Mechanisms of Planning and Problem Solving in the Brain

Classical AND/OR goal, or task, decomposition techniques are generalized to deal with the problem of sensory-interactive goal-directed behavior in biological organisms. A neurophysiological model is described which demonstrates the capacity to l e a r n , to generalize, to compute multivariate mathematical functions, and to decompose input commands into sequences of output commands in a context-sensitivemanner. Evidence is presented that clusters of neurons with such properties are arranged in hierarchical structures in the brain so as to produce AND/OR task compositions. At the lowest levels in the motor system these clusters transform coordinates and compute servo functions. At the middle levels they decompose input commands into sequences of output commands which give rise to behavior patterns. Mechanisms by which feedback can alter these decomposition sequences to compensate for perturbations and uncertainties in the environment are described. At the highest levels of the hierarchy there are goal selecting and evaluating mechanisms. I t is argued that in higher mammals these upper levels of the motor hierarchy are the mechanisms of planning and problem solving. PREFACE The following paper attempts as far as possible to present a notation which i s both intuitively clear and mathematically precise, and to offer supporting evidence wherever possible. The reader should understand, however, that any model of neuronal mechanisms of the higher cognitive processes must of necessity involve speculation and metaphorical language. I t should also be understood that a multidisciplinary approach to such a large and complex subject cannot avoid a mixing of jargon and an over simplification of many difficult issues.