Effect of lateralization on motor and mental speed in bipolar disorder

Effect of lateralization on motor and mental speed in bipolar disorder Objective: The correspondence between the motor and mood regulation systems may shed light on the physiopathology of mood disorders. Handedness is a reliable proxy measure for cerebral lateralization for right handed subjects. In this study we have investigated the effects of lateralization on cognitive performance as well as motor and mental speed in bipolar disorder. Methods: Sixty-eight euthymic bipolar patients (mean age: 33.66 +/- 6.38, 33 female), and 65 healthy subjects (mean age: 33.65+7.11, 27 females) were enrolled. Participants with medical or psychiatric comorbidities were excluded. The Montreal Cognitive Assessment (MOCA), finger-tapping, peg-board test, Adult Memory and Information Processing battery (AMIPB), Edinburgh Handedness Inventory and reaction time tests were the measures utilized in our study. Results: The groups were similar in terms of age, gender and education. The bipolar patients were more lateralized than the controls (p=0.027), whereas eye and foot lateralization did not differ between the groups. The patients performed poorer than the controls on the MOCA (p=0.049), peg-board (right and left, p<0.001), finger-tapping (right p<0.001; left p=0.002), AMIPB (motor and A subtest, p<0.001 for both) and the visual and auditory (p<0.001 for both) reaction time tests. The degree of lateralization was correlated with the speed of processing in the bipolar group, but not in the control group. Conclusion: Right handed patients with bipolar disorder are more lateralized than healthy subjects and lateralization provides an advantage for processing speed in bipolar patients. This finding may indicate a relationship between lateralizing physiopathology and slowed interhemispheric communication and thus, an increase in lateralization might be a compensatory mechanism to use less interhemispheric communication in bipolar disorder.