A STUDY ON SOMATOSENSORY EVOKED POTENTIAL PATTERNS ACCORDING TO VARIOUS VIBROTACTILE STIMULATION: FREQUENCIES AND INTENSITIES

This study investigates somatosensory evoked potential (SEP) patterns in the C3 somatosensory area with varying frequency and intensity of vibrotactile stimuli. The study subjects included 13 men ([Formula: see text] years) and seven women ([Formula: see text] years) who were right-handed and had normal cognitive function. The participants were subjected to three intensity levels (0.25, 0.38 and 1.3[Formula: see text]g) and eight frequencies (10, 50, 100, 150, 200, 225, 250 and 300[Formula: see text]Hz) of vibrotactile stimuli on the distal phalanx of their right index finger. The peak values of SEP patterns generated in response to high-frequency vibrotactile stimuli were greater than those generated because of low-frequency flutter. Moreover, the peak values increased as the stimulus intensity increased from 1[Formula: see text]g to 3[Formula: see text]g. In these results, the maximum and minimum peak, and peak to peak values of SEP pattern in the C3 somatosensory area increased with an increase in the stimulation intensity and frequency of the vibrotactile stimuli. Data on the SEP patterns generated in response to various frequencies and intensities of somatosensory stimuli and the development of relevant databases will elucidate the various clinical applications and applicable domains where SEP assessment can be beneficial.

Age related changes in the primary somatosensory area of the cerebral cortex

Background: Age-related changes in structural and functional part of brain have been the motivation of previous and ongoing neuroscientific research. The focus of most studies done, were on different motor areas of the of the cerebral cortex. Very few studies were done on primary somatosensory areas of the brain. Aims and Objective: The aim of the study was to investigate the age-related changes in primary somatosensory area of the cerebral cortex of the human brain. Materials and Methods: The study was conducted on 50 autopsied brain specimens. The specimens removed were of both sexes belonging to various age groups ranging from 9 months to 75 years. The specimens were collected from the Department of Forensic Medicine, Medical College Kottayam. During the autopsy the meninges were carefully stripped off. The sulci and gyri were then examined carefully. Results: The depth of the upper area of the central sulcus is more than the middle and lower areas, both in the right and left halves of the cerebral cortex. The laminae of the primary somatosensory area have shown that as age advances there is a progressive increase in thickness except in the case of lamina IV. From the ages of 61 years onwards, laminar degeneration takes place. The thickest lamina was lamina V. The thinnest laminawas lamina IV. The stellate cells that dominate in lamina II and IV show a difference in their arrangement. In foetal life, the pyramidal cells were almost indistinguishable from the stellate cells. The pyramidal cells were seen mostly in lamina III and V. Conclusion: The study results suggest the possibility that in the more advanced stages of aging, the structural integrity of lamina IV is more consistent than other layers present in primary somatosensory area of the cerebral cortex. Further study is needed to examine the impact of ageing on somatosensory area.

Developmental 'awakening' of primary motor cortex to the sensory consequences of movement

Before primary motor cortex (M1) develops its motor functions, it functions like a somatosensory area. Here, by recording from neurons in the forelimb representation of M1 in postnatal day (P) 8–12 rats, we demonstrate a rapid shift in its sensory responses. At P8-10, M1 neurons respond overwhelmingly to feedback from sleep-related twitches of the forelimb, but the same neurons do not respond to wake-related movements. By P12, M1 neurons suddenly respond to wake movements, a transition that results from opening the sensory gate in the external cuneate nucleus. Also at P12, fewer M1 neurons respond to individual twitches, but the full complement of twitch-related feedback observed at P8 is unmasked through local disinhibition. Finally, through P12, M1 sensory responses originate in the deep thalamorecipient layers, not primary somatosensory cortex. These findings demonstrate that M1 initially establishes a sensory framework upon which its later-emerging role in motor control is built.

Developmental “awakening” of primary motor cortex to the sensory consequences of movement

ABSTRACTBefore primary motor cortex (M1) develops its motor functions, it functions like a somatosensory area. Here, by recording from neurons in the forelimb representation of M1 in postnatal day (P) 8-12 rats, we demonstrate a rapid shift in its sensory responses. At P8-10, M1 neurons respond overwhelmingly to feedback from sleep-related twitches of the forelimb, but the same neurons do not respond to wake-related movements. By P12, M1 neurons suddenly respond to wake movements, a transition that results from opening the sensory gate in the external cuneate nucleus. Also at P12, few M1 neurons respond to twitches, but the full complement of twitch-related feedback observed at P8 can be unmasked through local disinhibition. Finally, through P12, M1 sensory responses originate in the deep thalamorecipient layers, not primary somatosensory cortex. These findings demonstrate that M1 initially establishes a sensory framework upon which its later-emerging role in motor control is built.