Anarchic-Hand-Syndrome with Split-Brain-Symptoms:Mechanisms revealed by ERPs
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1
University of Lübeck, Germany
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2
Univ. of Chemnitz, Germany
The “Anarchic Hand” Syndrome offers a fascinating perspective on the fragile normalcy of the feeling of an integrated self, particularly of the feeling of voluntarily causing one’s own actions. Only few experimentally controlled studies have been reported so far for understanding the neurophysiological bases of the syndrome. We report the case G.H. who, following an infarction of the arteria pericallosa, has suffered from his anarchic left hand and shows signs of a split-brain syndrome. Responses and EEG potentials of G.H. and an age-matched control group were measured in a Simon paradigm. In this task stimuli that require a choice about which hand to use for responding are presented randomly in the left or right visual field, making it necessary to transfer information between hemispheres whenever side of presentation is incompatible with the required side of responding. G.H.’s response times with response-incompatible stimulus sides were much slower with the left than with the right hand. Three features were notable in his EEG potentials: faster activation of the right than the left visual cortex with all stimuli, as indicated by asymmetries of the N1 component, broadly reduced positivity of the right hemisphere at 300-500 ms after all stimuli, and an occipital polarity reversal from left to right at 500 ms specifically with responses of the left hand to stimuli presented on the right. The positivity being reduced in G.H.’s right hemisphere may be interpreted as direct physiological correlate of the subjective loss of control over the right hemisphere. Moreover, the ERPs provided clues about some underlying mechanisms. Most relevant appeared the N1 latency difference between right and left visual cortices, presumably being due to a disturbed balance of top-down regulated neural excitability between hemispheres and possibly causing perceptual processing to occur faster in the right hemisphere. The status of the occipital polarity reversal is unclear; it might reflect compensatory transfer of information via intact posterior parts of the corpus callosum. To summarize, the paradigm proved suitable for quantifying the problem of anarchic hand in this extraordinary patient.
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Oral Presentation
Topic:
Cerebral Asymmetry
Citation:
Verleger
R,
Binkofski
F,
Friedrich
M,
Sedlmeier
P and
Kömpf
D
(2008). Anarchic-Hand-Syndrome with Split-Brain-Symptoms:Mechanisms revealed by ERPs.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.139
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Received:
05 Dec 2008;
Published Online:
05 Dec 2008.
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Correspondence:
Rolf Verleger, University of Lübeck, Lübeck, Germany, 665948@frontiersin.org