Sensations and reaction times evoked by electrical sinusoidal stimulation.

OBJECTIVE: To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. METHODS: One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1 x ST and reaction times to 5 Hz currents were also determined at 2 x ST. RESULTS: Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5 x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22s (0.11 to 0.34) for 5 Hz at 2 x ST. CONCLUSIONS: Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Abeta-fibers, 250 Hz Abeta- or A partial differential-fibers, 5 Hz Abeta-, A partial differential- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.

Recomendaçöes referentes ao registro clínico digital do EEG / Recommendations of Digital Clinical Recording (EEG)

Até recentemente o registro do EEG convencional era feito quase exclusivamente em papel, com a análise sendo executada visualmente. Considerando apenas a gravaçäo (aquisiçä) do EEG, pode-se atualmente dividi-la de forma arbitrária em: 1) sistemas convencionais de registro de EEG em papel; 2) sistemas híbridos com registro em papel e a presença de processadores, porém sem registro digital; os processadores podem permitir, por exemplo, a alteraçäo de programas; 3) sistemas do tipo "paperless" näo digital, com registro através de sistema de modulaçäo em "tape"; 4) sistemas de registro digital do EEG (DEEG). A análise do EEG continua sendo feita da forma visual clássica, porém o registro digital permite também executar diferentes tipos de processamento do sinal do DEEG. Estas recomendaçöes, envolvendo apenas aspectos referentes ao registro clínico digital do EEG, representam o trabalho de uma comissäo organizada pelo departamento de mapeamento topográfico da SBNC e visam näo somente delinear requisitos mínimos como também comentá-los do ponto de vista didático