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PubMed2005

Learning performance on the discrimination-shift task in patients with cortical and subcortical lesions.

Patients with brain damage completed reversal and nonreversal shift-learning tasks and we compared their performance with that of normal adults. The overall group differences revealed that many patients could not reach the task criterion regardless of the location of damage and the shift condition of the task. When we compared patients with subcortical and cortical damage, we also found no group differences with regard to the total number of trials required to reach the learning criterion and in terms of their learning processes during shift learning. However, when we compared patients with subcortical and unilateral cortical damage, the results revealed that the learning processes of patients with subcortical damage were normal, whereas the patients with unilateral cortical damage showed lesion-specific effects on shift learning. These findings are discussed in light of previous developmental findings and the proposed role of subcortical structures in learning.

Aged↗
PubMed2006

Response-based strengthening in task shifting: evidence from shift effects produced by errors.

The hypothesis is introduced that 1 source of shift costs is the strengthening of task-related associations occurring whenever an overt response is produced. The authors tested this account by examining shift effects following errors and error compensation processes. The authors predicted that following a specific type of error, called task confusion, shift benefits instead of shift costs should result. A series of 3 experiments confirmed this prediction showing that task confusions produce shift benefits in subsequent trials (Experiment 1), even when the error is detected (Experiment 2). Moreover, only posterror processes that imply an error correction response produce shift costs (Experiment 3). These results additionally suggest that error detection cannot prevent errors from affecting subsequent performance.

Adult↗
PubMed2002

Functional MRI of macaque monkeys performing a cognitive set-shifting task.

Functional brain organization of macaque monkeys and humans was directly compared by functional magnetic resonance imaging. Subjects of both species performed a modified Wisconsin Card Sorting Test that required behavioral flexibility in the form of cognitive set shifting. Equivalent visual stimuli and task sequence were used for the two species. We found transient activation related to cognitive set shifting in focal regions of prefrontal cortex in both monkeys and humans. These functional homologs were located in cytoarchitectonically equivalent regions in the posterior part of ventrolateral prefrontal cortex. This comparative imaging provides insights into the evolution of cognition in primates.

Animals↗
PubMed1978

Performance of MA-matched nonretarded and retarded children on discrimination learning and transfer-shift tasks.

The effects of the nature of the relevant dimension, response mode, imagery, and age on discrimination learning and shift performance was examined. Three age groups were used, CA 8 years-MA 8 years, CA 5 years-MA 5 years. CA 8 years-MA 5 years. The latter group learned both intradimensional and extradimensional shifts slower than did the former two groups. Subsequent analyses suggested that the reason for the slower learning in the retarded group was their greater frequency of control by dominant dimensions and/or the initial control by novel stimuli. A second finding was related to the particular procedure employed. Children were required to either press a button to indicate which of two stimuli was correct or pick up the correct stimulus. Form-relevant but not color-relevant problems were facilitated by the pick-up procedure. These findings suggest that dimensional dominance may be a consequence of the procedures employed in previous reports where children were or were not permitted to manipulate the stimuli.

Age Factors↗
PubMed2006

Learned irrelevance and response perseveration in a total change dimensional shift task.

Thirty-six healthy participants received a discrimination learning task requiring the identification of a relevant stimulus dimension. After successful learning, the relevant dimension was shifted unannounced. All exemplars of the two dimensions presented after the shift were novel, implying a 'total change' design. In three experimental conditions, participants could either make only errors reflecting perseveration of responding to the former relevant dimension, continued ignoring of the former irrelevant dimension, or both. After the shift, the participants in the perseveration condition made fewer errors than did those in the other two conditions, which did not differ. These results imply a predominance of the learned irrelevance mechanism even when any direct transfer of learning about exemplars in the pre-shift phase is precluded.

Adult↗
PubMed2005

Spontaneously hypertensive, Wistar-Kyoto and Sprague-Dawley rats differ in performance on a win-shift task in the water radial arm maze.

The spontaneously hypertensive rat (SHR) is a commonly used animal model of attention deficit hyperactivity disorder. Previous literature is inconclusive with respect to the exact nature of memory impairments in this strain. The objective of this study was to assess spatial memory as measured by performance of male SHR, Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats on a win-shift version of the water radial arm maze. On this task, all strains made more errors on Trial 4 when the mnemonic demand was highest, and showed a similar response when the delay was increased from 60s to 2h on Week 3. Both SHR and WKY rats made more reference memory errors than SD, however, SHR showed minimal improvement over weeks. The increase in errors may be due to a greater inclination of SHR and WKY to use a chaining strategy of entering consecutive arms than SD. Furthermore, the number of incomplete arm entries into reference memory arms decreased over weeks in WKY and SD, but increased in SHR, suggesting increased impulsivity of SHR at the later stages of testing. Although based on number of errors, the data indicate that SHR may have memory deficits, the data relating to arm entries suggest that the minimal improvement in SHR over weeks may have been due to greater impulsivity in the later weeks, rather than defective memory. Thus, these findings are consistent with SHR having impairments with selection of appropriate behavioural responses in a goal-directed task.

Analysis of Variance↗
PubMed2006

Selective attention for negative information and depression in schizophrenia.

OBJECTIVES: Depression is a frequent feature of schizophrenia but the cognitive processes involved in its development and maintenance are unclear. Recent studies have shown that clinical depression is associated with faulty inhibitory mechanisms of selective attention for negative information. The current study examined whether patients with schizophrenia also have an attentional bias towards negative stimuli. The inhibitory processes of interference control and task-shifting abilities were also examined to assess whether patients would show a selective impairment. METHOD: Forty-three patients with schizophrenia and 24 healthy controls completed the Affective Shifting Task. RESULTS: As a group, schizophrenia patients did not show an attentional bias for negative material. However, those patients with high levels of depression demonstrated faster latencies when negative words were the targets, and higher depression scores were found to be associated with an increasing number of false alarms for negative words when they were not the targets. The results also showed that patients had impaired interference control but intact task-shifting abilities. CONCLUSIONS: Faulty inhibitory mechanisms of selective attention for negative information are not a general feature of schizophrenia but appear to be selective to those with a depressed mood. The results highlight the need for further studies examining the exact nature of the affective dysfunction in schizophrenia and the cognitive processes supporting negative emotions.

Adult↗
PubMedDate not supplied

Challenging the serotonergic system in Parkinson disease patients: effects on cognition, mood, and motor performance.

BACKGROUND: Parkinson disease (PD) is a neuropsychiatric disease that is characterized by motor and neuropsychiatric symptoms. Multiple neurotransmitter systems, including the serotonergic system, are involved in the pathophysiology of this disease. The exact role of the serotonergic system in PD is still unclear. OBJECTIVE: To investigate the role of serotonin on specific aspects of cognition, mood, and motor performance in PD. METHODS: In a double-blind, randomized, placebo-controlled, crossover design, the effects of a nonspecific serotonergic challenge with citalopram, a selective serotonin reuptake inhibitor, and a 5-HT1a receptor-specific challenge with buspirone on the Visual Verbal Learning Task, Concept Shifting Task, Profile of Mood State Questionnaire, motor section of the Unified Parkinson Disease Rating Scale (section 3), Simple Reaction Time Task, and Finger Precuing Task were studied in 21 PD patients in early stages of their disease and 21 age-, sex-, and education-matched healthy volunteers. RESULTS: The serotonergic challenges resulted in similar effects for both groups. No changes of scores on the cognitive tasks (Visual Verbal Learning Task and Concept Shifting Task) were observed. Results of the Profile of Moods State Questionnaire indicated that, at baseline, PD patients scored less than controls on all 5 subscales. Motor performance (measured by reaction time) was negatively affected by the interventions. CONCLUSIONS: The effects of nonspecific and 5-HT1a receptor-specific challenging of the serotonergic neurotransmitter system had similar effects in both PD patients and healthy control subjects. These findings indicate that serotonergic function is not impaired in early PD and that serotonin, although involved in the pathophysiology of PD, does not seem to play a direct role in cognition, mood, and motor performance in PD patients, but may be involved in hypokinesia.

Affect↗
PubMed2004

Total sleep deprivation increases the costs of shifting between simple cognitive tasks.

In two experiments we studied the effects of one night of total sleep deprivation on task-shift costs. In different conditions shifts were between types of judgment (extradimensional shifts) and between stimulus-response mappings (intradimensional shifts). In addition, with an alternating-runs procedure we used short and long response-to-stimulus intervals and also external precues to vary the opportunities for advance configuration of task sets. Under all conditions sleep deprivation increased shift costs derived from the 20% slowest reaction times, which were insensitive to the opportunities for advance configuration. Shift costs derived from the 20% fastest reaction times were increased only for extradimensional shifts. As indicated by congruency effects, the increase of shift costs after a night without sleep cannot be attributed to increased interference between competing task sets. The findings suggest that total sleep deprivation increases task-set instability and thus lapsing, in particular in conditions with long stimulus-to-response intervals and in shift trials. In addition total sleep deprivation seems to increase the duration of an exogenously controlled process involved in extradimensional shifts.

Adult↗
PubMed2003

Sleep deprivation influences some but not all processes of supervisory attention.

Does one night of sleep deprivation alter processes of supervisory attention in general or only a specific subset of such processes? Twenty college-aged volunteers, half female, performed a choice reaction time task. A cue indicated that compatible (e.g., right button, right-pointing arrow) or incompatible (e.g., left button, right-pointing arrow) responses were to be given to a stimulus that followed 50 or 500 ms later. The paradigm assessed response inhibition, task-shifting skill, and task strategy-processes inherent in supervisory attention. Performance, along with heart rate, was assessed for 12 hr following normal sleep or a night of complete sleep deprivation. Sleep deprivation altered neither preparation for task shifting nor response inhibition. The ability to use preparatory bias to speed performance did decrease with sleep deprivation. Sleep deprivation appears to selectively affect this supervisory attention process, which is perceived as an active effort to cope with a challenging task.

Adult↗
PubMed2006

Aging affects executive functions and memory in mouse lemur primates.

The decline of cognitive capacities with age in mouse lemur primates (Microcebus murinus) was assessed. Eight young adults (2-4 years) and nine aged adults (7-11 years) were examined on tasks designed to measure executive functions, procedural and declarative memory. The mouse lemurs were tested on the go-no go successive discrimination task, set shifting tasks (including extra-dimensional shift and reversal discrimination) and a spatial rule-guided discrimination task. There were four major findings. First, the deficits observed were not global but only on specific tasks indicating that only specific cognitive abilities are impaired with aging. Second, there were variations among aged subjects suggesting different patterns of cognitive aging. Third, alterations in cognitive abilities with aging in mouse lemurs seemed to be comparable to those described in aged monkeys and humans. Indeed, executive functions and declarative memory were affected in subpopulations of aged subjects whereas procedural memory remained intact in all the tested aged subjects. Finally, two forms of executive dysfunctions were distinguished among the aged subjects. The ultimate goal is to correlate age-related cognitive deficit with brain alterations and this study has helped to select candidate regions to be thoroughly scrutinized in aged mouse lemurs.

Aging↗
PubMed2005

Noradrenergic modulation of cognitive function in rat medial prefrontal cortex as measured by attentional set shifting capability.

The brain noradrenergic system is thought to facilitate neuronal processes that promote behavioral activation, alertness, and attention. One region in which norepinephrine may exert such effects is the medial prefrontal cortex, which has been implicated in many cognitive functions including arousal, attention, motivation, working memory, response inhibition, and behavioral flexibility. The present study addressed the modulatory influence of noradrenergic neurotransmission in medial prefrontal cortex on cognitive function in rats, as measured by performance in an attentional set shifting task. In experiment 1, we tested effects of increasing and decreasing brain noradrenergic neurotransmission by systemic administration of the alpha2-adrenergic autoreceptor antagonist and agonist drugs, atipamezole and clonidine, respectively. Atipamezole pretreatment significantly improved performance on the stages of the attentional task requiring an extradimensional shift in attention, and those involving stimulus reversals, whereas clonidine had no effect at any stage. In experiment 2, we then tested effects of microinjecting alpha1- or beta-adrenergic receptor antagonists into medial prefrontal cortex on the enhancement of performance on the extradimensional task produced by atipamezole. The atipamezole-induced enhancement of performance on the extradimensional set shifting task was blocked by alpha1-, but not beta-adrenergic receptor antagonists in medial prefrontal cortex. Neither antagonist alone had any effect on extradimensional set shift performance in the absence of atipamezole-induced enhancement. These results indicate that elevating noradrenergic activity at alpha1-receptors in medial prefrontal cortex facilitates cognitive performance of rats in an attentional set-shifting task, which may contribute to the role of norepinephrine in behavioral state changes such as arousal, or to the beneficial cognitive effects of psychotherapeutic drugs that target noradrenergic neurotransmission.

Adrenergic alpha-Agonists↗
PubMed1989

[A comparison of win-shift and win-stay performance of rats in a radial arm maze].

The purpose of the present experiment was to compare the performance of rats in a win-shift task and a win-stay task in a radial arm maze. To this end, three experiments were conducted using a variety of procedures. In general, the win-shift task required the rats to choose the unvisited arms and the win-stay task required the rats to return the visited arms. In Experiment 1, a free-choice memory recognition procedure was used, and in Experiments 2 and 3, a forced-choice memory recognition procedure was used. All three experiments showed that in the win-shift task, rats rapidly learned the task and performed well whereas in the win-stay task, the rats consistently showed a chance-level performance despite of the prolonged training. In addition to these findings, when the tasks were reversed (i.e. from the win-shift to the win-stay, and vice versa), the rats still showed a response strategy previously adopted (Experiment 3). These findings seem to be important in considering the characteristics of spatial memory in rats.

Animals↗
PubMed2004

Semantic generalization of stimulus-task bindings.

People find it difficult to switch between two tasks, even if they have time to prepare-the so-called residual task shift cost. We studied a switch of tasks from picture naming to word reading, using picture-word Stroop stimuli. Consistent with previous findings, we demonstrate that a large part of the observed task shift cost was due to priming from prior stimulus-response episodes, in which the current task stimulus was encountered in a competing task. We further show that this task-priming effect generalizes to semantically related stimuli, which opens the possibility that most or all of these residual shift costs reflect some sort of generalized proactive interference from previous stimulus-task episodes.

Adult↗
PubMed2004

A comparison of performance on the Towers of London and Hanoi in young children.

BACKGROUND: The Towers of London (TOL) and Hanoi (TOH) have been viewed as equivalent measures of planning and/or problem solving, although recent evidence in adults suggests that the underlying measurement characteristics of these two tasks may differ. As tower tasks are one of the few instruments that can be used to assess executive functioning in young children, the cognitive demands for both tasks merit further examination. METHODS: The relation among tower tasks and those of short-term memory, inhibition, and shifting ability were examined in a sample of 118 typically developing young children (M age = 4 years, 9 months, SD = 6 months). Half the children completed TOL and half completed TOH, with groups matched with respect to age, sex, and child vocabulary. RESULTS: Whilst performance on a shifting task uniquely predicted TOH performance, none of the executive function measures were related to TOL performance after statistically controlling for the influence of baseline naming speed. For both tower tasks, performance on a shifting task contributed more strongly on complex trials that required more moves in the counter-intuitive direction relative to the end-state goal, whereas inhibition task performance only predicted performance on complex TOL trials. CONCLUSIONS: Successful tower task performance may be determined, at least at higher levels of complexity, by mental flexibility in this age range. However, overall the findings suggest that TOL and TOH are not interchangeable tasks even in young children, and more generally, raise methodological issues regarding the complex nature of executive function tasks.

Age Factors↗
PubMedDate not supplied

Set shifting in anorexia nervosa: an examination before and after weight gain, in full recovery and relationship to childhood and adult OCPD traits.

Deficits in set shifting tasks are present in anorexia nervosa (AN), but it is not known whether these deficits are traits independent of current disease or nutritional status or merely a temporary consequence of starvation or psychopathology. The aims of the present study were to determine if set-shifting sub-optimal performance are state or trait-related by examining set shifting in patients with current or past AN, and the extent of association of these deficits with obsessive compulsive traits and behaviours. To achieve this we examined set shifting abilities in three groups of subjects: (a) AN patients with current illness, prior to receiving treatment (AN); (b) people with past AN currently in long term recovery (ANRec) and a healthy comparison group (HC). We also longitudinally followed up a subset for the AN group who showed weight recovery in response to in patient treatment (ANWR). We administered a group of set shifting tests, which included cognitive, perceptual and motor shifting tasks. A semi-structured interview was obtained to ascertain obsessive compulsive personality disorder (OCPD) traits as a child and adult. Set-shifting difficulties were observed in the AN group, but to a lesser extent in the ANRec group. In the AN group these difficulties did not show any improvement follow re-testing after weight recovery. Performance on set shifting tasks was associated with childhood rigidity and inflexibility. Some aspects of set shifting sub-optimal performance in AN appear to be a trait rather than a state marker.

Adult↗
PubMed2004

More learned irrelevance than perseveration errors in rule shifting in healthy subjects.

The present experiments examined the extent to which two possible sources of error affect healthy subjects' performance in a rule-shift task. All 115 participants first received a discrimination learning task, in which a pair of different visual stimuli was presented on each trial, one of which had to be identified as 'correct.' Each stimulus varied in two dimensions: a task-relevant and a task-irrelevant dimension. Feedback on correctness was given after each choice. After eight successive correct choices, the nature of the task-relevant dimension changed: the post-shift learning phase. Two types of error can occur in this phase: continued responding to the former relevant, but now irrelevant, dimension, a perseverative error, and non-responding to the former irrelevant, but now relevant, dimension, an error due to learned irrelevance. Different groups received a post-shift task in which none, one, or both of these two types of error could affect performance. The number of incorrect choices in the post-shift phase was significantly affected by learned-irrelevance errors but not by perseverative errors. An associative-learning model incorporating feedback-induced changes in both associative strength and saliency of the elements comprising the stimuli can explain these results.

Adolescent↗