Processing of global, but not local, motion direction is deficient in schizophrenia.
Visual motion processing is compromised in a substantial proportion of schizophrenic patients, but precise neural mechanisms underlying the motion-processing deficit have not yet been elaborated. The visual motion pathway includes a local and a global processing stage, each of which has distinct neural substrates. Here, we attempt to identify the stage(s) that are implicated in impaired motion processing of schizophrenia-local, global, or both. For schizophrenia patients (n=23) and normal controls (n=26), we measured (1) the thresholds for detecting the motion direction of a random dot pattern, a task that requires global motion processing, and (2) the thresholds for detecting the motion direction of a grating, a task that requires only local motion processing, using psychophysical methods. Schizophrenia patients showed elevated thresholds for detecting the direction of coherent motion, particularly for the high dot-density target. In contrast, schizophrenia patients showed normal thresholds for detecting the direction of motion of a grating. The results indicate that the global, but not the local, processing stage of the visual motion system is compromised in schizophrenia patients, thus implicating motion-sensitive brain areas that possess large receptive fields for spatial and temporal integration, such as Middle Temporal Area/Medial Superior Temporal Area.
Department of Psychiatry, Harvard Medical School/McLean Hospital, USA. ychen@wjh.harvard.edu
Y
Y
Chen
K
K
Nakayama
D
D
Levy
S
S
Matthysse
P
P
Holzman
D000328:Adult; D001288:Attention; D005260:Female; D005364:Field Dependence-Independence; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception; D009483:Neuropsychological Tests; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics; D011698:Pursuit, Smooth; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology; D012684:Sensory Thresholds