Neural mechanisms for perceptual organization based on color and shape similarity revealed by fMRI
Chang, Hsiao-Chueh; Chen, Chien-Chung; Hsu, Chia-Hung; Chen, Jyn HorngDepartment of Psychology, National Taiwan University
MRI Lab., National Taiwan University
Objective. Visual elements with similar properties tend to be grouping together. We investigated the neural mechanisms fore Gestalt principles of similarity and examined whether grouping processes based on different element properties share the same neural mechanisms by using fMRI.
Method. The test stimuli consisted of 6 by 6 elements in different color (red/green) or shape (circle/square). In the color condition, elements with the same color were arranged into columns or rows. In the shape condition, elements with the same shape were arranged into columns or rows. In the compound condition, elements were arranged by both similar color and shape. The control stimuli consisted of elements randomly distributed in the 6 by 6 array regardless of their color or shape. Each of the three block-design runs had one test condition alternating with the control condition in 36s period. The BOLD activation for each subjects was collected on a Brucker 3T magnet (EPI, TR=3s, TE=35ms, flip angle = 90 deg.)
Results. The color condition activated inferior temporal (IT), superior frontal gyrus (SFG), middle frontal gyrus and angular gyrus (AG). The shape condition activated middle occipital gyrus (MOG), AG, SFG and insula. The compound condition activated MOG, IT, SFG and AG.
Conclusion. In all condition, both AG and SFG were activated. Our results suggested that these areas were involved in general processes of grouping by similarity. The color similarity activated IT but not MOG while the shape similarity had an opposite effect. This suggests that there are different neural mechanisms for grouping by similarity based on different element properties.
Method. The test stimuli consisted of 6 by 6 elements in different color (red/green) or shape (circle/square). In the color condition, elements with the same color were arranged into columns or rows. In the shape condition, elements with the same shape were arranged into columns or rows. In the compound condition, elements were arranged by both similar color and shape. The control stimuli consisted of elements randomly distributed in the 6 by 6 array regardless of their color or shape. Each of the three block-design runs had one test condition alternating with the control condition in 36s period. The BOLD activation for each subjects was collected on a Brucker 3T magnet (EPI, TR=3s, TE=35ms, flip angle = 90 deg.)
Results. The color condition activated inferior temporal (IT), superior frontal gyrus (SFG), middle frontal gyrus and angular gyrus (AG). The shape condition activated middle occipital gyrus (MOG), AG, SFG and insula. The compound condition activated MOG, IT, SFG and AG.
Conclusion. In all condition, both AG and SFG were activated. Our results suggested that these areas were involved in general processes of grouping by similarity. The color similarity activated IT but not MOG while the shape similarity had an opposite effect. This suggests that there are different neural mechanisms for grouping by similarity based on different element properties.
Supported by NSC 92-2413-H-002-027
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