Cognitive control in children of Mexico and the United States.
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This article represents the proceedings of a symposium at the 2000 RSA Meeting in Denver, Colorado. The organizer/chair was Muriel Vogel-Sprott. The presentations were (1) Alcohol-induced impairment of inhibitory control: Some commonalities with attention deficit hyperactivity disorder, by Mark Fillmore; (2) Neural interactions that underlie response inhibition under alcohol: A functional magnetic resonance imaging investigation, by Craig Easdon; (3) Intentional control of behavior under alcohol, by Muriel Vogel-Sprott; and (4) Working memory and the disinhibiting effects of alcohol on passive avoidance learning, by Alicia Justius and Peter Finn.
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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.
The cold-pressor task was used with 102 female undergraduates in 2 experiments to determine (a) whether self-efficacy has validity as a true causal determinant of behavior change or is a correlate of change that has already occurred and (b) how perceptions of control and self-efficacy interact to determine choice behavior, persistence, and the impact of an aversive stimulus. Results of Experiment 1 indicate that self-efficacy expectations affected performance beyond what would have been expected from past performance alone. Changes in self-efficacy expectations predicted changes in cold-pressor tolerance. These findings suggest that self-efficacy expectations can be causal determinants of behavior in an aversive situation. Results of Experiment 2 indicate that self-efficacy was separable from control and that performance was best if both high levels of perceived control and self-efficacy were present. These findings support the notion that self-efficacy expectations can mediate the desirability of providing control, in that those who benefit most from control are those who are most confident they can exercise it.
The influence of aging and frontal function on the neural correlates of regulative and evaluative control was examined by means of event-related brain potentials (ERPs). The behavioral data indicated that interference was greater for older than for younger adults and that this difference was mediated by frontal function. The ERP data revealed effects of aging on the neural correlates of both regulative and evaluative control. Prestimulus neural activity was correlated with response time and frontal function, and these relationships were moderated by the response-to-stimulus interval (RSI); the poststimulus data also revealed age-related differences in the neural correlates of evaluative control that interacted with RSI. These data support predictions derived from the context processing deficit theory of aging.
Switching between different tasks is associated with performance deficits, or 'switch costs', relative to repeating the same task. Recent evidence suggests that response rather than task selection processes may be a major cause of switch costs [Schuch, S., Koch, I., 2003. The role of response selection for inhibition of task sets in task shifting. J Exp Psychol Hum Percept Perform, 29 (1) 92-105]. Thus, switch costs are not incurred if on the preceding trial a task has been prepared for but no response required (a 'no-go' trial). We investigated the relationship between response selection and the subsequent preparation of an alternative task set. While switch costs were absent following 'no-go' trials, ERP differences during the precueing interval showed that response selection has implications for subsequent task preparation as well as for task performance per se. The results are discussed in relation to the dissociation of intention versus action in behavioural control and the role of inhibition in switching between task sets.
We investigated the extent to which a common neural mechanism is involved in task set-switching and response withholding, factors that are frequently confounded in task-switching and go/no-go paradigms. Subjects' brain activity was measured using event-related electrical potentials (ERPs) and event-related functional MRI (fMRI) neuroimaging in separate studies using the same cognitive paradigm. Subjects made compatible left/right keypress responses to left/right arrow stimuli of 1000 msec duration; they switched every two trials between responding at stimulus onset (GO task-green arrows) and stimulus offset (WAIT task-red arrows). With-holding an immediate response (WAIT vs. GO) elicited an enhancement of the frontal N2 ERP and lateral PFC activation of the right hemisphere, both previously associated with the "no-go" response, but only on switch trials. Task-switching (switch vs. nonswitch) was associated with frontal N2 amplification and right hemisphere ventrolateral PFC activation, but only for the WAIT task. The anterior cingulate cortex (ACC) was the only brain region to be activated for both types of task switch, but this activation was located more rostrally for the WAIT than for the GO switch trials. We conclude that the frontal N2 ERP and lateral PFC activation are not markers for withholding an immediate response or switching tasks per se, but are associated with switching into a response-suppression mode. Different regions within the ACC may be involved in two processes integral to task-switching: processing response conflict (rostral ACC) and overcoming prior response suppression (caudal ACC).
For successful negotiation of our environment, humans must be readily able to switch from one task to another. This ability relies on 'executive control' processes and despite extensive efforts to detail the nature of these processes, there is little consensus as to how the brain achieves this critical function. Behavioural studies show that as subjects are given more time to prepare to switch task, performance improves; yet even with the longest preparation intervals, there remains an ineradicable performance cost on switch trials. As such, some elements of the switching process must wait until the stimulus to be acted upon has actually been presented. Here, using the methods of high-density mapping of brain potentials, we show that early visual processes are substantially different on switch trials than on later trials. Our data show that while there is clearly a degree of preparatory processing that occurs prior to a predictable switch of task, some elements of switching are only achieved after the switch stimulus has been presented. Our findings are discussed in the context of a new model of executive control processes that suggests that preparing to switch task may not be a separate (control) process per se, but rather, the beginning of a competition between the potentially relevant tasks, a competition that is ultimately resolved during the switch trial.
In response to the high rate of learning problems among socially deprived children, the Baltimore Early School Admission Project set up a system intervention model engaging three points of entry: parents, educators, and mental health workers. The emphasis was on: a) the redefinition of the roles of all participants; b) the school as a self-reliant system, discouraging referrals to outside agencies; c) the development of the children's functioning and adaptive potentials, based on their individual cognitive styles. The program included five public schools. Ninety-one children between the ages of 4 and 5 years were involved. All of these were selected from a hard core socioeconomically deprived population. Eighty-three percent were black and 17 per cent white. Fifteen children were identified as "vulnerable" according to specific criteria provided to the teachers and the parents. Of the vulnerable group, nine children's learning problems were related primarily to emotional and environmental factors, five had perceptual, sensory-motor dysfunction mixed with emotional factors, and one suffered primarily from brain damage. Results indicated that only one of the vulnerable children required referral outside of that provided in the above design. Eleven vulnerable children performed as well as the nonvulnerable group, and three showed a moderate improvement. Furthermore, five children with serious learning problems responded to the systemic intervention as well as they might have with specialized professional help.
A dissociable set of regions was active for the executive processing associated with overcoming a prepotent response tendency and task switching. Regions associated with overcoming prepotency were primarily frontal and may be part of a system involved in top-down biasing for conflict reduction. Posterior regions were recruited for switching between tasks and likely play a role in reconfiguring stimulus-response mappings. Precuneus activity was common to both manipulations and may reflect increased visual attention due to more difficult task demands.
Simultaneous recording of eye and head movements during reading revealed that head movements consisted of two components: a modulatory-velocity component coupled to eye saccades, and a constant-velocity component that was independent of eye saccades. Whereas the constant-velocity component increased as subjects repeatedly read the same text, neither the magnitude of the modulatory-velocity component, nor the amplitude of the eye movement, increased. This outcome could be closely simulated when the head movement command was assumed to be stronger, and issued earlier with repeated reading. These results suggest that higher-level processes related to text familiarity modulate eye-head coordination through head movements.
Recent development of neural prosthetics for assisting paralyzed patients has focused on decoding intended hand trajectories from motor cortical neurons and using this signal to control external devices. In this study, higher level signals related to the goals of movements were decoded from three monkeys and used to position cursors on a computer screen without the animals emitting any behavior. Their performance in this task improved over a period of weeks. Expected value signals related to fluid preference, the expected magnitude, or probability of reward were decoded simultaneously with the intended goal. For neural prosthetic applications, the goal signals can be used to operate computers, robots, and vehicles, whereas the expected value signals can be used to continuously monitor a paralyzed patient's preferences and motivation.
In this review, we summarize a new line of experimentation showing that attentional orienting can bias information processing in the working memory domain as well as in the perceptual domain to optimize goal-directed behavior. A new experimental paradigm was developed, which revealed that spatial orienting cues that appear after perceptual events (retro-cues), when these have been internalized into working memory representations, can retrospectively enhance performance to a similar degree as spatial precues appearing before perceptual events. As part of their facilitatory action, retro-cues diminish the costs of retrieving items from increasing loads within working memory. Hemodynamic and electrophysiological brain imaging experiments show a high degree of overlap between brain areas and dynamics involved in spatial orienting in the working memory domain compared to the perceptual domain. In addition, functional magnetic resonance imaging points to the selective involvement of frontal areas during spatial orienting in the working memory domain. The roles of different frontal areas remain to be clarified but may include both early roles in guiding spatial shifts occurring within a mnemonic context as well as selection of memorized targets amidst distracting stimuli. Experiments have also begun to reveal the ability to orient attention selectively to object-based representations in working memory and suggest that the neural representations of objects in working memory can be directly modulated by this process. The findings bolster contemporary notions of a strong theoretical relationship between attentional orienting and working memory, suggesting that these two cognitive functions interact in more ways and directions than previously considered.