Peripheral Representation Research Articles

Inhibitory organization of the thalamic ventrobasal neurons with different peripheral representations.

In thalamic ventrobasal relay cells of the cat the excitability depression following electrical stimulation of the medial lemniscus (ML), receptive fields (RFs) and the sensorimotor cortex (SMC) was studied. The excitability depression was identified as the discharge depression in poststimulus time histograms or as IPSPs in intracellular records.

Exotic Exchange for Inclusive Reactions and for Quasi—Two-Body Processes

The reaction ${K}^{+}+p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}$ + anything with the ${\ensuremath{\pi}}^{\ensuremath{-}}$ fast and forward is analyzed with a peripheral representation that allows one to extract the two-body exotic-exchange amplitude with high statistics that are otherwise hard to come by. By representing the inclusive spectrum in a Reggeized scaled form, we then predict the energy dependence of the two-body reactions ${\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{K}^{+}+{\ensuremath{\Sigma}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{K}^{+}+{Y}^{*\ensuremath{-}}(1385)$ in good agreement with the experimentally measured data.

Changes in axonal transport during regeneration of feline ventral roots

1. (1) Changes in axonal transport of proteins, including the enzymes choline acetyltransferase (ChAc) and acetylcholinesterase (AChE) were studied during ventral root regeneration. The L 7 ventral root, with its peripheral representation in the sciatic nerve, was used as the experimental preparation in 69 adult cats, which, after various surgical procedures, could be grouped into regenerating, denervated and control series. 2. (2) Following intramedullary applications of [ 3H]leucine the intra-axonal transport of labelled proteins was followed along regenerating and intact ventral root nerve pathways. After a regenerating period of 36–38 weeks, the transport rate of rapidly migrating proteins was 104 mm 24 hr as compared to 139 mm 24 hr for intact control roots. A slow phase of migrating proteins with a maximal transport rate of 7–8 mm 24 hr was registered in both regenerating and intact roots. The average transport rate of this phase was 3 mm 24 hr in regenerating roots and 5 mm 24 hr in intact roots. 3. (3) After transection of the L 7 ventral root the activity of ChAc and AChE showed an initial accumulation proximal to the lesion. The root-nerve segment distal to the lesion showed a marked decline of the activity of both enzymes. During the course of regeneration a significant increase in the activity of the 2 enzymes was observed in the distal root-nerve segment. Thirty-six weeks postoperatively the restitution of ChAc activity was about 70% and that of AChE about 85% compared with control values. 4. (4) Evidence of functional regeneration was registered by clinical observations, EMG studies and determination of the reversal of muscle atrophy. Positive evidence of efferent neuromuscular reconnections was obtained about 12 weeks postoperatively according to EMG studies in gastrocnemius-soleus muscles. After 36–38 weeks functional recovery was present in 9 of 11 animals studied according to clinical observations supported by data from EMG studies and determination of muscle weight. 5. (5) The studies revealed a terminal delay in the restoration of axonal continuity, as represented by the reversal of ChAc activity and recovery of proper muscle function. Possible reasons for this time discrepancy are discussed.

Connexions of the somatic sensory cortex of the rhesus monkey. I. Ipsilateral cortical connexions.

THE current interest in the commissural connexions of the cerebral cortex derives from the work of Sperry (1961), Myers (1962a), Gazzaniga (1966) and others, who have clearly shown that the fore-brain commissures play a significant part in the interhemispheric transfer of learning based upon peripheral sensory cues. A recent investigation by Kaas, Axelrod and' Diamond (1967) indicates that commissural fibres may also be involved in mechanisms more complex than mere transfer, for in their study an auditory memory trace appeared to be kept out of one hemisphere by an active suppression originating in the contralateral hemisphere. The anatomical basis for the transfer of learning and for the more subtle effects shown by Kaas et al. is as yet unclear, but there are reasons for considering that the organization of the pathway joining the two hemispheres is not a simple one. This is particularly so in regard to the primary sensory areas of the cortex, for some subdivisions of these areas receive commissural fibres from more than one area of the opposite side while parts of others neither send nor receive such fibres (Myers, 1962Z>; Choudhury, Whitteridge and Wilson, 1965; Ebner and Myers, 1965; Garey, Jones and Powell, 1968; Jones and Powell, 1968; Pandya and Vignolo, 1968). In the absence of commissural connexions between certain significant parts of the peripheral representation of the primary sensory areas such as the freer parts of the limbs or the periphery of the visual field, it is unlikely that information ultimately concerned in learning is transferred (or withheld from transfer) at this level of cortical function. On the other hand, the parts of the sensory areas which are commissurally connected should be functionally different from those which are not. It seemed worth while, therefore, to extend the study on the somatic sensory cortex of the cat to the monkey not only for the obvious reason of its closer affinity to man, but also because the larger size and clearer boundaries of the architectonic and functional subdivisions of the first somatic sensory area make these individual subdivisions more amenable to investigation .

A single unit analysis of trigeminal projections to bulbar reticular nuclei of the rat.

AbstractThe lateral bulbar reticular formation of anesthetized rats was explored with microelectrodes in order to compare the response and field characteristics of its somatosensory cells with properties of units located in the adjacent spinal trigeminal complex. Responses were evoked in the cells using natural and electrical stimulation of the skin. Neurons in the reticular nuclei tended to exihibit long latencies, low folowing capacities and large receptive fields. On the other hand, trigeminal complex cells generally revealed opposite characteristics, more typical of primary sensory structures, such as short latencies, high following capacities and punctate‐to‐small fields. The distinction between the regions was emphasized by additional qualities which were peculiar to the reticular neurons: Bilateral peripheral representation, into very coarse mechnical stimulation. In amny respects, the data indicate that the lateral reticular formation is intimately involved in the mediation of facial pain. They also support the view that it participated in this function by regulating the flow of nocioceptive activity from receptive mechanisms of the skin to the lemniscal pathway.

Aspectos neurológicos da doença de chagas: sistema nervoso central

The lesions of the nervous system in the Trypanosomiasis Cruzi are quite frequent and are not only limited to the encephalo-spinal-axis. Actually, they are much more common in the peripheral representations of the autonomic nervous system, resulting in the so-called enteromegalies (mega-esophagus, megacolon, etc.) so frequent in Brazil. However, only the clinical manifestations due to the encephalic and spinal lesions have been included in the neurological aspects of Chagas' disease (as formerly contended for by Carlos Chagas). In the acute phase of the central nervous system infestation, the Trypanosoma cruzi,as leishmanias, is found in cellular elements of the neuroglia (microglia, astroglia) and may be isolated from the peripheral blood and cerebrospinal fluid (inoculation in sensitive animals). The corresponding clinical manifestations are the severe difuse meningo-encephalo-myelitis with a high degree of lethality and also signs of infection, hepatomegaly and splenomegaly. The infants from endemic areas are much more compromised. The clinical-pathologic as well as experimental confirmations on that acute phase of the disease are numerous and irrefutable. In the chronic phase of the disease, the neurological manifestations are not very clear. Early in 1909, Chagas, impressed with the great number of cases of infantile encephalopathy found in infested regions, imputed to the T. cruzithe etiology of such cases of encephalopathy and considered them as pertaining to a chronic phase of the disease. This has not been confirmed by other investigations, and even if the etiologic agent were the T. cruzithe clinical manifestations have no evolutive character and seem more sequelae than symptoms of a real chronic nervous phase. Even experimentally it has not been possible to demonstrate the presence of parasites in the nervous system of infested animals after clearing of the signs of the acute phase. In patients with chronic Chagas' disease with lesions in several organs and with nervous symptoms (especially mental disturbances) it has not been possible to get positive results from the complement fixation test (Machado-Guerreiro's reaction) when performed using cerebrospinal fluid, yet this test is positive in about 97% of the cases when blood is used instead. Recently, Koberle and coworkers have shown a great diminution in the number of nerve cells in the intramural plexuses of hollow viscera and in the cerebellum and spinal cord of men and experimental animals with Chagas' disease. It is hoped this approach using neuronal countings will in a near future show which are the true cases of chronic Chagas nervous disease. Regarding the embolic phenomena of Chagas heart disease, they do not have particular symptomatological aspects, except the high degree of mortality. Theoretically, cerebral thrombotic phenomena may also develop under the same etiology, but they have not been demonstrated through a pathological study.

A new spinal pathway for cutaneous impulses.

A new spinal pathway for cutaneous impulses.