Systematic analysis of deficits in visual attention.

Abstract

A variety of impairments in visual attention can follow damage to the brain. The authors develop systematic methods for analyzing such impairments in terms of C. Bundesen's (1990) Theory of Visual Attention and apply these in a group of 9 patients with parietal lobe lesions and variable spatial neglect. In whole report, patients report letters from brief, vertical arrays in left or right visual field. The results show substantial, largely bilateral impairments in processing capacity, implying a major nonlateralized aspect to neglect. In partial report, arrays contain 1 or 2 letters in red and/or green. The task is to report only those letters in a specified target color. In addition to the expected bias against left-sided letters, patients show striking, bilateral preservation of top-down control, or attentional priority for targets. The results show how differentiation of attentional impairments can be informed by a theory of normal function.

A non-spatial bias favouring fixated stimuli revealed in patients with spatial neglect

“…Confirming previous studies using tasks evaluating global alertness (Robertson, 1989), the attentional blink (Husain et al, 1997), global attentional processing capacity (Duncan et al, 1999) or speed of visual processing (Battelli et al, 2003) this central bias shows that neglect patients have severe spatially unspecific processing deficits. An influential hypothesis explains the increase of saccade latency by a fixated distracter in terms of impaired disengagement of attention from fixation (Fischer and Breitmeyer, 1987).…”

Perception of biological motion in parietal patients

“…It is very well documented in the literature (Duncan et al, 1999;Posner, Walker, Friedrich, & Rafal, 1984;Robertson & Marshall, 1993) that attentional abilities are disrupted in parietal patients.…”

“…While a great deal of research has tested the visuo-spatial abilities of neglect patients, both in vision (Duncan et al, 1999;Vuilleumier & Rafal, 2000) and audition (Bellmann, Meuli, & Clarke, 2001;Griffith et al, 1997), much less is known about their perception of motion. Conversely, visual motion perception in parietal patients has rarely been studied (Braun, Petersen, Schonle, & Fahle, 1998;Greenlee, Lang, Mergner, & Seeger, 1995;Greenlee & Smith, 1997;Schenk & Zihl, 1997) and the exception is a large body of work that has concentrated on 'motion-blind' patients who are usually affected by bilateral lesions involving the human homologue of motion area V5 (McLeod, Dittrich, Driver, Perrett, & Zihl, 1996;Vaina, Lemay, Bienfang, Choi, & Nakayama, 1990;Zihl, von Cramon, & Mai, 1983) with no involvement of the parietal cortices.…”

Orienting of attention in left unilateral neglect

“…Duncan et al [116] explored neglect patients' behavior in terms of Bundesen's Theory of Visual Attention [117]. Duncan et al [116] tested nine patients with lesions affecting the right parietal lobe and variable left unilateral neglect (which was absent in two patients and resolving in one). Patients were shown letters brie¯y presented in bilaterally arranged arrays and had to report either all of the letters or only those letters in a prespeci®ed color.…”

“…In other words, target letters received attentional priority over non-targets even on the neglected side, thus indicating an unexpected, bilateral preservation of top-down attentional control in neglect patients. Duncan et al [116] recalled that top-down control is often associated with frontal lobe function. This might explain its preservation in patients with predominantly posterior lesions.…”