Role of the Parietal Cortex for Sensorimotor Transformation

Abstract

Somatosensory and motor functions of both hands were examined in 10 patients with unilateral parietal cortex lesions as revealed by computerized tomography. Tests of elementary somatosensory functions comprised surface sensibility, vibration, and position sense. For evaluation of complex somatosensory functions, the recognition of surface textures and object forms was tested. Motor performance was examined by measuring force and position control as well as manipulative and explorative motor behaviour. All patients showed varying degrees of sensory disturbance. Although the patients had no or minor paresis, they all had motor deficits concerning force control, fine movements, and manipulation with the hand contralateral to the lesion. Patients with more posteriorly located parietal lesions revealed predominantly severe disturbances of complex sensibility, precision grip, manipulation, and explorative finger movements. The characteristic and consistent feature of the disturbed motor behaviour was the loss of the purposive nature of the motor acts which were no longer adequate for the tasks (tactile apraxia). Paresis or ataxia could not account for these deficits.

The Determination of Sensory Deficits in Children With Hemiplegic Cerebral Palsy

“…Posterior parietal lobule lesions or excision leads to complex moter and sensory deficits (Hyvarian and Poranen, 1974;Seal, 1989). Spatial disorientation and stereognosis of the contralateral body surface (Roland, 1987) and severe disturbance in manipulation of objects (Deuel and Regan, 1985;Pause and Freund, 1989) (Carmon, 1971;Corkin et al, 1973).…”

“…This probably encompasses the posterior parietal lobule. Studies have shown that excision of the posterior parietal lobule leads to astereognosis, spatial disorientation of the contralateral side of the body (Roland, 1987) and an impairment in object manipulation (Pause and Freund, 1989). This was reflected by subject test scores on the clinical sensory battery, ln which the subject showed a bilateral deficit of stereognosis with difficulty in object manipulation.…”

“…(i.e. manipulation of objects for stereognoSls, JOint movement for proprioception) LeSions of S Il, whlch IS responslble for the sensory-motor integration of the Ipsllateral and contralateral sides of the body (Roland, 1987), could also result ln impaired proprioception and stereognoslS-InJu ry to any part of the somesthetic cortex would have a greater probabliity of leadlng to a deficit of stereognosis and propnoceptlon, than the other more passive sensory Inputs whlch are medlated only by SI (Pause and Freund, 1989) Thus, these 2 sensations are more prone ta be affected and this is clearly illustrated ln this study An interesting observation of thls study was that left hemipleglcs (LH) demonstrated an ove rail greater degree of btlateral sensory impairment, as compared ta nght hemlpleglcs (RH). The children with right hemiplegia had primanly bilateral Impalrment of stereognosis, with other modalitles betng Impalred ta a lesser degree on the affected side.…”

Effects of sexual arousal on vibrotactile detection thresholds in aged men with and without erectile dysfunction

“…8 Lesions of the parietal cortex have an adverse effect on vibrotactile sensation, and sexual seizures may result from lesions in the parietal cortex. 8,9 Patients with temporal lobe epilepsy have impaired ability to interpret tactile information. 10 The temporal lobe is also activated during sexual arousal.…”

Functional Outcome of Patients with Parietal Lobe Stroke

“…Parietal lesions often cause severe disturbances of purposeful movement of the hand during exploratory finyr movements and in object handling (7), in the absence of motor and sensory impairment (8). The term tactile apraxia is used for such deficits (9) and is often associated with astereognosis.…”