Individual Resonant Frequencies at Low-Gamma Range and Cognitive Processing Speed

Abstract

Brain electrophysiological activity within the low gamma frequencies (30–80 Hz) has been proposed to reflect information encoding and transfer processes. The 40-Hz auditory steady-state response (40-Hz ASSR) is frequently discussed in relation to changed cognitive processing in neuropsychiatric disorders. However, the relationship between ASSRs and cognitive functioning still remains unclear. Most of the studies assessed the single frequency ASSR, while the individual resonance frequency in the gamma range (30–60 Hz), also called individual gamma frequency (IGF), has received limited attention thus far. Nevertheless, IGF potentially might better reflect individual network characteristics than standardly utilized 40-Hz ASSRs. Here, we focused on the processing speed across different types of cognitive tasks and explored its relationship with responses at 40 Hz and at IGFs in an attempt to uncover how IGFs relate to certain aspects of cognitive functioning. We show that gamma activity is related to the performance speed on complex cognitive task tapping planning and problem solving, both when responses at 40 Hz and at IGFs were evaluated. With the individualized approach, the observed associations were found to be somewhat stronger, and the association seemed to primarily reflect individual differences in higher-order cognitive processing. These findings have important implications for the interpretation of gamma activity in neuropsychiatric disorders.

Responses at Individual Gamma Frequencies Are Related to the Processing Speed but Not the Inhibitory Control

“…The baseline correction of the signal was performed by dividing the signal during the stimulation by the signal during the baseline averaged from −500 to −150 ms for each frequency. In accordance with previous studies utilizing chirps and classical gamma-range auditory steady-state responses, a clear fronto-central distribution of the response was observed [ 15 , 24 ]. For further evaluation, the PLIs and ERSPs at frequencies spanning 30–60 Hz were averaged for the fronto-central (Fz, Cz, FCz, C1, C2, F1, F2, FC1, and FC2) region where responses were most pronounced.…”

“…The sounds were similar to previously used [ 24 ] click-based chirps. Stimulus train was created of single white-noise bursts spaced with changing inter-click periods to cover a range from 30 to 60 Hz in a descending order.…”

“…The offline preprocessing of EEG data was performed in EEGLAB for MatLab© [ 25 ], as described previously [ 24 ]. The power-line noise was removed using multi-tapering and Thomas F-statistics (CleanLine plugin for EEGLAB).…”

“…Following the proposed approach [ 24 ], responses to chirps were analyzed by extracting the curve representing time–frequency points of the stimulation. This curve was used to define the exact time points for each stimulation frequency (seen as a white bold line in the time–frequency plot in Figure 2 ).…”

Clinical Neurophysiology, Neuroimaging, and Neuromodulation of Neuropsychiatric Disorders

“…The results showed that, when assessing ASSR with 40 Hz and IGF, gamma activity was associated with performance speed in both complex cognitive tasks, i.e., tapping planning and problem solving. However, in the individualized approach with IGF, the observed associations were stronger than with 40 Hz stimulation, and the associations mainly reflected individual differences in higher-order cognitive processing [2].…”