ATTENTION AND VOLUNTARY ACTION IN PREFRONTAL CORTEX

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This proposal is concerned with how the brain constructs its representation of visual space and how this representation is used in movement planning and control. There are many views on the relationship between visual-spatial awareness and voluntary action. One view is that what we perceive as a unitary awareness is nothing more than the sum total of a multitude of low-level sensory-motor programs interacting with the physical world. Another view is that the brain explicitly constructs a "mental workspace" or general purpose representation of space which is independent of any particular effector system, and that it uses this representation for motor planning. Attention and working memory are important components of this high-level spatial representation. What parts of the brain might be involving in forming such a representation? One promising candidate is area 46 of prefrontal cortex. Previous work has shown that area 46 neurons encode the locations of behaviorally relevant visual stimuli and hold these representations on-line during working memory tasks, including memory- guided saccade tasks. The current proposal examines the relationship between neuronal activity in area 46 and the programming of saccadic eye movements and visually-guided arm movements. Three experiments will address the following questions: 1) Are area 46 neurons capable of providing the signals needed for saccade initiation and target selection? 2) Is the representation of space in area 46 stable and robust in the face of ongoing motor activity? 3) Can the activity of individual neurons in area 46 support the planning of more than one type of movement? The overall goal is to determine whether area 46 plays specific role in the planning and execution of particular movements or a more general role in providing a multi-purpose representation of space that can be used by several effector systems as well as guiding covert shifts of spatial attention. The issues dealt with in this proposal are of practical importance to sufferers of psychiatric disorders who lack the ability to maintain appropriate control over their actions, and also those who are unable to initiate or control voluntary movements due to Parkinson's disease, stroke, epilepsy or other forms of neurological damage. The proposed experiments should provide useful information about the cognitive and motor function of prefrontal cortex. This will aid in the understanding of frontal lobe diseases such as schizophrenia and frontal lobe epilepsy.