Left hemisphere involvement in left spatial neglect from right-sided lesions.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Unilateral neglect syndrome is typically attributed to right hemisphere lesions causing left-sided unawareness.
• This view assumes the left hemisphere lacks awareness for its contralateral side.

Purpose of the Study:

• To investigate the awareness capabilities of the isolated left hemisphere in patients with complete forebrain commissurotomy.
• To re-evaluate the underlying mechanisms of unilateral neglect syndrome.

Main Methods:

• Administered lateralized tests for left hemineglect to three split-brain patients.
• Assessed awareness for the left side of the body and extrapersonal space in the disconnected left hemisphere.

Main Results:

• The disconnected left hemisphere demonstrated significant awareness of the left body and space.
• This awareness was considerably greater than predicted by unilateral lesion data.

Conclusions:

• The independent left hemisphere possesses cognitive mechanisms to prevent neglect syndrome.
• The explanation for unilateral neglect must address the failure of left hemisphere compensation following right-sided lesions.