scholarly journals How Reliable are Prefrontal tDCS Effects – Zero–effects on the Keep–track Task?

2019 ◽  
Author(s):  
Dunja Paunović ◽  
Danka Purić ◽  
Jovana Bjekić ◽  
Saša Filipović
Keyword(s):  
Cognitive Processes ◽  
Dorsolateral Prefrontal Cortex ◽  
Posterior Parietal Cortex ◽  
Control Measure ◽  
Reaction Time Task ◽  
Left Dlpfc ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal ◽  
Neural Underpinnings

AbstractRecent neuroimaging studies showed that in addition to the dorsolateral prefrontal cortex (dlPFC), the posterior parietal cortex (PPC) plays a significant role in higher cognitive processes such as executive functions. In this study we aimed to explore the neural underpinnings of executive function of updating by exploring the effects of transcranial direct current stimulation (tDCS) over dlPFC and PCC. Nineteen healthy right–handed participants took part in a cross–over sham–controlled experiment. All participants underwent three tDCS conditions (active tDCS over the left dlPFC; active tDCS over the left PPC; and sham) in counterbalanced order. Following tDCS participants completed the keep–track task, with parallel forms being used in different test–sessions. As a control measure, we used a choice reaction time task. Results showed no significant effects of tDCS regardless of the localization of stimulation. Our results are in contrast with results of other studies exploring prefrontal tDCS effects on updating and do not allow for deriving conclusions about the role of the left PPC in the ability to update information in working memory.

scholarly journals Cerebral cortex activation during the Sternberg verbal working memory task

2020 ◽  
pp. 40-48
Author(s):  
I.S. Bakulin ◽  
A.H. Zabirova ◽  
P.N. Kopnin ◽  
D.O. Sinitsyn ◽  
A.G. Poydasheva ◽  
...  
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Temporal Dynamics ◽  
Memory Task ◽  
Occipital Cortex ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal ◽  
Sternberg Task

Despite intensive study, the data regarding functional role of specific brain regions in the working memory processes still remain controversial. The study was aimed to determine the activation of cerebral cortex regions at different stages of the working memory task (information encoding, maintenance and retrieval). Functional magnetic resonance imaging (fMRI) with the modified Sternberg task was applied to 19 healthy volunteers. The objective of the task was to memorize and retain in memory the sequence of 7 letters with the subsequent comparison of one letter with the sequence. Activation was analyzed during three periods of the task compared to the rest period, as well as temporal dynamics of changes in BOLD signal intensity in three regions: left dorsolateral prefrontal, left posterior parietal and left occipital cortex. According to the results, significant activation of the regions in prefrontal and posterior parietal cortex was observed during all periods of the task (p < 0.05), but there were changes in its localization and lateralization. The activation pattern during the maintenance period corresponded to the fronto-parietal control network components. According to the analysis of temporal dynamics of changes in BOLD signal intensity, the most prominent activation of the dorsolateral prefrontal cortex and parietal cortex was observed in the end of the encoding period, during the maintenance period and in the beginning of the retrieval period, which confirmed the role of those areas in the working memory processes. The maximum of occipital cortex activation was observed during encoding period. The study confirmed the functional role of the dorsolateral prefrontal cortex and posterior parietal cortex in the working memory mechanisms during all stages of the Sternberg task.

scholarly journals Unilateral deactivation of macaque dorsolateral prefrontal cortex induces biases in stimulus selection

2016 ◽  
Vol 115 (3) ◽  
pp. 1468-1476 ◽  
Author(s):  
Kevin Johnston ◽  
Stephen G. Lomber ◽  
Stefan Everling
Keyword(s):  
Prefrontal Cortex ◽  
Dorsolateral Prefrontal Cortex ◽  
Nonhuman Primates ◽  
Reaction Times ◽  
Stimulus Onset ◽  
Middle Frontal Gyrus ◽  
Stimulus Selection ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal

Following unilateral brain injury, patients are often unable to detect a stimulus presented in the contralesional field when another is presented simultaneously ipsilesionally. This phenomenon has been referred to as extinction and has been conceptualized as a deficit in selective attention. Although most commonly observed following damage to posterior parietal areas, extinction has been observed following lesions of prefrontal cortex (PFC) in both humans and nonhuman primates. To date, most studies in nonhuman primates have examined lesions of multiple PFC subregions, including the frontal eye fields (FEF). Theoretical accounts of attentional disturbances from human patients, however, also implicate other PFC areas, including the middle frontal gyrus. Here, we investigated the effects of deactivating PFC areas anterior to the FEF on stimulus selection using a free-choice task. Macaque monkeys were presented with two peripheral stimuli appearing either simultaneously, or at varying stimulus onset asynchronies, and their performance was evaluated during unilateral cryogenic deactivation of part of dorsolateral prefrontal cortex or the cortex lining the caudal principal sulcus, the likely homologue of the human middle frontal gyrus. A decreased proportion of saccades was made to stimuli presented in the hemifield contralateral to the deactivated PFC. We also observed increases in reaction times to contralateral stimuli and decreases for stimuli presented in the hemifield ipsilateral to the deactivated hemisphere. In both cases, these results were greatest when both PFC subregions were deactivated. These findings demonstrate that selection biases result from PFC deactivation and support a role of dorsolateral prefrontal subregions anterior to FEF in stimulus selection.

scholarly journals The Role of Left Dorsolateral Prefrontal Cortex in Language Processing

2017 ◽  
Author(s):  
Jana Klaus ◽  
Dennis J. L. G. Schutter
Keyword(s):  
Prefrontal Cortex ◽  
Language Processing ◽  
Language Comprehension ◽  
Language Production ◽  
Dorsolateral Prefrontal Cortex ◽  
Production Task ◽  
Double Blind ◽  
Left Dlpfc ◽  
Dorsolateral Prefrontal

In addition to the role of left frontotemporal areas in language processing, there is increasing evidence that language comprehension and production require control and working memory resources involving the left dorsolateral prefrontal cortex (DLPFC). The aim of this study was to investigate the role of the left DLPFC in both language comprehension and production. In a double-blind, sham-controlled crossover experiment, thirty-two participants received cathodal or sham transcranial direct current stimulation (tDCS) to the left DLPFC while performing a language comprehension and a language production task. Results showed that cathodal tDCS increases reaction times in the language comprehension task, but decreases naming latencies in the language production task. However, additional analyses revealed that the polarity of tDCS effects was highly correlated across tasks, implying differential individual susceptibility to the effect of tDCS within participants. Overall, our findings demonstrate that left DLPFC is part of the complex cortical network associated with language processing.

scholarly journals Concurrent neuroimaging and neurostimulation reveals a causal role for dlPFC in coding of task-relevant information

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jade B. Jackson ◽  
Eva Feredoes ◽  
Anina N. Rich ◽  
Michael Lindner ◽  
Alexandra Woolgar
Keyword(s):  
Magnetic Stimulation ◽  
Dorsolateral Prefrontal Cortex ◽  
Relevant Information ◽  
Irrelevant Information ◽  
Visual Object ◽  
Information Coding ◽  
Frontoparietal Cortex ◽  
Dorsolateral Prefrontal ◽  
The Impact

AbstractDorsolateral prefrontal cortex (dlPFC) is proposed to drive brain-wide focus by biasing processing in favour of task-relevant information. A longstanding debate concerns whether this is achieved through enhancing processing of relevant information and/or by inhibiting irrelevant information. To address this, we applied transcranial magnetic stimulation (TMS) during fMRI, and tested for causal changes in information coding. Participants attended to one feature, whilst ignoring another feature, of a visual object. If dlPFC is necessary for facilitation, disruptive TMS should decrease coding of attended features. Conversely, if dlPFC is crucial for inhibition, TMS should increase coding of ignored features. Here, we show that TMS decreases coding of relevant information across frontoparietal cortex, and the impact is significantly stronger than any effect on irrelevant information, which is not statistically detectable. This provides causal evidence for a specific role of dlPFC in enhancing task-relevant representations and demonstrates the cognitive-neural insights possible with concurrent TMS-fMRI-MVPA.

Functional role of dorsolateral prefrontal cortex in the modulation of cognitive bias

2021 ◽  
Author(s):  
Xue Xia ◽  
Yansong Li ◽  
Yanqiu Wang ◽  
Jing Xia ◽  
Yitong Lin ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Cognitive Bias ◽  
Functional Role ◽  
Dorsolateral Prefrontal Cortex ◽  
Dorsolateral Prefrontal
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