Planning Sensory-Motor Associations: A Control Principle Inspired by the Cerebellum", Centre for Neural and Adaptive Systems Research Report CNAS-9901

The Brain is a slow computer yet humans can skilfully play games where very fast reactions are required. A review of data on motor and cognitive effects of cerebellar lesions leads to propose that the brain minimises reaction time during skilled behaviour by eliminating on-line planning. Behaviour then results from direct mapping from perceptions to actions. The proposed role for the cerebellum is to i) learn sensory-motor associations planned off-line and ii) enable the set of sensory-motor associations most appropriate for a given goal. In that framework, planning defines both the stimulus and the action that will be triggered. In the performance of plans comprising sequences of actions, the cerebellum controls eye fixation to obtain the sensory trigger that initiates the next action in the plan. For producing effective behaviour, such a scheme requires in principle that, for each goal, a large set of sensory motor associations are prepared to cover a wide range of possible initial conditions and variations in execution. Hence the planning process may need to produce not a single optimal solution but a field of solutions. Such a scheme can then solve the paradox of so-called automatic behaviour often seeming to proceed via situation-dependent plannin