Showing papers on "Somatosensory system published in 1971"

Somatosensory System: Organizational Hierarchy from Single Units in Monkey Area 5

Abstract: The receptive fields of single cells in area 5 of monkey parietal cortex were studied by extracellular recording. Cells were driven primarily by gentle manipulation of multiple joints residing on one or more limbs. Both excitatory and inhibitory convergence were demonstrated. It is postulated that the multijoint receptive fields of area 5 are the result of convergence from single-joint cells of the primary receiving area. An analogy is drawn between the modification of information in the visual and somatosensory systems.

Rhesus monkey vestibular cortex: a bimodal primary projection field.

Abstract: Single units in the rhesus monkey (Macaca mulata) cortex responded to both vestibular and proprioceptive somatosensory stimuli. This bimodal response characteristic is unlike the modality specificity noted for other primary sensory fields. The vestibular field is located, contrary to previous opinion, within a distinct cytoarchitectonic area outside of area 2.

Somatosensory responses of bulboreticular units in awake cat: relation to escape-producing stimuli.

Abstract: In awake, unrestrained cats, bulboreticular neurons respond after electrical stimulation of cutaneous nerve with increasing discharge as stimulus intensity is raised to levels eliciting escape behavior. These cells discharge most vigorously to noxious natural somatic stimuli and are not driven by other sensory modalities. Electrical stimulation through the recording microelectrode also elicits escape, which further suggests bulboreticular participation in pain sensory mechanisms.

A comparison of somatotopic organization in sensory neocortex of newborn kittens and adult cats

Abstract: To determine the state of functional development in the newborn kitten's somatic sensory system, the organization of mechanoreceptive projections to the sensorimotor cortex was compared to that of the adult Cat. Microelectrode mapping procedures were used. Projections from all contralateral body surfaces to the primary somatomotor cortex (SmI) are present at birth and respond to mechanical stimulation of the receptors. The somatotopic organization of these projections in the newborn kitten is similar to that in the adult cortex with respect to the cortical region receiving projections from each part of the body and to the detailed arrangement of the projections within each of these cortical subdivisions. The relative sizes of peripheral receptive fields, and the intensity of stimulation effective for eliciting a response were similar for projections in SmI cortex of both kittens and adults. At both ages receptive field sizes decreased as their locations approached the distal portion of the limbs or rostral part of the face. In adults and newborns, over 75% of the neuronal responses were elicited by gentle bending of the hairs or light touch to the glabrous skin surfaces. Other similarities between adult and newborn sensorimotor cortexes included: (a) receptive fields of projections to SmI cortex were of fixed, local field type; (b) projections to SmII cortex responded to mechanical stimulation of the receptors; (c) ipsilateral as well as contralateral body surfaces were represented in SmII cortex; (d) the columnar arrangement of neurons and their receptive fields were apparent in the SmI cortex; (e) the coronal sulcus formed a division between the representations of the forepaw and face. Differences between newborn kittens and adult cats included: (a) shorter latency from electrical stimulation of the skin to a SmI cortical response in adults; (b) projections to SmI cortex having “disjunctive” receptive fields were not found in newborn kittens but existed in the adults; (c) the diversity of receptive field types found in neurons of the adult postcruciate MsI cortex was not found in newborn kittens; (d) newborn subjects displayed less variability in the somatotopic organization of projections and less overlap in the receptive fields of projections to SmI cortex. It is suggested that the SmI cortex develops as a point-to-point reflection of the distribution of mechanosensitive receptors in the body and that the complexities in this organization seen in the adult cortex occur during postnatal development.

Differential Effects of Anesthetics on Mesencephalic Reticular NeuronsII. Responses to Repetitive Somatosensory Electrical Stimulation

Abstract: The differential effects of anesthetics on unitary behavior of the cat's mesencephalic reticular formation in response to repetitive electrical stimulation of the skin were studied by means of longterm microelectrode recording and computer analysis. In most units the anesthetics decreased the total number of firings in response to repetitive electrical stimulation of the skin. However, the ratio of evoked to spontaneous activity varied from unit to unit. Generally, the ratio was highest with sodium thiopental, and lowest during diethyl ether anesthesia. Evoked activity was easily distinguished from background activity during sodium thiopental and halothane anesthesia, but hardly distinguishable during diethyl ether anesthesia. The poststimulus times of short-latency discharges were hardly affected by the anesthetics in most units until the units ceased to respond to stimulation. In contrast, long-latency discharges were easily affected by anesthetics.

Evoked Responses After Hemispherectomy

Abstract: Somatosensory, visual and auditory evoked responses were studied in a left hemispherectomized patient. Median nerve stimulation and light flashes produced typical answers over only the unoperated hemi

Spatial principle of organization of specific afferent projections and generation of evoked potentials in the somatosensory cortex

Abstract: Here we investigate the functional organization of structures involved in sensory analysis in a restricted region of a cortical projection area. We have shown that stimulation of somatosensory areas I and II (SI and SII) may block an afferent volley at the level of the thalamic relay nucleus, and that SII may be selectively blocked by stimulation of SI. Also definite somatosensory connections have been demonstrated between SII, SI, and the motor cortex. We suggest that common mechanisms underlie the generation of focal reactions in projection areas of the cortex induced by stimulation of various structures. The properties of two groups of neurones from area SII are described: those having a short latency and receiving direct projections from the thalamic relay nucleus, and those of long latent period with a well-marked convergence, and reacting to stimulation of various afferent pathways. It is suggested that each path to a local point of a cortical projection areas terminates with its relay element. The signal is then directed to a common intracortical system of neurones where signals from various sources occurs (afferent, interhemispherical, subcortico-cortical, and intracortical) converge and interact. All groups of neurones are involved in the formation of the common components of evoked potentials.