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

2021 ◽  
pp. 107444
Author(s):  
Alyssa Meng ◽  
Max Kaiser ◽  
Tom de Graaf ◽  
Felix Duecker ◽  
Alexander T. Sack ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Alternating Current ◽  
Memory Encoding ◽  
Perceptual Memory ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Left Parietal Cortex

scholarly journals Failure to modulate reward prediction errors in declarative learning with theta (6 Hz) frequency transcranial alternating current stimulation

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0237829
Author(s):  
Kate Ergo ◽  
Esther De Loof ◽  
Gillian Debra ◽  
Bernhard Pastötter ◽  
Tom Verguts
Keyword(s):  
Memory Performance ◽  
Alternating Current ◽  
Transcranial Electrical Stimulation ◽  
Prediction Errors ◽  
Memory Encoding ◽  
Neurophysiological Mechanism ◽  
Reward Prediction ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Declarative Learning

Recent evidence suggests that reward prediction errors (RPEs) play an important role in declarative learning, but its neurophysiological mechanism remains unclear. Here, we tested the hypothesis that RPEs modulate declarative learning via theta-frequency oscillations, which have been related to memory encoding in prior work. For that purpose, we examined the interaction between RPE and transcranial Alternating Current Stimulation (tACS) in declarative learning. Using a between-subject (real versus sham stimulation group), single-blind stimulation design, 76 participants learned 60 Dutch-Swahili word pairs, while theta-frequency (6 Hz) tACS was administered over the medial frontal cortex (MFC). Previous studies have implicated MFC in memory encoding. We replicated our previous finding of signed RPEs (SRPEs) boosting declarative learning; with larger and more positive RPEs enhancing memory performance. However, tACS failed to modulate the SRPE effect in declarative learning and did not affect memory performance. Bayesian statistics supported evidence for an absence of effect. Our study confirms a role of RPE in declarative learning, but also calls for standardized procedures in transcranial electrical stimulation.

scholarly journals Failure to modulate reward prediction errors in declarative learning with theta (6 Hz) frequency transcranial alternating current stimulation

2020 ◽  
Author(s):  
Kate Ergo ◽  
Esther De Loof ◽  
Gillian Debra ◽  
Bernhard Pastötter ◽  
Tom Verguts
Keyword(s):  
Memory Performance ◽  
Alternating Current ◽  
Transcranial Electrical Stimulation ◽  
Prediction Errors ◽  
Memory Encoding ◽  
Neurophysiological Mechanism ◽  
Reward Prediction ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Declarative Learning

AbstractRecent evidence suggests that reward prediction errors (RPEs) play an important role in declarative learning, but its neurophysiological mechanism remains unclear. Here, we tested the hypothesis that RPEs modulate declarative learning via theta-frequency oscillations, which have been related to memory encoding in prior work. For that purpose, we examined the interaction between RPE and transcranial Alternating Current Stimulation (tACS) in declarative learning. Using a between-subject (real versus sham stimulation group), single-blind stimulation design, 76 participants learned 60 Dutch-Swahili word pairs, while theta-frequency (6 Hz) tACS was administered over the medial frontal cortex (MFC). Previous studies have implied MFC in memory encoding. We replicated our previous finding of signed RPEs (SRPEs) boosting declarative learning; with larger and more positive RPEs enhancing memory performance. However, tACS failed to modulate the SRPE effect in declarative learning and did not affect memory performance. Bayesian statistics supported evidence for an absence of effect. Our study confirms a role of RPE in declarative learning, but also calls for standardized procedures in transcranial electrical stimulation.

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

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.

scholarly journals Effects of theta transcranial alternating current stimulation (tACS) on exploration and exploitation during uncertain decision-making

2021 ◽  
Author(s):  
Miles Wischnewski ◽  
Boukje Compen
Keyword(s):  
Risk Taking ◽  
Current Flow ◽  
Flow Direction ◽  
Alternating Current ◽  
Double Blind ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Exploration Exploitation ◽  
The Relationship ◽  
Posterior Anterior

Exploring ones surroundings may yield unexpected rewards, but is associated with uncertainty and risk. Alternatively, exploitation of certain outcomes is related to low risk, yet potentially better outcomes remain unexamined. As such, risk-taking behavior depends on perceived uncertainty and a trade-off between exploration-exploitation. Previously, it has been suggested that risk-taking may relate to theta activity in the prefrontal cortex. Furthermore, previous studies hinted at a relationship between a right-hemispheric bias in frontal theta asymmetry and risky behavior. In the present double-blind sham-controlled within-subject study, we applied bifrontal transcranial alternating current stimulation (tACS) at the theta frequency (5 Hz) on eighteen healthy volunteers during a gambling task. Two tACS montages with either left-right or posterior-anterior current flow were employed at an intensity of 1 mA. Results showed that, compared to sham, theta tACS increased perceived uncertainty irrespective of current flow direction. Despite this observation, no direct effect of tACS on exploration behavior and general risk-taking was observed. Furthermore, frontal theta asymmetry was more right-hemispherically biased after posterior-anterior tACS, compared to sham. Finally, we used electric field simulation to identify which regions were targeted by the tACS montages as an overlap in regions may explain why the two montages resulted in comparable outcomes. Our findings provide a first step towards understanding the relationship between frontal theta oscillations and different features of risk-taking.

Online Theta Frequency Transcranial Alternating Current Stimulation for Cognitive Remediation in Schizophrenia

2019 ◽  
Vol 35 (2) ◽  
pp. 139-143 ◽  
Author(s):  
Vanteemar S. Sreeraj ◽  
Venkataram Shivakumar ◽  
Selvaraj Sowmya ◽  
Anushree Bose ◽  
Hema Nawani ◽  
...  
Keyword(s):  
Cognitive Remediation ◽  
Alternating Current ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation

scholarly journals Theta Phase-dependent Modulation of Perception by Concurrent Transcranial Alternating Current Stimulation and Periodic Visual Stimulation

2020 ◽  
Vol 32 (6) ◽  
pp. 1142-1152
Author(s):  
Elif Somer ◽  
John Allen ◽  
Joseph L. Brooks ◽  
Vaughan Buttrill ◽  
Amir-Homayoun Javadi
Keyword(s):  
Visual Cortex ◽  
Visual Stimulus ◽  
Auditory Perception ◽  
Visual Stimulation ◽  
Alternating Current ◽  
Matching Task ◽  
Phase 0 ◽  
Theta Frequency ◽  
Transcranial Alternating Current Stimulation ◽  
Visual Matching

Sensory perception can be modulated by the phase of neural oscillations, especially in the theta and alpha ranges. Oscillatory activity in the visual cortex can be entrained by transcranial alternating current stimulation (tACS) as well as periodic visual stimulation (i.e., flicker). Combined tACS and visual flicker stimulation modulates BOLD response, and concurrent 4-Hz auditory click train, and tACS modulate auditory perception in a phase-dependent way. In this study, we investigated whether phase synchrony between concurrent tACS and periodic visual stimulation (i.e., flicker) can modulate performance on a visual matching task. Participants completed a visual matching task on a flickering visual stimulus while receiving either in-phase (0°) or asynchronous (180°, 90°, or 270°) tACS at alpha or theta frequency. Stimulation was applied over either occipital cortex or dorsolateral pFC. Visual performance was significantly better during theta frequency tACS over the visual cortex when it was in-phase (0°) with visual stimulus flicker, compared with antiphase (180°). This effect did not appear with alpha frequency flicker or with dorsolateral pFC stimulation. Furthermore, a control sham group showed no effect. There were no significant performance differences among the asynchronous (180°, 90°, and 270°) phase conditions. Extending previous studies on visual and auditory perception, our results support a crucial role of oscillatory phase in sensory perception and demonstrate a behaviorally relevant combination of visual flicker and tACS. The spatial and frequency specificity of our results have implications for research on the functional organization of perception.

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