| Switching attention is considered a core cognitive ability underlying the executive control of thought and action, but relatively little work has evaluated whether switching is a unitary ability or if it is composed of multiple types. We conducted a meta-analysis of neuroimaging studies of various types of switching, using novel quantitative techniques. Although there was some evidence for segregation among types of switching, different types of switching activated largely the same regions. Furthermore, switching regions overlapped substantially with regions derived from meta-analysis of working memory. To further explore relationships among types of switching, we tested behavioral performance (n = 249) on a task involving four types, and used event-related fMRI to investigate brain correlates of switching in those who showed very high or very low switch costs (n = 43). Participants switched between either (1) which of two superimposed objects was relevant and/or (2) which of two object attributes (dimensions) was used to make a response, in a 2 x 2 factorial design. Switches were performed either on visible objects (external) or on objects maintained in working memory (internal). Behavioral results showed additive effects of the two types for external switches, but a dual-switch cost for internal switches, suggesting that objects may be selected "of a piece" in working memory. Individual differences analyses supported a model with general factors for preparatory task-set configuration processes and residual switch costs across types, and suggested further that the stronger an individual's bias is toward one task, the harder it is to switch away from that task to a weaker one. Imaging results showed activation across multiple switching types in many regions associated with cognitive control and working memory, including bilateral anterior and dorsolateral prefrontal, insular, and temporal/occipital cortices, and in the caudate nucleus and cerebellum. Higher behavioral switching costs were correlated with greater BOLD switching effects in these regions and in the thalamus and hippocampus. The only region to show larger BOLD switching effects in better performers in each of the four switch types was rostra] medial prefrontal cortex, highlighting the potential importance of this region in cognitive control. |
