This study compares the effectiveness of the frequency-based recognition of short acoustic stimuli in groups of adolescents with attention deficit and normal measures of attention in conditions of the standard "oddball" paradigm. Stimuli of duration 50 msec yielded insignificant intergroup differences, though adolescents with attention deficit discriminated signal of duration 11 msec significantly worse. These showed significant differences in evoked brain potentials even with standard stimuli, with a significantly greater amplitude for N2b waves and a decreased P3b component. Evoked potentials obtained in response to the deviant stimulus were characterized by a P3b wave of reduced amplitude in the group with attention deficit. These data provide evidence that adolescents with attention deficit show defined abnormalities in the processing of acoustic sensory information at the cortical level.
Our aim was to study the influence of fatigue development on sensory gating during a muscle load. The fatiguing task was sustained contraction of a handgrip dynamometer with 7 and 30% maximum voluntary contraction (MVC). The suppression of P50, an auditory event-related potential, was used as the sensory gating index in the paired-click paradigm with a 500 ms interstimulus interval; the difference between the P50 amplitudes of the first and the second stimuli of the pair was used as the sensory gating index. We found that the 30% MVC fatigue development strongly decreased sensory gating, sometimes totally suppressing it. We concluded that central fatigue impaired motor performance and strongly suppressed inhibitory processes, as shown by the decreased P50 amplitude to the second stimulus. Therefore, muscle central fatigue influences sensory gating, similar to schizophrenia spectrum disorders.
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