Whether measured by MRI or direct cortical physiology, infraslow rhythms have defined state invariant cortical networks. The time scales of this functional architecture, however, are unlikely to be able to accommodate the more rapid cortical dynamics necessary for an active cognitive task. Using invasively monitored epileptic patients as a research model, we tested the hypothesis that faster frequencies would spectrally bind regions of cortex as a transient mechanism to enable fast network interactions during the performance of a simple hear-and-repeat speech task. We term these short-lived spectrally covariant networks functional spectral networks (FSNs). We evaluated whether spectrally covariant regions of cortex, which were unique in their spectral signatures, provided a higher degree of task-related information than any single site showing more classic physiologic responses (i.e., single-site amplitude modulation). Taken together, our results showing that FSNs are a more sensitive measure of task-related brain activation and are better able to discern phonemic content strongly support the concept of spectrally encoded interactions in cortex. Moreover, these findings that specific linguistic information is represented in FSNs that have broad anatomic topographies support a more distributed model of cortical processing. T he brain's intrinsic functional architecture of correlated fluctuations in resting state metabolic and electrophysiologic activity has been well established (1, 2). This functional architecture has been shown to be present in the absence of a task, during all stages of sleep, and even under anesthesia (3). How anatomically distributed regions of cortex interact during the performance of a cognitive task is less understood. Due to slower time scales associated with the hemodynamic response of current neuroimaging techniques (4) and their electrophysiologic correlates (1), the more static networks are not adequate to accommodate the more rapid dynamics associated with many behavioral tasks. Given the limitations of the described time scales, we hypothesized that faster frequencies would "spectrally bind" regions of cortex as a transient mechanism to enable fast network interactions that accommodate the flexible use of neuronal resources. Beyond previously described notions that single higher-frequency synchronization enables neuronal interactions (5), we postulated that dynamic networks are represented by a multitude of spectral characteristics. These transient spectrally covariant networks, which we term functional spectral networks (FSNs), would enable a higher level of fidelity in the transmission of cortical-cortical information.Using invasively monitored epileptic patients as a research model, we tested this hypothesis in the setting of a simple hearand-repeat task. Given that human speech processing involves a widely distributed area located predominantly in perisylvian regions (6), this provided a robust model to evaluate networkderived behavior. We evaluated whether spectrally covariant...