Fig. 6.

Adjacent coronal sections through the central part of a human hemisphere in which the cholinergic muscarinic M2 (a), the cholinergic nicotinic (b) and the glutamatergic kainate (c) were visualized by means of [³H]oxotremorine-M, [³H]epibatidine and [³H]kainate, respectively. Local changes in the regional and laminar distribution patterns enable the receptor-based delineation of borders (white arrows in a–c) between cortical areas. None of the single receptor images shows all borders (as displayed in d), but when a given border is revealed by two or more different receptors, this border is found at precisely the same position. If all areal borders detected by autoradiographs of 12 different transmitter receptors are summarized, a complete receptor-based cortical segregation can be presented (as shown in d). This multireceptor map shows all borders demonstrated by the previous cytoarchitectonic observations of Brodmann (1909), but in addition a considerable number of novel areas (e.g. 3a, 3b, 4a, 4p, SMA, cmc, three S II areas, two insular areas) not visible in the classic cytoarchitectonic maps. 1, unimodal somatosensory cortex (BA 1); 2, multimodal parietal cortex (BA 2); 3a, cortical representation of proprioceptive input; 3b, primary somatosensory cortex; 4a and 4p, two subareas of the primary motor cortex; 20, multimodal inferior temporal cortex (BA 20); 21, multimodal middle temporal cortex (BA 21); 22, unimodal acoustic cortex (BA 22); 41, primary auditory cortex (BA 41); 42, secondary auditory cortex (BA 42); 52, parainsular cortex (BA 52); cing, two different areas of the cingulate cortex; cmc, cingulate motor cortex; IN, two different areas of the insular cortex; MD, mediodorsal thalamic nucleus; pallo, two different areas of the periallocortex; S II, three different areas of the secondary somatosensory cortex; SMA, supplementary motor cortex; snigra, substantia nigra.