Bilateral cutaneous stimulation of the somatosensory system in hemidecorticate rats


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Abstract

In Exp I with 12 male Long-Evans hooded rats, small adhesive stimuli were attached to the forelimbs of hemidecorticate Ss, and the latencies to contact and to remove each stimulus were recorded. Neglect of the contralateral (C) stimulus lasted 2–3 days. Thereafter, the ipsilateral (I) stimulus was removed first, followed immediately by the C stimulus. This I sensorimotor bias lasted several months. Further analysis with unremovable tactile stimuli provided evidence for true extinction. During the 1st 2 postoperative weeks, Ss ignored the stimulus on the C limb and persisted in their attempts to remove the I stimulus. A key feature of the extinction was its complete reversibility. Simply by adjusting the sensory fields occupied by the C and I stimuli (specifically, by increasing the C/I ratio), the sensorimotor bias was totally shifted to C. During recovery, the size of the C/I ratio necessary to reverse sensorimotor asymmetry gradually decreased. In Exp II, asymmetrical sensorimotor behavior and amphetamine-induced circling were examined in 3 additional groups of 6 hemidecorticate rats (and 6 anesthetized controls), which were given their initial behavioral tests at 2, 12, or 52 postoperative weeks. This confirmed Exp-I findings and controlled for practice. (46 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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