Show Reference: "A general deficit of the 'automatic pilot' with posterior parietal cortex lesions?"

A general deficit of the 'automatic pilot' with posterior parietal cortex lesions? Neuropsychologia, Vol. 44, No. 13. (2006), pp. 2749-2756, doi:10.1016/j.neuropsychologia.2006.04.030 by Marc Himmelbach, Hans-Otto Karnath, Marie-Therese Perenin, Volker H. Franz, Kerstin Stockmeier
@article{himmelbach-et-al-2006,
abstract = {Lesions of the parieto-occipital junction ({POJ}) in humans cause gross deviations of reaching movements and impaired grip formation if the targets are located in the subjects' peripheral visual field. Movements to central targets are typically less impaired. This disorder has been termed "optic ataxia". It has been suggested that a general deficit of online corrections under central as well as peripheral viewing conditions might be sufficient to explain this discrepancy. According to this hypothesis, patients with optic ataxia should demonstrate an impaired online correction of grip aperture under central viewing conditions if the target object changes its size during the grasping movement. We investigated this prediction in a patient with optic ataxia ({I.G}.) in a virtual visuo-haptic grasping task. We imposed an isolated need for online corrections of the hand aperture independently of positional changes of the target object. While we found some general inaccuracies of her grasping movements, the patient did not show a specific impairment of online adjustment of grip aperture. On the contrary, {I.G}. smoothly adjusted her grip aperture comparable to healthy subjects. A general deficit of fast movement correction affecting targets in peripheral as well as central visual fields thus does not appear to account for the overt visuomotor deficits in optic ataxia. Rather, it seems more likely that an anatomical dissociation between visuomotor pathways related to actions in the central and in the peripheral visual field underlies the dissociation of visuomotor performance depending on the retinotopic target position in optic ataxia.},
address = {Section Neuropsychology, Center of Neurology, Hertie-Institute for Clinical Brain Research, University of T\"{u}bingen, Hoppe-Seyler-Str. 3, 72076 T\"{u}bingen, Germany.},
author = {Himmelbach, Marc and Karnath, Hans-Otto and Perenin, Marie-Therese and Franz, Volker H. and Stockmeier, Kerstin},
doi = {10.1016/j.neuropsychologia.2006.04.030},
issn = {0028-3932},
journal = {Neuropsychologia},
keywords = {grasping, haptic, multisensory-integration, reaching, visual},
number = {13},
pages = {2749--2756},
pmid = {16777146},
posted-at = {2013-07-09 11:14:46},
priority = {2},
title = {A general deficit of the 'automatic pilot' with posterior parietal cortex lesions?},
url = {http://dx.doi.org/10.1016/j.neuropsychologia.2006.04.030},
volume = {44},
year = {2006}
}


People with lesions of the parieto-occipital cortex (POJ) are impaired in reaching and grasping objects in their peripheral visual field (an effect called 'optic ataxia').

Himmelbach et al. studied one patient in a visuo-haptic grasping task and found that she had a healthy-like ability to adapt her grip online to changes of object size when it was in the central viewing field. This indicates that the problem for patients with lesions of parieto-occipital cortex (POJ) is not an inability to adapt online, but more likely the connection between visuomotor pathways and pathways necessary for grasping.