Search

Background: Oculomotor abnormality is one of the endophenotypes in schizophrenia. The predictive component of smooth pursuit can be studied by comparing the gain, i.e., the ratio of smooth eye position to target position, during predictable (pure sinusoidal) and unpredictable (pseudorandom) target motions. The aim of this experiment was to study predictive and nonpredictive components of smooth pursuit in two groups of schizophrenia patients compared with control subjects., Methods: Fifty-one schizophrenia patients (40 nondeficit and 11 deficit) and 21 control subjects were studied. During a predictable task, subjects were asked to track a sinusoidal target (.4 Hz). For the unpredictable task, the pseudorandom target motion consisted of five superimposed sinusoidal waveforms (.1, .2, .4, .6, and .8 Hz). The smooth eye position (eye position without saccades), gain, and phase were calculated for each frequency in each participant and for both tasks., Results: The mean sinusoidal smooth eye position gain was significantly lower in patients than in control subjects with no significant difference between deficit and nondeficit patients. During the pseudorandom task, all groups had a similar gain at .4 Hz., Conclusions: Our study reveals that patients have a normal nonpredictive component of smooth pursuit, regardless of their level of negative symptoms. In contrast, the predictive mechanisms involved in eye pursuit were impaired in schizophrenia patients. These results indicate that poor pursuit performance during smooth pursuit is primarily a consequence of a predictive problem and is not related to the ability to generate an accurate pursuit maintenance response., (Copyright 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Abnormal sensory gating in schizophrenia has frequently been reported. The strength of central inhibitory pathways was measured using the P50 component of the auditory evoked potential in a conditioning-testing paradigm. The relationships between a relative decrease in P50 amplitude to repeated auditory stimuli and clinical symptoms remain controversial. Using the Positive and Negative Syndrome Scale, we studied the P50 auditory conditioning-testing paradigm in 81 schizophrenic subjects, categorized into subgroups with and without prominent negative symptoms, in comparison with 88 control subjects. We found increased ratios of testing stimuli to conditioning stimuli in both schizophrenic subgroups relative to findings in the control group. In addition, we found significantly increased mean latencies of the P50 responses to conditioning (C) and testing (T) stimuli and significantly increased T/C ratios in the subgroup with negative symptoms compared with the subgroup with non-negative symptoms.

Objective: The authors evaluated concordance rates among three electrophysiological measures in patients with schizophrenia, nonschizophrenic first-degree relatives of schizophrenia patients, and healthy comparison subjects. The purpose of the study was to provide data for defining a common endophenotype for genetic studies of schizophrenia and for improving the criteria for diagnosis., Method: P50 event-related potential inhibition, antisaccade, and smooth pursuit eye tracking paradigms were measured. Data for all three paradigms were available for 81 patients with schizophrenia, 25 parents of patients with schizophrenia, and 60 healthy comparison subjects., Results: The schizophrenia patients and the patients' parents showed a high rate of inhibitory deficits measured by the P50 inhibition and antisaccade paradigms. Both groups had a high prevalence of eye tracking dysfunction. Smooth pursuit gain and the error rate in the antisaccade paradigm were significantly correlated in the schizophrenia patients and the parents, whereas P50 inhibition showed no correlation with smooth pursuit gain or antisaccade paradigm measurements., Conclusions: Despite superficial similarities, two paradigms designed to measure central inhibition processes (antisaccade and P50 inhibition) do not appear to reflect the same neurobiological substrates. In contrast, the convergence in performance data for the antisaccade and eye tracking paradigms suggests that the neural circuitry underlying these tasks may overlap. P50 inhibition and antisaccade errors were the optimal paradigms for discrimination between comparison subjects, patients with schizophrenia, and the parents of patients with schizophrenia.

Abnormality in the P50 auditory-evoked potential gating is an endophenotype associated with schizophrenia. Biochemical and genetic studies have suggested that the alpha 7 nicotinic acetylcholine receptor (nAChR) is involved in this sensory gating deficit. Two related alpha 7 genes (CHRNA7 and CHRNA7-like gene) resulting from a partial duplication (from exon 5 to exon 10) are present in the human genome. Two types of genetic variation, a large deletion and a -2 base-pair deletion in exon 6 resulting in a truncation of the open reading frame, affect specifically the CHRNA7-like gene. We developed a simple multiplex PCR assay on genomic DNA, allowing the quantification of the number of exons 6 and the distinction of all possible exon 6 genotypes. Genotyping of 70 schizophrenic patients and 77 controls showed that carrying at least one -2 bp deletion of exon 6 did not constitute a risk factor for schizophrenia. In contrast, the distribution of genotypes differed significantly between subjects with normal and abnormal P50 ratios, with an over-representation of genotypes carrying at least one -2 bp deletion of exon 6 among subjects exhibiting an abnormal P50 ratio. We thus conclude that the -2 bp deletion within the CHRNA7-like gene is a risk factor for P50 sensory gating deficit. Interestingly, most of the effect came from the non schizophrenic group, which may suggest that in schizophrenic patients other risk factors account for the large proportion of subjects exhibiting an abnormal P50 ratio.

A 44-year-old woman demonstrated a musical hallucinosis four months after a massive infarction in the territory of the right middle cerebral artery. This musical hallucinosis consisting of familiar tunes, was continuous and perceived by both ears. Magnetic Resonance Imaging, middle and late auditory evoked potentials suggested that right Heschl's gyrus and associative areas were imparied. Audiometry demonstrated a low right transmission deafness. The hallucinosis was persistent for seven months and stopped just after hemorrhage of the right ear. This case gives the opportunity to review the different mechanisms responsible for musical hallucinosis.

We have analyzed eye movement performances in schizophrenics showing primary negative or deficit symptoms (n=16) and non-deficit schizophrenics (n=55), and compared them with those of controls (n=34) in order to study the relationships between negative symptoms and eye movement abnormalities. Patients were subtyped into deficit and non-deficit subgroups using the Schedule for the Deficit Syndrome. Three oculomotor paradigms were used: smooth pursuit, a reflexive saccade paradigm and an antisaccadic task. The smooth pursuit gain was significantly decreased (and the rate of catch-up saccades increased) in schizophrenics as compared with controls, but no difference was observed between patient groups. In the reflexive saccade paradigm, no difference was found between controls and patients, except for latency in deficit patients. In the antisaccade paradigm, the number of errors and the latency of successful antisaccades were significantly increased in schizophrenics as compared with controls. The latency of successful antisaccades in both directions was significantly increased in deficit patients as compared with non-deficit patients. The latency of rightward successful antisaccades was significantly increased as compared with the latency of leftward antisaccades in deficit patients only. However, when patients were classified into negative and non-negative groups using the PANSS, no difference was found in the antisaccade paradigm. Smooth pursuit impairment does not seem to depend on the primary enduring negative symptoms.In deficit schizophrenics, the abnormalities observed in the antisaccadic task are consistent with prefrontal dysfunction, and may suggest parietal lobe dysfunction as well.

The Swedes for more than twenty years, and the Germans for over five years have been able to maintain inert or active prostheses with permanent percutaneous connections, thanks to the dependable and proven material and techniques of extraoral implants. The significant improvement extra-oral implants have brought about is not only in a new therapeutic approach to the treatment of important facial defects or transmission deafness; it is also because for some twenty old years now, the few millimeter wide cylinders of Titanium, the <> affixed on the implants, have crossed the cutaneous barrier for extended periods without complications. The percutaneous abutment thus creates a permanent communication between the interior and the exterior of the organism. If the abutment, instead of simply carrying a Maxillo-Facial Prosthesis or an auditive prosthesis, is modified by placing an electric conductor inside it, the simple "percutaneous peg" will turn out to be, in a way, a "percutaneous electric plug". By adapting classic "mechanical" abutments and implants, authors have created a Permanent Percutaneous Electric Connection (PPEC) which has been successfully experimented on rabbits to record EEG. Clinical applications on humans would make it possible either to receive "bio-electrical information" coming from within the organism, or to send electrical energy into the organism. This last application opens vast perspectives of improvement both in diagnosis and therapy in many fields.

A 27 year-old man initially considered as a schizophrenic patient was later diagnosed as having Kleine-Levin syndrome.

Smooth-pursuit eye movements (SPEM) were assessed in healthy subjects and in drug-naive, chronic, and residual schizophrenic patients. SPEM gain was found to be decreased in all the schizophrenic patients who also exhibited a significant increase in the rate of saccades. The frequency of square-wave jerks was the same in schizophrenic patients and normal controls, suggesting that the primary abnormality in schizophrenic patients was a low gain rather than a defect of the saccadic system. Patients were retested 1 month later, and stability of gain was high even in formerly drug-naive subjects who had been treated for 1 month with neuroleptic drugs. Altogether these results confirm the conclusions of most previous studies, extend them to drug-naive schizophrenic patients, and favor the hypothesis that SPEM impairment is a trait marker in schizophrenia.

A method first described in 1978, and improved since that date, is a reliable mean of assessing gain in hearing from prosthetic aids by the use of brain stem early auditory evoked potentials. The type of signal used with the prosthesis must be the click and click type with a high-pass filter, and the principle of shunt potentials must be applied.

The authors describe the results of click at a recurrence frequency of 10 C/S in evoked responses of the brain stem, firstly in twenty normal individuals, with headphones or in a free area, making it possible to define a range of physiological responses to the different intensities, then in seventeen pathological individuals consisting of six cases of conduction deafness and eleven of perceptive deafness. On the basis of this study, they attempt to demonstrate the value of this type of examination not only in the determination of objective auditory threshold, but also in that of the type of deafness: conductive or perceptive. The method even makes it possible to approximately define the general appearance of the frequency distribution at the threshold according to the slope of the different latencies of P5. In the opinion of the authors, the chief advantages are the decrease in the time required for the test and the possibility of its use in the study of prosthetic gain.

By means of spectral analysis, this research of alpha rhythm's modifications upon effects of electromagnetic fields makes conspicuous an increasing frequency and amplitude of this rhythm, proportionally to the time passage, and proposes questions and interpretations.