Functional wiring of the human medial temporal lobe

Solomon, Ethan A.; Stein, Joel M.; Das, Sandhitsu R.; Gorniak, Richard; Sperling, Michael R.; Worrell, Gregory A.; Inman, Cory S.; Lega, Bradley; Jobst, Barbara C.; Rizzuto, Daniel S.; Kahana, Michael J.

doi:10.1101/257899

Cited by 4 publications

(4 citation statements)

References 64 publications

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“…Furthermore, cells with overlapping place fields may fire within the same gamma and theta cycle, suggesting that assemblies of neurons with similar tuning properties are organized by a theta-gamma code 37,38 . Based on these findings, we suggest that theta and gamma oscillations promote information transfer between HC and PHG during retrieval of episodic information encoded in a spatial environment 27,39 . Specifically, we explore whether theta phase to gamma amplitude coupling between HC and PHG increases during recall to facilitate information transfer from HC to PHG.…”

Section: Introductionmentioning

confidence: 73%

“…Theta oscillations have been suggested to support the formation of both spatial and episodic associations by organizing spike-timing and associated plasticity 26 , but evidence in favor of this idea is scarce. In fact, successful episodic memory operations are often associated with a wide-spread decrease in low-and increase in high-frequency power 27,28 . Despite such broad-band tilt effects, however, there also seem to be more localized increases in temporal narrow-band theta oscillations during successful encoding 29 and retrieval 28 , which might more specifically be linked to recollection of contextual information 30,31 .…”

Section: Introductionmentioning

confidence: 99%

“…Finally, we ask how retrieved information is transferred between PHG and HC. Theta oscillations have been strongly implicated in inter-regional connectivity during successful memory operations 27,30,34 and in rodents place-responsive cells are locked to both theta and gamma oscillations 35,36 . Furthermore, cells with overlapping place fields may fire within the same gamma and theta cycle, suggesting that assemblies of neurons with similar tuning properties are organized by a theta-gamma code 37,38 .…”

Section: Introductionmentioning

confidence: 99%

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Reactivated spatial context guides episodic recall

Herweg

Sharan

Sperling

et al. 2018

Preprint

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25The medial temporal lobe (MTL) is known as the locus of spatial coding and episodic memory, 26 but the interaction between these cognitive domains, as well as the extent to which they rely on 27 common neurophysiological mechanisms is poorly understood. Here, we use a hybrid spatial-28 episodic memory task to determine how spatial information is dynamically reactivated in sub-29 regions of the MTL and how this reactivation guides recall of episodic information. Our results 30 implicate theta oscillations across the MTL as a common neurophysiological substrate for spatial 31 coding in navigation and episodic recall. We further show that spatial context information is 32 initially retrieved in the hippocampus (HC) and subsequently emerges in the parahippocampal 33 gyrus (PHG). Finally, we demonstrate that hippocampal theta phase modulates parahippocampal 34 gamma amplitude during retrieval of spatial context, suggesting a role for cross frequency coupling 35 in coding and transmitting retrieved spatial information. 36

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reactivated spatial context guides episodic recall

Herweg

Sharan

Sperling

et al. 2018

Preprint

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“…If theta oscillations provide a time compression mechanism that can act independently of spatial navigation and establishes temporal associations between successively experienced items, evidence consistent with this idea should be observable in electrophysiological studies of human recall and recognition. Although a large number of studies highlight a role for low-frequency oscillations in episodic memory encoding, they provide mixed results of increases ( Guderian et al, 2009 ; Hanslmayr et al, 2011 ; Lega et al, 2012 ; Lin et al, 2017 ) and decreases ( Sederberg et al, 2007 ; Lega et al, 2012 ; Burke et al, 2013 ; Lin et al, 2017 ; Solomon et al, 2018 ) associated with successful encoding in the MTL, as well as in cortical brain regions or at the scalp (increases: Klimesch et al, 1996 ; Osipova et al, 2006 ; Sederberg et al, 2007 ; Khader et al, 2010 ; Burke et al, 2013 ; decreases: Sederberg et al, 2007 ; Guderian et al, 2009 ; Burke et al, 2013 ). It is noteworthy that several of these studies simultaneously report both increases and decreases which are separated in time and/or precise localization ( Sederberg et al, 2007 ; Guderian et al, 2009 ; Lega et al, 2012 ; Burke et al, 2013 , 2014 ).…”

Section: Functional Overlap In the Mtl: A Common Map For Physical Andmentioning

confidence: 99%

Spatial Representations in the Human Brain

Herweg

Kahana

2018

Front. Hum. Neurosci.

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While extensive research on the neurophysiology of spatial memory has been carried out in rodents, memory research in humans had traditionally focused on more abstract, language-based tasks. Recent studies have begun to address this gap using virtual navigation tasks in combination with electrophysiological recordings in humans. These studies suggest that the human medial temporal lobe (MTL) is equipped with a population of place and grid cells similar to that previously observed in the rodent brain. Furthermore, theta oscillations have been linked to spatial navigation and, more specifically, to the encoding and retrieval of spatial information. While some studies suggest a single navigational theta rhythm which is of lower frequency in humans than rodents, other studies advocate for the existence of two functionally distinct delta–theta frequency bands involved in both spatial and episodic memory. Despite the general consensus between rodent and human electrophysiology, behavioral work in humans does not unequivocally support the use of a metric Euclidean map for navigation. Formal models of navigational behavior, which specifically consider the spatial scale of the environment and complementary learning mechanisms, may help to better understand different navigational strategies and their neurophysiological mechanisms. Finally, the functional overlap of spatial and declarative memory in the MTL calls for a unified theory of MTL function. Such a theory will critically rely upon linking task-related phenomena at multiple temporal and spatial scales. Understanding how single cell responses relate to ongoing theta oscillations during both the encoding and retrieval of spatial and non-spatial associations appears to be key toward developing a more mechanistic understanding of memory processes in the MTL.

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Medial temporal lobe functional connectivity predicts stimulation-induced theta power

et al. 2018

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Focal electrical stimulation of the brain incites a cascade of neural activity that propagates from the stimulated region to both nearby and remote areas, offering the potential to control the activity of brain networks. Understanding how exogenous electrical signals perturb such networks in humans is key to its clinical translation. To investigate this, we applied electrical stimulation to subregions of the medial temporal lobe in 26 neurosurgical patients fitted with indwelling electrodes. Networks of low-frequency (5–13 Hz) spectral coherence predicted stimulation-evoked increases in theta (5–8 Hz) power, particularly when stimulation was applied in or adjacent to white matter. Stimulation tended to decrease power in the high-frequency broadband (HFB; 50–200 Hz) range, and these modulations were correlated with HFB-based networks in a subset of subjects. Our results demonstrate that functional connectivity is predictive of causal changes in the brain, capturing evoked activity across brain regions and frequency bands.

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Functional wiring of the human medial temporal lobe

Cited by 4 publications

References 64 publications

Reactivated spatial context guides episodic recall

Reactivated spatial context guides episodic recall

Spatial Representations in the Human Brain

Medial temporal lobe functional connectivity predicts stimulation-induced theta power

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