Nuchal adaptations inPerodicticus potto

Anatomical and behavioural evidence is put forward that supports the view that the spines of the neck of the potto are not used for abrasive or aggressive purposes but are part of a very sensitive tactile zone. It is claimed that the nuchal region is probably a tactile focus for peaceable interactions in this species.     

Dental receptor projections to the sensomotor zone of the rabbit cerebral cortex

Topic organization of the dental representation was studied in experiments on rabbits by the method of induced potentials. Every tooth proved to be locally represented in the sensory-motor zone of the brain cortex. These zones do not overlap in the case of stimulation of the threshold strength. Topic dental projection region occupies a territory including fields Par I, Praecag, Preacgr, and PC.     

Cell fate and axonal projections from the cerebral cortex

The formation of axonal connections in the nervous system involves cell-specific decisions of the growth cone. In this article we examine the contribution of early fate decisions to axonal pathfinding. Evidence is accumulating that different neuronal cell types in the cerebral cortex are specified during their final mitosis. It would seem that cortical projection neurons are pre-specified to choose particular pathways, since the newly generated neurons send out their axons in the correct direction from the onset of outgrowth. Pathfinding decisions that are made much later during development, such as the recognition of specific target-derived chemoattractants and the retraction of inappropriate axon collaterals, also seem to be at least partially pre-specified at much earlier developmental stages. Hence, the early determination of a neuron's phenotype includes the specification of axonal growth occuring over a protracted phase of development. Understanding more about the regulative events targeted to the growth cone should help us to unravel the decisions made by this specialized neuronal organelle.     

Sensory mapping of the rat cerebral cortex by thermographic methods

Using thermovision and digital image processing, the dynamics of thermomap in the brain cortex has been studied on albino rats through the opened skull before and during sensory stimulation. Photic, sonic and somatosensory stimuli lead to the onset of local heating foci in the corresponding cortical zones, as well as to local multiple thermoresponses in other areas. Some quantitative parameters of these effects are given and their possible mechanisms are discussed.     

Topical organization of somatic projections in the fur seal cerebral cortex

To map somatic projections in the cerebral cortex of the fur sealCallorhinus ursinus multiple spike activity of cortical neurons evoked by tactile stimulation of different parts of the body surface was recorded in acute experiments. The region of somatic representation is bounded rostrally by the postcruciate and coronal sulci, caudally by the anterior suprasylvian sulcus, and dorsomedially by the ansate sulcus. The somatotopic map is oriented so that the projection of the head faces ventrolaterally, and that of the caudal part of the trunk faces dorsomedially; the projection region of the forelimb is buried in the coronal sulcus. The projection area of the head occupies the greatest area, and in it, the greatest area is occupied by the region of the superior labial vibrissae.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 344–351, May–June, 1985.     

Sensory projections to the nucleus basalis prosencephali of the pigeon

Summary The afferent pathways to the nucleus basalis prosencephali of the pigeon were studied by use of the horseradish peroxidase (HRP) technique. It was confirmed that this nucleus receives a direct pathway from the nucleus sensorius principalis nervi trigemini and that, as in the starling, it receives a direct input from the nucleus lemnisci lateralis, pars ventralis, an auditory relay. Totally novel is the finding that the nucleus basalis prosencephali is the target of a direct pathway originating in the medullary nucleus vestibularis superior. All three pathways bypass the thalamus. From within the telencephalon the nucleus basalis prosencephali also receives fibres from the tuberculum olfactorium and the peri-ectostriatal belt, suggestive of olfactory and visual input. Marked cell bodies were also found in the neostriatum frontolaterale. It is assumed that these arose from HRP uptake by axons of the tractus fronto-archistriatalis that course through the nucleus basalis prosencephali to the anterodorsal archistriatum. Marked fibres and bouton-like formations were observed in the latter structure. The afferents to the nucleus basalis prosencephali are discussed in conjunction with the probable role of the nucleus as a sensorimotor coordinator of the pecking/feeding behaviour of the pigeon.     

The niche of the potto,Perodicticus potto

Some new field observations on West African pottos are presented and compared with previously published information on substrate use and diet. This evidence suggests that the predominant means by which pottos find food is by carefully searching branches in the forest canopy with their noses and that gums and slow-moving invertebrates found on branch surfaces are major components of their diet. When fruits are scarce, gums may be the potto’s chief source of energy. It is argued that the potto’s deliberate locomotion and some of its anatomical peculiarities are related primarily to this diet and foraging behavior, rather than to concealment from predators or the capture of birds, two factors previously suggested to have been important in the evolution of the potto’s locomotor technique. The potto’s niche is compared to that of other lorisid primates and is found to resemble closely that of Galago crassicaudatusin several respects.     

Vestibular projections in the cat temporal cortex

Boundaries of vestibular projections in the temporal cortex during stimulation of the vestibular nerve were studied in cats anesthetized with pentobarbital and chloralose or chloralose alone. The caudal boundary of the vestibular zone was shown to run along the anterior ectosylvian gyrus. A focus of evoked activity was found in the suprasylvian sulcus or 1–2 mm rostrally to it. All short-latency evoked potentials recorded during vestibular nerve stimulation in the temporal region caudally to the zone mentioned above were connected with the spread of current to auditory structures. To verify the extent of spread of the stimulating current, focal potentials were recorded in the vestibular and superior olivary groups of nuclei. Special experiments were carried out to study the topography of these potentials at the level of bulbar structures during stimulation of vestibular and auditory nerves. According to the results, there is no second vestibular area in the temporal cortex in cats. Vestibular afferentation is projected mainly into the contralateral hemisphere, and the response latency is 5.2±0.7 msec. The ipsilateral evoked potentials had a long latent period (8.4±1.3 msec), and their amplitude depended on the type of anesthesia; it was accordingly postulated that additional synaptic relays exist in this vestibulocortical pathway.     

Medial temporal lobe projections to the retrosplenial cortex of the macaque monkey

The projections to the retrosplenial cortex (areas 29 and 30) from the hippocampal formation, the entorhinal cortex, perirhinal cortex, and amygdala were examined in two species of macaque monkey by tracking the anterograde transport of amino acids. Hippocampal projections arose from the subiculum and presubiculum to terminate principally in area 29. Label was found in layer I and layer III(IV), the former seemingly reflecting both fibers of passage and termination. While the rostral subiculum mainly projects to the ventral retrosplenial cortex, mid and caudal levels of the subiculum have denser projections to both the caudal and dorsal retrosplenial cortex. Appreciable projections to dorsal area 30 [layer III(IV)] were only seen following an extensive injection involving both the caudal subiculum and presubiculum. This same case provided the only example of a light projection from the hippocampal formation to posterior cingulate area 23 (layer III). Anterograde label from the entorhinal cortex injections was typically concentrated in layer I of 29a-c, though the very caudal entorhinal cortex appeared to provide more widespread retrosplenial projections. In this study, neither the amygdala nor the perirhinal cortex were found to have appreciable projections to the retrosplenial cortex, although injections in either medial temporal region revealed efferent fibers that pass very close or even within this cortical area. Finally, light projections to area 30V, which is adjacent to the calcarine sulcus, were seen in those cases with rostral subiculum and entorhinal injections. The results reveal a particular affinity between the hippocampal formation and the retrosplenial cortex, and so distinguish areas 29 and 30 from area 23 within the posterior cingulate region. The findings also suggest further functional differences within retrosplenial subregions as area 29 received the large majority of efferents from the subiculum. ? 2012 Wiley Periodicals, Inc.     

Sensory neuroscience: from skin to object in the somatosensory cortex

Humans can perceive the shape of objects by touch alone, by extracting geometric features such as edges. Recently recorded responses of single neurons in the secondary somatosensory cortex of monkeys suggest how the brain integrates tactile shape information across different regions of skin and builds up a representation of tactile objects.     

Direct projections of the thalamic centrum medianum in the cerebral cortex of the cat (radioautographic studies)

After injection of radioactive amino acids into the cat thalamic centrum medianum, its projections have been revealed in the ipsilateral hemisphere in the frontal, motor, limbic, orbital and basal temporal cortex, in the parasubiculum and striatum. The anterograde tracing of the fibers and terminals reveals the centrum medianum projections in the layers VI-V and I of the frontal and limbic cortex and in the layers VI-V, IV or III (or in both) and in I of the motor and orbital cortex.