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Interference with existing memories alters offline intrinsic functional brain connectivity.

ABSTRACT: The notion that already existing memories can be modified after their reactivation has received an increasing amount of experimental support, with empirical data accumulating across species and memory paradigms. However, there is no evidence for systems-level task-free intrinsic signatures of memory modification. Here, using a combination of behavioral, brain stimulation, and neuroimaging paradigms, we report that noninvasive transcranial magnetic stimulation interference with a reactivated motor memory altered offline task-free corticostriatal interregional functional connectivity, reducing it compared to stimulation in which the reactivated memory was intact. Furthermore, the modulated functional connectivity predicted offline memory modification. This reduction in functional connectivity recovered after additional execution of the memorized task, and the interference did not affect control cerebellar-cortical functional connectivity. This demonstrates that intrinsic task-free offline brain activity can be modulated by noninvasive interaction with existing memories and strongly correlates with behavioral measurements of changes in memory strength.

SUBMITTER: Censor N

PROVIDER: S-EPMC3894578 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Interference with existing memories alters offline intrinsic functional brain connectivity.

Censor Nitzan N Horovitz Silvina G SG Cohen Leonardo G LG

Neuron 20140101 1

The notion that already existing memories can be modified after their reactivation has received an increasing amount of experimental support, with empirical data accumulating across species and memory paradigms. However, there is no evidence for systems-level task-free intrinsic signatures of memory modification. Here, using a combination of behavioral, brain stimulation, and neuroimaging paradigms, we report that noninvasive transcranial magnetic stimulation interference with a reactivated moto ...[more]

PMID: 24411732

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Project description:Animal functional magnetic resonance imaging (fMRI) has provided key insights into the physiological mechanisms underlying healthy and diseased brain states. In non-human primates, resting-state fMRI studies are commonly conducted under isoflurane anesthesia, where anesthetic concentration is used to roughly infer anesthesia depth. However, within the recommended isoflurane concentration range (1.00-1.50%), the brain state can switch from moderate anesthesia characterized by stable slow wave (SW) electroencephalogram (EEG) signals to deep anesthesia characterized by burst suppression (BS), which is electrophysiologically distinct from the resting state. To confirm the occurrence rate of BS activity in common setting of animal fMRI study, we conducted simultaneous resting-state EEG and fMRI experiments on 16 monkeys anesthetized using 0.80-1.30% isoflurane, and detected BS activity in two of them. Datasets either featured with BS or SW activity from these two monkeys were analyzed to investigate the intrinsic functional connectivity (FC) patterns during BS. In datasets with BS activity, we observed robust coupling between the BS pattern (the binary alternation between burst and suppression activity in EEG signal) and filtered BOLD signals in most brain areas, which was associated with a non-specific enhancement in whole brain connectivity. After eliminating the BS coupling effect by regressing out the BS pattern, we detected an overall increase in FC with a few decreased connectivity compared to datasets with SW activity. These affected connections were preferentially distributed within orbitofrontal cortex, between orbitofrontal and prefrontal/cingulate/occipital cortex, and between temporal and parietal cortex. Persistence of the default mode network and recovery of thalamocortical connections were also detected under deep anesthesia with BS activity. Taken together, the observed spatially specific alterations in BS activity induced by isoflurane not only highlight the necessity of EEG monitoring and careful data preprocessing in fMRI studies on anesthetized animals, but also advance our understanding of the underlying multi-phased mechanisms of anesthesia.

Dataset Information

Interference with existing memories alters offline intrinsic functional brain connectivity.

Publications

Interference with existing memories alters offline intrinsic functional brain connectivity.

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