Spatial Limitation of Eye Movements During Ocular Exploration of Simple Line Drawings in Neglect Syndrome

Abstract

The eye movement behaviour of a patient suffering from a right basal ganglia infarction with left-sided neglect but without any visual field defects was investigated during the ocular exploration of simple line drawings. The eye movements were registered by means of an i.r. light technique. Each line drawing consisted of different figural elements located in the centre and both the left and the right half of the picture. In each case, only the contextual connection of the left and right elements in a drawing allowed the spectator to describe the whole scene consistently and to perceive the correct theme of the drawing. The drawings fell into two categories. The cognitive impact of the elements in the drawings' centre was varied by “pointing” to the elements located in the left and right halves with a different strength of connection. When exploring the two types of drawings (weak vs. strong connective elements in the centre) the patient showed a similar eye movement pattern, exploring exclusively the right halves of the drawings. Irrespective of the cognitive impact of the drawing's central elements in “pointing” towards supplementary information in the picture's left half, exploration of this half took place in neither case. A striking difference between the two categories was, however, found concerning the patient's ability to recognize the general context, i.e. to describe the correct theme of the whole drawing. While the patient could not correctly depict any of the scenes from the drawings with weak connective elements in the centre, he was easily capable of properly describing the themes from the group of drawings with strong connective elements, which implies that he must have analysed and perceived the figural elements of both halves of the picture. Different possibilities are discussed to explain the similarity of the patient's exploratory eye movements but discrepancy in his verbal responses when dealing with the two different types of drawings.