Simple reaction-time changes in patients with unilateral brain damage.

Changes of simple visual reaction time were analysed in two groups of unilateral brain-damaged patients in order to evaluate to what extent properties of lesions, clinical parameters and experimental variables might influence speed of motor response. The results confirmed that brain damage, independent of its side, produces a retardation of speed. However, the two hemispheric groups differed in so far as volume of damage had a different bearing depending on side of lesion. In spite of such a difference the presence of a general interaction between size of damage and rate of progression of lesion was noted in both the hemispheres, reminiscent of Jackson's concept of 'lesion momentum'. Aphasia was related to a significant retardation of speed in left-hemisphere-diseased patients, although a specific effect of the disturbance of language could not be demonstrated. Experimental variables such as warned vs unwarned stimulation did not affect significantly the performance of brain-damaged patients.