Efeitos dos estímulos elétricos senoidais na resposta induzida cerebral: estudo da seletividade das fibras sensitivas

Abstract

Different frequencies of the sine-wave electric stimulation (EES) would activate the Aβ (2 and 3 kHz) and C (5 Hz) fibers specifically, especially at intensities close to the sensorial threshold (LS). The EES-induced cortical responses are unknown, in addition to whether they are capable of differentiating between the tactile and thermoalgesic systems. The present study investigated EEG’s induced responses through synchronism and desynchronism index (ERD/ERS) during ESS. The LS, reaction time, cognitive response and ERD/ERS profiles of the alpha, beta, gamma and high-gamma bands were evaluated 3 kHz and 5 Hz, at intensities 1,2xLS, 2xLS and 3xLS. Results indicate habituation in the contralateral parietal region for the 3 kHz stimulus, as opposed to 5 Hz’s, at 1.2xLS in the alpha band. Results show lower latencies at 3 kHz in the bilateral sensorimotor region (beta band), also in 1.2xLS. Both results suggest fiber activation selectivity at intensities close to LS. At 3xLS, this was not observed, suggesting fiber coactivation. An increase in energy observed in the higher bands for 3 kHz in 3xLS suggest a greater intensity perceived, also reported in the cognitive evaluation. Psychophysical studies of LS and sensations subjectively perceived during EES are important for the evaluation of patients with peripheral neuropathies (ex., leprosy and neuropathic diabetes). Induced brain responses may have applicability as a new alternative in cognitive evaluation to EES (including patients with central lesions, such as in stroke).