Increased attentional load moves the left to the right

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurorehabilitation

Background:

• Unilateral brain damage often impairs spatial processing, leading to neglect (failure to report contralesional items) or mislocalization.
• Attentional load manipulation can induce omissions in contralesional space, even in unimpaired individuals.

Purpose of the Study:

• To investigate if increased attentional load (dual-tasking) induces spatial mislocalizations in patients with unilateral brain damage.
• To compare omissions and mislocalizations under varying attentional loads.

Main Methods:

• Nine right-hemisphere-damaged patients performed visual target detection tasks under varying attentional loads (single-task vs. dual-task: visual or auditory).
• Patient responses (omissions and mislocalizations) were analyzed at individual and group levels.

Main Results:

• Ipsilesional target representation remained accurate regardless of task load.
• Contralesional targets were frequently omitted. Four patients exhibited mislocalizations under dual-task conditions.
• Specific phenomena included alloesthesia (left targets reported as right) and synchiria (contralesional targets perceived as two).

Conclusions:

• Increased task load in patients with spatial processing deficits can result in either neglect or spatial bias (mislocalization).
• Spatial mislocalization may represent a more profound deficit than neglect, akin to complete erasure of contralesional space.