Tactile sensation--an all-or-none effect of cerebral damage

Compared the Von Frey Hair scores of 158 brain-damaged Ss and 40 normals to scores on Speech Perception, Block Design and Trail Making B tests, in order to examine the distribution of organically affected tactile sensation. Organic impairment produced an all-or-none distribution pattern on the tactile test in that almost all scores fell either within the normal range or in the severely impaired range. By contrast, scores of the cognitive functions formed a graded continuous distribution. These results are related to Luria's concept of diminishing modality specificity. In addition, the neurological examination evidently is designed to measure all-or-none functions, while the neuropsychological examination is concerned with graded continuous functions.