Medial Prefrontal–Medial Temporal Theta Phase Coupling in Dynamic Spatial Imagery

Hippocampal–medial prefrontal interactions are thought to play a crucial role in mental simulation. Notably, the frontal midline/medial pFC (mPFC) theta rhythm in humans has been linked to introspective thought and working memory. In parallel, theta rhythms have been proposed to coordinate processing in the medial temporal cortex, retrosplenial cortex (RSc), and parietal cortex during the movement of viewpoint in imagery, extending their association with physical movement in rodent models. Here, we used noninvasive whole-head MEG to investigate theta oscillatory power and phase-locking during the 18-sec postencoding delay period of a spatial working memory task, in which participants imagined previously learned object sequences either on a blank background (object maintenance), from a first-person viewpoint in a scene (static imagery), or moving along a path past the objects (dynamic imagery). We found increases in 4- to 7-Hz theta power in mPFC when comparing the delay period with a preencoding baseline. We then examined whether the mPFC theta rhythm was phase-coupled with ongoing theta oscillations elsewhere in the brain. The same mPFC region showed significantly higher theta phase coupling with the posterior medial temporal lobe/RSc for dynamic imagery versus either object maintenance or static imagery. mPFC theta phase coupling was not observed with any other brain region. These results implicate oscillatory coupling between mPFC and medial temporal lobe/RSc theta rhythms in the dynamic mental exploration of imagined scenes.

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Material-specific lateralization of working memory in the medial temporal lobe

Neuropsychologia ◽

10.1016/j.neuropsychologia.2008.08.010 ◽

2009 ◽

Vol 47 (1) ◽

pp. 112-122 ◽

Cited By ~ 28

Author(s):

Dylan D. Wagner ◽

Viviane Sziklas ◽

Krista E. Garver ◽

Marilyn Jones-Gotman

Keyword(s):

Working Memory ◽

Temporal Lobe ◽

Medial Temporal Lobe

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Modulation of medial temporal lobe activity in epilepsy patients with hippocampal sclerosis during verbal working memory

Journal of the International Neuropsychological Society ◽

10.1017/s135561770909078x ◽

2009 ◽

Vol 15 (4) ◽

pp. 536-546 ◽

Cited By ~ 10

Author(s):

PABLO CAMPO ◽

FERNANDO MAESTÚ ◽

IRENE GARCÍA-MORALES ◽

ANTONIO GIL-NAGEL ◽

BRYAN STRANGE ◽

...

Keyword(s):

Working Memory ◽

Episodic Memory ◽

Temporal Lobe ◽

Medial Temporal Lobe ◽

Time Course ◽

Hippocampal Sclerosis ◽

Stimulus Presentation ◽

Verbal Working Memory ◽

Compelling Evidence ◽

Electrophysiological Studies

AbstractIt has been traditionally assumed that medial temporal lobe (MTL) is not required for working memory (WM). However, animal lesion and electrophysiological studies and human neuropsychological and neuroimaging studies have provided increasing evidences of a critical involvement of MTL in WM. Based on previous findings, the central aim of this study was to investigate the contribution of the MTL to verbal WM encoding. Here, we used magnetoencephalography (MEG) to compare the patterns of MTL activation of 9 epilepsy patients suffering from left hippocampal sclerosis with those of 10 healthy matched controls while they performed a verbal WM task. MEG recordings allow detailed tracking of the time course of MTL activation. We observed impaired WM performance associated with changes in the dynamics of MTL activity in epilepsy patients. Specifically, whereas patients showed decreased activity in damaged MTL, activity in the contralateral MTL was enhanced, an effect that became significant in the 600- to 700-ms interval after stimulus presentation. These findings strongly support the crucial contribution of MTL to verbal WM encoding and provide compelling evidence for the proposal that MTL contributes to both episodic memory and WM. Whether this pattern is signaling reorganization or a normal use of a damaged structure is discussed. (JINS, 2009, 15, 536–546.)

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A putative high risk diplotype of the G72 gene is in healthy individuals associated with better performance in working memory functions and altered brain activity in the medial temporal lobe

NeuroImage ◽

10.1016/j.neuroimage.2008.12.054 ◽

2009 ◽

Vol 45 (3) ◽

pp. 1002-1008 ◽

Cited By ~ 29

Author(s):

Andreas Jansen ◽

Sören Krach ◽

Axel Krug ◽

Valentin Markov ◽

Thomas Eggermann ◽

...

Keyword(s):

Working Memory ◽

High Risk ◽

Temporal Lobe ◽

Medial Temporal Lobe ◽

Brain Activity ◽

Healthy Individuals ◽

Memory Functions

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Distinct Cortical Anatomy Linked to Subregions of the Medial Temporal Lobe Revealed by Intrinsic Functional Connectivity

Journal of Neurophysiology ◽

10.1152/jn.00077.2008 ◽

2008 ◽

Vol 100 (1) ◽

pp. 129-139 ◽

Cited By ~ 288

Author(s):

Itamar Kahn ◽

Jessica R. Andrews-Hanna ◽

Justin L. Vincent ◽

Abraham Z. Snyder ◽

Randy L. Buckner

Keyword(s):

Functional Connectivity ◽

Temporal Lobe ◽

Medial Temporal Lobe ◽

Temporal Cortex ◽

Memory System ◽

Retrosplenial Cortex ◽

The Body ◽

Parallel Pathways ◽

Ventral Medial Prefrontal Cortex ◽

Adjacent Structures

The hippocampus and adjacent cortical structures in the medial temporal lobe (MTL) contribute to memory through interactions with distributed brain areas. Studies of monkey and rodent anatomy suggest that parallel pathways converge on distinct subregions of the MTL. To explore the cortical areas linked to subregions of the MTL in humans, we examined cortico-cortical and hippocampal-cortical correlations using high-resolution, functional connectivity analysis in 100 individuals. MTL seed regions extended along the anterior to posterior axis and included hippocampus and adjacent structures. Results revealed two separate brain pathways that correlated with distinct subregions within the MTL. The body of the hippocampus and posterior parahippocampal cortex correlated with lateral parietal cortex, regions along the posterior midline including posterior cingulate and retrosplenial cortex, and ventral medial prefrontal cortex. By contrast, anterior hippocampus and the perirhinal/entorhinal cortices correlated with distinct regions in the lateral temporal cortex extending into the temporal pole. The present results are largely consistent with known connectivity in the monkey and provide a novel task-independent dissociation of the parallel pathways supporting the MTL memory system in humans. The cortical pathways include regions that have undergone considerable areal expansion in humans, providing insight into how the MTL memory system has evolved to support a diverse array of cognitive domains.

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