Response bias reveals the role of interhemispheric inhibitory networks in movement preparation and execution

Human movement is influenced by various cognitive processes, such as bias, that dynamically shape competing movement representations. However, the neurophysiological mechanisms underlying the effects of bias on movement selection across the lifespan remains poorly understood.Healthy young (n = 21) and older (n = 20) adults completed a choice reaction time task necessitating left- or right-hand responses to imperative stimuli (IS). Response bias was manipulated via a cue that informed participants a particular response was 70% likely (i.e., the IS was either congruent, or incongruent, with the cue); biasing was either fixed for blocks of trials (block-wise bias) or varied from trial-to-trial (trial-wise bias). As well as assessing the behavioural manifestations of bias, we used transcranial magnetic stimulation to determine changes in corticospinal excitability (CSE) and short- and long-interval interhemispheric inhibition (SIHI, LIHI) during movement preparation and execution. Participants responded more quickly, and accurately, in congruent compared to incongruent trials. CSE decreases occurred in both hands following the cue, consistent with the ‘inhibition for impulse control’ hypothesis of preparatory inhibition. In contrast, IHI modulations occurred in a hand-specific manner. Greater SIHI was observed during movement preparation in the hand biased away from, compared to the hand biased towards, the cue; furthermore, greater SIHI was observed during movement execution in the hand biased towards the cue when it was not required to respond (i.e., incongruent trial) compared to when it was required to respond (congruent trial). Additionally, during the movement preparation period, the LIHI ratio of the hand biased towards, compared to the hand biased away from, the cue was greatest when the cue varied trial-by-trial. Overall, the IHI results provide support for the ‘inhibition for competition resolution’ hypothesis, with hand specific modulation of inhibition during movement preparation and execution.

Thematic bootstrapping: Performance differences between expert chess players and novices

Previous research has revealed that memory-based processes are one of the most consistent differences between a novice and a chess expert. The current study used a priming task in 57 adults to investigate whether priming improves the accuracy in finding the best candidate move for a given chess configuration. The stimuli were theme-based chess configurations that served as the prime and target during the procedure. Results indicated for experts that accurate processing of a prime's theme in a congruent trial results in a response priming effect, that is, more correct answers and a decrease in response time. The theoretical implications along with the possible applications of the results are discussed.

Multiple expectancies underlie the congruency sequence effect in confound-minimized tasks

The congruency sequence effect (CSE) occurs when the congruency effect observed in tasks such as the Eriksen flanker task is smaller on trials preceded by an incongruent trial relative to trials preceded by a congruent trial. The CSE has been attributed to a range of factors including repetition expectancy, conflict monitoring, feature integration, and contingency learning. To clarify the debate surrounding the CSE and the mechanisms underlying its occurrence, researchers have developed confound-minimized congruency tasks designed to control for feature-integration and contingency-learning effects. A CSE is often observed in confound-minimized tasks, indicating that the effect is driven by repetition expectancy, conflict monitoring, or a combination of the two. Here, we propose and test a variant of the repetition expectancy account that emphasizes how multiple expectations can be formed simultaneously based upon the congruency type (congruent vs. incongruent) and the congruency repetition type (congruency repetition vs. congruency alternation) of the most recent trial. Data from confound-minimized versions of the prime-probe task were found to support this novel account. Data from confound-minimized versions of the Eriksen flanker, Simon, and Stroop tasks indicate that repetition-priming confounds often remain in these tasks, potentially undermining the conclusions of previous work. We discuss the implications of these findings for ongoing theoretical debates surrounding the CSE.

RTs across Dual Stimuli, Gender, GPA and Trialtype

This psychophysics experiment of Eriksen Flanker Task experiment is built in four independent variables (stimuli, gender, GPA, and trial type) with one dependent variable (RTs). CAF was also examined between stimuli arrow and letter. The data was analyzed using four-way ANOVA. The result revealed that 1) Arrow stimuli needed few RTs than letter stimuli (F value = 17.964, and p-value = 2.34e-05). 2) In gender, there was a significantly different effect of RTs between female and male groups(F value = 91.203, p-value = 2e-16 (p < 0.001). 3) In trial type, incongruent trial required more RTs than congruent trial (F value = 144.569, p-value = <2e-16 (p < 0.001). 4) Arrow stimuli was more accurate than letter with t-value = 6.4099, df = 2220.5, p-value = 1.773e-10. The result found the differences between the stimuli were caused by horizontal and vertical attention, so were in trial-type with parallel and focus phase. Across gender,the male group has proven to be faster in both stimuli than the female counterpart. This RTs pattern suggest that in conflict flanker task research, people tend to show the same architecture processing. Therefore the finding is quite universal in several research.

Performance on Auditory and Visual Tasks of Inhibition in English Monolingual and Spanish–English Bilingual Adults: Do Bilinguals Have a Cognitive Advantage?

Purpose Bilingual individuals have been shown to be more proficient on visual tasks of inhibition compared with their monolingual counterparts. However, the bilingual advantage has not been evidenced in all studies, and very little is known regarding how bilingualism influences inhibitory control in the perception of auditory information. The purpose of the current study was to examine inhibition of irrelevant information using auditory and visual tasks in English monolingual and Spanish–English bilingual adults. Method Twenty English monolinguals and 19 early balanced Spanish–English bilinguals participated in this study. All participants were 18–30 years of age, had hearing thresholds < 25 dB HL from 250 to 8000 Hz, bilaterally (American National Standards Institute, 2003), and were right handed. Inhibition was measured using a forced-attention dichotic consonant–vowel listening task and the Simon task, a nonverbal visual test. Results Both groups of participants demonstrated a significant right ear advantage on the dichotic listening task; however, no significant differences in performance were evidenced between the monolingual and bilingual groups in any of the dichotic listening conditions. Both groups performed better on the congruent trial than on the incongruent trial of the Simon task and had significantly faster response times on the congruent trial than on the incongruent trial. However, there were no significant differences in performance between the monolingual and bilingual groups on the visual test of inhibition. Conclusions No significant differences in performance on auditory and visual tests of inhibition of irrelevant information were evidenced between the monolingual and bilingual participants in this study. These findings suggest that bilinguals may not exhibit an advantage in the inhibition of irrelevant information compared with monolinguals.

Conflict adaptation and cognitive control adjustments following traumatic brain injury

Survivors of severe traumatic brain injury (TBI) often demonstrate impairments in the cognitive control functions of detecting response conflict and signaling for recruitment of cognitive resources to appropriately adjust performance. These cognitive control functions can be measured using conflict adaptation effects, wherein manifestations of conflict detection and processing are reduced following high- relative to low-conflict trials. Event-related potentials (ERPs) were collected while 18 survivors of severe traumatic brain injury (TBI) and 21 demographically matched control participants performed a modified Stroop task. The incongruent-minus-congruent trial Stroop effect for trials preceded by incongruent (high conflict) and congruent (low conflict) trials were compared for behavioral (response time [RT] and error rate) and ERP reflections of cognitive control. Behavioral data showed a reduction in the Stroop effect for both control and TBI participant RTs when preceded by incongruent trials. The magnitude of these effects did not differentiate control and TBI participants. ERP data revealed a centro-parietal conflict slow potential (conflict SP) that differentiated incongruent from congruent trials. Planned comparisons showed a decreased amplitude conflict SP when ERPs were preceded by incongruent trials in control, but not TBI participants. Results indicate subtle TBI-related impairments in conflict resolution mechanisms in the context of intact RT-related conflict adaptation. (JINS, 2009, 15, 927–937.)