Spectral-power associations reflect amplitude modulation and within-frequency interactions on the sub-second timescale and cross-frequency interactions on the seconds timescale
Suzuki, Satoru; Menceloglu, Melisa (2020), Spectral-power associations reflect amplitude modulation and within-frequency interactions on the sub-second timescale and cross-frequency interactions on the seconds timescale, Dryad, Dataset, https://doi.org/10.5061/dryad.hdr7sqvf9
We investigated the global structure of intrinsic cross-frequency dynamics by systematically examining power-based temporal associations among a broad range of oscillation frequencies both within and across EEG-based current sources (sites). We focused on power-based associations that could reveal unique timescale dependence independently of interacting frequencies. Large spectral-power fluctuations across all sites occurred at two characteristic timescales, sub-second and seconds, yielding distinct patterns of cross-frequency associations. On the fast sub-second timescale, within-site (local) associations were consistently between pairs of beta-gamma frequencies differing by a constant Delta-f (particularly Delta-f ~ 10 Hz at posterior sites and Delta-f ~ 16 Hz at lateral sites) suggesting that higher-frequency oscillations are organized into Delta-f amplitude-modulated packets, whereas cross-site (long-distance) associations were all within-frequency (particularly in the >30 Hz and 6-12 Hz ranges, suggestive of feedforward and feedback interactions). On the slower seconds timescale, within-site (local) associations were characterized by a broad range of frequencies selectively associated with ~10 Hz at posterior sites and associations among higher (>20 Hz) frequencies at lateral sites, whereas cross-site (long-distance) associations were characterized by a broad range of frequencies at posterior sites selectively associated with ~10 Hz at other sites, associations among higher (>20 Hz) frequencies among lateral and anterior sites, and prevalent associations at ~10 Hz. Regardless of timescale, within-site (local) cross-frequency associations were weak at anterior sites indicative of frequency-specific operations. Overall, these results suggest that the fast sub-second-timescale coordination of spectral power is limited to local amplitude modulation and insulated within-frequency long-distance interactions (likely feedforward and feedback interactions), while characteristic patterns of cross-frequency interactions emerge on the slower seconds timescale. The results also suggest that the occipital alpha oscillations play a role in organizing higher-frequency oscillations into ~10 Hz amplitude-modulated packets to communicate with other regions. Functional implications of these timescale-dependent cross-frequency associations await future investigations.
EEG was recorded while participants (N=24) rested with their eyes closed (for about 5 minutes) with 64 scalp electrodes using a BioSemi ActiveTwo system (www.biosemi.com). The EEG data have been pre-processed as described in the Materials and Methods section of the associated article. The file named "rest_eyes_closed.mat" contains the data prior to applying a surface-Laplacian transform. The file named "rest_eyes_closed_SL.mat" contains the surface-Laplacian transformed data. The data are formated for MATLAB.
National Institutes of Health, Award: T32