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Preparatory control in task-switching has been suggested to rely upon a set of distributed regions within a frontoparietal network, with frontal and parietal cortical areas cooperating to implement switch-specific preparation processes. Although recent causal evidences using transcranial magnetic stimulation (TMS) have generally supported this model, alternative evidences from both functional neuroimaging and neurophysiological studies have questioned the switch-specific role of both frontal and parietal cortices. The aim of the present study was to clarify the role of prefrontal and parietal areas supporting preparatory cognitive control in task-switching. Within this purpose, an fMRI study during task-switching performance was conducted to identify the specific brain areas involved in preparatory control during performance of a task-switching paradigm. Then, TMS was applied over the specific coordinates previously identified through fMRI, that is, the anterior portion of the inferior frontal junction (aIFJ) and the intraparietal sulcus (IPS). Results revealed that TMS over the aIFJ disrupted performance in both switch and repeat trails in terms of delayed responses as compared to Sham condition. In contrast, TMS over the IPS selectively interfered performance in switch trials. These findings support a multicomponent model of executive control with the aIFJ being involved in more general switch-unspecific process such as the episodic retrieval of goals, and the IPS being related to the implementation of switch-specific preparation mechanisms for activating stimulus-response mappings. The results help conciliating preceding evidences about the role of a frontoparietal network during task-switching, and support current models about a hierarchical organization within prefrontal cortex.Significance StatementA combined fMRI and TMS study was conducted to clarify the brain areas involved in the executive control of attention during a cueing task-switching paradigm.Functional dissociations were observed during TMS stimulation, with prefrontal and parietal areas playing different roles during task-switching preparation. While the anterior portion of the inferior prefrontal junction seemed to be involved in a general mechanism of memory retrieval for goal identification, the intraparietal sulcus seemed to be engaged in a switch-specific mechanism for the translation of abstract task goals into action rules.The results help conciliating preceding evidences about the role of a frontoparietal network during task-switching, and support current models about a hierarchical organization within prefrontal cortex.

The aim of this research was to assess cognitive-motor interactions though dual tasks of working memory in patients with traumatic brain injury (TBI) and control subjects. Methods: Twenty patients ...

Patients with Obsessive-Compulsive Disorder (OCD) present neuropsychological deficits across different cognitive domains, especially in executive functioning and information processing speed. Some studies have even suggested that speed deficits may underlie poor neuropsychological performance. However, this hypothesis remains unanswered in both OCD general population and OCD refractory subgroup. In addition, it is not clear whether such deficits are secondary to the clinical symptoms or may constitute a primary deficit. The aim of this study was to explore the speed of processing hypothesis in treatment-refractory OCD patients, and to clarify to what extent slowness is related to psychopathological symptoms. Both clinical and neuropsychological examination was conducted to assess 39 OCD refractory patients candidates for neurosurgery and 39 healthy matched individuals. Principal component analysis revealed a three-component structure in the neuropsychological battery being used, including a speed of processing, working memory, and conflict monitoring components. Group comparisons revealed that OCD patients performed significantly worse than healthy individuals in speed measures, but no differences were found in executive tests not influenced by time. Correlation analyses revealed a lack of association between neuropsychological and clinical measures. The results suggest that treatment-refractory OCD patients exhibit a primary deficit in information processing speed independent of clinical symptoms.

Introduction Bradyphrenia is a key cognitive feature in Parkinson's disease (PD). There is no consensus on whether information processing speed is impaired or not beyond motor performance. Objective This study aims to explore which perceptual, motor, or cognitive components of information processing are involved in the slowdown affecting cognitive performance. Methods The study included 48 patients with PD (age: 63, 3 ± 8, 18; HY I‐III; UPDRS 15,46 ± 7,76) and 53 healthy controls (age: 60,09 ± 12,83). Five reaction time (RT) tasks were administered to all participants. The average RT in each of the tasks and the percentage of correct answers were measured. Patients with PD were in "ON state" at the time of the evaluation. Perceptual, motor, and cognitive components were isolated by means of a series of ANCOVAs. Results As expected, the motor component was slowed down in patients with PD. Moreover, while patients with PD showed slower RT than controls in all tasks, differences between groups did not exponentially increase with the increasing task complexity. ANCOVA analyses also revealed that the perceptual and sustained alert component resulted to be slowed down, with no differences being found in any of the remaining isolated cognitive components (i.e., response strategy‐inhibition, decisional, visual search, or interference control). Conclusions The results revealed that slowness of information processing in PD was mainly associated with an impaired processing speed of the motor and perceptual‐alertness components analyzed. The results may help designing new neurorehabilitation strategies, focusing on the improvement of perceptual and alertness mechanisms., The level of cognitive deceleration in PD is determined by a deterioration focused on perceptual and motor components and independently of the task complexity. Alterations in the brain networks involved in alertness to react to stimuli could justify the slowness of information processing in Parkinson´s disease

Objective: Phonological and semantic verbal fluency (VF) tasks are frequently used to assess language and executive functions in both clinical and research settings. F, A, and S are the most commonly used letters in phonological tasks across languages and cultures. Unfortunately, the lack of norms for the native Spanish population for these letters, and for certain semantic categories such as “proper names,” may lead to misinterpretation of scores due to demographic differences. The aim of the present study was to provide normative data for F, A, and S and for “proper names,” “animals,” and “fruits and vegetables” for the native Spanish population. Method: 257 healthy subjects took part in the study (ages: 17–100 years, 3–20 years of education). Correlation, multiple regression, and t-tests were used to select the most appropriate variables for stratification. Results: Education was the best predictor of performance in all tasks, followed by age. Given that t-test results showed no differences related to gender, with the only exception of the semantic category “animals,” this variable was not considered for stratification. Consequently, the data were stratified in two education levels (

Background: Parkinson’s disease (PD) patients are known to suffer from subtle cognitive and balance deficits from the early stages although they usually manifest in advanced stages. Postural instability (PI) has been correlated with slower information processing speed. Simple reaction time (SRT) tasks can be used to measure the speed of information processing. The main objective of this study was to examine the usefulness of SRT as a valid predictor of balance in PD, thus providing a simple and complementary assessment method. Methods: This cross-sectional study included 52 PD patients without dementia who were evaluated for balance using the pull test (PT) maneuver and Biodex® limits of stability (LOS). In addition, a reaction time task was used to measure processing speed. Correlation and linear regression analyses were performed. Results: The performance of SRT tasks was correlated with the evaluation of LOS% and PT, suggesting that the SRT may be a predictor of balance performance. Longer reaction time and poorer postural stability were also associated with disease duration but not with age. Conclusions: Poor performance in a simple reaction task can predict altered PI and can complement staging and evaluation in PD patients.

Objective 85 years after the description of the Stroop interference effect, there is still a lack of consensus regarding the cognitive constructs underlying scores from standardized versions of the test. The present work aimed to clarify the cognitive mechanisms underlying direct (word-reading, color-naming, and color-word) and derived scores (interference, difference, ratio, and relative scores) from Golden’s standardized version of the test. Method After a comprehensive review of the literature, five cognitive processes were selected for analysis: speed of visual search, phonemic verbal fluency, working memory, cognitive flexibility, and conflict monitoring. These constructs were operationalized by scoring five cognitive tasks (WAIS-IV Digit Symbol, phonemic verbal fluency [letter A], WAIS-IV Digit Span, TMT B-A, and reaction times to the incongruent condition of a computerized Stroop task, respectively). About 83 healthy individuals (mean age = 25.2 years) participated in the study. Correlation and regression analyses were used to clarify the contribution of the five cognitive processes on the prediction of Stroop scores. Results Data analyses revealed that Stroop word-reading reflected speed of visual search. Stroop color-naming reflected working memory and speed of visual search. Stroop color-word reflected working memory, conflict monitoring, and speed of visual search. Whereas the interference score was predicted by both conflict monitoring and working memory, the ratio score (color-word divided by color-naming) was predicted by conflict monitoring alone. Conclusion The present results will help neuropsychologists to interpret altered patient scores in terms of a failure of the cognitive mechanisms detailed here, benefitting from the solid background of preceding experimental work.

Internalized stigma reduces chances of clinical and subjective recovery in people with schizophrenia and other severe mental illness. To date, there is not enough evidence about an effective intervention to reduce internalized stigma that promotes clinical and subjective recovery in people with high internalized stigma and severe mental illness. The aim of this study was to evaluate the efficacy of a new psychological intervention named “Coping Internalized Stigma Program” (PAREI). An eight-session structured group-based integrative intervention was designed including psychoeducation, cognitive behavioural therapy, and mutual support. Fifty-four individuals with severe mental illness and a high level of internalized stigma were selected and randomly assigned to the PAREI intervention (n = 29) or to the control group (n = 25). The results of mixed ANOVAs revealed improvements in the PAREI group after treatment in the emotional dimension of internalized stigma, perceived legitimacy of discrimination, recovery expectations, and social functioning as compared to the control group. The results indicate that the PAREI represents a promising intervention tool to reduce internalized stigma, and to improve clinical and subjective recovery markers in people with severe mental illness and high internalized stigma.

Background: Slowness of information processing has been suggested as a fundamental factor modulating cognitive impairment in multiple sclerosis (MS). However, the contribution of depressive symptoms (DS) to slowness remains unclear. One of the most accepted hypotheses on the impact of depression on the general population suggests that depression interferes only with tasks requiring high cognitive demands. However, no studies have investigated if the same pattern occurs in MS. Objective: The aim of this study was to determine the profile of the contribution of DS to slowness. Methods: Four Reaction Time (RT) tasks requiring an increasing level of cognitive demands were administered to 35 relapsing remitting MS patients with DS, 33 MS patients without DS, 17 depressed non-MS patients and 27 controls. Results: MS patients without DS obtained longer RTs than controls in all the tasks. On the contrary, depressed non-MS patients were slower than controls only in the most demanding task. Finally, MS patients with DS were slower than MS patients without DS not only in the most demanding task but also in the task requiring a lower level of cognitive demands. Conclusion: The contribution of DS to slowness depends on the level of cognitive demands. However, its impact on MS is more deleterious than on the general population.

INTRODUCTION: The importance of knowing the pattern of evolution of cognitive deficits in the first months after a traumatic brain injury (TBI) has encouraged the development of numerous longitudinal studies. However, the results of most of them should be taken with caution due to the lack of adequate control of practice effects that can lead to overestimating the genuine recovery of cognitive processes. AIM: To describe the cognitive changes between the acute and subacute phases of the TBI controlling the effect of the practice. PATIENTS AND METHODS: Twenty-two patients were assessed in two different time points after TBI (immediately and after six months) using the following tests: Trail Making Test (A, B, B/A, B-A), Stroop Test (W, C, CW, interference), Digit Symbol-Coding, Symbol Search, Digits Forward and Backward, Verbal Fluency and Short-term Memory. To control for the practice effects, a transformation of the scores was performed applying the procedure proposed by Calamia et al. RESULTS. Before controlling the practice effects, the scores of all tests improved (p > 0.001). However, afterward, the improvement remained only in the Trail Making Test-B, B/A and B-A, Digit Symbol-Coding, Symbol Search, Stroop CW and Digits Backward. CONCLUSIONS: The lack of control of practice effects in longitudinal studies can generate misleading interpretations about the evolution of cognitive deficits. The pattern of recovery after a TBI varies depending on the cognitive process.

In this study, we sought to dissociate event-related potentials (ERPs) and the oscillatory activity associated with signals indicating feedback about performance (outcome-based behavioral adjustment) and the signals indicating the need to change or maintain a task set (rule-based behavioral adjustment). With this purpose in mind, we noninvasively recorded electroencephalographic signals, using a modified version of the Wisconsin card sorting task, in which feedback processing and task switching could be studied separately. A similar late positive component was observed for the switch and correct feedback signals on the first trials of a series, but feedback-related negativity was observed only for incorrect feedback. Moreover, whereas theta power showed a significant increase after a switch cue and after the first positive feedback of a new series, a selective frontal beta-gamma increase was observed exclusively in the first positive feedback (i.e., after the selection of the new rule). Importantly, for the switch cue, beta-alpha activity was suppressed rather than increased. This clear dissociation between the cue and feedback stimuli in task switching emphasizes the need to accurately study brain oscillatory activity to disentangle the role of different cognitive control processes.

Task-cueing studies suggest that the updating of sensory and task representations both contribute to behavioral task-switch costs [Forstmann, B. U., Brass, M., & Koch, I. (2007). Methodological and empirical issues when dissociating cue-related from task-related processes in the explicit task-cuing procedure. Psychological Research, 71(4), 393–400]. Here we used transition cues to orthogonally manipulate Cue- and Task updating (switches vs. repetitions), in order to identify distinct behavioral indicators and event-related potentials (ERPs) associated with the exogenous and endogenous control of task preparation and execution. Both Cue- and Task updating, as well as their interaction, yielded significant behavioral costs, and evoked distinct cue- and target-locked ERPs. Task-switches enhanced cue-locked early P3 amplitudes (180–220 ms) over mid-central scalp regions, whereas cue switches reduced a fronto-central negativity (N2; 255–295 ms). In contrast, both cue- and task-switches enhanced cue-locked late P3 amplitudes (300–340 ms; novelty P3) over centro-parietal regions, supporting the hypothesis of a common neural substrate for processing stimulus and task novelty [Barcelo, F., Escera, C., Corral, M. J., & Perianez, J. A. (2006). Task switching and novelty processing activate a common neural network for cognitive control. Journal of Cognitive Neuroscience, 18(10), 1734–1748]. In the target period, both cue- and task-switches reduced target P3 activity (310–730 ms) with short cue-target intervals only, suggesting that behavioral switch costs reflect the accrual of various time-dependent control operations during task preparation and execution. We conclude that the cognitive control of task-switching seems to emerge from a dynamic interplay between exogenous and endogenous sources of information.

El objetivo del presente trabajo fue analizar los factores que promueven la experiencia subjetiva de recuperación en personas con diagnóstico de esquizofrenia, y su relación con los indicadores de recuperación objetiva. Para ello, tras revisar la literatura existente, se evalúo el valor predictivo de diferentes variables psicosociales y clínicas sobre la recuperación subjetiva en una muestra de 43 personas con esquizofrenia. El análisis de regresión múltiple reveló que el uso de estrategias adaptativas de afrontamiento, un bajo estigma internalizado y una elevada autoestima predijeron un 55% de la variable recuperación subjetiva (F = 12,5; p < 0,0001). Los síntomas negativos y el funcionamiento social no predijeron recuperación subjetiva, pese a la presencia de correlaciones significativas. Se discuten los resultados en relación con la superior predicción de los indicadores subjetivos de recuperación, y se refl exiona sobre las implicaciones de estos resultados en el tratamiento y la promoción de mejores expectativas de recuperación en esta población, The aim of the present study was to analyze factors that promote the experience of subjective recovery in people with a diagnosis of schizophrenia, and their relationship with objective recovery indicators. To do so, and after reviewing the existing literature, the predictive value of a set of different clinical and psychosocial variables on subjective recovery was evaluated of a sample of 43 adults with schizophrenia. Multiple regression analysis revealed that using adaptive coping strategies, low internalized stigma, and high self-esteem predicted 55% of the variance of subjective recovery (F = 12.5; p < 0.0001). Negative symptoms and social functioning did not predict subjective recovery, in spite of significant correlations. Both the lack of predictive value of objective compared to subjective recovery measures, and the implications of the present fi ndings for the treatment and promotion of increased recovery expectancies in this population are discussed

Attention is a basic cognitive function and a prerequisite for other cognitive processes and is frequently impaired after traumatic brain injury. In the present study, 29 severe traumatic brain injury patients and 30 control subjects completed a battery of three neuropsychological tests of attention (WCST, TMT, Stroop). The aim was to clarify the attentional mechanisms underlying tests performance and to explore the types of attentional impairment after severe traumatic brain injury. Significant differences were found between the control and clinical groups in almost all measures. However, some of these differences disappeared when the speed of information processing was controlled using covariance analysis. In addition, a factor analysis revealed a four-factor solution explaining 89.6% of the variance in the data, i.e. cognitive flexibility, speed of processing, interference and working memory. This result supports the view of at least four different subprocesses of attentional control underlie test performance and allows one to differentiate between high- and low-level processes. The implications for neuropsychological assessment and rehabilitation are discussed.

Cognitive £exibility hinges on a readiness to direct attention to novel events, and on an ability to change one’s mental set to ¢nd new solutions for old problems. Human event-related potential (ERP) studies have described a brain‘orienting’ response to discrete novel events, marked by a frontally distributed positive potential peaking 300^ 400 ms post-stimulus (P3a). This brain potential has been typically related to bottom-up processing of novel non-targets under a ¢xed task-set (i.e., press a button to coloured targets), but had never been related to top-down attention control in dual-task paradigms. In this study, 27 subjects had their ERPs measured while they performed a version of the Wisconsin card sorting test (WCST), a dual-task paradigm where the same feedback cue signalled unpredictable shifts to a new task set (i.e., from ‘sort by colour’ to ‘sort by shape’).Feedback cues that directed a shift in the subject’s mental set to a new task-set elicited frontally distributed P3a activity, thus suggesting a role of the P3a response system in task-set shifting. Feedback cues also evoked a longer latency positive potential (350^ 600 ms; P3b), that was larger the more task rules were held in memory. In line with current models of prefrontal function in the executive control of attention, this P3a/P3b response system appears to re£ect the co-ordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory. NeuroReport 13:1887^1892 � c 2002 Lippincott Williams & Wilkins.

The Stroop Color-Word Test is a useful tool to evaluate executive attention and speed of processing. Recent studies have provided norms for different populations of healthy individuals to avoid misinterpretation of scores due to demographic and cultural differences. In addition, clinical norms may improve the assessment of cognitive dysfunction severity and its clinical course. Spanish normative data are provided for 158 closed traumatic brain injury (TBI) and 149 first-episode schizophrenia spectrum disorder (SCH) patients. A group of 285 Spanish healthy individuals (HC) was also considered for comparison purposes. Differences between groups were found in all Stroop scores with HC outperforming both clinical groups (p < .002 in all cases; d > .3 in all cases). TBI patients scored lower than SCH patients in word-reading (p < .001 and d = .6), and color-naming conditions (p < .001 and d = .4), but not in the color-word condition (p = .34 and d = .03). However, SCH patients exhibited a higher interference effect as compared to TBI (p < .002 and d = .5). Three sets of norms stratified by age and education (HC), and by education (TBI and SCH) are presented for clinical use.

Cognitive dysfunctions are critical determinants of the quality of life and functionality in schizophrenia. Whether the cognitive deficits present at an early stage, are static or change across one's lifespan is still under debate. This study aims to investigate the long-term (3 years) course of cognitive deficits in a large and representative cohort of first episode schizophrenia spectrum patients (N = 155),and evaluate their influence on disability. In addition, a healthy control sample (N = 43) was also studied for comparison. This study evaluates the performance of patients and controls in a battery of cognitive assessments using baseline, 1-year and 3-year follow-up designs. The results show that, although cognitively outperformed by the controls at any time, the cognitive performance of the patients improved similar to the controls in all cognitive functions except verbal and visual memory. Even though the course of cognitive performance across the sample as a whole was stable, the subgroup of patients who experienced a cognitive decline had worse functionality and lesser amelioration of negative symptoms. Overall, there is no significant deterioration in the cognitive function in a group of first episode schizophrenia spectrum disorder patients, with the possible exception of tasks that were associated with episodic memory. However, patients whose cognitive performance demonstrated a declining trend may present with a poorer progression in terms of clinical and disability variables.

Exogenous attention can be understood as an adaptive tool that permits the detection and processing of biologically salient events even when the individual is engaged in a resource-consuming task. Indirect data suggest that the spatial frequency of stimulation may be a crucial element in this process. Behavioral and neural data (both functional and structural) were analyzed for 36 participants engaged in a digit categorization task in which distracters were presented. Distracters were biologically salient or anodyne images, and had three spatial frequency formats: intact, low spatial frequencies only, and high spatial frequencies only. Behavior confirmed enhanced exogenous attention to biologically salient distracters. The activity in the right and left intraparietal sulci and the right middle frontal gyrus was associated with this behavioral pattern and was greater in response to salient than to neutral distracters, the three areas presenting strong correlations to each other. Importantly, the enhanced response of this network to biologically salient distracters with respect to neutral distracters relied on low spatial frequencies to a significantly greater extent than on high spatial frequencies. Structural analyses suggested the involvement of internal capsule, superior longitudinal fasciculus and corpus callosum in this network. Results confirm that exogenous attention is preferentially captured by biologically salient information, and suggest that the architecture and function underlying this process are low spatial frequency-biased., This work was supported by the grant PSI2008-03688 from the Ministerio de Ciencia e Innovación (MICINN) of Spain.

Cannabis is one of the most widely used illicit drugs in the world. In healthy individuals cannabis is associated with cognitive impairments. Research into the effect of cannabis use in schizophrenia has yielded contradictory findings. Our aim has been to explore the correlates of cannabis use in cognitive and psychopathological features, both cross-sectional and longitudinally, in early phases of schizophrenia. 104 patients with a first episode of non-affective psychosis and 37 healthy controls were studied. Patients were classified according to their use of cannabis prior to the onset of the illness (47 users vs. 57 non-users). They were cross-sectionally and longitudinally studied and compared on clinical and cognitive variables and also on their level of premorbid adjustment. Cannabis user patients had better attention and executive functions than non-cannabis user patients at baseline and after 1 year of treatment. Both groups showed similar improvement in their cognitive functioning during the 1-year follow-up period. We also found that users had a better social premorbid adjustment, particularly during the early periods of life. The amount of cannabis consumed and the length of time of consumption did not significantly relate to cognitive performance. The use of cannabis does not seem to be associated with a negative effect on cognition in a representative sample of first-episode schizophrenia patients. Cannabis user patients appear to comprise a subgroup of patients with a better premorbid adjustment and premorbid frontal cognitive functions.

Theoretical models suggest the existence of at least three relatively independent attentional mechanisms implemented in partially segregated brain networks: vigilance, orienting, and executive attention. In this article, we review tasks for assessment, related neuroanatomy, and impairments of these mechanisms. We also exemplify how these attentional networks interact in daily life activities for an efficient adjustment to environmental demands, and how they can be hindered after different pathological states, such as acquired brain injury, degenerative diseases, and developmental changes (in the child and in the aging process). Finally, the importance of speed of information processing as a key modulator of appropriate attentional functioning is discussed.

The aim of this study was to clarify which cognitive mechanisms underlie Trail Making Test (TMT) direct and derived scores. A comprehensive review of the literature on the topic was carried out to clarify which cognitive factors had been related to TMT performance. Following the review, we explored the relative contribution from working memory, inhibition/interference control, task-switching ability, and visuomotor speed to TMT performance. Forty-one healthy old subjects participated in the study and performed a battery of neuropsychological tests including the TMT, the Digit Symbol subtest [Wechsler Adult Intelligence Scale (Third Version) (WAIS-III)], a Finger Tapping Test, the Digits Forward and Backward subtests (WAIS-III), Stroop Test, and a task-switching paradigm inspired in the Wisconsin Card Sorting Test. Correlation and regression analyses were used in order to clarify the joint and unique contributions from different cognitive factors to the prediction of TMT scores. The results suggest that TMT-A requires mainly visuoperceptual abilities, TMT-B reflects primarily working memory and secondarily task-switching ability, while B-A minimizes visuoperceptual and working memory demands, providing a relatively pure indicator of executive control abilities. (JINS, 2009, 15, 438–450.)

This study aimed to clarify the neural substrates of behavioral switch and restart costs in intermittently instructed task-switching paradigms. Event-related potentials (ERPs) were recorded while participants were intermittently cued to switch or repeat their categorization rule (Switch task), or else they performed two perceptually identical control conditions (NoGo and Oddball). The three tasks involved different task-sets with distinct stimulus-response associations in each, but identical visual stimulation, consisting of frequent colored shapes (p = 0.9) and randomly interspersed infrequent black shapes (p = 0.1; ‘+’ and ‘x’ symbols). Behavioral restart costs were observed in the fi rst target responses following all black shapes in the Switch and NoGo tasks – but not in the Oddball task – and corresponded with enhanced fronto-centrally distributed early cue-locked P3 activity (peak latency 325–375 ms post-cue onset at the vertex). In turn, behavioral switch costs were associated with larger late cue-locked P3 amplitudes in the Switch task only (peak latency 400–450 ms post-cue onset at mid-parietal sites). Together with our information theoretical estimations, ERP results suggested that restart and switch costs indexed two neural mechanisms related to the preparatory resolution of uncertainty: (1) the intermittent re-activation of task-set information, and (2) the updating of stimulus-response mappings within an active task set, as indexed by early and late cue-locked P3 activations, respectively. In contrast, target-locked P3 activations refl ected a functionally distinct mechanism related to the implementation of task-set information. We conclude that task-switching costs consist of both switch-specifi c and switch-unspecifi c processes during the preparation and execution stages of task performance.

Introduccion. El empleo de paradigmas de tarea dual ha mostrado interacciones conductuales entre ciertas tareas motoras, como el equilibrio o la marcha, y tareas cognitivas al ser realizadas simultaneamente. Pese a la potencial relevancia de estos hallazgos en la explicacion de ciertos sintomas neurologicos (por ejemplo, caidas) o en el diseno de nuevas intervenciones, son escasos los datos sobre tales efectos en traumatismos craneoencefalicos (TCE). Objetivo. Evaluar la presencia de interacciones cognitivomotoras durante la realizacion de tareas duales en TCE. Sujetos y metodos. Veinte pacientes con TCE y 19 controles sanos realizaron diferentes tareas cognitivas de atencion y memoria operativa (tareas de tiempo de reaccion simple, tiempo de reaccion compleja, 1-back numerica y 1-back espacial) en tarea dual, es decir, al tiempo que una tarea motora (bipedestacion y marcha), y en tarea simple (sin tarea motora). Se registraron los tiempos de reaccion en respuesta a las tareas cognitivas. Resultados. Los pacientes mostraron peor rendimiento que los controles en todas las tareas (p < 0,05). Mientras que ninguno de los grupos mostro cambios en los tiempos de reaccion medidos en las tareas atencionales durante la ejecucion dual en comparacion con la ejecucion simple, los pacientes con TCE si mostraron mejoria en las tareas de memoria operativa (F(2, 74) = 2,9; p < 0,05) durante la tarea dual de marcha (p < 0,02). Conclusiones. Se discuten las posibles causas de interacciones cognitivomotoras positivas durante la ejecucion simultanea de tareas de marcha y memoria operativa en pacientes con TCE, y el potencial valor terapeutico de los paradigmas duales en la rehabilitacion de estos pacientes.

The Trail Making Test (TMT) has been a useful assessment tool to investigate executive function. Several studies have recently improved the existing TMT norms by mean of large samples of healthy individuals stratified by a number of demographic variables from different populations. In contrast, criticisms have been raised about the utility of norms from healthy samples to detect changes across time in clinical samples where TMT performance used to be altered. In addition, few studies have compared groups of patients with deficits in TMT performance, making it difficult to decide whether a single set of norms is sufficient to assess different clinical populations. We provide normative data from three large samples of patients with traumatic brain injury (TBI) (n = 90), schizophrenia spectrum disorders (n = 127), and healthy Spanish speakers (n = 223). Differences between healthy participants and patients in all TMT direct (TMT-A, TMT-B) and derived (B–A, B:A, B–A/A) scores were found. TMT performance was poorer in TBI patients than in schizophrenia patients except for the B:A and B–A/A scores, suggesting a similar underlying executive deficit. Normal ageing impaired both direct and derived TMT indices, as revealed by lower scores in the healthy elderly group (55–80 years old) as compared with young (16–24) and middle-aged (25–54) healthy participants. Three different sets of norms stratified by age, education, or both are presented for clinical use. Recommendations on TMT scores are made for future research. © 2007 National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved.

Humans can flexibly alter a plan of action to adjust their behavior adaptively in changing environments. Functional neuroimaging has shown distinct patterns of activation across a frontoparietal network responsible for switching and updating such plans of action or 'task sets.' However, little is known about the temporal order of activations within prefrontal or across with posterior regions subserving set-shifting operations. Here, whole-head magnetoencephalography (MEG) was used to explore the spatiotemporal brain dynamics in a modified version of the Wisconsin card-sorting test (WCST). Our task was designed to examine preparation of set-shifting rather than set-acquisition operations time locked to context-informative cues. Three cortical regions showed a larger number of MEG activity sources in response to shift and relative to nonshift cues: (a) inferior frontal gyrus (IFG; BA 45, 47/12), (b) anterior cingulate cortex (ACC; BA 24, 32), and (c) supramarginal gyrus (SMG; BA 40). Importantly, the timing of MEG activation differed across these regions. The earliest shift-related MEG activations were detected at the IFG (100-300 ms postcue onset), followed by two further peaks at the ACC (200-300 and 400-500 ms) and the SMG (300-400 and 500-600 ms). Several other prefrontal and posterior cortical areas were similarly activated by both shift and nonshift preparatory cues. The resulting temporal pattern of interactions within prefrontal and across with posterior association cortices is coherent with current models of task switching and provides novel information about the temporal course of brain activations responsible for the executive control of attention.

In attempting to integrate the authors' proposed model with results from analogous human event-related potential (ERP) research, we found difficulties with: (1) its apparent disregard for supraordinate representations at posterior multimodal association cortices, (2) its failure to address contextual task effects, and (3) its strict architectural dichotomy between memory storage and control functions.

Introduccion. Este articulo expone un ejemplo de la utilidad de la magnetoencefalografia (MEG) en la localizacion anatomica del inicio y la propagacion de las crisis epilepticas. Caso clinico. Se trata de un paciente de 34 anos con crisis parciales complejas farmacorresistentes. La resonancia magnetica presenta una probable displasia cortical frontobasal izquierda. El electroencefalograma ictal de superficie revela ondas theta frontotemporales izquierdas. En el registro con electrodos subdurales se demuestra la existencia de anomalias epileptiformes interictales durante el sueno, entre las que predominan las polipuntas, y crisis de inicio focal en la cara lateroorbitaria del lobulo frontal izquierdo. La MEG registra tres crisis clinicamente similares a las experimentadas por el paciente y permite localizar el inicio de las crisis en la circunvolucion frontal inferior izquierda, con propagacion a otras areas frontales, la insula y el lobulo temporal, todo ello en el hemisferio izquierdo. Conclusion. La MEG puede considerarse como un elemento diagnostico util en el estudio de la fisiopatologia de las crisis parciales, asi como en la evaluacion prequirurgica

Introduccion. La Neuropsicologia define las funciones ejecutivas cerebrales como aquellas que coordinan el procesamiento de la informacion en el cerebro. Su estudio ha experimentado un importante avance en la ultima decada promovido por la utilizacion de las tecnicas de neuroimagen funcional. Desarrollo. Las tecnicas de medicion electrofisiologica han permitido establecer una relacion entre dos componentes especificos del potencial evocado (PE) cerebral y determinados procesos de control y monitorizacion descritos en modelos teoricos sobre funcionamiento ejecutivo, como el de Norman y Shallice. Por un lado, los aspectos anterior (P3a; latencia 300-350 ms) y posterior (P3b; latencia 450-600 ms) del componente P3 a la novedad (del ingles, novelty P3), se han vinculado con un sistema generico de cambio atencional ante las demandas novedosas del entorno y de la tarea, gracias al empleo de los paradigmas experimentales de cambio de set atencional. Por otro lado, el PE denominado negatividad relacionada con los errores (del ingles, error related negativity o ERN) se ha mostrado sensible a los procesos de monitorizacion de la conducta (p. ej., deteccion de errores y generacion de acciones correctivas), durante la ejecucion de tareas de seleccion de respuesta con tiempo de reaccion. Conclusiones. La comprension de estos dos subprocesos ejecutivos supone un elemento clave en el concepto del funcionamiento del cerebro con aplicaciones directas sobre la generacion, tanto de modelos teoricos como de protocolos de evaluacion y rehabilitacion de pacientes con alteraciones disejecutivas

econventional WCST. Subjects and methods. The two tests were applied to a group of 60 young persons with no cerebral disorders. The principal components of both tests were analysed for determine their internal structure. Results. We found statistically significant differences between the scores of Spanish persons and the standard data for WCST. Analysis of the main components showed a solution of two components in the conventional WCST and a solution of three components in our adaptation. Conclusions. The American rating system underestimated the level of performance in the Spanish sample. Analysis of the internal consistency showed the excessively redundant and simple factorial structure of the conventional WCST. Our adaptation was shown to have a richer internal structure, with the order of error scores more in accord with the type of cognitive process involved. These advantages may be attributed to more exact analysis of non-perseverant errors, subclassified as efficient errors (i.e linked to comparison of hypotheses) and random errors (i.e. linked to loss of criteria for attention). [REV NEUROL 2001; 33:]