CORTICAL NETWORKS FOR VISUAL REACHING - INTRINSIC FRONTAL-LOBE CONNECTIVITY

The anatomical substrates of reaching to visual targets were studied i n monkeys (Macaca nemestrina) by combining behavioural neurophysiology and neuroanatomy. An instructed-delay reaching task was used to chara cterize the arm-related regions of the dorsolateral frontal cortex. Th is task revealed gradients of signal-, set-, movement- and position-re lated activity along the rostrocaudal extent of the frontal lobe. The frontal mesial projections to these physiologically defined gradients were studied through anatomical methods based on the retrograde transp ort of distinguishable tracers. The tangential distribution of the cel ls of origin of these projections displayed a gradient-like arrangemen t similar to that defined physiologically in their terminal territory. These mesial projections to the dorsolateral frontal cortex may there fore be considered part of a cortical network wherein connections make only a limited contribution to the integration of different sources o f information for the control of reaching movements. Further combinati on of such information must occur within each given cortical region by intrinsic local connections