Residual costs in task switching: testing the failure-to-engage hypothesis

Reaction time is typically longer on trials on which the task changes. Thisswitch cost is reduced by the opportunity to prepare for the change before the stimulus onset, but there remains aresidual cost that resists reduction by further opportunity for preparation. De Jong (2000) proposed a model for evaluating the contribution to the residual cost of (1) failure to achieve endogenous task-set reconfiguration on a proportion of trials, and (2) limitations to the completeness of reconfiguration attainable by endogenous means. We report good fits of the model to the data from one previous and one new task-switching experiment, suggesting that the residual switch cost may indeed be attributable to a probabilistic failure to complete advance preparation. But strong incentives for preparation only marginally increased the estimated preparation probability, suggesting some intrinsic limitation to the ability to achieve endogenous preparation for a task switch on every trial.     

Medial frontal cortex function: An introduction and overview

The growing attention being given to medial frontal cortex (MFC) in cognitive neuroscience studies has fostered a number of theoretical and paradigmatic perspectives that diverge in important ways. This has led to a great deal of research fractionation, with investigators studying domains and issues in MFC function that sometimes bear (at least at the surface) little relation to the questions addressed by others studying the same brain region. The present issue of Cognitive, Affective, & Behavioral Neuroscience presents articles inspired by a conference bringing together views from across this diversity of research, highlighting both the richness and vibrancy of the field and the challenges to be faced in terms of integration, synthesis, and precision among the theoretical accounts. The present article presents a brief introduction, overview, and road map to the field and to the special issue devoted to MFC function.     

Drink alcohol and dim the lights: The impact of cognitive deficits on medial frontal cortex function

Scalp electroencephalogram (EEG) recordings indicate that regions in the medial frontal cortex (MFC) are active following errors. Alcohol consumption reduces this error-related activity, perhaps suggesting that alcohol disrupts the operation of an error-monitoring system in the MFC. However, it could also be that alcohol consumption affects the MFC only indirectly, by impairing stimulus processing and thus making errors harder to detect. This interpretation leads to the prediction that stimulus degradation should likewise reduce error-related activity in the MFC. To test this hypothesis, behavioral and EEG data were collected as participants performed a speeded response task with either bright or very dim stimuli. The results using dim stimuli replicated the observed effects of alcohol consumption—with slowed responses accompanied by reduced error-related MFC activity. The sensitivity of the MFC to disrupted processing elsewhere in the brain suggests complications in interpreting evidence of disturbed MFC function. This research was supported by the National Institutes of Health Conte Center for Neuroscience Research (Grant P50-MH62196 to N.Y.) and by the Netherlands Organization for Scientific Research (to S.N.).     

The role of the locus coeruleus in mediating the attentional blink: a neurocomputational theory

The attentional blink refers to the transient impairment in perceiving the 2nd of 2 targets presented in close temporal proximity. In this article, the authors propose a neurobiological mechanism for this effect. The authors extend a recently developed computational model of the potentiating influence of the locus coeruleus-norepinephrine system on information processing and hypothesize that a refractoriness in the function of this system may account for the attentional blink. The model accurately simulates the time course of the attentional blink, including Lag 1 sparing. The theory also offers an account of the close relationship of the attentional blink to the electrophysiological P3 component. The authors report results from two behavioral experiments that support a critical prediction of their theory regarding the time course of Lag 1 sparing. Finally, the relationship between the authors' neurocomputational theory and existing cognitive theories of the attentional blink is discussed.     

Inhibitory inefficiency and failures of intention activation: age-related decline in the control of saccadic eye movements

Young and older adults' control of saccadic eye movements was compared using an antisaccade task, which requires the inhibition of a reflexive saccade toward a peripheral onset cue followed by an intentional saccade in the opposite direction. In 2 experiments, an age-related decline was found in the suppression of reflexive eye movements, as indicated by an increased proportion of saccades toward the cue, and a longer time needed to initiate correct antisaccades. The results from Experiment 2 suggested that older adults' slower antisaccades may be explained partly in terms of increased failures to maintain the cue-action representation at a sufficient activation level. The results suggest that the notion of selective preservation with age of the ability to inhibit spatial responses does not apply to the active inhibition of prepotent spatial responses.     

How does bilingualism improve executive control? A comparison of active and reactive inhibition mechanisms

It has been claimed that bilingualism enhances inhibitory control, but the available evidence is equivocal. The authors evaluated several possible versions of the inhibition hypothesis by comparing monolinguals and bilinguals with regard to stop signal performance, inhibition of return, and the attentional blink. These three phenomena, it can be argued, tap into different aspects of inhibition. Monolinguals and bilinguals did not differ in stop signal reaction time and thus were comparable in terms of active-inhibitory efficiency. However, bilinguals showed no facilitation from spatial cues, showed a strong inhibition of return effect, and exhibited a more pronounced attentional blink. These results suggest that bilinguals do not differ from monolinguals in terms of active inhibition but have acquired a better ability to maintain action goals and to use them to bias goal-related information. Under some circumstances, this ability may indirectly lead to more pronounced reactive inhibition of irrelevant information.     

Memory trace stabilization leads to large-scale changes in the retrieval network: a functional MRI study on associative memory

Spaced learning with time to consolidate leads to more stabile memory traces. However, little is known about the neural correlates of trace stabilization, especially in humans. The present fMRI study contrasted retrieval activity of two well-learned sets of face-location associations, one learned in a massed style and tested on the day of learning (i.e., labile condition) and another learned in a spaced scheme over the course of one week (i.e., stabilized condition). Both sets of associations were retrieved equally well, but the retrieval of stabilized association was faster and accompanied by large-scale changes in the network supporting retrieval. Cued recall of stabilized as compared with labile associations was accompanied by increased activity in the precuneus, the ventromedial prefrontal cortex, the bilateral temporal pole, and left temporo–parietal junction. Conversely, memory representational areas such as the fusiform gyrus for faces and the posterior parietal cortex for locations did not change their activity with stabilization. The changes in activation in the precuneus, which also showed increased connectivity with the fusiform area, are likely to be related to the spatial nature of our task. The activation increase in the ventromedial prefrontal cortex, on the other hand, might reflect a general function in stabilized memory retrieval. This area might succeed the hippocampus in linking distributed neocortical representations.     

Reappraisal modulates the electrocortical response to unpleasant pictures

Cognitive strategies such as reappraisal reduce the intensity of negative experience and brain activity that is sensitive to emotional salience. The time course of reappraisal-related neural modulation remains unclear, and it is unknown whether the electrocortical response to emotional stimuli is sensitive to reappraisal. Event-related brain potentials were recorded first while participants passively viewed pleasant, unpleasant, and neutral pictures, and then during an emotion regulation block in which participants were instructed to attend to or reappraise unpleasant pictures. The late positive potential (LPP) was enhanced for pleasant and unpleasant pictures in the passive viewing block, and reappraisal resulted in a reliably reduced LPP—a protracted modulation that began 200 msec after stimulus onset. The degree of LPP modulation was positively related to reductions in the self-reported emotional intensity that followed emotion regulation instructions. These results indicate that reappraisal modulates early electrocortical activity that is related to emotional salience, and that the LPP is a useful tool for studying emotion regulation.     

The beneficial effect of concurrent task-irrelevant mental activity on temporal attention

It is believed that the human cognitive system is fundamentally limited in deploying attention over time. This limitation is reflected in the attentional blink, the impaired ability to identify the second of two visual targets presented in close succession. We report the paradoxical finding that the attentional blink is significantly ameliorated when observers are concurrently engaged in distracting mental activity, such as free-associating on a task-irrelevant theme or listening to music. This finding raises questions about the fundamental nature of the attentional blink, and suggests that the temporal dynamics of attention are determined by task circumstances that induce either a more or a less distributed state of mind.     

Decision making, the P3, and the locus coeruleus-norepinephrine system

Psychologists and neuroscientists have had a long-standing interest in the P3, a prominent component of the event-related brain potential. This review aims to integrate knowledge regarding the neural basis of the P3 and to elucidate its functional role in information processing. The authors review evidence suggesting that the P3 reflects phasic activity of the neuromodulatory locus coeruleus-norepinephrine (LC-NE) system. They discuss the P3 literature in the light of empirical findings and a recent theory regarding the information-processing function of the LC-NE phasic response. The theoretical framework emerging from this research synthesis suggests that the P3 reflects the response of the LC-NE system to the outcome of internal decision-making processes and the consequent effects of noradrenergic potentiation of information processing.