Prof. R. Lemon
Cortical Control of Skilled Hand Function
My main scientific interest is to understand the cerebral control of hand and finger movements in humans and in non-human primate models.
This interest is prompted by the need to understand why hand and finger movements are particularly affected by damage to the cortex, and its major descending pathways, for instance as a result of stroke, spinal injury, motor neurone disease or cerebral palsy.
Sensorimotor control systems show marked differences across species, reflecting different capacities and skills. We have conducted a number of studies showing major differences between the corticospinal system of different primate and rodent species.
We have provided evidenced that macaque monkeys provide the best available animal model for the human sensorimotor system controlling the hand. Our work has provided important evidence that direct cortico-motoneuronal (CM) projections from primary motor cortex to spinal motoneurons are particularly important for the performance of skilled hand and finger movements in primates.
We have also studied visuomotor control of the CM system. We have characterised the cortico-cortical pathways which allow visual information about the shape, size and other properties of graspable objects to modulate corticospinal outputs from primary motor cortex (M1).
We have also studied the brain mechanisms involved in tool use by non-human primates, and in particular how corticospinal and CM activity contributes to tool use. In a long-term collaboration with Atsushi Iriki and Cathy Price, we have carried out a number of voxel-based morphometry studies of the acquisition of tool-using skills by macaques and marmosets.
I have a long-standing interest in the effects of stroke on hand movement. I am currently involved in a clinical trial, led by Valerie Pomeroy, of the rehabilitative effects and mechanisms of functional strength training on hand use in long-term stroke patients.
Together with Alexander Kraskov, we demonstrated that corticospinal neurons in both M1 and premotor cortex F5 show mirror neuron properties and discovered a particular type of activity, the suppression mirror neuron, which shut down their activity during action observation. This has led to new research led by Alexander Kraskov which is aimed at understanding how self-movement is inhibited during action observation, and the involvement of sub-cortical structures in generation and inhibition of movement.