A fuzzy clustering approach to study the auditory P50 component in schizophrenia

Author(s): Boutros, N. N., Jansen, B. H.

Journal/Book: Psychiatry Res. 1997; 69: Customer Relations Manager, Bay 15, Shannon Industrial, Estate Co, Clare, Ireland. Elsevier Sci Ireland Ltd. 169-181.

Abstract: We have recently provided evidence that selective evoked response averaging based on a fuzzy clustering approach is a useful way to increase the signal-to-noise ratio, particularly when recording low-amplitude components, such as the auditory P50. We have also reported that, when stimuli are delivered in pairs (S-1 followed by S-2) with a short interstimulus interval, the first stimulus (S-1) results in synchronization of the EEG producing a large-amplitude evoked response, whereas the second stimulus (S-2) causes phase opposition resulting in a lower amplitude average evoked response. In the current study we reanalyzed data previously obtained from 13 normal volunteers and 17 chronic schizophrenia patients. Our results show that the partial EPs corresponding to the S-1 stimulus are highly synchronized in normal subjects but not in schizophrenia patients. However, such a synchronization is not present after delivery of the S-2 stimulus, neither in normal controls nor in patients. These findings are in agreement with previous reports of decreased amplitude of the S-1 response without a significant further decrease in the amplitude of the S-2 response in schizophrenia patients.

Note: Article Zouridakis G, Univ Texas, Sch Med, Dept Neurosurg, 6431 Fannin, Suite 7148, Houston,TX 77030 USA

Keyword(s): evoked potentials; fuzzy clustering; EEG synchronization; sensory gating; P50 attenuation; EVOKED-RESPONSE; RELIABILITY

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