the chiasma. the axons of the temporal field do not cross. this is very important in clinical neurology. after the chiasma, axons form the visual tracts turning around the peduncles and arriving into the polar anterior part of the geniculate nucleus. retinal axons from the controlateral retina end in stratae 1,4 and 6. those from the ipsilateral retina end in 2,3 and 5. the axons from the lateral geniculate nucleus, through the optic radiation, end in the primary visual cortex around the calcarine fissure. see visual system. lateral region l (or v) this corresponds to the part of isothalamus located laterally to the medial lamina and in front of the pulvinar (the noyau externe of dejerine after burdach). it receives abundant and diverse infrathalamic afferences. some main afferent systems occupy a particular portion in the lateral region. several "main territories" are spatially separate. this allows functionally significant subdivisions. other afferent systems may end in one or the other main territories to which they are coterritories. still other can end in several main territories. the topographic description of the territories was made using experiments in monkeys. this showed that they are no dorsal nuclei. what was believed to be dorsal was simply the posterior extension of the more anterior territory. this makes it difficult to follow the terminologia anatomica (1998). to follow common usage, lateral nuclei are called "ventral". it is today possible to transfer the data experimentally obtained in monkeys to the human brain using immunostaining. the sequence described by c. vogt (1909) hold true. starting from caudally one may describe the lemniscal territory, made up of two components cutaneous or tactile and deep (musculoarticular), the cerebellar territory also made up of two nuclei, the pallidal territory and the nigral territory . gustatory territory varc further information: gustatory system tied to vcm into the classic arcuate nucleus (in fact heterogeneous), it has neurons of an own type. also, it does not receive lemniscal afferent and is thus not a part of vc. it receives axons from the nucleus of the solitary tract. its thalamocortical neurons send axons to the primary gustatory area located in the opercule of the insula. tactile lemniscal territory vpc=vpl+vpm the nuclei corresponding to the lemniscal territory are called vp. the tactile part nucleus ventralis posterior caudalis vpc is the posterior part of the lateral region, in front of the pulvinar. it is the addition of a lateral nucleus vpl and of the superior part of the classic arcuate nucleus vpm. vpc receives axons from the dorsal column nuclei located in the lower medulla oblongata: the nucleus gracilis (goll) medial and the nucleus cuneatus (burdach) lateral. starting from these nuclei, axons go ventralwards and decussate (to the other side) still in the medulla oblongata forming the "lemniscal decussation". axons from the two sides form the thick medial lemniscus close to the midline. higher, it separates in order to reach the lower border of the two vpc. in this nucleus, the axons terminate forming lamellae and a somatotopic map. the axons conveying information from the leg are the most lateral and the most dorsal. those conveying information from the mouth and tongue are the most medial and ventral (in vpm). the axonal arborisations are rather small and very dense. the mediator of the lemniscus system is glutamate. the thalamocortical axons of the vpc send their axons to the primary somatosensory area (areas 3b and 1) where there is also a clear somatotopic map. deep lemniscal territory vpo (or vps) within the somesthetic nucleus, physiological maps, including in humans, have found a spatial separation between the representation of the tactile and the deep stimuli. friedman and jones (1986) designated the deep region the "shell" as opposed to the tactile "core". kaas et al. (1986) initially retained one vpo and one vps. the present nucleus ventralis posterior oralis vpo is the addition of the two. this, made up very large neurons, the largest of the thalamus, is located in front and superior to the vpc. it receives axons from the accessory cuneate nucleus of the medulla. the axons of this nucleus conveys information from muscles, tendons and joints. they decussate and participate in the formation of the medial lemniscus. the vpo which receives "deep" information has about the same somatotopic map as the tactile. the thalamocortical neurons from vpo send their axons in the fundic area 3a (in the depth of the rolando sulcus) and to the parietal area 5. cerebellar territory vim or vl the nucleus ventralis intermedius receives through the brachium conjunctivum axons from all cerebellar nuclei, more particularly from the dentate nucleus (percheron, 1977, asanuma et al. 1983). the mediator is glutamate. in primates, the dentate nucleus is subdivided into two nuclei: one anterior and the other posteroventral, the first "motor" and the other not (dum and strick, 2002). vim is in fact made up of two parts, one ventrolateral (viml) and one dorsomedian (vimm). viml (the vim of neurosurgeons) receives electively sensorimotor information. viml also receives axons from the vestibulum and from the spinothalamic tract. it is organized according to a somatotopic map grossly analogous to that of vpc. the cortical target of the viml thalamocortical neurons is principally the primary motor cortex (prerolandic) (schell and strick, 1984, orioli and strick, 1989) . vimm receives mainly "associative" information from the dentate, plus tectal and spinothalamic information. it is organized according to another map, looser than that of viml. its thalamocortical neurons send their axons to the premotor and to the parietal cortex. as it was not clearly distinguished, there are poor physiological data. pallidal territory vo starting from cercopithecidae, the two sources from the basal ganglia system medial pallidum and nigra have distinct, spatially separate, thalamic territories. the pallidal territory arrives in evolution as a lateral addition to the nigal va, forming a new nucleus individualized by another name : the nucleus ventralis oralis, vo. on the contrary there is no more vm (which receives convergent afferences in rodents and carnivora). vo receives its pallidal afferent axons from the medial pallidum. the trajectory of pallidal afferent axons is complex. axons form first the ansa lenticularis and the fasciculus lenticularis which place the axons on the medial border of the pallidum. from there, the axons cross the internal capsule as the comb system. axons arrives at the lateral border of the subthalamic nucleus. they pass over it as the h2 field of forel (1877) then turn down at h and suddenly go up in h1 in direction to the inferior border of the thalamus. the distribution of pallidal axons within the territory is wide with terminal "bunches" (arrechi-bouchhioua et al. 1996,1997, parent and parent, 2004 ). this offers few chance for a fine somatotopic organization. the territory is stained for calbindin. the mediator of the pallido-thalamic connection is the inhibitor gaba. the thalamocortical neurons send their axons to the supplementary motor area (sma), presma, the premotordorsal and medial and to a lesser extent to the motor cortex. nigral territory va the nigral afferences come from the pars reticulata of the substantia nigra. the axons do not constitute a conspicuous bundle. they are placed medially to the pallidal and ascend almost vertically. a part of the territory is posterior and inferior going up to the anterior pole of the central complex. this part sometimes designated as vm is simply the posterior continuation of the nigral territory. there is indeed no more vm in the upper primates where the pallidal and nigral territories are everywhere separated. in the whole territory axons expand widely (françois et al., 2002) allowing no precise map, which is confirmed by physiology (wichemann and kliem, 2004). va is crossed by the mammillothalamic bundle. the mediator of the nigro-thalamic connection is, as for the pallido-thalamic the inhibitor gaba. in addition to nigral, va receives amygdalar and tectal (superior colliculus) axons. the thalamo-cortical axons go to the frontal cortex, the cingulate cortex, the premotor cortex and the oculomotor fields fef and sef. it is important to stress the necessity from now to clearly distinguish the pallidal vo and the nigral va territories. the fact that they do not lead to the same cortical areas and systems is alone one reason for this. the physiology of the two territories is also different (van donkelaar et al., 1999).