Chen Y, Grossman E, Bidwell L C, Yurgelun-Todd D, Gruber S, Levy D, Nakayama K, Holzman P, 2005, "Underactivation of the sensory system and overaction of the complementary cognitive system during motion perception in schizophrenia" Perception 34 ECVP Abstract Supplement
Underactivation of the sensory system and overaction of the complementary cognitive system during motion perception in schizophrenia
Y Chen, E Grossman, L C Bidwell, D Yurgelun-Todd, S Gruber, D Levy, K Nakayama, P Holzman
Visual motion perception is normally supported by neural processing of the sensory system. Indeed, focal damage to motion-sensitive areas such as the middle temporal area (MT) induces an acute motion-perception impairment that may recover gradually over time. It is unclear how distributed cortical damage affects motion perception and its neural correlates. Schizophrenia, compared with neurological disorders, shows (i) few signs of gross organic changes in any single cortical area, but (ii) a variety of functional abnormalities including motion perception. This mental disorder may thus provide a model for understanding the roles of cortical network in motion processing. Here, we studied the pattern of cortical activations, measured by functional magnetic resonance imaging (fMRI), during motion as well as non-motion discrimination in schizophrenia patients (N = 10) and normal people (N = 8). Psychophysical thresholds of three visual tasks, direction discrimination, velocity discrimination (both motion), and contrast discrimination (non-motion), were measured first. For fMRI, task difficulty conditions were set (a) at easy levels (70% of motion coherence for direction discrimination, 50% difference in velocity for velocity discrimination, 80% difference in contrast for contrast discrimination; performance: 90% correct or better) and (b) at difficult levels (two times perceptual thresholds of individual subjects; performance: 70% correct or better). Compared with normal controls, cortical response in patients was shifted from occipital to frontal regions during direction and velocity discrimination but not during contrast discrimination. The fMRI BOLD signals to motion discrimination in schizophrenia were significantly reduced in MT and significantly increased in the left inferior convexity of the prefrontal cortex (ICPFC), which is normally involved in high-level cognitive processing, such as visual object representation. This shift in neural processing suggests a recruitment of the complementary cognitive system to compensate for the deficient sensory system for motion perception in schizophrenia.
[Supported by NIH, NARSAD, and the Milton Fund of Harvard University.]
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