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The first, introductory part of this paper presents an overview of the long quest for a universal map of the human cortex, useful as a standard reference for all remaining studies on this brain part. It is pointed out that such a map does still not exist, but that systematic comparison of some recently produced 3D maps may well be conducive toward this important goal. Hence, the second part of this article is devoted to a detailed comparison of two of such maps, the multimodal MRI-based parcellation of Glasser et al. (Nature 536:171-178, 2016) and the myeloarchitectonic parcellation presented by Nieuwenhuys and Broere (Brain Struct Funct 228:1549-1559, 2023), with the specific aim to detect areal concordances between these two maps. In the search for these concordances, the following three criteria were used: (1) the relative or topological position of the various areas, (2) the relation of the areas to particular invariant sulci, and (3) the overall myelin content of the areas. In total 61 concordances were detected, most of which were located in the frontal and parietal lobes. These concordances were recorded in standard views of the two maps compared (Figs. 5, 6, 7, 8), as well as in Table 1. We consider these findings as a first step towards the creation of a unified, consensus (canonical) parcellation of the human neocortex., Competing Interests: Declarations. Conflict of interest: The authors declare no competing interests., (© 2024. The Author(s).)

The human cerebral cortex contains numerous myelinated fibres, the arrangement and density of which is by no means homogeneous throughout the cortex. Local differences in the spatial organization of these fibres render it possible to recognize areas with a different myeloarchitecture. The neuroanatomical subdiscipline aimed at the identification and delineation of such areas is known as myeloarchitectonics. During the period extending from 1910 to 1970, Oscar and Cécile Vogt and their numerous collaborators (The Vogt-Vogt school) published a large number of myeloarchitectonic studies on the cortex of the various lobes of the human cerebrum. Recently, one of us (Nieuwenhuys in Brain Struct Funct 218: 303-352, 2013) extensively reviewed these studies. It was concluded that the data available are adequate and sufficient for the composition of a myeloarchitectonic map of the entire human neocortex. The present paper is devoted to the creation of this map. Because the data provided by the Vogt-Vogt school are derived from many different brains, a standard brain had to be introduced to which all data available could be transferred. As such, the colin27 structural scan, aligned to the MNI305 template was selected. The procedure employed in this transfer involved computer-aided transformations of the lobar maps available in the literature, to the corresponding regions of the standard brain, as well as local adjustments in the border zones of the various lobes. The resultant map includes 180 myeloarchitectonic areas, 64 frontal, 30 parietal, 6 insular, 17 occipital and 63 temporal. The designation of the various areas with simple Arabic numbers, introduced by Oscar Vogt for the frontal and parietal cortices, has been extended over the entire neocortex. It may be expected that combination of the myeloarchitectonic data of the Vogt-Vogt school, as expressed in our map, with the results of the detailed cytoarchitectonic and receptor architectonic studies of Karl Zilles and Katrin Amunts and their numerous associates, will yield a comprehensive 'supermap' of the structural organization of the human neocortex. For the time being, i. e., as long as this 'supermap' is not yet available, our map may provide a tentative frame of reference for (a) the morphological interpretation of the results of functional neuroimaging studies; (b) the selection of starting points (seed voxels, regions-of-interest) in diffusion tractography studies and, ((c) the interpretation of putative myeloarchitectonic features, visualized by in vivo and ex vivo mappings of the cerebral cortex with high-field magnetic resonance imaging.)

The efferent connections of the hypothalamic area of the rat, where attack behaviour can be elicited by electrical stimulation, were studied using iontophoretic injections of Phaseolus vulgaris-leucoagglutinin. Specificity for the hypothalamic "attack area" was investigated by comparison with efferents of hypothalamic sites outside the attack area. The hypothalamic attack area consists of the intermediate hypothalamic area and the ventrolateral pole of the ventromedial hypothalamic nucleus. Fibres from the hypothalamic attack area, as well as fibres from several other hypothalamic sites, form diffuse fibre "streams" running rostrally or caudally. Many varicosities that are found on the fibres suggest, that these fibres are capable of influencing many brain sites along their way. Projection sites were found throughout the brain. In the comparison between attack area efferents and controls, many overlapping brain sites were found. Hypothalamic efferents preferentially originating in the largest part of the attack area, i.e. the intermediate hypothalamic area, were found in the mediodorsal and parataenial thalamic nuclei. Within the septum, a spatial organization of hypothalamic innervation was found. Fibres from the attack area formed specialized "pericellular baskets" in the dorsolateral aspect of the intermediate part of the lateral septal nucleus. Fibres from other hypothalamic sites were found in other septal areas and did not form these septal baskets. Within the mesencephalic central gray, fibres from the attack area were found specifically in the dorsal part and dorsal aspect of the lateral part of the central gray. Physiological and pharmacological studies have shown that several brain sites are involved in different aspects of aggressive behaviour. Some of these areas, as for instance the dorsomedial thalamic nucleus, septum and central gray, are innervated by efferents from the hypothalamic attack area, whereas other sites, like ventral premammillary nucleus and ventral tegmental area, are not. It is concluded from the present findings, that a number of brain sites, that are known to be involved in agonistic behaviour, receive hypothalamic information preferentially from the hypothalamic attack area through diffusely arranged varicose fibres. The function of each connection in the regulation of specific behaviours remains to be further investigated.

The efferent connections of the hypothalamic area, where grooming can be elicited by local electrical stimulation or injection of various substances, were studied using iontophoretic injections of Phaseolus vulgaris leucoagglutinin. This hypothalamic "grooming area" consists of parts of the hypothalamic paraventricular nucleus and of the dorsal hypothalamic area. The specificity of these efferents for the hypothalamic "grooming area" was investigated by comparison with efferents of hypothalamic sites adjacent to this area. In addition, the distribution of oxytocinergic fibres was studied, since oxytocinergic neurons are present in the hypothalamic "grooming area" and oxytocin is possibly involved in grooming behaviour. The efferents of the hypothalamic "grooming area" as well as of hypothalamic sites surrounding this area and the oxytocinergic fibres studied do not form well determined bundles, but rather spread out throughout the hypothalamus. Clusters of fibres could be traced rostrally and caudally, forming diffuse fibre "streams". Three rostral, two thalamic and three caudal fibre "streams" have been distinguished along which efferent fibres innervate different brain areas. The many varicosities on labelled fibres "en passant" suggest that hypothalamic fibres are able to influence many parts of the brain along their way. The anterior periventricular area, the median preoptic nucleus, the ventral tegmental area and nucleus of the solitary tract were found to be more or less specifically innervated by hypothalamic "grooming area" fibres and oxytocinergic fibres. Other brain areas, like the septum, the medial amygdaloid nucleus, the central gray and the paraventricular nucleus of the thalamus were found to receive efferent projections from the hypothalamic "grooming area" and hypothalamic loci outside this area, as well as from the oxytocinergic system. Within the septum and the mesencephalic central gray, differences in the spatial organization of terminating fibres from the hypothalamic "grooming area" and hypothalamic "non-grooming" sites have been found. Fibres from the grooming area clustered in the ventral part of the lateral septal nucleus, while fibres from surrounding hypothalamic loci innervated other parts of that brain area. In the central gray, fibres from the hypothalamic "grooming area" clustered in rostrodorsal and caudoventral parts. A number of brain areas, that are innervated by hypothalamic "grooming area" fibres and oxytocinergic fibres, like central gray, ventral tegmental area and the noradrenergic A5 area, have been reported previously to be involved in grooming behaviour. It is concluded from the present findings, that the hypothalamic "grooming area" has preferential connections with a number of brain sites, not shared with hypothalamic projections from outside the "grooming area".(ABSTRACT TRUNCATED AT 400 WORDS)