O-07 Sensory high-frequency-neural-oscillations play a role in the timing of excitatory-inhibitory balance of the human brain

Abstract

Background Two consecutive high frequency bursts (around 600 Hz) are evoked after sensory peripheral stimulation (s-HFO). The early burst is probably generated from action potentials of thalamocortical fibres, whereas the late burst might reflect the coordinated pattern of firing between pyramidal cells and GABA-ergic interneurons within the somatosensory cortex. The role of these bursts in the excitatory/inhibitory balance in the sensory-motor cortex in not completely elucidated yet. Material and methods On 24 healthy adults we evaluated the relation between s-HFO and the temporal evolution of short interval afferent inhibition (SAI), which measures the sensory-afferent inhibition on the transcranial magnetic stimulation (TMS) motor output. Moreover, since the primary motor cortex responds to TMS with high frequency oscillation, termed I-waves, we compared it to the s-HFO frequencies. Finally, we investigated the relation with the somatosensory temporal discrimination task, a measure of the re-established sensory readiness, which allows the perception of a new stimulus after the end of the inhibitory time interval. Results Our correlation analyses disclosed that late and early burst of s-HFO are associated with the magnitude of sensory afferent inhibition in the primary motor cortex (M1) in a time-dependent manner. Interestingly, the frequency of intracortical s-HFO parallels with that of I-waves in M1. On the opposite the early s-HFO are connected to the temporal perception of incoming sensory stimuli. Conclusions Our findings show a fundamental role of s-HFO in the timing of the excitatory/inhibitory balance in the sensory-motor cortex, information that is fundamental in investigation of neuropsychiatric disorders.