scholarly journals T54. EFFECTS OF GAMMA TRANSCRANIAL ALTERNATING CURRENT STIMULATION TO THE LEFT DORSOLATERAL PREFRONTAL CORTEX ON WORKING MEMORY IN SCHIZOPHRENIA PATIENTS

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S251-S252
Author(s):  
Irina Papazova ◽  
Wolfgang Strube ◽  
Lina Hoffmann ◽  
Tobias Schwippel ◽  
Frank Padberg ◽  
...  
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Cognitive Load ◽  
Dorsolateral Prefrontal Cortex ◽  
Reaction Times ◽  
Alternating Current ◽  
Primary Study ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation ◽  
Healthy Participants

Abstract Background Working memory (WM) impairment is characteristic for schizophrenia patients, lowering their occupational status and quality of life. Recent research suggests that non-invasive brain stimulation could have the potential to treat such cognitive deficits. One novel and promising approach is the transcranial alternating current stimulation (tACS) that could entrain the endogenous gamma oscillations in the dorsolateral prefrontal cortex (DLPFC), previously shown to be abnormal in schizophrenia patients and associated with WM deficits. Indeed, first studies demonstrated WM improvement in healthy participants following tACS at the gamma frequency (γ-tACS) to the DLPFC in healthy participants. However, till date, there is only one pilot study with ten schizophrenia patients, where cognitive enhancement was not evident. Here, we aimed to investigate the efficacy and feasibility of γ-tACS on simultaneous WM performance in schizophrenia patients with a bigger study sample and in regard of cognitive load Methods A total of fifteen patients with schizophrenia (N = 15, 8 female) participated in the current study. They underwent a pre-stimulation baseline, an active γ-tACS and a sham single-session in a double-blind, cross-over design. Stimulation was administered over the left DLPFC (F3, anode) and the contralateral region (F4, cathode) at a current of -1mA to 1mA (peek-to-peek) at 40 Hz for 20 min (48000 cycles). We assessed WM during stimulation using a verbal n-back task with three cognitive loads (1- to 3-back). Reaction times and discriminability index d prime served as primary study outcomes. Using several RM-ANOVAs, we compared working memory performance during γ-tACS and sham across all cognitive loads. Results Data analysis showed no significant main effect of γ-tACS compared to sham on both d prime values (p = .269) and reaction times (p = .166). However, we observed a significant stimulation x load interaction effect on reaction times (p = .043), suggesting that with increasing cognitive load participants responded slightly slower during active than during sham γ-tACS. Discussion The current work is one of the first to investigate the effects of γ-tACS to the DLPFC on simultaneous WM performance in schizophrenia patients. In line with previous research, we did not find any significant changes in cognition due to stimulation. Surprisingly, we observed a slight decrease in WM speed with higher cognitive load during active compared to sham tACS. Results are discussed in line of study protocol and tACS feasibility and emphasize the need for future research on the specific study design parameters.

scholarly journals Alpha and Theta Transcranial Alternating Current Stimulation Over the Right Dorsolateral Prefrontal Cortex Modulates Vigilance Performance, but Only When Arousal Levels Are Non-optimal

2021 ◽  
Author(s):  
Víctor Martínez-Pérez ◽  
Miriam Tortajada ◽  
Lucía B. Palmero ◽  
Guillermo Campoy ◽  
Luis J. Fuentes
Keyword(s):  
Prefrontal Cortex ◽  
Dorsolateral Prefrontal Cortex ◽  
Alternating Current ◽  
Time Of Day ◽  
Time On Task ◽  
Frontoparietal Network ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation ◽  
The Right

Abstract BackgroundCurrent theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on the frontoparietal network could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e. arousal and executive vigilance) and the potential role of differences in arousal baseline. MethodWe examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex on both components of vigilance and on participants that differed in arousal baseline according to their chronotype and the time of testing. Intermediate-types performed the vigilance tasks when their arousal baseline was at the optimal level, whereas evening-types performed the vigilance tasks when their arousal baseline was at non-optimal levels. ResultsBoth theta- and alpha-tACS improved arousal vigilance, whereas alpha-tACS, but not theta-tACS, improved accuracy and attenuated the typical vigilance decrement in the executive vigilance task. Importantly, these stimulation effects were only found when arousal baseline was low (i.e., with evening-types performing the tasks at their non-optimal time of day).ConclusionThe results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal baseline, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the frontoparietal network.

scholarly journals Effects of transcranial alternating current stimulation over right-DLPFC on vigilance tasks depend on the arousal level

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Víctor Martínez-Pérez ◽  
Miriam Tortajada ◽  
Lucía B. Palmero ◽  
Guillermo Campoy ◽  
Luis J. Fuentes
Keyword(s):  
Prefrontal Cortex ◽  
Sustained Attention ◽  
Dorsolateral Prefrontal Cortex ◽  
Alternating Current ◽  
Arousal Level ◽  
Time On Task ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation ◽  
The Right

AbstractCurrent theoretical accounts on the oscillatory nature of sustained attention predict that entrainment via transcranial alternating current stimulation (tACS) at alpha and theta frequencies on specific areas of the prefrontal cortex could prevent the drops in vigilance across time-on-task. Nonetheless, most previous studies have neglected both the fact that vigilance comprises two dissociable components (i.e., arousal and executive vigilance) and the potential role of differences in arousal levels. We examined the effects of theta- and alpha-tACS over the right dorsolateral prefrontal cortex in both components of vigilance and in participants who differed in arousal level according to their chronotype and time of testing. Intermediate-types performed the vigilance tasks when their arousal level was optimal, whereas evening-types performed the vigilance tasks when their arousal levels were non-optimal. Both theta- and alpha-tACS improved arousal vigilance in the psychomotor vigilance task (PVT), whereas alpha-tACS, but not theta-tACS, improved executive vigilance in the sustained attention to response task (SART), and counteracted the typical vigilance decrement usually observed in this task. Importantly, these stimulation effects were only found when arousal was low (i.e., with evening-types performing the tasks at their non-optimal time of day). The results support the multicomponent view of vigilance, the relevance of heeding individual differences in arousal, and the role of alpha oscillations as a long-range cortical scale synchronization mechanism that compensates the decrements in performance as a function of time-on-task by exerting and maintaining cognitive control attributed to activation of the right dorsolateral prefrontal cortex.

scholarly journals Effects of β-Lactolin on Regional Cerebral Blood Flow within the Dorsolateral Prefrontal Cortex during Working Memory Task in Healthy Adults: A Randomized Controlled Trial

2021 ◽  
Vol 10 (3) ◽  
pp. 480
Author(s):  
Yasuhisa Ano ◽  
Masahiro Kita ◽  
Keiko Kobayashi ◽  
Takashi Koikeda ◽  
Ryuta Kawashima
Keyword(s):  
Working Memory ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Prefrontal Cortex ◽  
Regional Cerebral Blood Flow ◽  
Dorsolateral Prefrontal Cortex ◽  
Healthy Adults ◽  
Regional Cerebral Blood ◽  
Total Hemoglobin ◽  
Dorsolateral Prefrontal

Epidemiological studies have reported that consumption of dairy products rich in β-lactolin is beneficial for cognitive decline among elderly individuals. Although previous studies have shown that β-lactolin supplementation improves memory function and attention in healthy adults, the mechanism through which β-lactolin affects human brain function has yet to be elucidated. This placebo-controlled randomized double-blind study therefore examined the effects of β-lactolin on human regional cerebral blood flow (rCBF) using near-infrared spectroscopy (NIRS) according to the Consolidated Standards of Reporting Trials guidelines. A total of 114 healthy participants aged between 50 and 75 years with relatively low cognition were randomly allocated into the β-lactolin or placebo groups (n = 57 for both groups) and received supplementation for 6 weeks. After the 6 weeks of supplementation, total hemoglobin during cognitive tasks (Kraepelin and 2-back tasks) was measured using two-channel NIRS to determine rCBF. Accordingly, the β-lactolin group had significantly higher changes in total hemoglobin at the left dorsolateral prefrontal cortex (DLPFC) area measured using the left-side channel during the 2-back tasks (p = 0.027) compared to the placebo group. The present study suggests that β-lactolin supplementation increases rCBF and DLPFC activity during working memory tasks.

scholarly journals Prefrontal and Parietal Attractor Networks Mediate Working Memory Judgments

2020 ◽  
Author(s):  
Sihai Li ◽  
Christos Constantinidis ◽  
Xue-Lian Qi
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Dorsolateral Prefrontal Cortex ◽  
Critical Role ◽  
Memory Task ◽  
Delayed Response ◽  
Persistent Activity ◽  
Neural Basis ◽  
Brain Areas ◽  
Dorsolateral Prefrontal

ABSTRACTThe dorsolateral prefrontal cortex plays a critical role in spatial working memory and its activity predicts behavioral responses in delayed response tasks. Here we addressed whether this predictive ability extends to categorical judgments based on information retained in working memory, and is present in other brain areas. We trained monkeys in a novel, Match-Stay, Nonmatch-Go task, which required them to observe two stimuli presented in sequence with an intervening delay period between them. If the two stimuli were different, the monkeys had to saccade to the location of the second stimulus; if they were the same, they held fixation. Neurophysiological recordings were performed in areas 8a and 46 of the dlPFC and 7a and lateral intraparietal cortex (LIP) of the PPC. We hypothesized that random drifts causing the peak activity of the network to move away from the first stimulus location and towards the location of the second stimulus would result in categorical errors. Indeed, for both areas, when the first stimulus appeared in a neuron’s preferred location, the neuron showed significantly higher firing rates in correct than in error trials. When the first stimulus appeared at a nonpreferred location and the second stimulus at a preferred, activity in error trials was higher than in correct. The results indicate that the activity of both dlPFC and PPC neurons is predictive of categorical judgments of information maintained in working memory, and the magnitude of neuronal firing rate deviations is revealing of the contents of working memory as it determines performance.SIGNIFICANCE STATEMENTThe neural basis of working memory and the areas mediating this function is a topic of controversy. Persistent activity in the prefrontal cortex has traditionally been thought to be the neural correlate of working memory, however recent studies have proposed alternative mechanisms and brain areas. Here we show that persistent activity in both the dorsolateral prefrontal cortex and posterior parietal cortex predicts behavior in a working memory task that requires a categorical judgement. Our results offer support to the idea that a network of neurons in both areas act as an attractor network that maintains information in working memory, which informs behavior.

scholarly journals Modulation of Conflict Processing by Theta-Range tACS over the Dorsolateral Prefrontal Cortex

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Albert Lehr ◽  
Niklas Henneberg ◽  
Tarana Nigam ◽  
Walter Paulus ◽  
Andrea Antal
Keyword(s):  
Prefrontal Cortex ◽  
Cognitive Control ◽  
Stroop Task ◽  
Stroop Effect ◽  
Dorsolateral Prefrontal Cortex ◽  
Control Network ◽  
Control Mechanisms ◽  
Cognitive Control Network ◽  
Dorsolateral Prefrontal ◽  
Transcranial Alternating Current Stimulation

Behavioral response conflict arises in the color-word Stroop task and triggers the cognitive control network. Midfrontal theta-band oscillations correlate with adaptive control mechanisms during and after conflict resolution. In order to prove causality, in two experiments, we applied transcranial alternating current stimulation (tACS) at 6 Hz to the dorsolateral prefrontal cortex (DLPFC) during Stroop task performance. Sham stimulation served as a control in both experiments; 9.7 Hz tACS served as a nonharmonic alpha band control in the second experiment. We employed generalized linear mixed models for analysis of behavioral data. Accuracy remained unchanged by any type of active stimulation. Over both experiments, the Stroop effect (response time difference between congruent and incongruent trials) was reduced by 6 Hz stimulation as compared to sham, mainly in trials without prior conflict adaptation. Alpha tACS did not modify the Stroop effect. Theta tACS can both reduce the Stroop effect and modulate adaptive mechanisms of the cognitive control network, suggesting midfrontal theta oscillations as causally involved in cognitive control.

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