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Network interaction in motor cortex in relation to behavior

Altough the motor cortex is one of the most studied brain areas, it is still unclear how motor cortical organization and activity relate to the planning and execution of complex movements. In the past, researchers focused on analyzing population rate responses in relation to movement parameters and sensory feedback. However, an increasing body of evidence suggests that also synchronized spiking activity on a milisecond time scale plays an important role in understanding the network activity associated with movement preparation ( Riehle et al. 1997 , Kilavik et al. 2009). These studies were performed using multiple single electrodes resulting in only small samples of neurons that could be recorded in parallel. Therefore such recordings were limited to the analysis of pairwise interactions, leaving open the question if they are part of a correlation structure of higher order exhibited by the complete network.

Massively parallel recordings of spike data and LFPMassively parallel recordings of spike data and LFP

To overcome the severe undersampling of cortical networks, we conduct (in collaboration with Alexa Riehle and Thomas Brochier at the INT in Marseille) a new experimental study with chronically implanted multielectrode arrays (Utah Array) which record massively parallel activity from 96 channels. In this experiment the animal is instructed to reach, grasp and hold either a heavy or light weighted object using either a precision or a side grip. By revealing either the required grip type or the object weight, the animal was allowed to partially prepare the movement during a delay period preceeding movement execution. The recordings allow not only to record from a large number of neurons of the network, but also yield information about the spatial structure of neuronal activity across the cortical surface on a milimeter scale (Riehle et al. 2013). In addition to studying the task related coordination of network activity, we now also have access to a series of recordings using the same recording technology where an animal was either asleep or sitting still. By comparing these different recording conditions (task, sleep, rest) we aim to disambiguate functionally relevant dynamics from the activity due to the network structure.

Selected references:

-Milekovic, truccolo, Grün, Riehle and Brochier (2015) Local field potentials in primae motor cortex encode grasp kinetic parameters. NeuroImage 114:338-355
-Riehle, Wirtssohn, Grün, and Brochier (2013) Mapping the spatio-temporal structure of motor cortical LFP and spiking activities during reach-to-grasp movements. Front Neural Circuits 7:48
-Kilavik, Roux, Ponce-Alvarez, Confais, Grün, and Riehle (2009) Long-term modifications in motor cortical dynamics induced by intensive practice. J Neurosci 29(40): 12653-12663
-Riehle, Grün, Diesmann, and Aertsen (1997) Spike Synchronization and Rate Modulation Differentially Involved in
Motor Cortical Function. Science 278, 1950