Deficits in response initiation, but not attention, following excitotoxic lesions of posterior parietal cortex in the rat

Damage to posterior parietal cortex in humans is known to cause hemineglect, and specifically difficulty in disengaging attention in tests of covert orienting. Aspirative lesions of a region of cortex in rats which is thought to be homologous to primate posterior parietal cortex has also been reported to cause what appears to be multimodal neglect. In order to make an assessment of the nature of this disorder, a variety of tests were employed: (1) a test of somatosensory neglect after Schallert et al. (Pharmacol. Biochem. Behav., 16 (1982) 455-462); (2) a skilled paw-reaching test after Whishaw et al. (Brain 109 (1986) 805-843); (3) a visual reaction time task with peripheral cues analogous to Posner's test of covert orienting (Q. J. Exp. Psychol., 32 (1980) 3-25). Following the posterior parietal lesion there was a global increase in reaction time of responses made contralateral to the lesion in the reaction time task, but there was no evidence of a deficit in covert orienting. There was also no evidence of somatosensory neglect. There was a decrease in the number of attempted reaches with the contralateral paw and a tendency to spend a smaller proportion of time in the contralateral half of the reaching cage. (C) 1997 Elsevier Science B.V.