Ipsilesional line bisection bias in patients with chronic parietal lesions.

The current study investigated whether an ipsilesional bias in line bisection, a conventional measure for diagnosing hemispatial neglect, persists even in the absence of this syndrome in patients with chronic lesions restricted to posterior association cortex or dorsolateral prefrontal cortex. Both left and right hemisphere parietal lesions produced ipsilesional bisection errors, and to a comparable degree. Patients with lesions in frontal cortex, on the other hand, did not show a consistent bias. We conclude that chronic parietal lesions produce an ipsilesional bias in line bisection, even in the absence of other clinical signs of neglect, and that left hemisphere lesions can affect line bisection to the same degree as right hemisphere lesions.