Visual-spatial attention was examined in two 14-year-olds who had undergone occipital-parietal craniotomies for removal of mesial parietal tumors, one in the right and one in the left hemisphere. Neither patient showed clinically significant visual neglect. They were administered two visual search tasks from Treisman and Souther  that make significantly different demands on visual-spatial attention. In feature-present (parallel) search, they searched for the presence of a feature. In feature-absent (serial) search, they searched for its absence. Search rate was estimated from the slope of the function relating display size to response time. Both patients had flat slopes in feature-present search to target-present (TP) displays, indicating that they could conduct parallel search at the same rate as controls. Although the patient with the right-hemisphere lesion also had a flat slope to target-absent (TA) displays, the patient with the left- hemisphere lesion had a steep slope (30 ms/item) in this condition. In feature-absent search, the patients had equally slow search rates compared to controls, suggesting that the mesial parietal cortex is part of the network that mediates serial shifts of attention. Results support the distinction between detection of the target in parallel vs serial search and suggest that processes involved in TP and TA trials in parallel search are also dissociable.
Bibliographical noteFunding Information:
We thank D, J, and their families for participating in the research project. We are grateful to Joshua Emerson, BA for preparing the drawings and to Patrick Carlyle for writing the computer programs for presenting and analyzing the data. This research was supported in part by a grant to Robert F. Asarnow, PhD from the Della Martin Foundation and by a grant to Jorge A. Lazareff, MD from the Friends of Pediatric Neurosurgery.
- Hemispheric differences
- Visual-spatial attention