Academic journal article Cognitive, Affective and Behavioral Neuroscience

Toward a Taxonomy of Attention Shifting: Individual Differences in fMRI during Multiple Shift Types

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Toward a Taxonomy of Attention Shifting: Individual Differences in fMRI during Multiple Shift Types

Article excerpt

Although task switching is often considered one of the fundamental abilities underlying executive functioning and general intelligence, there is little evidence that switching is a unitary construct and little evidence regarding the relationship between brain activity and switching performance. We examined individual differences in multiple types of attention shifting in order to determine whether behavioral performance and fMRI activity are correlated across different types of shifting. The participants (n = 39) switched between objects and attributes both when stimuli were perceptually available (external) and when stimuli were stored in memory (internal). We found that there were more switch-related activations in many regions associated with executive control-including the dorsolateral and medial prefrontal and parietal cortices-when behavioral switch costs were higher (poor performance). Conversely, activation in the ventromedial prefrontal cortex (VMPFC) and the rostral anterior cingulate was consistently correlated with good performance, suggesting a general role for these areas in efficient attention shifting. We discuss these findings in terms of a model of cognitive-emotional interaction in attention shifting, in which reward-related signals in the VMPFC guide efficient selection of tasks in the lateral prefrontal and parietal cortices.

Over the last 15 years, neuroimaging studies have consistently identified a set of structures associated with the maintenance and manipulation of information and the control of attention. The function of this set of brain regions has been associated with a set of psychological processes described collectively as executive control operations, due to their central role in coordinating perceptual and motor processes in the service of internal goals. These mechanisms, broadly associated in traditional neuropsychology with the frontal lobes, allow us to focus on learning a novel task, listen to a friend when we have something else on our minds, notice and correct inappropriate behavior, and, possibly, even regulate our emotional responses (Posner& Rothbart, 1998).

All major simulated cognitive architectures of which we are aware include an executive system or set of systems, although much work in the field has been directed toward understanding whether there is a single executive system underlying performance on various tasks or whether separate domain-specific systems govern cognitive regulation (Anderson & Lebiere, 1998; Baddeley, 1992; Meyer & Kieras, 1997; Newell, 1992; Shallice & Burgess, 1996). These architectures, most of them explicit computational simulations capable of modeling human performance, provide ideas about a number of candidate executive operations. These include the shifting of attention, the active maintenance of goals and information in working memory (WM), task scheduling and prioritization, and the mental manipulation of information in WM (e.g., rotating a mental image or updating and releasing stored items).

Although the importance of such control operations is virtually unquestioned, we are at the beginning stages of understanding the cognitive and brain mechanisms that underlie them. How many executive control systems are there, and what distinctions among control operations are the most meaningful? Are the candidate operations we have listed unitary, or can they be fractionated? In this study, we focus on attention shifting as a candidate control operation and ask whether performance on shifting tasks can be dissociated on the basis of three factors: (1) Among what representations is attention shifted? (2) In what locus are the items between which attention is shifted stored-in WM or in perceptual buffers? (3) And finally, when does the shift occur-when an actual stimulus is presented and a behavioral response is required, or in advance of stimulus presentation and response selection?

What Representations and What Locus of Storage? …

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