Frequency of gamma oscillations routes flow of information in the hippocampus

Abstract

Gamma oscillations are thought to transiently link distributed cell assemblies that are processing related information, a function that is probably important for network processes such as perception, attentional selection and memory. This 'binding' mechanism requires that spatially distributed cells fire together with millisecond range precision; however, it is not clear how such coordinated timing is achieved given that the frequency of gamma oscillations varies substantially across space and time, from approximately 25 to almost 150 Hz. Here we show that gamma oscillations in the CA1 area of the hippocampus split into distinct fast and slow frequency components that differentially couple CA1 to inputs from the medial entorhinal cortex, an area that provides information about the animal's current position, and CA3, a hippocampal subfield essential for storage of such information. Fast gamma oscillations in CA1 were synchronized with fast gamma in medial entorhinal cortex, and slow gamma oscillations in CA1 were coherent with slow gamma in CA3. Significant proportions of cells in medial entorhinal cortex and CA3 were phase-locked to fast and slow CA1 gamma waves, respectively. The two types of gamma occurred at different phases of the CA1 theta rhythm and mostly on different theta cycles. These results point to routeing of information as a possible function of gamma frequency variations in the brain and provide a mechanism for temporal segregation of potentially interfering information from different sources.

Transitions in neural oscillations reflect prediction errors generated in audiovisual speech

“…3b). The observation that mid-and high-gamma activity were related to the phase consistency of beta and theta activity, respectively, extends the ideas that gamma frequency variations reflect information routing 32,34,45,46 and that message-passing is indexed by specific hierarchical combinations of slow and high frequencies (low/high frequency ratio) 47 .…”

“…3b). The observation that mid-and high-gamma activity were related to the phase consistency of beta and theta activity, respectively, extends the ideas that gamma frequency variations reflect information routing 32,34,45,46 and that message-passing is indexed by specific hierarchical combinations of slow and high frequencies (low/high frequency ratio) 47 .The current data demonstrate that violating intermodal expectations changes the neural dynamics of slow (delta and theta) brain activity, and increases the coordination between local low-beta and high-gamma oscillatory activity. Our data suggest that this transition occurs in brain regions where audio-visual predictions are likely updated (STS) and new prediction errors generated (auditory and visual cortices).…”

Altered cross-frequency coupling in resting-state MEG after mild traumatic brain injury

“…Results from recent studies in both animals and humans support a mechanism that oscillations at higher frequencies are often modulated by the phase of slower phase fluctuations (Osipova et al, 2008;Tort et al, 2008Tort et al, , 2009Tort et al, , 2010Cohen et al, 2009a, b;Colgin et al, 2009;Axmacher et al, 2010a, b;Voytek et al, 2010). Important elements of nonlinear coupling across different frequencies reveal different types of CFC, such as phase-amplitude coupling (Tort et al, 2008(Tort et al, , 2009(Tort et al, , 2010Cohen et al, 2009a,b;Colgin et al, 2009;Axmacher et al, 2010a,b), n:m phase locking (Dimitriadis et al, 2015b), and amplitude-amplitude coupling (Hipp et al, 2012;Engel et al, 2013).…”

“…There is ample evidence that the last type of CFC, also called phase-amplitude modulation, occurs very often in both animals and humans in the prefrontal cortices, the hippocampus, and other distributed cortical areas (Osipova et al, 2008;Tort et al, 2008Tort et al, , 2009Tort et al, , 2010Cohen et al, 2009a, b;Colgin et al, 2009;Axmacher et al, 2010a, b;Voytek et al, 2010).…”

Visual stimulus eccentricity affects human gamma peak frequency

“…Neuronal synchronization in the gamma frequency band (30-100Hz) has been implicated in several cognitive functions (Singer and Gray, 1995;Buschman and Miller, 2007;Buzsaki and Draguhn, 2004;Colgin et al, 2009;Fries, 2009). Gamma-band synchronization is observed during visual (Hoogenboom et al, 2006;Muthukumaraswamy et al, 2009), somatosensory (Bauer et al, 2006), and auditory (Brosch et al, 2002) stimulation; it is involved in memory processes (Fell et al, 2001;Howard et al, 2003) and motor control (Brown et al, 1998;Schoffelen et al, 2005).…”