Low-frequency modulations bridge the language and default mode networks

As you read this sentence, you integrate meanings of individual words into complex, higher-order representations. In addition to the core language network (LN), this dynamic process recruits other domain-general networks such as the default mode network (DMN), with which it partially overlaps anatomically but segregates from functionally. To evaluate interactions between LN and DMN, we extracted instantaneous frequency, power, and phase (4-30 Hz) from intracranial electrodes in 32 participants who read sentences and wordlists. We isolated a complex low-frequency modulation, most reliably measured as a ramping of instantaneous frequency in the alpha band throughout sentences, greater than wordlists, occurring robustly across both the LN and DMN. Granger causal networks demonstrate this coincided with ramping increases in alpha-band connectivity between and within DMN and LN. We suggest that alpha-band modulations index dynamic interactions between core LN and broader domain-general networks and may be crucial for higher order semantic integration and the derivation of crossmodal knowledge from the language domain.