Attentional modulation of perceptual grouping in human visual cortex: Functional MRI studies

• Published in: Human brain mapping Vol. 25; no. 4; pp. 424 - 432
• Main Authors: Han, Shihui, Jiang, Yi, Mao, Lihua, Humphreys, Glyn W., Gu, Hua
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.2005; Wiley-Liss
• Subjects: Adult; attention; Attention - physiology; Biological and medical sciences; Brain Mapping; calcarine cortex; Electrodiagnosis. Electric activity recording; Female; fMRI; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Humans; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging; Male; Medical sciences; Nervous system; Parietal Lobe - anatomy & histology; Parietal Lobe - physiology; Perception; perceptual grouping; Photic Stimulation; proximity; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Temporal Lobe - anatomy & histology; Temporal Lobe - physiology; Vision; Visual Cortex - anatomy & histology; Visual Cortex - physiology; Visual Pathways - anatomy & histology; Visual Pathways - physiology; Visual Perception - physiology; Human; Visual cortex; Nervous system diseases; Proximity; Radiodiagnosis; Central nervous system; Attention; perceptual grouping; Nuclear magnetic resonance imaging; Encephalon; calcarine cortex; fMRI; Visual pathway; Modulation
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.20119

When presented with a complex visual scene, our visual system has to organize the discrete entities present into useful perceptual units. The current work investigated the neural substrates of perceptual grouping defined by Gestalt laws of proximity and similarity of shape, and whether the neural substrates underlying perceptual grouping are modulated by task relevance and spatial attention. In visual discrimination tasks, subjects identified the orientations of perceptual groups formed by proximity or similarity of local elements or alternatively identified colors of either dots around the grouped stimuli or the fixation cross. Using functional magnetic resonance imaging (fMRI), we identified that the calcarine cortex was involved in proximity grouping but not in the grouping process defined by similarity of shape. Moreover, we showed evidence that the neural correlates of proximity grouping in the calcarine cortex were weakened when the elements were of low task relevance and fell outside an attended area of field. The findings reveal the neural basis for basic grouping operations, as well as illustrating how attention and proximity grouping interact in human visual cortex. Hum Brain Mapp 2005. © 2005 Wiley‐Liss, Inc.