Theta and Gamma Oscillations during Encoding Predict Subsequent Recall

Abstract

Electrophysiological and hemodynamic measures of human brain activity have been shown to distinguish between episodes of encoding items that are later recalled versus those that are not recalled (Paller and Wagner, 2002). Using intracranial recordings from 793 widespread cortical and subcortical sites in 10 epileptic patients undergoing invasive monitoring, we compared oscillatory power at frequencies ranging from 2 to 64 Hz as participants studied lists of common nouns. Significant increases in oscillatory power during encoding predicted subsequent recall, with this effect predominantly in the 4-8 Hz (theta) and 28-64 Hz (gamma) frequency bands. Sites exhibiting increased theta activity during successful encoding were clustered in right temporal and frontal cortex, whereas those exhibiting increased gamma activity appeared bilaterally at widespread cortical locations. These findings implicate theta and gamma oscillatory activity, across a widespread network of cortical regions, in the formation of new episodic memories.

Frontal midline theta connectivity is related to efficiency of WM maintenance and is affected by aging

“…Up till know electrophysiological studies compared only resting state with memory retention period characteristics. According to these results decreased interactions between the entire fronto-temporo-parietal networks were found during the resting state compared to WM tasks (Sarnthein et al, 1998;Sederberg et al, 2003;Sauseng et al, 2005; for review see Klimesch et al, 2008). Contrary to the above, the present results indicate that maintenance of visual information in WM enhances thetasynchrony within the frontal and between the fronto-temporal cortices while attentional functions required by both WM and oddball tasks may be supported by the same fronto parieto-occipital theta phase synchrony.…”

“…By establishing sustained coordinated timing of neuronal firing between distant cortical areas oscillatory synchronization integrates anatomically distributed processing and facilitates neuronal communication, thus for instance has a central role in input selection and synaptic plasticity (Fell & Axmacher, 2011). Maintenance of visual information in WM enhances theta-synchrony between frontal and temporo-parietal as well as between occipito-temporal regions (Sarnthein et al, 1998;Sederberg et al, 2003;Sauseng et al, 2005; for review see Klimesch et al, 2008). Decreased interactions between fronto-temporo-parietal networks was found during resting state and perception (Sarnthein et al, 1998) compared during WM tasks.…”

Slow-theta power decreases during item-place encoding predict spatial accuracy of subsequent context recall

“…These positive SMEs were usually seen over frontal and temporal regions and corroborated by intracranial EEG (iEEG) recordings (Lega et al, 2012;Sederberg et al, 2003). It has been proposed that theta power increases during successful encoding might reflect the recruitment of cortical regions (Sederberg et al, 2003), where theta oscillations could be induced via hippocampo cortical feedback loops (Klimesch et al, 1996).…”

Increased mesiotemporal delta activity characterizes virtual navigation in humans

“…There are a branch of studies with direct medial temporal lobe recording reporting various theta-related phenomena such as theta reset and theta/gamma interaction during a word recognition task (Mormann et al, 2005), pre-stimulus theta predicting successful memory encoding and stimulus-triggered theta related to subsequent recall (Sederberg et al, 2003;Fell et al, 2011), phase-coupling of gamma (Axmacher et al, 2010) and single neuronal activity (Rutishauser et al, 2010) to theta. Despite the diversity of paradigms and electrophysiological measures used in these studies theta power increase was generally not found however this would be the most parsimonious measure to justify that theta is indeed a correlate of cognition.…”