Disturbances of verbal memory in local lesions of the left and right cerebral hemispheres.

Abstract

Views regarding the multichannel character of information coding that have been put forward suggest that different zones of the left (dominant for speech) and right hemispheres make a specific contribution to verbal memory processes. Clinical facts have led to enunciation of the hypothesis that the left hemisphere participates in processing of the characteristics of verbal material at a higher level (semantic) and in the right hemisphere participate in processing of characteristics at a lower level (sensory) [8~ 9]. In the investigation described below the aim was to determine the role of the left and right hemispheres of the human brain in processing of various semantic and sensory characteristics of verbal material under conditions of voluntary memorizing. Altogether 20 patients with local brain lesions were studied: 12 had lesions of the left and eight lesions of the right hemisphere. Patients with lesions in the left hemisphere were divided into three groups: i) patients with variants of the frontal syndrome; 2) patients with variants of the temporal syndrome; 3) patients with variants of the parietal syndrome. Group 4 consisted of patients with lesions of the temporo-parietal zones of the right hemisphere. The location of the lesion was verified from the results of operation or the results of objective tests (angiography, roentgenography, electroencephalography, etc.) The patients were capable of being tested by the techn~aue chosen and they had no marked speech disorders. The control group consisted of !00 healthy subjects~ selected by age and level of education. A modified version of the technique known as '~two groups of words with three words in each group" that is traditionally used for the neuropsychoiogical investigation of memory [i] was used in the experiment. The words in the groups were chosen with allowance for frequency, various semantic, and sensory characteristics. In the experiments of series I the groups contained words similar or identical in meaning (the "semantic field" structure~ for example: "boldness -- valor -- courage"). In series II the words were grouped together in accordance with the principle of situation association, so that they could be combined into a larger semantic unit -- a pattern or sentence (a "situation association" structure~ for example: "thunderstorm-- lane -- puddle)."In series III phonetically similar words were used (the "phonetic similarity" structure~ for example: "Uzor --Upor -- Ukor~')o The choice of