Neural theta oscillations support semantic memory retrieval

AbstractLexical–semantic retrieval emerges through the interactions of distributed prefrontal and perisylvian brain networks. Growing evidence suggests that synchronous theta band neural oscillations might play a role in this process, yet, their functional significance remains elusive. Here, we used transcranial alternating current stimulation to induce exogenous theta oscillations at 6 Hz (θ-tACS) over left prefrontal and posterior perisylvian cortex with a 180° (anti-phase) and 0° (in-phase) relative phase difference while participants performed automatic and controlled retrieval tasks. We demonstrate that θ-tACS significantly modulated the retrieval performance and its effects were both task- and phase-specific: the in-phase tACS impaired controlled retrieval, whereas the anti-phase tACS improved controlled but impaired automatic retrieval. These findings indicate that theta band oscillatory brain activity supports binding of semantically related representations via a phase-dependent modulation of semantic activation or maintenance.

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Frontal Brain Activity during Episodic and Semantic Retrieval: Insights from Event-Related Potentials

Journal of Cognitive Neuroscience ◽

10.1162/089892999563661 ◽

1999 ◽

Vol 11 (6) ◽

pp. 598-609 ◽

Cited By ~ 29

Author(s):

Charan Ranganath ◽

Ken A. Paller

Keyword(s):

Prefrontal Cortex ◽

Memory Retrieval ◽

Brain Activity ◽

Novelty Detection ◽

Event Related Potentials ◽

Episodic Retrieval ◽

Semantic Retrieval ◽

Retrieval Task ◽

Related Potentials ◽

The Right

Previous neuropsychological and neuroimaging results have implicated the prefrontal cortex in memory retrieval, although its precise role is unclear. In the present study, we examined patterns of brain electrical activity during retrieval of episodic and semantic memories. In the episodic retrieval task, participants retrieved autobiographical memories in response to event cues. In the semantic retrieval task, participants generated exemplars in response to category cues. Novel sounds presented intermittently during memory retrieval elicited a series of brain potentials including one identifiable as the P3a potential. Based on prior research linking P3a with novelty detection and with the frontal lobes, we predicted that P3a would be reduced to the extent that novelty detection and memory retrieval interfere with each other. Results during episodic and semantic retrieval tasks were compared to results during a task in which subjects attended to the auditory stimuli. P3a amplitudes were reduced during episodic retrieval, particularly at right lateral frontal scalp locations. A similar but less lateralized pattern of frontal P3a reduction was observed during semantic retrieval. These findings support the notion that the right prefrontal cortex is engaged in the service of memory retrieval, particularly for episodic memories.

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Changes in TMS measures of cortical excitability induced by transcranial direct and alternating current stimulation

The Oxford Handbook of Transcranial Stimulation, Second Edition ◽

10.1093/oxfordhb/9780198832256.013.20 ◽

2021 ◽

Author(s):

Michael A. Nitsche ◽

Walter Paulus ◽

Gregor Thut

Keyword(s):

Brain Stimulation ◽

Cortical Excitability ◽

Brain Activity ◽

Alternating Current ◽

Transcranial Electrical Stimulation ◽

Electrical Currents ◽

After Effects ◽

Brain Physiology ◽

Transcranial Alternating Current Stimulation ◽

Oscillatory Brain Activity

Brain stimulation with weak electrical currents (transcranial electrical stimulation, tES) is known already for about 60 years as a technique to generate modifications of cortical excitability and activity. Originally established in animal models, it was developed as a noninvasive brain stimulation tool about 20 years ago for application in humans. Stimulation with direct currents (transcranial direct current stimulation, tDCS) induces acute cortical excitability alterations, as well as neuroplastic after-effects, whereas stimulation with alternating currents (transcranial alternating current stimulation, tACS) affects primarily oscillatory brain activity but has also been shown to induce neuroplasticity effects. Beyond their respective regional effects, both stimulation techniques have also an impact on cerebral networks. Transcranial magnetic stimulation (TMS) has been pivotal to helping reveal the physiological effects and mechanisms of action of both stimulation techniques for motor cortex application, but also for stimulation of other areas. This chapter will supply the reader with an overview about the effects of tES on human brain physiology, as revealed by TMS.

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Motor Learning Based on Oscillatory Brain Activity Using Transcranial Alternating Current Stimulation: A Review

Brain Sciences ◽

10.3390/brainsci11081095 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1095

Author(s):

Naoyuki Takeuchi ◽

Shin-Ichi Izumi

Keyword(s):

Motor Learning ◽

Brain Activity ◽

Alternating Current ◽

Social Effects ◽

Motor Deficits ◽

Noninvasive Brain Stimulation ◽

Transcranial Alternating Current Stimulation ◽

Oscillatory Brain Activity ◽

Teaching Learning ◽

The Relationship

Developing effective tools and strategies to promote motor learning is a high-priority scientific and clinical goal. In particular, motor-related areas have been investigated as potential targets to facilitate motor learning by noninvasive brain stimulation (NIBS). In addition to shedding light on the relationship between motor function and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can noninvasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted attention as a possible technique to promote motor learning. This review focuses on the use of tACS to enhance motor learning through the manipulation of oscillatory brain activity and its potential clinical applications. We discuss a potential tACS–based approach to ameliorate motor deficits by correcting abnormal oscillatory brain activity and promoting appropriate oscillatory communication in patients after stroke or with Parkinson’s disease. Interpersonal tACS approaches to manipulate intra- and inter-brain communication may result in pro-social effects and could promote the teaching–learning process during rehabilitation sessions with a therapist. The approach of re-establishing oscillatory brain communication through tACS could be effective for motor recovery and might eventually drive the design of new neurorehabilitation approaches based on motor learning.

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Transcranial alternating current stimulation at theta frequency to the parietal cortex impairs associative, but not perceptual, memory encoding

10.1101/2020.11.19.387407 ◽

2020 ◽

Author(s):

Alyssa Meng ◽

Max Kaiser ◽

Tom de Graaf ◽

Felix Duecker ◽

Alexander T. Sack ◽

...

Keyword(s):

Associative Memory ◽

Parietal Cortex ◽

Brain Stimulation ◽

Brain Activity ◽

Memory Performance ◽

Alternating Current ◽

Theta Oscillations ◽

Memory Encoding ◽

Transcranial Alternating Current Stimulation ◽

Hippocampal Network

AbstractNeural oscillations in the theta range (4-6 Hz) are thought to underlie associative memory function in the hippocampal-cortical network. While there is ample evidence supporting a role of theta oscillations in animal and human memory, most evidence is correlational. Non-invasive brain stimulation (NIBS) can be employed to modulate cortical oscillatory activity to influence brain activity, and possibly modulate deeper brain regions, such as hippocampus, through strong and reliable cortico-hippocampal functional connections. We applied high-definition transcranial alternating current stimulation (HD-tACS) at 6 Hz over left parietal cortex to modulate brain activity in the putative cortico-hippocampal network to influence associative memory encoding. After encoding and brain stimulation, participants completed an associative memory and a perceptual recognition task. Results showed that theta tACS significantly decreased associative memory performance but did not affect perceptual memory performance. These results show that parietal theta tACS modulates associative processing separately from perceptual processing, and further substantiate the hypothesis that theta oscillations are implicated in the cortico-hippocampal network and associative encoding.

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Inefficient Encoding as an Explanation for Age-Related Deficits in Recollection-Based Processing

Journal of Psychophysiology ◽

10.1027/0269-8803/a000122 ◽

2014 ◽

Vol 28 (3) ◽

pp. 148-161 ◽

Cited By ~ 12

Author(s):

David Friedman ◽

Ray Johnson

Keyword(s):

Older Adults ◽

Young Adults ◽

Cognitive Processes ◽

Brain Activity ◽

Memory Performance ◽

Brain Regions ◽

Semantic Retrieval ◽

Age Related ◽

The Face ◽

Episodic Memories

A cardinal feature of aging is a decline in episodic memory (EM). Nevertheless, there is evidence that some older adults may be able to “compensate” for failures in recollection-based processing by recruiting brain regions and cognitive processes not normally recruited by the young. We review the evidence suggesting that age-related declines in EM performance and recollection-related brain activity (left-parietal EM effect; LPEM) are due to altered processing at encoding. We describe results from our laboratory on differences in encoding- and retrieval-related activity between young and older adults. We then show that, relative to the young, in older adults brain activity at encoding is reduced over a brain region believed to be crucial for successful semantic elaboration in a 400–1,400-ms interval (left inferior prefrontal cortex, LIPFC; Johnson, Nessler, & Friedman, 2013 ; Nessler, Friedman, Johnson, & Bersick, 2007 ; Nessler, Johnson, Bersick, & Friedman, 2006 ). This reduced brain activity is associated with diminished subsequent recognition-memory performance and the LPEM at retrieval. We provide evidence for this premise by demonstrating that disrupting encoding-related processes during this 400–1,400-ms interval in young adults affords causal support for the hypothesis that the reduction over LIPFC during encoding produces the hallmarks of an age-related EM deficit: normal semantic retrieval at encoding, reduced subsequent episodic recognition accuracy, free recall, and the LPEM. Finally, we show that the reduced LPEM in young adults is associated with “additional” brain activity over similar brain areas as those activated when older adults show deficient retrieval. Hence, rather than supporting the compensation hypothesis, these data are more consistent with the scaffolding hypothesis, in which the recruitment of additional cognitive processes is an adaptive response across the life span in the face of momentary increases in task demand due to poorly-encoded episodic memories.

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Synesthetic Binding and the Reactivation Model of Memory

10.1093/oso/9780199688289.003.0007 ◽

2017 ◽

Author(s):

Berit Brogaard

Keyword(s):

Sensory Neurons ◽

Memory Retrieval ◽

Brain Activity ◽

Receptive Fields ◽

Memory Model ◽

Multisensory Perception ◽

Feedback Mechanisms

Despite the recent surge in research on, and interest in, synesthesia, the mechanism underlying this condition is still unknown. Feedforward mechanisms involving overlapping receptive fields of sensory neurons as well as feedback mechanisms involving a lack of signal disinhibition have been proposed. Here I show that a broad range of studies of developmental synesthesia indicate that the mechanism underlying the phenomenon may in some cases involve the reinstatement of brain activity in sensory or cognitive streams in a way that is similar to what happens during memory retrieval of semantically associated items. In the chapter’s final sections I look at the relevance of synesthesia research, given the memory model, to our understanding of multisensory perception and common mapping patterns.

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