Effects of spatial working memory in balance during dual tasking in traumatic brain injury and healthy controls.

OBJECTIVES: 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 with chronic TBI with good functional level and 19 matched healthy controls performed dual working memory tasks (1-back numeric and 1-back spatial (S)) while sitting, standing, and walking. The center of pressure (COP) displacement amplitude, cadence, and error percentage (PER) were recorded as dependent variables. Results: The results revealed main effects of Group (TBI, controls) (p = .011) and Task factors (Single, Dual Standing 1-back, Dual Standing 1-back (S); p = .0001) for the COP. Patients showed greater displacement than controls (p = .011), and an analysis of the Task factor showed a minor displacement for the dual 1-back (S) task compared with the 1-back and single task (p = .002 and p = .001, respectively). Conclusions: Postural control during both standing and walking improved during performance of the spatial working memory task. In the dual task, both patients and controls showed a postural prioritization as an adaptive response to the increase in cognitive demand.

Computerized Simple Reaction Time and Balance in Nondemented Parkinson's Patients.

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.

The contribution of depressive symptoms to slowness of information processing in relapsing remitting multiple sclerosis.

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.

New functional dissociations between prefrontal and parietal cortex during task switching: A combined fMRI and TMS study.

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 evidence using transcranial magnetic stimulation (TMS) have generally supported this model, alternative results 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 involvement of prefrontal and parietal areas in preparatory cognitive control. With this purpose, an fMRI study was conducted to identify the brain areas activated during cue events in a task-switching paradigm, indicating whether to switch or to repeat among numerical tasks. Then, TMS was applied over the specific coordinates previously identified through fMRI, that is, the right inferior frontal gyrus (IFG) and right intraparietal sulcus (IPS). Results revealed that TMS over the right IFG disrupted performance in both switch and repeat trails in terms of delayed responses as compared to Sham condition. In contrast, TMS over the right IPS selectively interfered performance in switch trials. These findings support a multi-component model of executive control with the IFG 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 are discussed within the framework of contemporary hierarchical models of prefrontal cortex organization, suggesting that distinct prefrontal areas may carry out coordinated functions in preparatory control.

Cognitive versus emotional modulation within a Stroop paradigm in patients with schizophrenia.

BACKGROUND: Schizophrenia is a complex disorder involving deficits in both cognitive and emotional processes. Specifically, a marked deficit in cognitive control has been found, which seems to increase when dealing with emotional information. AIMS: With the aim of exploring the possible common links behind cognitive and emotional deficits, two versions of the emotional Stroop task were administered. METHOD: In the cognitive-emotional task, participants had to name the ink colour (while ignoring the meaning) of emotional words. In contrast, the emotional-emotional task consisted of emotional words superimposed on emotional faces, and the participants had to indicate the emotional valence of the faces. Fifty-eight participants (29 in-patients diagnosed with schizophrenia and 29 controls) took part in the study. RESULTS: Patients and controls showed similar response times in the cognitive-emotional task; however, patients were significantly slower than controls in the emotional-emotional task. This result supports the idea that patients show a more pronounced impairment in conflict modulation with emotional content. Besides, no significant correlations between the tasks and positive or negative symptoms were found. This would indicate that deficits are relatively independent of the clinical status of patients. However, a significant correlation between the emotional-emotional task and cognitive symptoms was found. CONCLUSIONS: These findings suggest a restricted capacity of patients with schizophrenia to deal with the attentional demands arising from emotional stimuli.

Verbal Fluency Tasks: Influence of Age, Gender, and Education and Normative Data for the Spanish Native Adult Population.

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 (<13, ≥13 years of education) and in two age levels (<60, ≥60) within the low-educational level group. Mean, standard deviation, and percentile scores for each group are provided. CONCLUSIONS: The present norms provide a reference for clinicians assessing VF. This data may also facilitate comparisons with other normative studies in cross-cultural and cross-linguistic research.

An effective psychological intervention in reducing internalized stigma and improving recovery outcomes in people with severe mental illness.

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.

Construct Validity of the Stroop Color-Word Test: Influence of Speed of Visual Search, Verbal Fluency, Working Memory, Cognitive Flexibility, and Conflict Monitoring.

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.

Components determining the slowness of information processing in parkinson's disease.

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.

Cognitive deficits and clinical symptoms in patients with treatment-refractory obsessive-compulsive disorder: The role of slowness in information processing.

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.

Identifying Perceptual, Motor, and Cognitive Components Contributing to Slowness of Information Processing in Multiple Sclerosis with and without Depressive Symptoms.

Increasing findings suggest that different components of the stimulus-response pathway (perceptual, motor or cognitive) may account for slowed performance in Multiple Sclerosis (MS). It has also been reported that depressive symptoms (DS) exacerbate slowness in MS. However, no prior studies have explored the independent and joint impact of MS and DS on each of these components in a comprehensive manner. The objective of this work was to identify perceptual, motor, and cognitive components contributing to slowness in MS patients with and without DS. The study includes 33 Relapsing-Remitting MS patients with DS, 33 without DS, and 26 healthy controls. Five information processing components were isolated by means of ANCOVA analyses applied to five Reaction Time tasks. Perceptual, motor, and visual search components were slowed down in MS, as revealed by ANCOVA comparisons between patients without DS, and controls. Moreover, the compounding effect of MS and DS exacerbated deficits in the motor component, and slowed down the decisional component, as revealed by ANCOVA comparisons between patients with and without DS. DS seem to exacerbate slowness caused by MS in specific processing components. Identifying the effects of having MS and of having both MS and DS may have relevant implications when targeting cognitive and mood interventions.

Updating sensory versus task representations during task-switching: insights from cognitive brain potentials in humans.

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 [Barceló, 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.

Evolución de las alteraciones cognitivas tras un traumatismo craneoencefálico: ¿hay mejoría tras controlar el efecto de la práctica? / Evolution of cognitive impairment after a traumatic brain injury: is there any improvement after controlling the practice effect?

Introducción: La importancia de conocer el patrón de evolución de los déficits cognitivos en los primeros meses tras un traumatismo craneoencefálico (TCE) ha fomentado el desarrollo de numerosos estudios longitudinales. Sin embargo, los resultados de la mayoría de ellos deberían tomarse con cautela debido a la falta de un control adecuado del efecto de la práctica, que puede llevar a sobreestimar la recuperación genuina de los procesos cognitivos. Objetivo: Describir los cambios cognitivos entre las fases aguda y subaguda del TCE controlando el efecto de la práctica. Pacientes y métodos: Veintidós pacientes realizaron dos evaluaciones neuropsicológicas tras el TCE (inmediata y tras seis meses) mediante los siguientes tests: Trail Making Test (A, B, B/A y B-A), test de Stroop (P, C, PC e interferencia), clave de números, búsqueda de símbolos, dígitos directos e inversos, fluidez verbal y memoria inmediata. Para controlar el efecto de la práctica se realizó una transformación de las puntuaciones aplicando el procedimiento propuesto por Calamia et al. Resultados: Antes de controlar el efecto de la práctica, se evidenció una mejoría en las puntuaciones de todos los tests (p > 0,001). Sin embargo, tras él, la mejoría permaneció sólo en el Trail Making Test-B, B/A y B-A, la clave de números, la búsqueda de símbolos, el test de Stroop PC y los dígitos inversos. Conclusiones: La falta de control del efecto de la práctica en estudios longitudinales puede generar interpretaciones erróneas sobre el perfil de evolución de los déficits cognitivos. El patrón de recuperación tras un TCE varía en función del proceso cognitivo

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

Think differently: a brain orienting response to task novelty.

Cognitive flexibility hinges on a readiness to direct attention to novel events, and on an ability to change one's mental set to find 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 fixed 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 reflect the co-ordinated action of prefrontal and posterior association cortices during the switching and updating of task sets in working memory.

Clinical Spanish norms of the Stroop test for traumatic brain injury and schizophrenia.

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 .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.

The role of low and high spatial frequencies in exogenous attention to biologically salient stimuli.

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.

Identifying perceptual, motor, and cognitive components contributing to slowness of information processing in multiple sclerosis with and without depressive symptoms

Increasing findings suggest that different components of the stimulus-response pathway (perceptual, motor or cognitive) may account for slowed performance in Multiple Sclerosis (MS). It has also been reported that depressive symptoms (DS) exacerbate slowness in MS. However, no prior studies have explored the independent and joint impact of MS and DS on each of these components in a comprehensive manner. The objective of this work was to identify perceptual, motor, and cognitive components contributing to slowness in MS patients with and without DS. The study includes 33 Relapsing-Remitting MS patients with DS, 33 without DS, and 26 healthy controls. Five information processing components were isolated by means of ANCOVA analyses applied to five Reaction Time tasks. Perceptual, motor, and visual search components were slowed down in MS, as revealed by ANCOVA comparisons between patients without DS, and controls. Moreover, the compounding effect of MS and DS exacerbated deficits in the motor component, and slowed down the decisional component, as revealed by ANCOVA comparisons between patients with and without DS. DS seem to exacerbate slowness caused by MS in specific processing components. Identifying the effects of having MS and of having both MS and DS may have relevant implications when targeting cognitive and mood interventions

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An information theoretical approach to task-switching: evidence from cognitive brain potentials in humans.

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 first 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 reflected a functionally distinct mechanism related to the implementation of task-set information. We conclude that task-switching costs consist of both switch-specific and switch-unspecific processes during the preparation and execution stages of task performance.

Task switching and novelty processing activate a common neural network for cognitive control.

The abrupt onset of a novel event captures attention away from, and disrupts, ongoing task performance. Less obvious is that intentional task switching compares with novelty-induced behavioral distraction. Here we explore the hypothesis that intentional task switching and attentional capture by a novel distracter both activate a common neural network involved in processing contextual novelty [Barcelo, F., Periáñez, J. A., & Knight, R. T. Think differently: A brain orienting response to task novelty. NeuroReport, 13, 1887-1892, 2002.]. Event-related potentials were recorded in two task-cueing paradigms while 16 subjects sorted cards following either two (color or shape; two-task condition) or three (color, shape, or number; three-task condition) rules of action. Each card was preceded by a familiar tone cueing the subject either to switch or to repeat the previous rule. Novel sound distracters were interspersed in one of two blocks of trials in each condition. Both novel sounds and task-switch cues impaired responses to the following visual target. Novel sounds elicited novelty P3 potentials with their usual peak latency and frontal-central scalp distribution. Familiar tonal switch cues in the three- and two-task conditions elicited brain potentials with a similar latency and morphology as the novelty P3, but with relatively smaller amplitudes over frontal scalp regions. Covariance and principal component analyses revealed a sustained frontal negative potential that was distorting concurrent novelty P3 activity to the tonal switch cues. When this frontal negativity was statistically removed, P3 potentials to novel sounds and task-switch cues showed similar scalp topographies. The degree of activation in the novelty P3 network seemed to be a function of the information (entropy) conveyed by the eliciting stimulus for response selection, over and above its relative novelty, probability of occurrence, task relevance, or feedback value. We conclude that novelty P3 reflects transient activation in a neural network involved in updating task set information for goal-directed action selection and might thus constitute one key element in a central bottleneck for attentional control.

Efectos de la actividad motora en el rendimiento cognitivo de pacientes con traumatismo craneoencefálico durante tareas duales / Effects of motor activity on cognitive performance of patients with traumatic brain injury during dual tasking

Introducción. 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 simultáneamente. Pese a la potencial relevancia de estos hallazgos en la explicación de ciertos síntomas neurológicos (por ejemplo, caídas) o en el diseño de nuevas intervenciones, son escasos los datos sobre tales efectos en traumatismos craneoencefálicos (TCE). Objetivo. Evaluar la presencia de interacciones cognitivomotoras durante la realización de tareas duales en TCE. Sujetos y métodos. Veinte pacientes con TCE y 19 controles sanos realizaron diferentes tareas cognitivas de atención y memoria operativa (tareas de tiempo de reacción simple, tiempo de reacción compleja, 1-back numérica y 1-back espacial) en tarea dual, es decir, al tiempo que una tarea motora (bipedestación y marcha), y en tarea simple (sin tarea motora). Se registraron los tiempos de reacción 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 mostró cambios en los tiempos de reacción medidos en las tareas atencionales durante la ejecución dual en comparación con la ejecución simple, los pacientes con TCE sí mostraron mejoría 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 ejecución simultánea de tareas de marcha y memoria operativa en pacientes con TCE, y el potencial valor terapéutico de los paradigmas duales en la rehabilitación de estos pacientes (AU)

Introduction. The use of dual task paradigms has revealed behavioural interactions between certain motor tasks, like standing or walking, and cognitive tasks when performed simultaneously. Despite the potential relevance of these findings accounting for certain neurological symptoms (i.e., falls), or for the design of new therapeutic interventions, there is few information available about such interaction effects in traumatic brain injury (TBI). Aim. To assess the presence of cognitive-motor interactions during dual tasking in TBI patients. Subjects and methods. Twenty TBI patients and 19 healthy matched controls performed two attentional and two working memory tasks (simple reaction times, complex reaction times, 1-back numeric, 1-back spatial) during dual task conditions, that is, at the same time than one motor task (standing and walking), and during single task conditions (without a motor task). Reaction times were recorded in response to all cognitive tasks. Results. Patients exhibit slower performance than controls in all cognitive tasks (p < 0.05). While neither patients nor controls showed changes in reaction times in the two simpler attentional tasks during dual tasking as compared to single tasking conditions, TBI patients do exhibit improvements in working memory tasks (F(2, 74) = 2.9; p < 0.05) during dual tasking-walking (p < 0.02). Conclusions. The possible causes of positive cognitive-motor interactions during simultaneous execution of motor-working memory tasks in TBI patients are discussed, as well as the potential therapeutic value of dual task paradigms in the rehabilitation of these patients (AU)