Component processes in task switching

Participants switched between two randomly ordered, two-choice reaction-time (RT) tasks, where an instructional cue preceded the target stimulus and indicated which task to execute. Task-switching cost dissipated passively while the participants waited for the instructional cue in order to know which task to execute (during the Response-Cue Interval). Switching cost was sharply reduced, but not abolished, when the participants actively prepared for the task switch in response to the instructional cue (during the Cue-Target Interval). The preparation for a task switch has shown not to be a by-product of general preparation by phasic alertness or predicting target onset. It is suggested that task-switching cost has at least three components reflecting (1) the passive dissipation of the previous task set, (2) the preparation of the new task set, and (3) a residual component.

Modeling cognitive control in task-switching

This article describes a quantitative model, which suggests what the underlying mechanisms of cognitive control in a particular task-switching paradigm are, with relevance to task-switching performance in general. It is suggested that participants dynamically control response accuracy by selective attention, in the particular paradigm being used, by controlling stimulus representation. They are less efficient in dynamically controlling response representation. The model fits reasonably well the pattern of reaction time results concerning task switching, congruency, cue-target interval and response-repetition in a mixed task condition, as well as the differences between mixed task and pure task conditions.

Better Late Than Never? On the Dynamics of Online Regulation of Sadness Using Distraction and Cognitive Reappraisal

Real-life emotion regulation often occurs at some point after an emotion-triggering event (ETE) has been introduced, but most previous research has involved regulation before or after the ETE. In a series of experiments, the authors examined online regulation via distraction and cognitive reappraisal by manipulating the strategy initiation point in sadness-evoking films. Distraction was effective even when initiated late, presumably because it involves diluting the ETE contents by mixing them with a nonsad input. By contrast, reappraisal was less effective when initiated late, suggesting a possible point of no return for this strategy: Adopting a detached view late in the ETE may be difficult because it involves continued focus on the ETE and hence requires overcoming a previously formed tendency of identifying with the emotional content.

On the origins of the task mixing cost in the cuing task-switching paradigm

Poorer performance in conditions involving task repetition within blocks of mixed tasks relative to task repetition within blocks of single task is called mixing cost (MC). In 2 experiments exploring 2 hypotheses regarding the origins of MC, participants either switched between cued shape and color tasks, or they performed them as single tasks. Experiment 1 supported the hypothesis that mixed-tasks trials require the resolution of task ambiguity by showing that MC existed only with ambiguous stimuli that afforded both tasks and not with unambiguous stimuli affording only 1 task. Experiment 2 failed to support the hypothesis that holding multiple task sets in working memory (WM) generates MC by showing that systematic manipulation of the number of stimulus-response rules in WM did not affect MC. The results emphasize the role of competition management between task sets during task control.

Cognitive rigidity in unipolar depression and obsessive compulsive disorder: examination of task switching, Stroop, working memory updating and post-conflict adaptation

Obsessive compulsive disorder (OCD) and depressive rumination are both characterized by cognitive rigidity. We examined the performance of 17 patients (9 suffering from unipolar depression [UD] without OCD, and 8 suffering from OCD without UD), and 17 control participants matched on age, gender, language and education, on a battery covering the four main executive functions. Results indicated that, across both disorders, patients required more trials to adjust to single-task conditions after experiencing task switching, reflecting slow disengagement from switching mode, and showed abnormal post-conflict adaptation of processing mode following high conflict Stroop trials in comparison to controls. Rumination, which was elevated in UD and not in OCD, was associated with poor working memory updating and less task preparation. The results show that OCD and UD are associated with similar cognitive rigidity in the presently tested paradigms.

Old age is associated with a pattern of relatively intact and relatively impaired task-set switching abilities

In three experiments, we examined the effects of old age on the reaction time (RT) decrement associated with task alternation. Old age was associated with increased mixing-cost, which is the RT difference between two conditions: mixed-task, where trials involving two tasks were intermixed, and single-task, where all the trials involved the same task. Old age was also associated with an increased switching-cost, which is the RT difference between trials in which the task was just changed and trials in which it was repeated. There was also indication of a slowed passive dissipation of task set adopted in the preceding trial. In contrast to these impairments, old age was also associated with an almost intact ability to prepare for an upcoming task switch. This ability was indicated by a normal reduction in switching-cost due to an increase in the time allowed to prepare for the switch. We discuss the implications of the results in relation to theories of task-switching and to the underlying brain mechanisms, especially with respect to the effect of old age on the prefrontal cortex.

When the same response has different meanings:

The ability to adapt our behavioral repertoire to different situations and tasks is crucial for our behavioral control. Since the same motor behavior can have different meanings in different task situations, we often have to change the meaning of our responses when we get into a different task context. In a functional MRI experiment we manipulated this response recoding process. Subjects were required to execute two simple spatial tasks in a task switching paradigm. In one condition both tasks required the same set of responses, hence each response had two different meanings depending on the relevant task (bivalent condition). In the other condition subjects used a separate set of responses for each task (univalent condition). While subjects were required to recode the meaning when switching from one task to the next in the bivalent condition, response recoding was not required in the univalent condition. We demonstrate that the lateral prefrontal cortex is involved in recoding of response meaning. These results extend previous assumptions on the role of the prefrontal cortex in behavioral control.

The representation of instructions operates like a prepared reflex: flanker compatibility effects found in first trial following S-R instructions

The prepared reflex (PR) metaphor (Woodworth, R. S. (1938). Experimental psychology. New York: Holt, Rinehart and Winston) suggests that stimulus-response (S-R) instructions held in working memory (WM) can lead to autonomous response activation even without any practice. Cohen-Kdoshay and Meiran (Cohen-Kdoshay, O., & Meiran, N. (2007). The representation of instructions in working memory leads to autonomous response activation: Evidence from the first trials in the flanker paradigm. The Quarterly Journal of Experimental Psychology, 60 (8), 1140-1154) showed that the flanker compatibility effect (FCE) is found in the eight trials following S-R instructions supporting the PR hypothesis. Nonetheless, performance in the first trials forms long-term memory (LTM) traces which link abstract categories with responses and the retrieval of these LTM traces may be the reason for the autonomous response activation seen in the FCE. This account predicts FCEs to be absent in the first trial and present afterwards. The authors show that the FCE was present in the first trial immediately following the instructions, thus providing unequivocal support for the PR metaphor.

"Mind the trap": mindfulness practice reduces cognitive rigidity

Two experiments examined the relation between mindfulness practice and cognitive rigidity by using a variation of the Einstellung water jar task. Participants were required to use three hypothetical jars to obtain a specific amount of water. Initial problems were solvable by the same complex formula, but in later problems ("critical" or "trap" problems) solving was possible by an additional much simpler formula. A rigidity score was compiled through perseverance of the complex formula. In Experiment 1, experienced mindfulness meditators received significantly lower rigidity scores than non-meditators who had registered for their first meditation retreat. Similar results were obtained in randomized controlled Experiment 2 comparing non-meditators who underwent an eight meeting mindfulness program with a waiting list group. The authors conclude that mindfulness meditation reduces cognitive rigidity via the tendency to be "blinded" by experience. Results are discussed in light of the benefits of mindfulness practice regarding a reduced tendency to overlook novel and adaptive ways of responding due to past experience, both in and out of the clinical setting.

Advance preparation and stimulus-induced interference in cued task switching: further insights from BOLD fMRI

To switch from one cognitive task to another is thought to rely on additional control effort being indicated by performance costs relative to repeating the same task. This switch cost can be reduced by advance task preparation. In the present experiment the nature of advance preparation was investigated by comparing a situation where an explicit task cue was presented 2000 ms in advance of the target stimulus (CTI-2000) with a situation where cue and target were presented in close succession (CTI-100). We mapped the blood-oxygenation-level-dependent (BOLD) activation correlates of switch-related control effort and advance task preparation to test alternative explanations why advance preparation is reducing switch costs. A previously reported control-related cortical network of frontal and parietal brain areas emerged that was more strongly activated for switching between tasks. However, this was true exclusively for CTI-100 where no advance task preparation was possible. At CTI-2000 these same brain areas were equally engaged in both switch and repeat trials. For some of these areas, this common activation was time-locked to the presentation of both the cue as well as the target. Other areas were exclusively associated with target processing. The overall pattern of results suggests that advance task preparation is a common process of pre-activating (cue-locked activation) the currently relevant task set which does not face interference from a persisting N - 1 task set. During target processing the same brain areas are re-engaged (subsequent target-locked activation) to apply the pre-activated task set. Though being common to repeat and switch trials, advance preparation has a differential benefit for switch trials. This is because the instructed task set has time to settle into a stable state, thus becoming resistant against disruption from the previous task set, which is retrieved by the current target stimulus.

Do long tests yield a more accurate diagnosis of dementia than short tests? A comparison of 5 neuropsychological tests

OBJECTIVE

To provide comparative evidence for a valid and practical measure of mental-status functioning that could be used in dementia clinics.

DESIGN

Five mental-status neuropsychological tools for dementia screening were administered to patients in a memory disorder clinic. These included the Mini-Mental State Examination, the Dementia Rating Scale, the 6-item derivative of the Orientation-Memory-Concentration Test, a short Mental Status Questionnaire, and a composite tool we labeled the Ottawa Mental Status Examination, which assessed orientation, memory, attention, language, and visual-constructive functioning. The tools were compared using various criteria, including the statistical factors of sensitivity and reliability; effects of gender, native language, and language of testing; the utility of these tests for the differential diagnosis of Alzheimer-type and vascular dementia; and sensitivity to cognitive decline in the entire sample and among patients with severe dementia.

RESULTS

All of the tests were highly intercorrelated, suggesting that they are interchangeable.

CONCLUSION

The comparisons along the various criteria indicate that if the objective is to have a general index of dementia of the Alzheimer type, short tests are at least as good and sometimes better than the longer tests.

Task set switching in schizophrenia

The authors used a task-switching paradigm to investigate set shifting ability in schizophrenia. This paradigm included 2 choice reaction time (RT) tasks: up-down and right-left. Switching tasks were associated with costs (i.e., longer RT in task-switch trials than in task-repetition trials); patients responded more slowly than controls and suffered greater switching costs, were as efficient as controls in engaging in an upcoming task set, and were faster than controls in disengaging from the previous task set. There were indications that patients quickly forgot what each keypress indicated, making it necessary for them to acquire response meaning information anew in each trial. To test this notion, the authors subsequently tested normal participants in conditions in which response meaning information needed to be acquired anew in each trial. These participants produced a pattern of switching costs resembling that of patients. Results suggest that set switching difficulties in schizophrenia, as exhibited in the present paradigm, reflect poor memory for task context information.

Online order control in the psychological refractory period paradigm

The authors examined the role of online order control in the psychological refractory period (PRP) paradigm. In the first 2 experiments, participants switched between color-letter and letter-color orders so that subtask order was isolated as the only element being switched. The results indicated that order switching impaired the 2 PRP responses and modulated the PRP effect. Importantly, these effects were reduced by advance preparation, demonstrating that order representation was activated before the subtasks themselves. Preparation for subtask order did not reflect preparation for hand order, as shown in Experiment 3. In addition, there was no evidence that subtask order information dissipated between trials. The relevance of the results to theories of the PRP paradigm and task switching is discussed.

When planning results in loss of control: intention-based reflexivity and working-memory

In this review, the authors discuss the seemingly paradoxical loss of control associated with states of high readiness to execute a plan, termed "intention-based reflexivity." The review suggests that the neuro-cognitive systems involved in the preparation of novel plans are different than those involved in preparation of practiced plans (i.e., those that have been executed beforehand). When the plans are practiced, intention-based reflexivity depends on the prior availability of response codes in long-term memory (LTM). When the plans are novel, reflexivity is observed when the plan is pending and the goal has not yet been achieved. Intention-based reflexivity also depends on the availability of working-memory (WM) limited resources and the motivation to prepare. Reflexivity is probably related to the fact that, unlike reactive control (once a plan is prepared), proactive control tends to be relatively rigid.

The power of instructions: Proactive configuration of stimulus-response translation

Humans are characterized by an especially highly developed ability to use instructions to prepare toward upcoming events; yet, it is unclear just how powerful instructions can be. Although prior work provides evidence that instructions can be sufficiently powerful to proactively program working memory to execute stimulus-response (S-R) translations, in a reflexlike fashion (intention-based reflexivity [IBR]), the results to date have been equivocal. To overcome this shortcoming, we developed, and tested in 4 studies, a novel paradigm (the NEXT paradigm) that isolates IBR effects even prior to first task execution. In each miniblock, participants received S-R mapping instructions for a new task. Prior to implementing this mapping, responses were required to advance through screens during a preparatory (NEXT) phase. When the NEXT response was incompatible with the instructed S-R mapping, interference (IBR effect) was observed. This NEXT compatibility effect and performance in the implementation (GO) trials barely changed when prior practice of a few trials was provided. Finally, a manipulation that encouraged preparation resulted in relatively durable NEXT compatibility effects (indicating durable preparatory efforts) coupled with improved GO performance (indicating the success of these efforts). Together, these findings establish IBR as a marker of instructed proactive control.

Basal Ganglia Play a Unique Role in Task Switching within the Frontal-Subcortical Circuits: Evidence from Patients with Focal Lesions

The performance of patients with lesions involving the basal ganglia (BG) was compared to that of patients with prefrontal (PFC) lesions, thalamic (TH) lesions, and age-matched controls in order to examine the specific role of the BG within the frontal-subcortical circuits (FSCC) in task switching. All the BG patients and none of the other participants showed a marked increase in error rate in incongruent trials where correct responses depended upon the choice of the correct task rule. Some BG patients erred in failing to switch tasks and others failed despite their attempt to switch tasks. Additionally, reaction time results indicate abnormal response repetition effects among the BG patients; failure in benefiting from advance task information among all the patients; and increased task mixing costs following PFC lesions. The authors conclude that although the frontal-subcortical circuits jointly determine some behaviors (such as benefiting from preparation), the BG play a unique role within the FSCC in action selection and/or the inhibition of irrelevant information.

The task novelty paradox: Flexible control of inflexible neural pathways during rapid instructed task learning

Rapid instructed task learning (RITL) is one of the most remarkable human abilities, when considered from both computational and evolutionary perspectives. A key feature of RITL is that it enables new goals to be immediately pursued (and shared) following formation of task representations. Although RITL is a form of cognitive control that engenders immense flexibility, it also seems to produce inflexible activation of action plans in inappropriate contexts. We argue that this "prepared reflex" effect arises because RITL is implemented in the brain via a "flexible hub" mechanism, in which top-down influences from the frontoparietal control network reroute pathways among procedure-implementing brain areas (e.g., perceptual and motor areas). Specifically, we suggest that RITL-based proactive control - the preparatory biasing of task-relevant functional network routes - results in inflexible associative processing, demanding compensation in the form of increased reactive (in-the-moment) control. Thus, RITL produces a computational trade-off, in which the top-down influences of flexible hubs increase overall cognitive flexibility, but at the cost of temporally localized inflexibility (the prepared reflex effect).

Is there a general task switching ability?

Participants were tested on two analogous task switching paradigms involving Shape/Size tasks and Vertical/Horizontal tasks, respectively, and three measures of psychometric intelligence, tapping fluid, crystallized and perceptual speed abilities. The paradigms produced similar patterns of group mean reaction times (RTs) and the vast majority of the participants showed switching cost (switch RT minus repeat RT), mixing cost (repeat RT minus single-task RT) and congruency effects. The shared intra-individual variance across paradigms and with psychometric intelligence served as criteria for general ability. Structural equations modeling indicated that switching cost with ample preparation ("residual cost") and mixing cost met these criteria. However, switching cost with little preparation and congruency effects were predominantly paradigm specific.