Spatial attention and interhemispheric visuomotor integration in the absence of the corpus callosum.
|Title||Spatial attention and interhemispheric visuomotor integration in the absence of the corpus callosum.|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Authors||Mooshagian, E, Iacoboni M, Zaidel E|
|Date Published||2009 Feb|
|Keywords||Adult, Agenesis of Corpus Callosum, Attention, Corpus Callosum, Functional Laterality, Humans, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Male, Middle Aged, Motion Perception, Neural Pathways, Psychomotor Performance, Reaction Time, Space Perception, Visual Perception|
In the lateralized simple reaction time (SRT) task with unimanual responses (Poffenberger paradigm), reaction times (RTs) are faster with ipsilateral (uncrossed) than with contralateral (crossed) response hand-target hemifield combinations. The difference between crossed and uncrossed responses (CUD) has typically been interpreted to reflect callosal transfer time. Indeed, acallosal subjects and split-brain subjects have longer CUDs than control subjects. However, a few recent studies have demonstrated that, contrary to classical findings, the CUD is also affected by non-anatomical factors. Here we show that the CUD is also affected by non-anatomical factors in patients with agenesis of the corpus callosum and complete commissurotomy where interhemispheric transfer must be subcallosal. We tested acallosal subject M.M. and split brain patient A.A. on a lateralized SRT task with their arms alternately uncrossed (natural arms position) or crossed (unnatural arms position) across blocks of trials. The results revealed a significant effect of arms crossing on the size and direction of the CUD as previously found in normal subjects [Mooshagian, E., Iacoboni, M., & Zaidel, E. (2008). The role of task history in simple reaction time to lateralized light flashes. Neuropsychologia, 46(2), 659-664]. This suggests that non-anatomical factors that modulate interhemispheric visuomotor integration may occur in absence of the corpus callosum. Anterior commissure and interhemispheric cortico-subcortical pathways are likely implicated in these effects.