Amplitude Of Late Positive Component Research Articles

Effects of methylphenidate on hyperactive children's evoked responses during passive and active attention.

ABSTRACTEighteen hyperactive clinical responders to methylphenidate were taken off medication and tested in two sessions during which they received an acute dose of methylphenidate and placebo in counterbalanced order. Seventeen normal boys of comparable age were tested without drugs. For both samples, evoked potentials were recorded during a Continuous Performance Test. Normal children made fewer errors of commission and omission and displayed faster reaction times than hyperactives tested under placebo. In addition, under active attention, the late positive component (LPC) of placebo‐treated hyperactive boys' evoked responses exhibited smaller amplitude than normal controls'. Methylphenidate increased the amplitude of hyperactive patients' LPC and generally ameliorated their performance, especially commission errors and reaction times. The results confirmed previous findings of attentional disturbance in hyperactivity and normalization by methylphenidate of these patients' performance and electrophysiological activity during sustained attention.

VERs in normal and disabled adult readers.

ABSTRACTThe purposes of this study were to assess the visual evoked response (VER) technique in localizing the reading process and to explore VER differences between normal and disabled readers. VERs recorded from O1, O2, P3, and P4, all referenced to linked mastoids, were obtained from 9 normal and 9 carefully selected disabled adult readers under two test conditions: a series of non‐patterned flashes of light viewed passively and a series of common three‐letter words containing a target word. Peak‐to‐peak amplitude for P100‐N140 and N140‐P200, and amplitude from baseline for P200 and the late positive component (LPC) were obtained. The data were examined for hemispheric, parietal‐occipital, and group differences. The main findings were: 1) increased amplitude for P200 and the LPC on the left side for word stimuli only, 2) increased LPC amplitude on the parietal leads compared to occipital for flash and word stimuli with greater increase for words, and 3) a larger difference between words and flash on the left parietal electrode for normals compared to disabled on the P200 and LPC measures.

The late positive component of the auditory evoked potential in a shared reading and counting task

Eight subjects were presented with a series of low and high tones. When they were instructed to ignore the tones and perform a reading task, the late positive component (LPC) of the evoked EEG was absent. Both tones, however, produced LPCs when S counted the higher tone, with the counted tone showing greater LPC amplitude. Under a shared reading and counting task, LPC amplitudes were reduced and comparable to those observed in the read-only condition. These results were interpreted as most consistent with a selective attention hypothesis of the LPC.