Visual search for feature and conjunction targets with an attention deficit

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Neuropsychology

Background:

• Visual attention deficits can arise from brain damage.
• Feature integration theory posits that attention is required to combine visual features.

Purpose of the Study:

• To investigate the impact of visual attention deficits on feature integration during visual search.
• To test the hypothesis that feature integration, but not feature encoding, requires attention.

Main Methods:

• Brain-damaged subjects with visual attention disorders (VAD) and normal controls performed visual search tasks.
• Tasks included searching for single feature targets (color or orientation) and conjunction targets (color and orientation).
• Ocular fixation was monitored and controlled to exclude eye movements.

Main Results:

• VAD subjects performed similarly to controls in single feature search tasks.
• VAD subjects showed a significant deficit in conjunction search tasks, particularly for contralesional displays.
• Search rates for conjunction targets were markedly reduced in VAD subjects.

Conclusions:

• Visual attention deficits significantly impair feature integration, supporting Treisman's feature integration theory.
• Feature encoding appears to be unaffected by the visual attention deficits observed in these subjects.
• Attention is critical for binding visual features into coherent object perception.