Abstract
Paired associative stimulation (PAS), a form of non-invasive cortical stimulation pairing transcranial magnetic stimulation (TMS) with a peripheral sensory stimulus, has been shown to induce neuroplastic effects in the human motor, somatosensory and auditory cortex. The current study investigated the effects of acoustic PAS on late auditory evoked potentials (LAEP) and the influence of tone ...
Abstract
Paired associative stimulation (PAS), a form of non-invasive cortical stimulation pairing transcranial magnetic stimulation (TMS) with a peripheral sensory stimulus, has been shown to induce neuroplastic effects in the human motor, somatosensory and auditory cortex. The current study investigated the effects of acoustic PAS on late auditory evoked potentials (LAEP) and the influence of tone duration and placebo stimulation. In two experiments, 18 participants underwent a PAS with a 4kHz paired tone of 400ms duration using 200 pairs of stimuli (TMS-pulse over the left auditory cortex 45ms after tone-onset) presented at 0.1Hz. In Experiment 1 this protocol was contrasted with a protocol using a short paired tone of 23ms duration (PAS-23ms vs. PAS-400ms). In Experiment 2 this PAS protocol was contrasted with sham stimulation (PAS-400ms-sham vs. PAS-400ms). Before and after PAS, LAEP were recorded for tones of 4kHz (same carrier frequency as the paired tone) and 1kHz as control tone. In Experiment 1, there was a significant difference between LAEP amplitudes of the 4kHz tone after PAS-23ms and PAS-400ms with higher LAEP amplitudes after PAS-23ms. Before both conditions, no difference could be detected. In Experiment 2 we observed a significant overall decrease in LAEP amplitudes pre to post PAS. Unspecific decreases of LAEP following PAS with a long paired tone (PAS-400ms) might be related to habituation effects due to repeated presentation of sound stimuli which are not evident for PAS with a short paired tone (PAS-23ms). Interpreting this result using the concept of temporal integration time allows us to discuss it in the context of spike-timing dependent plasticity.
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