J Korean Neurol Assoc.
2003 Aug;21(4):364-371.
Effect of Cerebral Hemispheric Lesions on the Perception of Shape Distortion
- Affiliations
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- 1Department of Neurology, College of Medicine, Seoul National University, Korea. jisookim@snu.ac.kr
Abstract
- BACKGROUND
When two shapes are presented briefly and in succession, the perceived form of the second shape (test)is dissimilar to the form of the first shape (priming). This shape distortion effect may originate from the adaptation of non-retinotopic neurons in higher visual areas of the ventral stream. To determine effects of cerebral lesions on the perception of shape distortion, we measured the distortion effect in 25 patients with cerebral hemispheric lesions. METHODS: For each trial, a priming rectangle, a test circle, and a random-dot mask were flashed in succession with a gap of 180 ms. The priming rectangle and test circle were presented in each quadrant of the visual fields. Using the method of adjustment, the percent elongation of the reproduced circle or ellipse was computed after each trial. The extent of lesions in the brain MRI of each patient with abnormal shape distortion effects was mapped on templates of brain anatomy. RESULTS: Ten patients showed subnormal shape distortion effects. In patients with subnormal distortion effects, brain lesions were overlapped in the posterior part of the mid and inferior temporal lobes. The cortical area in the overlap region encompassed the Brodmann area 37, the posterior aspect of area 21, and the ventrocaudal portion of area 39. CONCLUSIONS: The perception of shape distortion is impaired after damage to the posterior part of the mid and inferior temporal lobes. The results provide evidence that the distortion effect depends on the coding of cells in the ventral stream.
