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We are using the Thomas Recording multiple electrode system to make simultaneous recordings of both single neurons and local field potentials (LFPs) from two key cortical regions involved in visual control of skilled digit movements: primary motor cortex (M1) and ventral premotor cortex (PMv, area F5). These two areas are anatomically and functionally heavily interconnected and form part of the ‘visuomotor grasping network’ controlling grasp. Our objectives are to understand
- how the information related to visually-guided grasp of different objects is encoded in these two areas
- how this information is transformed into the recruitment of populations of identified output neurons in M1: these are known to play a critical role in controlling hand shape appropriate for grasping a particular objects
- the pathways and circuits involved in the interactions between M1 and F5, explored with direct recordings from corticospinal output neurons, motoneurons and muscles, and also using intracortical stimulation and reversible inactivation
Monkeys are trained to perform a number of very different grasps ranging from single digit hook grip, to precision grip between thumb and index finger, and whole hand grasp. We are using a number of analytical approaches to identify reciprocal exchange of information between F5 and M1, both in spikes from populations of single neurons and in LFPs. This challenging project is of great importance in understanding how cortical networks function interactively.
References
Brochier T, Spinks RL, Umilta MA, Lemon RN (2004) Patterns of muscle activity underlying object-specific grasp by the Macaque monkey. J Neurophysiol 92:1770-1782.
Cattaneo L, Voss M, Brochier T, Prabhu G, Wolpert DM, Lemon RN (2005) A cortico-cortical mechanism mediating object-driven grasp in humans. Proc Natl Acad Sci USA 102:898-903.
Cerri G, Shimazu H, Maier MA, Lemon RN (2003) Facilitation from ventral premotor cortex of primary motor cortex outputs to macaque hand muscles. J Neurophysiol 90:832-842.
Lemon RN (2008) Descending pathways in motor control. Annual Review of Neuroscience 31:195-218.
Prabhu G, Shimazu H, Cerri G, Brochier T, Spinks RL, Maier MA, Lemon RN (2009) Modulation of primary motor cortex outputs from ventral premotor cortex during visually guided grasp in the macaque monkey. J Physiol 587:1057-1069.
Schmidlin E, Brochier T, Maier MA, Kirkwood PA, Lemon RN (2008) Pronounced reduction of digit motor responses evoked from macaque ventral premotor cortex after reversible inactivation of the primary motor cortex hand area. J Neurosci 28:5772-5783.
Shimazu H, Maier MA, Cerri G, Kirkwood PA, Lemon RN (2004) Macaque Ventral Premotor Cortex Exerts Powerful Facilitation of Motor Cortex Outputs to Upper Limb Motoneurons. Journal of Neuroscience 24:1200-1211.
Umilta MA, Brochier T, Spinks RL, Lemon RN (2007) Simultaneous recording of macaque premotor and primary motor cortex neuronal populations reveals different functional contributions to visuomotor grasp. J Neurophysiol 98:488-501.