Attentional Imbalances following Head Injury

Abstract

Unilateral left and right hemisphere lesions produce numerous well documented neuropsychological consequences (DeRenzi, 1982). Some of these sequelae are attentional, involving anatomical systems related to the selection of information for conscious detection (Nissen, 1986; Posner & Rafal, 1986). Such attentional deficits can often be demonstrated in tasks involving conflicts between stimuli (Posner & Presti, 1987). For example, patients with left hemisphere lesions have difficulty selecting a verbal input when it conflicts with a simultaneous spatial command. Patients with right hemisphere damage show the reverse pattern (Walker, Friedrich, & Posner, 1983). Similarly, patients with parietal lobe lesions often have great difficulty when an event in the contralesional visual field is in conflict with one in the ipsilesional field. In severe cases these patients may be completely unaware of contralesional targets while in milder cases the target may be detected but with longer latency (DeRenzi, 1982; Posner, Walker, Friedrich & Rafal, 1984).