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Brain Stimul. 2018 Jan - Feb;11(1):213-221. doi: 10.1016/j.brs.2017.09.016. Epub 2017 Oct 5.

Network-based brain stimulation selectively impairs spatial retrieval.

Author information

1
Department of Neurosurgery, University of Texas Health Science Center, 6431 Fannin Street, Houston, TX, 77030, USA.
2
Neuroscience Graduate Program, University of California Davis, 1544 Newton Court, Davis, CA 95616, USA.
3
Department of Psychology, University of California Davis, 135 Young Hall, One Shields Avenue, Davis, CA 95616, USA; Center for Neuroscience, University of California Davis, 1544 Newton Court, Davis, CA 95616, USA. Electronic address: adekstrom@ucdavis.edu.
4
Department of Neurosurgery, University of Texas Health Science Center, 6431 Fannin Street, Houston, TX, 77030, USA. Electronic address: Nitin.Tandon@uth.tmc.edu.

Abstract

BACKGROUND:

Direct brain stimulation via electrodes implanted for intracranial electroencephalography (iEEG) permits the modulation of endogenous electrical signals with significantly greater spatial and temporal specificity than non-invasive approaches. It also allows for the stimulation of deep brain structures important to memory, such as the hippocampus, that are difficult, if not impossible, to target non-invasively. Direct stimulation studies of these deep memory structures, though, have produced mixed results, with some reporting improvement, some impairment, and others, no consistent changes.

OBJECTIVE/HYPOTHESIS:

We hypothesize that to modulate cognitive function using brain stimulation, it is essential to modulate connected nodes comprising a network, rather than just alter local activity.

METHODS:

iEEG data collected while patients performed a spatiotemporal memory retrieval task were used to map frequency-specific, coherent oscillatory activity between different brain regions associated with successful memory retrieval. We used these to identify two target nodes that exhibited selectively stronger coupling for spatial vs. temporal retrieval. In a subsequent session, electrical stimulation - theta-bursts with a fixed phase-lag (0° or 180°) - was applied to the two target regions while patients performed spatiotemporal retrieval.

RESULTS:

Stimulation selectively impaired spatial retrieval while not affecting temporal retrieval, and this selective impairment was associated with theta decoupling of the spatial retrieval network.

CONCLUSION:

These findings suggest that stimulating tightly connected nodes in a functional network at the appropriate phase-lag may effectively modulate the network function, and while in this case it impaired memory processes, it sets a foundation for further network-based perturbation studies.

KEYWORDS:

Direct brain stimulation; ECoG; Intracranial EEG; Memory retrieval; Theta burst

PMID:
29042188
PMCID:
PMC5729089
[Available on 2019-01-01]
DOI:
10.1016/j.brs.2017.09.016
[Indexed for MEDLINE]

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