Improvements In Inhibitory Control Research Articles

Longitudinal Growth Curves of Brain Function Underlying Inhibitory Control through Adolescence

Neuroimaging studies suggest that developmental improvements in inhibitory control are primarily supported by changes in prefrontal executive function. However, studies are contradictory with respect to how activation in prefrontal regions changes with age, and they have yet to analyze longitudinal data using growth curve modeling, which allows characterization of dynamic processes of developmental change, individual differences in growth trajectories, and variables that predict any interindividual variability in trajectories. In this study, we present growth curves modeled from longitudinal fMRI data collected over 302 visits (across ages 9 to 26 years) from 123 human participants. Brain regions within circuits known to support motor response control, executive control, and error processing (i.e., aspects of inhibitory control) were investigated. Findings revealed distinct developmental trajectories for regions within each circuit and indicated that a hierarchical pattern of maturation of brain activation supports the gradual emergence of adult-like inhibitory control. Mean growth curves of activation in motor response control regions revealed no changes with age, although interindividual variability decreased with development, indicating equifinality with maturity. Activation in certain executive control regions decreased with age until adolescence, and variability was stable across development. Error-processing activation in the dorsal anterior cingulate cortex showed continued increases into adulthood and no significant interindividual variability across development, and was uniquely associated with task performance. These findings provide evidence that continued maturation of error-processing abilities supports the protracted development of inhibitory control over adolescence, while motor response control regions provide early-maturing foundational capacities and suggest that some executive control regions may buttress immature networks as error processing continues to mature.

Charting early trajectories of executive control with the shape school.

Despite acknowledgement of the importance of executive control for learning and behavior, there is a dearth of research charting its developmental trajectory as it unfolds against the background of children's sociofamilial milieus. Using a prospective, cohort-sequential design, this study describes growth trajectories for inhibitory control and cognitive flexibility across the preschool period in relation to child sex and sociofamilial resources. At ages 3, 3.75, 4.5, and 5.25 years, children (N = 388) from a broad range of social backgrounds were assessed using the Shape School, a graduated measure of executive control incorporating baseline, inhibitory control, and cognitive flexibility conditions. Measures of children's proximal access to learning resources and social network supports were collected at study entry. Findings revealed substantial gains in accuracy and speed for all Shape School conditions, these gains being particularly accelerated between ages 3 and 3.75 years. Improvements in inhibitory control were more rapid than those in flexible switching. Age-related differences in error and self-correction patterns on the Shape School also suggest qualitative changes in the underlying processes supporting executive performance across early childhood. Children from homes with fewer learning resources showed a subtle lag in inhibition and cognitive flexibility performance that persisted at kindergarten entry age, despite exhibiting gradual catch up to their more advantaged peers for the nonexecutive, baseline task condition. The study provides a unique characterization of the early developmental pathways for inhibitory control and cognitive flexibility and highlights the critical role of stimulating early educational resources for shaping the dynamic ontogeny of executive control.

Is transcranial direct current stimulation a potential method for improving response inhibition?

Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the transcranial direct-current stimulation condition or a sham-transcranial direct-current stimulation condition. All subjects consecutively performed the stop-signal task before, during, and after the delivery of anodal transcranial direct-current stimulation over the pre-supplementary motor area (pre-transcranial direct-current stimulation phase, transcranial direct-current stimulation phase, and post-transcranial direct-current stimulation phase). Compared to the sham condition, there were significant reductions in the stop-signal processing times during and after transcranial direct-current stimulation, and change times were significantly greater in the transcranial direct-current stimulation condition. There was no significant change in go processing-times during or after transcranial direct-current stimulation in either condition. Anodal transcranial direct-current stimulation was feasibly coupled to an interactive improvement in inhibitory control. This coupling led to a decrease in the stop-signal process time required for the appropriate responses between motor execution and inhibition. However, there was no transcranial direct-current stimulation effect on the no-signal reaction time during the stop-signal task. Transcranial direct-current stimulation can adjust certain behaviors, and it could be a useful clinical intervention for patients who have difficulties with response inhibition.

Cognitive Training for Schizophrenia in Developing Countries: A Pilot Trial in Brazil

Cognitive deficits in schizophrenia can massively impact functionality and quality of life, furthering the importance of cognitive training. Despite the development of the field in Europe and in the United States, no programmes have been developed and tested in developing countries. Different cultural backgrounds, budget restrictions, and other difficulties may render treatment packages created in high income countries difficult for adoption by developing nations. We performed a pilot double-blind, randomized, controlled trial in order to investigate the efficacy and feasibility of an attention and memory training programme specially created in a developing nation. The intervention used simple, widely available materials, required minimal infrastructure, and was conducted in groups. The sample included seventeen stable Brazilians with schizophrenia. Sessions were conducted weekly during five months. The cognitive training group showed significant improvements in inhibitory control and set-shifting over time. Both groups showed improvements in symptoms, processing speed, selective attention, executive function, and long-term visual memory. Improvements were found in the control group in long-term verbal memory and concentration. Our findings reinforce the idea that cognitive training in schizophrenia can be constructed using simple resources and infrastructure, facilitating its adoption by developing countries, and it may improve cognition.

An examination of the effects of stimulant medication on response inhibition: A comparison between children with and without attention deficit hyperactivity disorder

This study investigated whether methylphenidate is effective in improving response inhibition in children with Attention Deficit Hyperactivity Disorder (ADHD). Children with ADHD were compared with normally developing children on measures of response inhibition. Participants with ADHD were compared across two conditions--medicated and unmedicated. There was no significant difference between the inhibitory control of children with and without ADHD. Children with ADHD showed significant improvements in inhibitory control following methylphenidate. The findings of the present study contrast with previous studies which document reduced inhibitory control in ADHD, compared with normally developing children. Reports of methylphenidate improving functioning in children with ADHD are supported. Limitation and implications of the study are discussed.

Poster 7: Use of Functional Near Infrared Spectroscopy to Assess Changes in Prefrontal Activation Associated With Recovery of Response Inhibition Following Traumatic Brain Injury

Objective: To determine the relationship of prefrontal cerebral activation to inhibitory control following traumatic brain injury and to assess the relationship of improvements in inhibitory control to increased prefrontal activation as a function of recovery. Design: Mixed design with repeated measures taken weekly. Setting: Functional near infrared spectroscopy (fNIRS) lab in a postacute brain injury rehabilitation clinic. Participants: Patients (n=16) with subacute severe traumatic brain injury (TBI) and age-matched controls (n=16). Interventions: All subjects performed a modified computerized Stroop task while measures of cerebral activation were obtained via a 3 × 11 optode configuration covering anterior temporal and frontal cerebral regions. Main Outcome Measures: Errors during performance of the Stroop task and measures of cerebral activation assessed by relative oxyhemoglobin concentrations obtained in one tenth second intervals. Results: Controls demonstrated significantly fewer Stroop errors (P<.01) and greater prefrontal activation (P<.01) compared with patients during the first week. By the third week, there were no significant differences between groups for either the number of Stroop errors or for prefrontal cerebral activation. Further analyses revealed that patients demonstrated significantly fewer Stroop errors (P<.01) and greater prefrontal activation (P<.01) by the third week. Conclusions: Improved inhibitory control was observed over a 3-week period for patients with severe TBI. This improved control appeared to be related to increased prefrontal activation. Although recovery is thought to have been the major reason for this improvement, practice effects due to repeated trials cannot be ruled out. This latter point is of note, since use of fNIRS may provide a useful procedure for assessing brain activation related change as a function of rehabilitation. Future research should assess changes in cerebral activation with fNIRS as related to specific rehabilitation approaches.

Effects of repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex on the attentional processing of emotional information in major depression: A pilot study

Repetitive transcranial magnetic stimulation (rTMS) is as a promising therapeutic tool for major depressive disorder. However, the degree of clinical improvement following rTMS treatment still remains questionable. This pilot study aimed at investigating potential working mechanisms of rTMS by examining the effects on attentional processing towards negative information, a proposed underlying cognitive vulnerability factor for depression. The antidepressant effect of high-frequency (10 Hz) rTMS over the left dorsolateral prefrontal cortex and possible effects on the inhibitory processing of emotional information was assessed in a sample of 14 depressed patients immediately after the first stimulation session and at the end of a 2-week treatment period. One session of rTMS caused neither significant self-reported mood changes, nor improvements in inhibitory control towards negative information. After a 10-day treatment period, nine out of our 14 patients demonstrated significant mood improvements, as indexed by a reduction of more than 50% on the Hamilton depression rating scale. Responders also demonstrated significant improvements in the inhibitory processing of negative information. This study contributed to the existing evidence of the antidepressant effect of rTMS in the treatment of depression and additionally was able to demonstrate improvements in underlying deficiencies in inhibitory processes towards negative information.

Effects of response preparation on developmental improvements in inhibitory control

Studies in adults indicate that response preparation is crucial to inhibitory control, but it remains unclear whether preparation contributes to improvements in inhibitory control over the course of childhood and adolescence. In order to assess the role of response preparation in developmental improvements in inhibitory control, we parametrically manipulated the duration of the instruction period in an antisaccade (AS) task given to participants from ages 8 to 31years. Regressions showing a protracted development of AS performance were consistent with existing research, and two novel findings emerged. First, all participants showed improved performance with increased preparation time, indicating that response preparation is crucial to inhibitory control at all stages of development. Preparatory processes did not deteriorate at even the longest preparatory period, indicating that the youngest participants were able to sustain preparation at even the longest interval. Second, developmental trajectories did not differ for different preparatory period lengths, highlighting that the processes supporting response preparation continue to mature in tandem with improvements in AS performance. Our findings suggest that developmental improvements are not simply due to an inhibitory system that is faster to engage but may also reflect qualitative changes in the processes engaged during the preparatory period.

The maturation of task set-related activation supports late developmental improvements in inhibitory control.

The ability to voluntarily inhibit a single response is evident early in development, even as the ability to maintain an inhibitory "task set" continues to improve. To date, functional neuroimaging studies have detailed developmental changes in systems supporting inhibitory control exerted at the single-trial level, but changes underlying the ability to maintain an inhibitory task set remain little understood. Here we present findings from a functional magnetic resonance imaging study that characterizes the development of systems supporting both transient (trial-related) and sustained (task set-related) activation during performance of the antisaccade task-an oculomotor test of inhibitory control (Hallett, 1978). Transient activation decreased from childhood to adolescence in regions known to support inhibitory processes and oculomotor control, likely reflecting less effortful response production. In contrast, sustained activation increased to adulthood in regions implicated in control. Our results suggest that development of the ability to maintain a task set is primary to the maturation of inhibitory control and, furthermore, that this ability is still immature in adolescence.

Thinking developmentally about counterfactual possibilities

AbstractByrne implies that working memory development underpins children's ability to represent counterfactuals as possibilities at 3 to 4 years of age. Recent findings suggest that (1) developments in the ability to consider alternatives to reality in children of this age are underpinned by improvements in inhibitory control, not working memory, and (2) children do not develop an understanding of counterfactuals as possibilities until mid-childhood.

Compensating for alcohol-induced impairment of control: effects on inhibition and activation of behavior

Studies have shown that expectations of alcohol-induced impairment can produce adaptive responses to alcohol that reduce the degree of behavioral impairment displayed. However, compensatory effects have been variable for cognitive and psychomotor tasks. Using a model-driven approach to understanding behavioral control, the present study examined compensatory and impairment effects following the expectation and actual administration of alcohol on the ability to inhibit and activate behavior. Social drinkers (N=17) performed a cued go/no-go task that required quick responses to go targets and inhibition of responses to no-go targets under four conditions: no treatment, alcohol expectancy (placebo), 0.45 g/kg alcohol, and 0.65 g/kg alcohol. Inhibitory and activational aspects of behavioral control were impaired by both active doses of alcohol. Alcohol slowed response activation and increased failures to inhibit responses in a dose-dependent manner. Subjects also displayed a small, but statistically significant, compensatory improvement in inhibitory control in response to the expectation of alcohol. Moreover, individual differences in the compensatory response were related to differences in alcohol impairment. Those who displayed greater compensatory responses to placebo displayed the least impairment in response to alcohol. By modeling behavioral control as the net effect of countervailing activational and inhibitory influences, the study suggests that fundamental mechanisms of control might not display uniform compensatory reactions to alcohol-related cues. Greater consideration of how alcohol-related expectancies shape behaviors under the drug should lead to a better understanding of individual differences with respect to risk for alcohol abuse.

Effects of d-amphetamine in human models of information processing and inhibitory control

Although stimulants are generally associated with enhanced information processing, reports of stimulant effects on behavioral functions that rely on inhibitory processes have been inconsistent. The present research tested the joint effects of d-amphetamine on information processing and inhibitory control in healthy adults ( N = 22) with no reported history of illicit stimulant use or drug dependence. Information processing was measured by a rapid information processing (RIP) task and inhibitory control was measured using a stop-signal task. Performance was measured in response to 15 mg/70 kg, 7.5 mg/70 kg, and 0 mg/70 mg (placebo) doses of d-amphetamine, administered double-blind in a randomized, within-subjects design. Results showed that d-amphetamine improved information processing in a dose-dependent manner. By contrast, no enhancement of response inhibition was observed. Stimulant effects were also observed in physiological and subjective effects measures. The findings indicate that a stimulant drug can enhance aspects of cognitive functioning without producing a concomitant improvement in inhibitory control of behavior. The findings highlight the complex nature of stimulant effects on human behavior and the utility of performance tasks as models of complex behavioral and cognitive functions.