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Study findings suggest attenuation of normal pseudoneglect in patients with schizophrenia and accentuation of pseudoneglect in patients with bipolar affective disorder (BPAD).
“Together, these findings indicate less cerebral lateralization in schizophrenia and perhaps greater lateralization in BPAD,” say Ganesan Venkatasubramanian and colleagues from the National Institute of Mental Health and Neurosciences in Bangalore, India.
Cerebral asymmetry is a unique feature of the human nervous system, and previous research has shown aberrant lateralization in patients with schizophrenia, increasing rates of left-handedness and reversing normal cerebral symmetries. Lateralization in patients with BPAD, however, has not been greatly studied.
The researchers used the line bisection task to examine laterality in 31 patients with BPAD in remission, 30 patients with schizophrenia, and 103 mentally healthy controls.
The test involves participants bisecting horizontal lines printed and arranged on either side of a sheet of paper. Mentally healthy individuals will have a tendency to bisect lines left of midline, as the right hemisphere dominates in spatial tasks; this is known as “right pseudoneglect.”
Damage in the right hemisphere results in the neglect of left hemispace and a marked tendency to bisect horizontal lines to the right of midline, the researchers explain.
The results showed that, on the whole, patients with schizophrenia or BPAD bisected significantly fewer lines at center than mentally healthy controls, with schizophrenia patients bisecting the fewest lines at center.
Using the right hand, schizophrenia patients showed significant deviation to the right of midline (total percentage deviation 10.6%), while BPAD patients showed significant deviation to the left (total percentage deviation 51.73%). However, no significant differences were seen with the left hand. Mentally healthy controls showed a tendency toward left deviation, but not to the extent seen in BPAD patients, at a total percentage deviation of just 2.02%
When the percentage deviation from both hands for each direction was calculated for the patients, a significant rightward deviation was evident for patients with schizophrenia, while a trend toward leftward deviation was seen for BPAD patients.
“Our study findings suggest attenuation of normal pseudoneglect in schizophrenia and its accentuation in BPAD, indicating less lateralization in schizophrenia and possibly greater lateralization in BPAD,” the team reports in the journal Bipolar Disorders.
“Thus, from an evolutionary perspective, schizophrenia, and BPAD might have antithetical origins.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
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