Luria: Visual agnosia explained through physiology

AR Luria Disorders of"simultaneous perception in a case of bilateral occipito-parietal brain injury. Brain 82:437-449 year?

Luria notes explanations in literature should but do not include the physiologic. He cites a case discussion by Pavlov in 1935 that the "occipital lobe is inhibited to such a degree that it cannot endure two simultaneous stimulations." The occipital lobe has a "low tonus of excitation" and can concentrate only on one point at a time. There is not a notion of space, and the patient feels lost. Luria takes off on the "restriction of attention in physiological terms" and discusses the deficit in terms of excessive cortical inhibition, leading to failure to synthesize excitation under complex stimulation.

The patient had signs of optic ataxia and simultanagnosia.Writing was poor but improved with the eyes closed. One interesting experiment (no 9 on this patient) the patient could see the rectangle formed by 6 dots but with the instruction to count the dots, had difficulty. Concentration on one detail led to loss of the whole. The injection of caffeine (.05-.1 gram) led to much better results. The improvement lasted about 35 minutes. It helppd tachistoscopic presentation and perception of two or more figures and helped oculomotor scanning.