Mapping task-switching in frontal cortex through neuropsychological group studies

This paper considers evidence provided by large neuropsychological group studies and meta-analyses of functional imaging experiments on the location in frontal cortex of the subprocesses involved in the carrying out of task-switching paradigms. The function of the individual subprocesses is also considered in the light of analyses of the performance of normal subjects

Age-Based Differences in Task Switching Are Moderated by Executive Control Demands

OBJECTIVES: Recent work has identified different aspects of executive function that may underlie cognitive changes associated with age. The current study used a multifactorial design to investigate age sensitivity in the ability to shift between different task sets and the interaction of this ability with several specific aspects of executive control. METHOD: A large, well-characterized sample of younger (n = 40) and clinically healthy older (n = 51) adults completed a task switching paradigm in which 3 aspects of executive control were manipulated between subjects: a) sensorimotor demand (the number of distinct stimulus-response options); b) stimulus-level interference (i.e., flanker effects); and c) updating/monitoring (the frequency of task switches). RESULTS: Unique age-related deficits were observed for different aspects of local task switching performance costs and updating/monitoring, but not for interference. Sensorimotor demand was also an important additional factor that interacted with task switching performance. DISCUSSION: Our findings suggest that task switching, coupled with infrequent and unexpected transitions from one task set to another, in the context of high motoric demands, is particularly difficult for older adults

Inhibition in Task Switching: The Reliability of the N-2 Repetition Cost

The n-2 repetition cost seen in task switching is the effect of slower response times performing a recently completed task (e.g. an ABA sequence) compared to performing a task that was not recently completed (e.g. a CBA sequence). This cost is thought to reflect cognitive inhibition of task representations and has been well replicated (Koch, Gade, Schuch, & Philipp, 2010). As such, the n-2 repetition cost has started to be used as a measure of individual differences in inhibitory control (e.g. Whitmer & Banich, 2007); however, the reliability of this measure has not been investigated in a systematic manner. The current study addressed this important issue. Seventy-two participants performed three task switching paradigms; participants were also assessed on rumination traits and processing speed-measures of individual differences potentially modulating the n-2 repetition cost. We found significant n-2 repetition costs for each paradigm. However, split-half reliability tests revealed that this cost was not reliable at the individual-difference level. Neither rumination tendencies nor processing speed predicted this cost. We conclude that the n-2 repetition cost is not reliable as a measure of individual differences in inhibitory control

Fronto-cerebellar connectivity mediating cognitive processing speed

Processing speed is an important construct in understanding cognition. This study was aimed to control task specificity for understanding the neural mechanisms underlying cognitive processing speed. Forty young adult subjects performed attention tasks of two modalities (auditory and visual) and two levels of task rules (compatible and incompatible). Block-design fMRI captured BOLD signals during the tasks. Thirteen regions of interest were defined with reference to publicly available activation maps for processing speed tasks. Cognitive speed was derived from task reaction times, which yielded six sets of connectivity measures. Mixed-effect LASSO regression revealed six significant paths suggestive of a cerebello-frontal network predicting the cognitive speed. Among them, three are long range (two fronto-cerebellar, one cerebello-frontal), and three are short range (fronto-frontal, cerebello-cerebellar, and cerebello-thalamic). The long-range connections are likely to relate to cognitive control, and the short-range connections relate to rule-based stimulus-response processes. The revealed neural network suggests that automaticity, acting on the task rules and interplaying with effortful top-down attentional control, accounts for cognitive speed

Age-based differences in task switching are moderated by executive control demands

Objectives: Recent work has identified different aspects of executive function that may underlie cognitive changes associated with age. The current study used a multifactorial design to investigate age sensitivity in the ability to shift between different task sets and the interaction of this ability with several specific aspects of executive control. Method: A large, well-characterized sample of younger (n = 40) and clinically healthy older (n = 51) adults completed a task switching paradigm in which 3 aspects of executive control were manipulated between subjects: a) sensorimotor demand (the number of distinct stimulus-response options); b) stimulus-level interference (i.e., flanker effects); and c) updating/monitoring (the frequency of task switches). Results: Unique age-related deficits were observed for different aspects of local task switching performance costs and updating/monitoring, but not for interference. Sensorimotor demand was also an important additional factor that interacted with task switching performance. Discussion: Our findings suggest that task switching, coupled with infrequent and unexpected transitions from one task set to another, in the context of high motoric demands, is particularly difficult for older adults

Inhibition in task switching: The reliability of the n-2 repetition cost

The n-2 repetition cost seen in task switching is the effect of slower response times performing a recently completed task (e.g. an ABA sequence) compared to performing a task that was not recently completed (e.g. a CBA sequence). This cost is thought to reflect cognitive inhibition of task representations and has been well replicated (Koch, Gade, Schuch, & Philipp, 2010). As such, the n-2 repetition cost has started to be used as a measure of individual differences in inhibitory control (e.g. Whitmer & Banich, 2007); however, the reliability of this measure has not been investigated in a systematic manner. The current study addressed this important issue. Seventy-two participants performed three task switching paradigms; participants were also assessed on rumination traits and processing speed-measures of individual differences potentially modulating the n-2 repetition cost. We found significant n-2 repetition costs for each paradigm. However, split-half reliability tests revealed that this cost was not reliable at the individual-difference level. Neither rumination tendencies nor processing speed predicted this cost. We conclude that the n-2 repetition cost is not reliable as a measure of individual differences in inhibitory control

A atenção selectiva na doença de Alzheimer : a manutenção do set mental nos doentes de Alzheimer

A presente Dissertação de Mestrado, após a revisão de literatura realizada no tema de interesse, colocou como objetivo estudar a atenção seletiva em doentes diagnosticados com uma provável doença de Alzheimer em estádio ligeiro. Mais precisamente, foi proposto estudar um componente executivo da atenção seletiva, designado como, set mental, sendo ainda colocada a questão se nestes sujeitos existe algum défice na capacidade de resolução de conflito. O termo atenção diz respeito a diferentes processos cognitivos como, a orientação para um determinado estimulo, a capacidade de manter um estado de alerta e a capacidade de realizar tarefas complexas no dia-a-dia (Fernandez-Duque & Posner, 1997 cf. Fernandez-Duque & Black, 2006). Com o objetivo de encontrarem alguma concordância quando se referem às redes atencionais, alguns autores dividiram-nas em diferentes categorias como, atenção mantida, atenção seletiva e atenção dividida. A atenção mantida é definida como a capacidade de focar a atenção numa tarefa durante um longo período de tempo (Wilkins et al. 1987 cf. Perry, Watson & Hodges, 1999). A atenção seletiva define-se como a capacidade de ignorar informação irrelevante, enquanto ocorre o processamento da informação relevante. A atenção seletiva é necessária para canalizar recursos para um número restrito de canais sensoriais, enquanto o processamento de informação paralela é suprimido (Perry, Watson & Hodges 1999 cf. Levinoff et al. 2004). A atenção dividida diz respeito á partilha de recursos cognitivos para duas tarefas que ocorrem em simultâneo (Perry, Watson & John, 2000). A bibliografia referente às funções executivas na doença de Alzheimer relata um defeito nestas funções ainda em fases ligeiras da patologia (Albert, Moss, Tanzi & Jones, 2001; Baudic et al. 2006). Sendo o set mental um controlo executivo da atenção seletiva, demonstrou-se relevante explorá-lo neste estudo. Desta forma, com a finalidade de cumprir o objetivo proposto, foram comparados dois grupos. O grupo experimental, constituído por sujeitos com provável doença de Alzheimer em fases iniciais (n=7) e um grupo de controlo, constituído por sujeitos sem qualquer patologia (n=7). Os dois grupos realizaram um paradigma de task-.switching onde foram manipuladas as exigências criadas ao set mental destes sujeitos. Para obtenção dos resultados estatísticos foram contabilizadas as médias dos tempos de resposta obtidos pelos sujeitos pertencentes aos dois grupos e comparadas entre si. Após realizada análise estatística, não se verificou qualquer diminuição no set mental de sujeitos com doença de Alzheimer em fases iniciais, no entanto verificou-se um défice na resolução de conflitoThis project aimed to study selective attention in patients diagnosed as mild Alzheimer’s disease, specifically an executive subcomponent of selective attention called, mental set. In this study we, also, wanted to verify if there was any deficit in situations that required conflict resolution. The term attention refers to several different cognitive abilities such as, orienting towards a stimulus; keep an alert state, and the ability to perform complex tasks of daily life (Fernandez-Duque & Posner, 1997 cf. Fernandez-Duque & Black, 2006). With the purpose of achieving some agreeance when referring to the attention networks, some authors divided them in different categories such as, sustained attention, selective attention and divided attention. Sustained attention refers to the ability to keep attention in one task for a long period of time (Wilkins et al. 1987 cf. Perry, Watson & Hodges, 1999). Selective attention refers to the ability to ignore irrelevant information, while processing the relevant one. Selective attention is necessary to keep resources directed to some sensorial inputs, while, irrelevant information is suppressed (Perry, Watson & Hodges 1999 cf. Levinoff et al. 2004). Divided attention is characterized as the sharing of cognitive resources for two tasks that are happening at the same time (Perry, Watson & John, 2000). In the bibliography referring to the executive functions in Alzheimer disease, there are references to a deficit already in mild stages of this pathology (Albert, Moss, Tazi & Jones, 2001; Baudic et al. 2006). Since the mental set is an executive control of selective attention, it seemed relevant to explore it in this study. To fulfill our objective, we compared an experimental group, with patients diagnosed with probable mild Alzheimer’s disease (n=7), with a control group of healthy subjects (n=7). The two groups were compared through a task-switching paradigm, where the mental set was manipulated. Reaction time was recorded. For purposes of statistical analysis the median reaction time of both groups were obtained and compared. The results of this study did not find any alteration in mental set, of patients diagnosed with probable mild Alzheimer’s disease; however, we did find deficits in situations of conflict resolution