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Neuroscientist PhD, UCSF

How the brain controls complex voluntary movement

Movement is the only way in which an organism can interact with the environment. It follows that brain function is directed towards the control of self-made movements and the perception of movement made by others. In humans, loss of movements of the mouth and hand render an individual unable to communicate with the external world. The exact role of auditory and motor systems in the production   and perception of complex movement remains unclear. My research explores these two areas of neuroscience to investigate how the brain controls higher order movement, or praxis, which will provide novel therapeutic targets for the rehabilitation of movement disorders, such as apraxia and ataxia.

The most dextrous of the movements made by the human body are those made by the upper limbs and the articulatory system. The ability to perform these movements comprises a significant milestone in human evolution, as they enable tool use, gestural language and the development of speech. My research focuses on the link between the production of complex voluntary movements made by the hands and the articulators, and the sensory information that occurs as a consequence of making movements and perceiving movements made by others. Movements of both the hands and articulators are commonly affected by stroke, leaving patients unable to manipulate objects and communicate, severely impairing their ability to interact with the material world and with other humans. A deeper understanding of how the brain controls the execution and perception of hand and mouth movements will lead to a greater understanding of how we can rehabilitate the impairment of movements in patients and ways in which we can improve the learning of new movements in healthy individuals.

My work to date has shown that, despite extensive evidence that the perception and production of action are encoded commonly in certain parts of the brain, different types of movements show a different picture. My data suggest that overlapping representations of action perception and production depend on the effector involved (hand, finger, articulators), and to some extent the modality of feedback (Agnew & Wise, 2009, Agnew et al., 2012, Agnew, McGettigan & Scott, 2013, Agnew et al, in prep).  This indicates that there are distinct differences in how we produce different classes of movements and in how we use sensory information to guide them. For example, I recently demonstrated for the first time that the neural underpinnings of emotional vocalizations and speech are at least in part dissociable (Agnew et al., in prep), which, along with clinical findings (Rohrer et al., 2009), may provide an alternative neural therapeutic target for rehabilitation of patients with speech deficits. I have shown a similar dissociation between the neural networks underlying tool use and meaningless movements of the upper limbs (Agnew, Wise & Leech, 2012) which I propose has clinical implications for patients with different forms of apraxia (Agnew et al., 2008). I am proposing that my future work will bring together my work in hand and mouth movements with implications for therapeutic targets in movement disorders and potentially for brain-machine interfacing.