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At least 19 recordsLinked to original sources
PubMed1979

Loss of hybridizable ribosomal DNA from human post-mitotic tissues during aging: II. Age-dependent loss in human cerebral cortex--hippocampal and somatosensory cortex comparison.

DNA was isolated from the hippocampal and from the somatosensory cortex of 13 humans (at autopsy). In both the cortex and hippocampus, the loss of ribosomal DNA (rDNA), as measured through hybridization in the liquid phase, approximates about 0.9% per year. The r value for somatosensory cortex was about -0.7 and that for the hippocampus was about -0.91. The correlation coefficient between the sets of two samples derived from the same individual (two different areas) in +0.945. These results are consistent with those reported concurrently for human myocardium and with earlier studies conducted with beagle dogs, in which only post-mitotic tissues (brain, heart and skeletal muscle) showed measurable decrements in these key genes. To the degree that the synthesis of new proteins is essential for sustained mental activity, these results are consistent with the observations that Nissl substance is more slowly replenished, following exhaustive work by motor cortical cells, and the fact that many older persons experience mental fatigue during continuous mental work at earlier times than do younger persons. The mechanism of loss is not certain, but may well be related to inadequacies in DNA repair systems, thereby allowing deletion of tandemly duplicated genes through cross-over "episome" formation, followed by degradation of the excised DNA segments. The ratio of loss of rDNA hybridizability in human and dogs in about 1 to 7, which approximates the relative ratios of their lifespans (reciprocals).

Adolescent↗
PubMed1992

Population analysis of single neurons in cat somatosensory cortex.

Single neurons in the somatosensory cortex are divisible into a population with receptive fields and a population without receptive fields. These two populations display different laminar distributions, and their respective functions are unknown. We compared other physiological characteristics of these two neuronal populations in an attempt to understand why some neurons lack a receptive field. Only 23% of 465 neurons isolated in the somatosensory cortex of halothane-anesthetized cats displayed a cutaneous receptive field. The iontophoretic administration of glutamate uncovered input from the periphery in another 34% of the sample, leaving 43% of the neurons without evidence of peripheral input under these experimental conditions. Neurons with a receptive field were spontaneously active much more often than neurons lacking peripheral inputs, and their rates of discharge were higher. No differences were found between neurons having a receptive field uncovered with glutamate and those unaffected by glutamate. In all classes of neurons, those cells with spontaneous activity were excited by smaller amounts of glutamate than were silent neurons, but sensitivity to glutamate was not correlated with the presence or absence of a receptive field. We infer that some classes of somatosensory cortical neurons receive strong thalamocortical inputs, whereas others have only relatively weak or no thalamocortical connections. In other experiments we have shown also that those neurons lacking a receptive field and/or spontaneous activity were more likely to be plastic than those with stronger inputs (see Warren and Dykes, 1993a,b), suggesting that neurons having weaker afferent inputs can be more readily modified under certain circumstances.

Afferent Pathways↗
PubMed1975

Effects of serial lesions of somatosensory cortex and further neodecortication on tactile retention in rats.

Four groups of rats with bilateral lesions of somatosensory cortex and one of animals sustaining only sham operations were tested for retention of a difficult tactile discrimination. Two of the lesion groups had serial ablations, in one case with interoperative testing, and two had one-stage lesions. Bilateral ablations of somatosensory cortex severely retarded retention in all lesion groups relative to the control group and serial and one-stage groups did not differ from each other. The sham operated rats then experienced lesions of cortex anterior and posterior to the somatosensory areas. These lesions only marginally affected retention. Somatosensory cortex then was ablated and severe performance decrements were seen. Removal of additional neocortex in animals that previously had relearned the discrimination after somatosensory cortex lesions also resulted in very poor retention. These data demonstrate the importance of the somatosensory cortex in mediating tactile discriminations and suggest that non-somatosensory cortex may play a role in recovery after somatosensory cortical lesions.

Animals↗
PubMedDate not supplied

Development of cat somatosensory cortex: structural and metabolic considerations.

Although research is beginning to clarify the relationship between structure and functional activity in the adult cerebral cortex, little is known about cortical development in the somatosensory cortex of cats. A number of parameters were used in this study to identify functional and anatomical correlates in the developing somatosensory cortex of kittens ranging in age from 3 to 33 d: 2-deoxyglucose (2DG) uptake, cytochrome oxidase (CO) activity, Nissl staining, and AChE activity. All of these parameters were found to reflect an immaturity that evolved to the adult-like pattern by 4-5 weeks of age. Nissl staining revealed an immature laminar pattern at birth, in which layers I, V, and VI were distinct whereas layers II-IV were homogeneous in appearance. Numerous cells could be observed at the layer VI-white matter junction and throughout the white matter, a feature not found in adults. The laminar distribution of Nissl-stained cells gradually became mature by 4-5 weeks of age. CO staining was homogeneous throughout all layers, in contrast to the adult pattern, which displays laminar differentiation. In young animals, many darkly stained CO+ cells were found at the layer VI-white matter border and in the white matter, a distribution not found in the adult. AChE staining in kittens was also distinctly different from that in adults. At birth, AChE+ fibers could be found in layers I, V, and VI but were scarce in layers II-IV. In the adult, a dense network of AChE+ fibers can be found in all layers. 2DG uptake was also immature, as little stimulus-evoked activity could be observed in animals younger than 2 weeks. A dense band of metabolic activity was found in the zone between layer VI and the white matter, whether or not a somatic stimulus was delivered. These results suggest a close correlation between the developing cytoarchitecture and the emergence of a mature pattern of functional activity in the somatosensory cortex.

Acetylcholinesterase↗
PubMed1979

The formation of afferent patterns in the somatosensory cortex of the neonatal rat.

In the rat, the clustered pattern of thalamocortical afferent terminals to the "barrel field" portion of primary somatosensory cortex replicates the arrangement of vibrissae on the face, and the pattern of the terminals can be altered by the removal of vibrissae on the face, and the pattern of the terminals can be altered by the removal of vibrissae at birth (Killackey et al., '76). These patterns of terminals were studied using enzyme succinic dehydrogenase (SDH) because in somatosensory cortex the activity levels of SDH closely correspond to the patterns of thalamocortical afferent terminals. The present experiments show that the pattern of high SDH segmentation in the portion of layer IV of somatosensory cortex that is related to the vibrissae develops during postnatal Day 3 through 6. Activity related to the centers of individual clusters is first visible, with indistinct boundaries. At later times the edges of individual clusters become apparent. Further, in animals with Row C of vibrissae removed at birth, the abnormal SDH segmentation in somatosensory cortex develops with a time course similar to that of normal animals. At ages when edge boundaries are first distinct, a fused band corresponding to the removed row of vibrissae is present. Thus the aberrant organization seen in the adult cortex is the result of an abnormal initial development, not a later reorganization from a normal pattern. And indeed, vibrissae removal at Day 5 or 6 does not result in an aberrant cortical SDH pattern. Finally, after removal of all five rows of mystacial vibrissae at birth, the cortical SDH pattern seen at postnatal Days 6 and 7 consists of five bands in place of the normally present five rows of clusters. This may indicate that closer relationships exist between vibrissae within one row than vibrissae in adjacent rows.

Animals↗
PubMed1976

Effects of serial lesions of somatosensory cortex and further neodecortication on retention of a rough-smooth discrimination in rats.

Five groups of rats with bilateral lesions of the somatosensory cortex and one of animals sustained only sham operations were tested for retention of a rough-smooth discrimination. Two of the lesion groups had sequential unilateral ablations, in one case with interoperative testing, and three groups had one-stage bilateral lesions. The two groups of animals with serial lesions did not differ from each other or from sham operates in relearning the task. RAts with one-stage lesions and preoperative overtraining also performed well, but the other one-stage groups showed deficits relative to control and serial lesion groups. In the second experiment the sham operated rats from Experiment 1 experiences lesions anterior and posterior to the somatosensory zones. These lesions did not affect retention. Somatosensory cortex then was ablated in one operation and severe performance decrements were seen. Removal of additional neocortex in a sample of animals that had relearned the discrimination after one-stage somatosensory cortex lesions (Exp. 1) also affected retention. In contrast, retention was not impaired on some of the measures in those animals that originally had two-stage ablations. The findings from these two experiments show that some ablation effects can be circumvented with overtraining or serial lesion techniques. The data also indicate that non-somatosensory cortex may play a role in recovery after somatic cortex lesions, but that the substrates underlying recovery might not be the same after one-stage and two-stage ablations.

Animals↗
PubMed1992

Distribution of calbindin and parvalbumin in the developing somatosensory cortex and its primordium in the rat: an immunocytochemical study.

Immunocytochemical techniques were used to analyze the distribution of the calcium-binding proteins calbindin and parvalbumin during the pre- and postnatal development of the rat somatosensory cortex. Calbindin occurs in most early differentiated neurons that form the primordial plexiform layer at embryonic day 14. This expression in transient; during the perinatal period, calbindin becomes immunologically undetectable within the structures derived from the primordial plexiform layer, i.e., the prospective layers I and VIb. Immunoreactive neurons are also absent from adult layers I and VIb. Calbindin is also detected in a second population of neurons which, from embryonic day 18 onwards, distributes diffusely within the cortical plate. Some neurons of this population show morphological traits of immaturity, while others show complete dendritic arborization. The definitive pattern of distribution of calbindin-immunoreactive neurons is achieved by postnatal day 22. Infragranular layers contain intensely-immunoreactive cells whose numerical density decreases during postnatal development, whereas in supragranular layers similar neurons are interspersed among numerous faintly-stained neurons. Parvalbumin is detected for the first time at postnatal day 6, within a small group of neurons located in cortical layer V, and extends afterwards through the whole thickness of the cerebral cortex. At this same postnatal stage, groups of immunoreactive puncta are also found in layer IV of the somatosensory cortex; these puncta increase in density progressively and, at embryonic day 13, immunoreactive cells appear also grouped at this level. At this postnatal age, parvalbumin immunostaining delineates the somatosensory map in cortical layer IV. From this stage to adulthood, the number of immunoreactive neurons increases in the whole thickness of the somatosensory cortex. Barrels in layer IV become less distinct as immunoreactive cells and processes invade the septa. Layer IV in the adult somatosensory cortex appears more densely populated by parvalbumin immunoreactive neurons and puncta than in the surrounding areas.

Aging↗
PubMed1979

Tooth pulp-driven neurons in somatosensory cortex of primates: role in pain mechanisms including a review of the literature.

The tooth pulp of primates was stimulated electrically while searching for evoked unit potentials in the cerebral cortex. Control procedures were employed to assure that the electrical stimuli reached only tooth pulp fibers but no extrapulpal sensory fibers. In addition, an electrode was inserted in soft tissue surrounding the tooth for separate excitation of extrapulpal axons. A tooth pulp projection area was identified in the "face area" of primary somatosensory cortex. Two major neuron groups were encountered, one excited only by the extrapulpal soft tissue stimulus, the other by tooth pulp stimuli. Within the pulp-projection area, soft tissue-driven neurons were most numerous in superficial cortex of the postcentral gyrus, pulp-driven neurons dominated in deep cortex in the base of the central sulcus. The pulp-driven population divided into several functional subsets: those excited from one pulp only (conceivably capable of localizing pulpal stimuli), those excited from more than one pulp and those excited from both pulp and extrapulpal soft tissue. Within each of these 3 pulp-driven subsets, some units responded to single shock, others only to a train of shocks. Mean discharge latency was shortest for the population excited only from soft tissue, intermediate for pulp-driven units excited by single shock and longest for pulp-driven units excited only by trains of shocks. Both soft tissue and pulp stimuli evoked extensive inhibitory effects. In the Discussion, the possible role of pulp-driven neurons in pain is considered. The functional properties of some neurons are consistent with a role in stimulus localization but those of the remaining neurons suggest other roles in pain. An examination of the literature on cortex and pain suggests that normally somatosensory cortex is important for localizing painful stimuli and that it contributes to other pain mechanisms as well. After certain lesions, somatosensory cortex has the capacity for generating "central" pain just like other structures in the nociceptive pathway.

Animals↗
PubMed1976

Spindle wave synchrony in the somatosensory cortex of the cat.

(1) Spontaneous barbiturate spindles were recorded from the primary and secondary somatosensory cortex. The recordings were concentrated to areas surrounding several reference loci. The recording sites producing the maximal response evoked by stimulation of an exposed nerve in a contralateral limb were used as reference loci. (2) Spindles recorded at various distances from the respective reference loci were cross-correlated to spindles developing simultaneously in the latter. High correlation coefficients, indicating a considerable degree of wave synchrony, were obtained between spindles in the reference locus and spindles recorded a few millimeters from this site. The correlation coefficients decreased with increasing interelectrode distance. A relatively sharp fall in the correlation coefficients was generally found 2-3 mm from the reference locus. Small amounts of sodium pentobarbital, given intravenously at intervals of 5 min, had no effect upon this pattern. (3) The change in the correlation coefficients was followed by a parallel change in the amplitude of the evoked potentials. The iso-correlation lines of spindle wave synchrony and the iso-amplitude lines of the evoked potentials had a similar distribution and extension for each particular reference locus. (4) Lateral spread of spindle waves in the cortex seems to be of minor importance, since a vertical lesion cutting the cortico-cortical fibres did not reduce the wave synchrony of the spindles recorded from either side of the lesion. (5) The majority of the spindles recorded in the close vicinity of a reference locus started simultaneously within +/- 0.1 sec. This pattern changed with increasing distance from the reference locus and 5.6 mm away only a fraction of the spindles started simultaneously. However, within the entire primary somatosensory cortex a small but significant coupling existed between onset of the spindles.

Animals↗
PubMed1979

Conductivity in the somatosensory cortex of the cat -- evidence for cortical anisotropy.

Orthogonal conductivity components were determined for 3 depths in the somatosensory cortex of cats and relative vertical conductivities were determined for all depths. (2) For cortical layers II--III, the conductivity was nearly twice as large (1.7 times) in the anteroposterior direction as it was in the mediolateral direction, whereas in layer IV the conductivity in the mediolateral direction was about 1.4 times greater than it was in the anteroposterior direction. (3) With the exception of the anteroposterior direction of layers II--III and the mediolateral direction of layer IV, the vertical conductivity of the cortex was always greater than either of the horizontal conductivities. (4) Vertical conductivities varied with cortical depth. The lowest vertical conductivity occurred in layer I. It increased in layers II--III, dropped in layer IV, and increased again in layer VI to a value comparable to layers II--III. (5) Adjacent determinations of conductivity indicated that over short distances (1--2 mm) the cortex was electrically homogeneous. (6) These data suggest that the cellular organization of the somatosensory cortex changes markedly and abruptly with cortical depth. Furthermore, they suggest that a significant portion of the coritcal neuropile in layers II--III and in layer IV is highly polarized. The possible anatomical basis for this polarization is discussed as are the effects of cortical anisotropy upon conductivity measurements.

Animals↗
PubMed1992

Development of long-term potentiation in the somatosensory cortex of rats of different ages.

The age dependence of possible long-term potentiation (LTP) induction in rat somatosensory cortex was studied in in vitro slice experiments. Coronal slices were prepared from the somatosensory cortex of rats of different ages, and excitatory postsynaptic potentials evoked by stimulation of the white matter (0.1 Hz, subthreshold for spike) were recorded intracellularly. In 70% of the slices taken from 2-week-old rats, a moderate potentiation (20-30%) could be induced by either 5 or 100 Hz stimulation. No LTP was observed in younger (1 week) or older (3 weeks) cortex. On the basis of our experiments an important ontogenetic role of increased synaptic efficacy is suggested in a critical developmental period of rats after birth.

Aging↗
PubMed1992

Expansion of stimulus-evoked metabolic activity in monkey somatosensory cortex after peripheral denervation.

The 2-deoxy-glucose (2DG) technique was used to study changes in stimulus-evoked metabolic activity in the somatosensory cortex of the squirrel monkey Saimiri sciureus after unilateral digit amputation. Two to 52 weeks after digit 2 on the left hand was removed, a somatic stimulus was applied to digit 3 bilaterally. In area 3b corresponding to the deafferented side of the brain, the area of stimulus-evoked metabolic activity was greater than that on the opposite, control side of the brain within the same animal. The extent of the topographic projection map of 2DG label in area 3b on the deafferented side of the brain was 1.92 to 4.75 times greater than that on the control side. There was no difference, however, in the topographical area of stimulus-evoked metabolic activity between the left and right somatosensory cortices in a normal, unoperated animal. These data suggest that the changes in functional organization observed using electrophysiological recordings in somatosensory cortex after peripheral denervation may have a metabolic substrate.

Animals↗
PubMed1976

Histochemical localization of potassium-stimulated P-nitrophenylphosphatase activity in the somatosensory cortex of the rat.

Potassium-stimulated p-nitrophenylphosphatase (K+-pNPPase) activity was investigated in rat somatosensory cortex where 64-88% of enzymatic activity survived 5-10 min of fixation with 3% formaldehyde in 0.1 M cacodylate buffer, pH 7.4. Potassium-stimulated activity was inhibited by 1-10 mM ouabain. Levamisole (1.7 mM) inhibited brain alkaline phosphatase activity, facilitating the detection of K+-pNPPase activity. Strontium (10-20 mM) inhibited enzymatic activity by 38-75%. In parallel histochemical studies reaction product was found in strata, with cortical layers 2, 3, 4 and the outer portion of 5 containing the heaviest deposits. Highly reactive, vertically oriented, large diameter fibers were seen as groups between the outer portion of layer 5 and the pail surface. These fibers apparently arborize in the superficial layers. Smaller fibers were also positive and were oriented in various planes. The highest density of smaller, positive fibers occurred in layers 2 through 5. All positive fibers appeared to be axons or dendrites. Reaction product was not heavily concentrated in neuron perikarya or in glial elements. Sections did not contain reaction product when incubated in media lacking K+ or containing ouabain. The convergence of data from parallel histochemical and biochemical approaches supports the conclusion that the reactivity localized in the cerebral cortex represented the site of K+-pNPPase, a known component of the Na+,K+-adenosine triphosphatase complex. Neuronal processes demonstrated the highest enzymatic activity and may be most important in the active transport of Na+ and K+ in somatosensory cortex.

4-Nitrophenylphosphatase↗
PubMed1992

Postnatal blockade of cortical activity by tetrodotoxin does not disrupt the formation of vibrissa-related patterns in the rat's somatosensory cortex.

Neuronal activity has been shown to influence pattern formation in the visual system. In the present study, we determined whether or not this was also true in the somatosensory system by silencing the primary somatosensory cortex of rats with tetrodotoxin (TTX) for the first 7-11 days of life. Application of TTX during this period did not prevent the formation of the normal vibrissa-related pattern in S-I as visualized by either staining cortical sections for cytochrome oxidase, demonstration of the pattern with an antibody directed against serotonin, or labelling of thalamocortical axons with the carbocyanine dye, Di-I. These results indicate that neither peripherally evoked nor spontaneous activity are required for qualitatively normal pattern formation in the rat's primary somatosensory cortex.

Animals↗
PubMed1992

Induction of transcription factors in somatosensory cortex after tactile stimulation.

Immediate early response genes have been shown to be inducible in the central nervous system after a variety of stimuli. Induction of these transcription factors in cerebral cortex by a physiological stimulus had not previously been demonstrated. In this study, tactile stimuli induced multiple transcription factors in the somatosensory cortex. Adult male rats were lightly anesthetized with urethane. Tactile stimuli was delivered by a paint brush gently stroking an animals whiskers on one side of its face for a 15 min period. Two h later, the animals were sacrificed. Cortex contralateral to the stimulation was compared with ipsilateral cortex using antibodies raised against immediate early response gene products NGFI-A, NGFI-B, and c-fos. The different transcription factors showed slightly different patterns of response to the tactile stimulus. However, the induction of immunohistochemical staining was most prominent in layer 4 with all antibodies under study. This increase in the number of cell bodies stained was less robust than that seen in the somatosensory cortex after a seizure, and showed more of a predominance in layer 4 cells. These data demonstrate that physiologic stimulation can induce immediate early response genes in cortical cells, and that multiple immediate early response genes react to a stimulus.

Animals↗
PubMed1977

Development of the barrels and barrel field in the somatosensory cortex of the mouse.

Barrels of the PMBSF of the mouse somatosensory cortex become apparent in Nissl-stained tangential sections simultaneously, on the fourth postnatal day. At this time they are miniatures of those in the adult and are situated in the deepest sublamina of the trilaminar cortical plate. An early barrel appears as a patch of decreased cell density: the prospective hollow of the barrel. Septa become noticeable during the sixth postnatal day. From that period to adulthood, the relative contribution of the PMBSF to the total cortical surface area increases -- an increase that goes against one's expectation: the barrel related periphery matures very early and so does the central, lateral region of the cortex. Barrel growth parallel to the pial surface is greater along the major axes than along the minor axes. By using the barrels to identify prospective layer IV in immature cortex, we could determine that layers V and VI attain their adult height during the sixth postnatal day -- an age when prospective layers I-IV are only half their adult height. The onset of barrel formation coincides with the moment after which injury to the pertinent somatosensory periphery (the vibrissal papillae) no longer causes profound alterations in barrel morphology.

Animals↗
PubMed1979

Multiple representations of the body within the primary somatosensory cortex of primates.

Microelectrode mapping experiments indicate that the classical primary somatosensory cortex of monkeys consists of as many as four separate body representations rather than just one. Two complete body surface representations occupy cortical fields 3b and 1. In addition, area 2 contains an orderly representation of predominantly "deep" body tissues. Area 3a may constitute a fourth representation.

Animals↗