[Place of the thalamus in the network of interconnections between the association and limbic cortices in the monkey].

Anatomophysiological criteria underlying the definition of associative cortex as well as limbic cortex include some imprecise data. The original notion of "cortical association spheres" (Flechsig) with no connections with the thalamus has rightly been abandoned, and that of the macroscopic "large limbic lobe" (Broca) fails to stand up to histologic or hodologic findings. However, the concept of cortical areas implicated specifically in multiple sensorial integration, sensory-motor coupling and control of behavior lasts due to necessity. In the monkey, the posterior parietal cortex of area 7 (PG area), the cortex of the upper slope of the superior temporal sulcus (STS) and the prefrontal cortex anterior to the sulcus arcuatus exchange direct corticocortical connections, receive afferents from sensory cortex and are not connected to specific thalamic relays. The term "associative" in its widest sense applies more particularly therefore to these cortical areas organized in networks. On the internal surface of the hemisphere, the cingular gyrus, retrosplenial cortex and parahippocampic gyrus (TF and TH areas) which occupy the major part of the limbic lobe, participate in the formation of this network and exchange direct cortico-cortical connections with the associative cortex defined above. The use of anterograde (labelled aminoacids) and retrograde (peroxidases) markers and of fluorescent dyes, allowing double retrograde labelling, demonstrates that the median pulvinar nucleus is connected with the knots of the associative cortical network. This thalamic nucleus, of a relatively increased size from phylogenetic evolution, is therefore excluded from the classification opposing specific and diffuse projection nuclei. In contrast to the thalamic reticular nucleus, which lacks cortical projections, and to the nuclei of the internal medullary band, which have the striatum as main target, the median pulvinar is a thalamic structure connected directly and specifically with each of the cortical areas, lesions of which result in negligence behavior.