scholarly journals Pre-trial predictors of conflict response efficacy in human dorsolateral prefrontal cortex

2021 ◽  
Author(s):  
Alexander B Herman ◽  
Elliot Smith ◽  
Mark Yates ◽  
Guy McKhann ◽  
Matthew Botvinick ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Firing Rate ◽  
Dorsolateral Prefrontal Cortex ◽  
Reaction Times ◽  
Initial State ◽  
Conflict Task ◽  
Dorsolateral Prefrontal ◽  
Cognitive Action ◽  
Response State ◽  
Motor Actions

The ability to perform motor actions depends, in part, on the brain's initial state, that is the ensemble firing rate pattern prior to the initiation of action. We hypothesized that the same principle would apply to cognitive functions as well. To test this idea, we examined a unique set of single unit data collected in human dorsolateral prefrontal cortex (dlPFC). Data were collected in a conflict task that interleaves Simon (motor-type) and Eriksen (flanker-type) conflict trials. Variability in pre-trial firing rate predicted the ability to resolve conflict, as inferred from reaction times. Ensemble patterns that predicted faster Simon reaction times overlapped slightly with those predicting Eriksen performance, indicating that the two conflict types are associated with near-orthogonal initial states, and suggesting that there is a weak abstract or amodal conflict preparatory state in this region. These codes became fully orthogonalized in the response state. We interpret these results in light of the initial state and dual-mechanisms of control hypotheses, arguing that the firing patterns in dlPFC immediately preceding the start of the task predispose it for the efficient implementation of cognitive action.

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 Monkey prefrontal neurons during Sternberg task performance: full contents of working memory or most recent item?

2017 ◽  
Vol 117 (6) ◽  
pp. 2269-2281 ◽  
Author(s):  
R. O. Konecky ◽  
M. A. Smith ◽  
C. R. Olson
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Firing Rate ◽  
Dorsolateral Prefrontal Cortex ◽  
Memory Task ◽  
Delay Period ◽  
Population Activity ◽  
Storage Mechanism ◽  
Dorsolateral Prefrontal ◽  
Recent Item

To explore the brain mechanisms underlying multi-item working memory, we monitored the activity of neurons in the dorsolateral prefrontal cortex while macaque monkeys performed spatial and chromatic versions of a Sternberg working-memory task. Each trial required holding three sequentially presented samples in working memory so as to identify a subsequent probe matching one of them. The monkeys were able to recall all three samples at levels well above chance, exhibiting modest load and recency effects. Prefrontal neurons signaled the identity of each sample during the delay period immediately following its presentation. However, as each new sample was presented, the representation of antecedent samples became weak and shifted to an anomalous code. A linear classifier operating on the basis of population activity during the final delay period was able to perform at approximately the level of the monkeys on trials requiring recall of the third sample but showed a falloff in performance on trials requiring recall of the first or second sample much steeper than observed in the monkeys. We conclude that delay-period activity in the prefrontal cortex robustly represented only the most recent item. The monkeys apparently based performance of this classic working-memory task on some storage mechanism in addition to the prefrontal delay-period firing rate. Possibilities include delay-period activity in areas outside the prefrontal cortex and changes within the prefrontal cortex not manifest at the level of the firing rate. NEW & NOTEWORTHY It has long been thought that items held in working memory are encoded by delay-period activity in the dorsolateral prefrontal cortex. Here we describe evidence contrary to that view. In monkeys performing a serial multi-item working memory task, dorsolateral prefrontal neurons encode almost exclusively the identity of the sample presented most recently. Information about earlier samples must be encoded outside the prefrontal cortex or represented within the prefrontal cortex in a cryptic code.

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.

Trait anxiety moderates the effects of tDCS over the dorsolateral prefrontal cortex (DLPFC) on creativity

2021 ◽  
Vol 177 ◽  
pp. 110804
Author(s):  
Shuoqi Xiang ◽  
Senqing Qi ◽  
Yangping Li ◽  
Luchun Wang ◽  
David Yun Dai ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Trait Anxiety ◽  
Dorsolateral Prefrontal Cortex ◽  
Dorsolateral Prefrontal
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