The statistical structure of intrinsic parietal and parieto-frontal connectivity in monkeys was studied through hierarchical cluster analysis. Based on their inputs, parietal and frontal areas were grouped into different clusters, including a variable number of areas that in most instances occupied contiguous architectonic fields. Connectivity tended to be stronger locally, that is within areas of the same cluster. Distant frontal and parietal areas were targeted through connections that in most instances were reciprocal and often of different strength. These connections linked parietal and frontal clusters formed by areas sharing basic functional properties. This led to 5 different medio-laterally oriented pillar domains spanning the entire extent of the parieto-frontal system, in the posterior parietal, anterior parietal, cingulate, frontal and prefrontal cortex. Different information processing streams could be identified thanks to inter-domains connectivity. These streams encode fast hand reaching and its control, complex visuomotor action spaces, hand grasping, action/intention recognition, oculomotor intention and visual attention, behavioral goals and strategies, reward and decision value outcome. Most of these streams converge on the cingulate domain, the main hub of the system. All of them are embedded within a larger eye-hand coordination network, from which they can be selectively set in motion by task demands.
Significance Statement: The statistics of corticocortical connectivity between the parietal and frontal lobes, as well as that of intrinsic parietal connectivity of macaque monkeys, have been studied through a hierarchical cluster analysis. In both parietal and frontal cortex we identified different clusters of interconnected areas. The analysis of their functional properties led to identification of five functional domains spanning posterior parietal, anterior parietal, cingulate, frontal and prefrontal cortex. The scrutiny of inter-domain connectivity revealed the existence of different information processing streams, related to the representation of action space, reaching, grasping, oculomotor intention and visual attention, action recognition, selection of behavioral goals and strategies. They were all embedded within a distributed eye-hand matrix from which they can be selected by task demands.
Authors report no conflict of interest.
This study was supported by grants from the University of Rome SAPIENZA (to ABM), from MIUR of Italy (protocol 2015AWSW2Y_002, to RC) and from the Intramural Research Program of NIMH (to BA).