Limitations of interhemispheric extracallosal transfer of visual information in callosal agenesis.
A 57-year-old patient with callosal but not anterior commissure agenesis was investigated with a visual interfield comparison and a naming task. Stimuli were presented tachistoscopically either bilateral-simultaneously or unilaterally in the LVF and/or RVF. The stimuli presented bilaterally differed with respect to their degree of similarity. Whereas the patient was able to detect gross differences between stimuli presented in the left and right half-field, he was impaired at discriminating similar and identical stimuli across the half-fields. Identification by naming was correct on unilateral presentation of a stimulus, while with bilateral presentation of two stimuli, errors increased considerably with the stimulus named second. The data are thought to indicate a limited capacity of the extracallosal commissures, probably the anterior, for the transfer of visual information.
Karnath
H O
HO
Department of Neurology, University of Freiburg, F.R.G.
Schumacher
M
M
Wallesch
C W
CW
D061085:Agenesis of Corpus Callosum; D002526:Cerebellar Diseases / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D002544:Cerebral Infarction / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D003337:Corpus Callosum / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D014057:Tomography, X-Ray Computed