Disorders of "simultaneous perception" in a case of bilateral occipito-parietal brain injury

Abstract

I. INTRODUCTION IN reports of the optico-gnostic disorders arising from cerebral lesions, a restriction of the field of visual perception to single objects or their parts has been repeatedly described. It was mentioned in some of the earliest descriptions of visual agnosia (Wilbrandt, 1887; Lissauer, 1890) .and subsequently analysed with particular thoroughness by Balint (1909). In Balint's case, the patient was said to have been able to see only one object at a time, irrespective of its size. Holmes later described very similar disorders in cases of bilateral posterior parietal gunshot wound (Holmes, 1919; Holmes and Horrax, 1919). Although placing the main emphasis upon loss of visual orientation, Holmes referred to a constriction of visual attention as an important element in the syndrome. In more recent years, Balint's syndrome has been reinvestigated by Hecaen and Ajuriaguerra (1954), who likewise stress the defect of attention and the bilaterality of the responsible lesion. Defects of visual synthesis of a somewhat less pronounced character have also been described in the literature (Gelb and Goldstein, 1920; Wolpert, 1924; Head, 1926; Paterson and Zangwill, 1944). In these cases, the lesion is commonly unilateral, orientation in space is usually preserved, and scanning movements of the eyes less obviously disturbed. But there may be gross incapacity to combine the elements of the perceptual display into a coherent and integrated whole. To this type of deficit the term simultanagnosia is commonly applied (Wolpert, 1924). It is clear that the limited and fragmentary character of perception so often associated with occipito-parietal lesions cannot be wholly accounted for in terms of visual field defects. Restriction of visual perception to individual objects or their parts has been described in the absence of significant field defects; conversely, perception may be more or less adequate in spite of extensive scotomata. This is not, however, to say that the perceptual deficit does not call for physiological explanation;