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A cw-probe Z-scan technique was employed to measure the photoinduced index change in a photorefractive SBN:60 crystal. For this experiment a three-detector data-acquisition system was used to account for temporal changes in the laser. The effects of various beam parameters such as intensity, polarization, and wavelength were studied. A theoretical simulation of the Z scan based on a band-transport model of photorefractive-index variation was also developed. This model provides reasonable agreement with the experimental results.

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In this final electroencephalographic (EEG) mapping study of our series on motor dysfunction in neuroleptic-treated schizophrenic patients, we studied 10 right-handed patients with marked negative symptomatology [type II; raw score on the SANS (Munich version) 31.4 +/- 5.1]. Simple and multisensorimotor tasks involving both the dominant and nondominant hand were used for cortical activation. All tasks were referred to resting states obtained after specially designed relaxation procedures. In contrast to predominantly type I patients (SANS-MV score 12.3 +/- 4.9) of our previous EEG mapping studies, we found for resting states minor evidence (only) of increased power values in the frequency bands delta and theta. Furthermore, in contrast to signs of "left hemisphere dysfunction" and possible "compensatory right hemisphere overactivation" during motor tasks, which we discussed previously for our type I patients, we found for the type II schizophrenics a bilateral brain dysfunction. This consisted of "nonreactivity" in all frequency bands except alpha, in which, on the contrary, a "hyperreactivity" seemed to be present. In combination with evidence of bilateral hemispheric dysfunction in type II patients reported by other authors using EEG, evoked potentials, regional cerebral blood flow (rCBF) and magnetic resonance imaging (MRI) methods, this suggests that marked bilateral brain dysfunction may be correlated in schizophrenia with a clinical syndrome corresponding rather to the "negative pole" of the positive-negative dimension. In contrast, "left hemisphere dysfunction" and "signs of compensatory overactivation" seem to be linked more to a "positive" symptomatology. Finally, discrepancies of our EEG mapping and rCBF findings during motor activity suggest, speculatively, "uncoupling" between electrical and circulatory parameters in schizophrenia involving both hemispheres in type II, and predominantly the left hemisphere in type I, patients.

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The brain electrical activity of right-handed normal subjects was studied while they were exposed to auditory stimulation of the music type. The material presented was a note, a scale and a melody, recorded on magnetic tape. Each stimulus condition lasted 45 sec. The first 30 sec were analysed using brain electrical activity mapping in the delta (1-4 Hz), alpha (8-12 Hz) and beta 2 (18-24 Hz) frequency bands. The results showed significant bilateral reaction differences for all conditions, showing a left midtemporal activation predominance for the note and scale conditions, but a right midtemporal and frontal predominance for the melody. The results are discussed in terms of functional specialization for different levels of processing.

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RESUMEN

With a newly developed system of brain electrical activity mapping we studied 10 right-handed, neuroleptic-treated schizophrenics (five of the disorganized, five of the paranoid type, corresponding to 295.1 and .3 in DSM-III), compared with 10 normal controls. Increasingly complex motor tasks were used for cortical activation, all functional states being referenced to resting states recorded after a special relaxation program. We found higher delta and theta amplitudes during rest, as noted in previous studies, and lower beta power values. As a major result, however, we found a widespread left hemisphere dysfunction in schizophrenics, predominantly in the left primary sensory and motor areas. Additionally, we found signs of a "compensatory" overactivation in patients in motor tasks, when this hemisphere is not "used" by normal persons. The results support our findings obtained with this method during multisensory motor coordination in schizophrenia. The results in these patients suggest that these are not merely vigilance, attention, or motivation dysfunctions, but rather specific cortical correlates of impaired motor performance.

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The brain electrical activity of right-handed normal subjects was studied while they were exposed to motor performance tasks that were of increasing difficulty. Each task lasted 45-60 s, and a 30-s period of each task was analyzed by a spectrum analyzer. Data are presented in topographic maps showing the electrical activity for each task, in delta (1-4 cycles [c]/s), alpha (8-12 c/s), and beta 2 (18-24 c/s). The results showed a bilateral decrease in amplitude in sensorimotor areas relative to baseline, for a single hand movement. Tasks that required the programming of movement showed baseline/task differences in amplitude in additional areas; the right frontal area, the prefrontal area, the posterior parietal area, and the left temporal area. The results obtained suggest that different topographical areas are involved in motor tasks that require increased level of programming.

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RESUMEN

Using a newly developed system of brain electrical activity mapping (Alvar Electronics, Paris), we studied 10 right-handed, schizophrenic subjects who had been treated with neuroleptics (5 of the disordered and 5 of the paranoid type) and compared them with 10 controls by applying a cortical activation schedule involving a multisensorimotor coordination task. All tasks were referenced to resting states after a specially designed relaxation program. In schizophrenics, we found high, predominantly bifrontal, delta and theta power values, which is in agreement with the literature, and low beta power values, which are possibly due to the neuroleptic treatment. The major result, however, was a widespread left hemisphere dysfunction during multisensorimotor activation, with a predominance over the primary sensory and motor cortical areas. The area of the supplementary motor regions was not affected. Combined with the evidence of genetic and psychometric studies, our results lend further support to the hypothesis that left hemisphere functioning in schizophrenia is impaired. They also suggest that there is a special and independent sensory and motor processing system impairment in schizophrenia.

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