Qualitative and quantitative aspects of information processing in first psychosis: latent class analyses in patients, at-risk subjects, and controls.

We aimed to determine profiles of information processing deficits in the pathway to first psychosis. Sixty-one subjects at ultrahigh risk (UHR) for psychosis were assessed, of whom 18 converted to a first episode of psychosis (FEP) within the follow-up period. Additionally, 47 FEP and 30 control subjects were included. Using 10 neurophysiological parameters associated with information processing, latent class analyses yielded three classes at baseline. Class membership was related to group status. Within the UHR sample, two classes were found. Transition to psychosis was nominally associated with class membership. Neurophysiological profiles were unstable over time, but associations between specific neurophysiological components at baseline and follow-up were found. We conclude that certain constellations of neurophysiological variables aid in the differentiation between controls and patients in the prodrome and after first psychosis.

Quantification of the auditory startle reflex in children.

OBJECTIVE: To find an adequate tool to assess the auditory startle reflex (ASR) in children. METHODS: We investigated the effect of stimulus repetition, gender and age on several quantifications of the ASR. ASR's were elicited by eight consecutive auditory stimuli in 27 healthy children. Electromyographic activity of orbicularis oculi, masseter, sternocleidomastoid, deltoid, abductor pollicis brevis, quadriceps muscles and the sympathetic skin response were recorded. ASR parameters (response probability in % and magnitude in area-under-the-curve) were: (1) combined response of all six muscles (2) blink response. RESULTS: Response probabilities were 78% in orbicularis oculi (median latency 41 ms), 17% in sternocleidomastoid (median latency 66 ms), 10% in masseter (median latency 66 ms) and lower in other muscles. The ASR combined response probability and the sympathetic skin response significantly decreased with the repetitive stimuli, but the blink response probability did not. The magnitude (area-under-the-curve) of both the blink response and the combined response did not decrease with the repetitive stimuli. There were no gender or age effects. CONCLUSION: As in adults, the blink response and the combined response of multiple muscles show different habituation patterns in children. SIGNIFICANCE: Investigation of multiple muscles seems appropriate to quantify the ASR in children.