensory and motor projections from several areas, but a major constraint in developing a mechanistic account of PPC and its inputs is that it is not yet practical in humans or primates to selectively inhibit these pathways. This limitation could be overcome by studying PPC in simpler organisms, such as rodents, in which genetic-based techniques can silence anatomical projections to PPC. Rodents also bring the advantage of multi-tetrode recordings and calcium imaging, powerful techniques for revealing population codes in freely-moving subjects. Importantly, the rodent PPC encodes behavior prospectively, analogous to predictive coding for hand or eye movements seen in primates, and a growing literature supports the hypothesis that rodents may have a mirror system. I thus propose two distinct but related research themes: one on the mechanisms of action planning, and the other on the mechanisms for action understanding. Specifically, the first project will test if population coding properties in PPC and pre-motor cortex change as a function of cognitive demand, depending on whether animals forage spontaneously or plan motor sequences in a memory-based navigation task. I propose to then test the function of fronto-parietal anatomical connections during motor planning and decision making by optically silencing premotor-PPC projections during the memory-guided navigation task. The riskier, more ambitious experiments will determine if PPC cells express mirror-like selectivity when mice observe cohorts performing a pellet reaching task or a running wheel task. If I find that mirroring exists in mouse PPC, I will utilize chemogenetic projection-silencing to determine which cortical inputs are critical to confer mirror selectivity to the cells. If successful, these experiments will uncover details of the functional anatomy of the mirror system which cannot currently be obtained using primates or humans as models. The discovery of mirror cells in a rodent would be of potentially profound significance, as it would open the door for the broader study of mirror cells as cellular substrates for social behavior and dysfunction in mouse models of human mental disorders, including autism and Fragile-X mental retardation.

Keywords: parietal cortex,action planning,mirror system