Changes In Executive Control Research Articles

Executive control and felt concentrative engagement following intensive meditation training

Various forms of mental training have been shown to improve performance on cognitively demanding tasks. Individuals trained in meditative practices, for example, show generalized improvements on a variety of tasks assessing attentional performance. A central claim of this training, derived from contemplative traditions, posits that improved attentional performance is accompanied by subjective increases in the stability and clarity of concentrative engagement with one's object of focus, as well as reductions in felt cognitive effort as expertise develops. However, despite frequent claims of mental stability following training, the phenomenological correlates of meditation-related attentional improvements have yet to be characterized. In a longitudinal study, we assessed changes in executive control (performance on a 32-min response inhibition task) and retrospective reports of task engagement (concentration, motivation, and effort) following one month of intensive, daily Vipassana meditation training. Compared to matched controls, training participants exhibited improvements in response inhibition accuracy and reductions in reaction time variability. The training group also reported increases in concentration, but not effort or motivation, during task performance. Critically, increases in concentration predicted improvements in reaction time variability, suggesting a link between the experience of concentrative engagement and ongoing fluctuations in attentional stability. By incorporating experiential measures of task performance, the present study corroborates phenomenological accounts of stable, clear attentional engagement with the object of meditative focus following extensive training. These results provide initial evidence that meditation-related changes in felt experience accompany improvements in adaptive, goal-directed behavior, and that such shifts may reflect accurate awareness of measurable changes in performance.

Lost in Transition: Aging-Related Changes in Executive Control by the Medial Prefrontal Cortex

Neural correlates of aging in the medial prefrontal cortex (mPFC) were studied using an operant delayed response task. The task used blocks of trials with memory-guided (delayed alternation) and visually-guided (stimulus-response) responding. Older rats (24 months) performed at a slow pace compared with younger rats (6 months). They wasted time engaged in nonessential behaviors (e.g., licking on spouts beyond the period of reward delivery) and were slow to respond at the end of the delay period. Aged mPFC neurons showed normal spatial processing. They differed from neurons in younger rats by having reduced modulations by imperative stimuli indicating reward availability and reduced activity associated with response latencies for reward collection. Older rats showed reduced sensitivity to imperative stimuli at three levels of neural activity: reduced fractions of neurons with changes in firing rate around the stimulus, reduced correlation over neurons at the time of the stimulus as measured with analysis of population activity, and reduced amplitudes of event-related fluctuations in intracortical field potentials at the time of the imperative stimulus. Our findings suggest that aging alters the encoding of time-sensitive information and impairs the ability of prefrontal networks to keep subjects "on task."

Depressive symptoms predict longitudinal change in executive control but not memory

Depression in non-demented persons has been identified as a possible risk factor for incident Alzheimer's disease (AD). Latent Growth Curve models were developed of baseline depressive symptoms as a predictor of longitudinal changes in cognition. Depressive symptoms were assessed using the 15-item Geriatric Depression Scale (GDS). Memory was assessed by the California Verbal Learning Task (CVLT). Executive control function (ECF) was assessed by the Executive Interview (EXIT25) and Trail-Making Test Part B (Trails-B). Five hundred forty-seven non-institutionalized older retirees living in a single comprehensive care retirement community participated. Depressive symptoms were significantly associated only with the 3-year rate of decline in psychomotor speed, as measured by Trails A, and ECF, as measured by the EXIT25. Both associations withstood adjustment for age, gender, education, and baseline level of care. Depressive symptoms are associated with longitudinal decline in cognition. However, this association selectively involves executive control, not memory, and possibly only a subset of 'executive' functions. Although depressive symptoms may hasten conversion from mild cognitive impairment (MCI) to dementia, depression-related conversion is not likely to be mediated by evolution of the AD pathological process.

S15-03 - The co-variation of mood variability with ADHD symptoms

ADHD in adults is frequently associated with unstable or irritable moods reflecting difficulties with emotion regulation. Effect sizes of drug treatments on symptoms that reflect difficulties with emotion regulation, are similar to those on core ADHD symptoms, with co-variation of around 0.8 between the two types of symptoms during the treatment response. We therefore set out to investigate whether variability in mood results from the same aetiological processes that lead to variability in behaviour and cognitive performance in ADHD. Using real-time self-monitoring of emotional states and ADHD symptoms every two hours for 3-5 days, we characterised the mood changes in ADHD. Variability in both mood and ADHD symptoms (measured as the standard deviation) were significantly correlated with self-rated ADHD symptoms of inattention and hyperactivity. Subsequent analyses will link the observed symptom changes to cognitive-electrophysiological measures which are reliable indicators of core processes that underlie cognitive deficits associated with ADHD. We previously showed that a familial reaction time (mean and variability) factor explains 70% and commission and omission errors 20%, of the familial effects on ADHD. This finding concurs with the developmental model of Halperin which postulates that ADHD is linked to an early-appearing and enduring subcortical dysfunction, reflected in reaction time variability, while persistence/desistence of ADHD is dependent on maturational changes in executive control during adolescence reflected in commission and omission errors. We propose that at a behavioural level the subcortical deficit leads to dysregulation of a number of processes, including attentional, impulsive and emotional control.

S16-01 - The co-variation of mood variability with ADHD symptoms

ADHD in adults is frequently associated with unstable or irritable moods reflecting difficulties with emotion regulation. Effect sizes of drug treatments on symptoms that reflect difficulties with emotion regulation, are similar to those on core ADHD symptoms, with co-variation of around 0.8 between the two types of symptoms during the treatment response. We therefore set out to investigate whether variability in mood results from the same aetiological processes that lead to variability in behaviour and cognitive performance in ADHD. Using real-time self-monitoring of emotional states and ADHD symptoms every two hours for 3-5 days, we characterised the mood changes in ADHD. Variability in both mood and ADHD symptoms (measured as the standard deviation) were significantly correlated with self-rated ADHD symptoms of inattention and hyperactivity. Subsequent analyses will link the observed symptom changes to cognitive-electrophysiological measures which are reliable indicators of core processes that underlie cognitive deficits associated with ADHD. We previously showed that a familial reaction time (mean and variability) factor explains 70% and commission and omission errors 20%, of the familial effects on ADHD. This finding concurs with the developmental model of Halperin which postulates that ADHD is linked to an early-appearing and enduring subcortical dysfunction, reflected in reaction time variability, while persistence/desistence of ADHD is dependent on maturational changes in executive control during adolescence reflected in commission and omission errors. We propose that at a behavioural level the subcortical deficit leads to dysregulation of a number of processes, including attentional, impulsive and emotional control.

Using developmental cognitive neuroscience to study behavioral and attentional control

Adult cognitive neuroscience employs a wide variety of techniques to investigate a broad range of behavioral and cognitive functions. One prominent area of study is that of executive control, complemented by a smaller but growing literature exploring the developmental cognitive neuroscience of executive control. To date this approach has often compared children with specific developmental disorders, such as ADHD and ASD, with typically developing controls. Whilst these comparisons have done much to advance our understanding of the neural markers that underpin behavioral difficulties at specific time-points in development, we contend that they should leave developmental cognitive neuroscientists wanting. Studying the neural correlates of typical changes in executive control in their own right can reveal how different neural mechanisms characteristic of the adult end-state emerge, and it can therefore inform the adult cognitive neuroscience of executive control itself. The current review addresses the extent to which developmentalists and adult cognitive neuroscientists have tapped this common ground. Some very elegant investigations illustrate how seemingly common processes in adulthood present as separable in childhood, on the basis of their distinctive developmental trajectories. These demonstrations have implications not only for an understanding of changing behavior from infancy through childhood and adolescence into adulthood, but, moreover, for our grasp of the adult end-state per se. We contend that, if used appropriately, developmental cognitive neuroscience could enable us to construct a more mechanistic account of executive control.

Sequential Compatibility Effects and Cognitive Control: Does Conflict Really Matter?

Although it is widely accepted that control mechanisms are necessary for human behavior to be adapted, very little is known about how such mechanisms are recruited. A suggestion to fill the gap was put forward by M. M. Botvinick, T. S. Braver, C. S. Carter, D. M. Barch, and J. D. Cohen (2001), who proposed the conflict-loop theory. This theory has been successful in accounting for the reduction of compatibility effects after an incompatible trial: The level of conflict being, on average, higher during an incompatible trial, more control occurs after such a trial. The authors have tested this prediction by sorting the trials on the basis of amount of conflict (quantified by the electromyographic activity) they presented. A reduction of the compatibility effect was observed after incompatible trials, but it was independent of the level of conflict on previous trials, suggesting that the conflict does not trigger changes in executive control. Consequences for the conflict monitoring model are discussed.

Task Switching Across the Life Span: Effects of Age on General and Specific Switch Costs.

The authors investigated age-related changes in executive control using an Internet-based task-switching experiment with 5,271 participants between the ages of 10 and 66 years. Speeded face categorization was required on the basis of gender (G) or emotion (E) in single task blocks (GGG... and EEE...) or switching blocks (GGEEGGEE...). General switch costs, the difference between switching block and single task block performance, decreased during development and then increased approximately linearly from age 18. In contrast, specific switch costs, the difference between switch trial and nonswitch trial performance in the switching block, were more stable across the same age range. These results demonstrate differential age effects in task-switching performance and provide a fine-grained analysis of switch costs from puberty to retirement.

On-line executive control: an electromyographic study.

In a choice reaction time (RT) task, electromyographic (EMG) recordings allowed us to fractionate RT into two subcomponents, namely premotor time and motor time. This has been done for correct trials and errors. The analysis of the EMG burst and motor time (between EMG onset and overt response) showed that the EMG burst amplitude was reduced and the motor time was longer for errors than for correct responses. In the same way as posterror slowing on the RT was interpreted as revealing between-trials changes in executive control, the present data provide direct evidence for an on-line, within-trial, executive control.

Changes in executive control across the life span: Examination of task-switching performance.

A study was conducted to examine changes in executive control processes over the life span. More specifically, changes in processes responsible for preparation and interference control that underlie the ability to flexibly alternate between two different tasks were examined. Individuals (N = 152) ranging in age from 7 to 82 years participated in the study. A U-shaped function was obtained for switch costs (i.e., the time required to switch between tasks compared with a repeated-task baseline), with larger costs found for young children and older adults. Switch costs were reduced with practice, particularly for children. All age groups benefited from increased preparation time, with larger benefits observed for children and older adults. Adults benefited to a greater extent than children when the interval between the response to one task and the cue indicating which task to perform next was lengthened, which suggested faster decay of interference from the old task set for adults than for children. A series of hierarchical analyses indicated that the age-related variance in task-switching performance is independent, at least in part, from the age-related variance in other cognitive processes such as perceptual speed and working memory. The results are discussed in terms of the development and decline of executive control processes across the life span.

Changes in executive control across the life span: Examination of task-switching performance.

Changes in executive control across the life span: Examination of task-switching performance.