Abstract
Visual imagery is a form of sensory imagination, involving subjective experiences typically described as similar to perception, but which occur in the absence of corresponding external stimuli. We used the Activation Likelihood Estimation algorithm (ALE) to identify regions consistently activated by visual imagery across 40 neuroimaging studies, the first such meta-analysis. We also employed a recently developed multi-modal parcellation of the human brain to attribute stereotactic co-ordinates to one of 180 anatomical regions, the first time this approach has been combined with the ALE algorithm. We identified a total 634 foci, based on measurements from 464 participants. Our overall comparison identified activation in the superior parietal lobule, particularly in the left hemisphere, consistent with the proposed ‘top-down’ role for this brain region in imagery. Inferior premotor areas and the inferior frontal sulcus were reliably activated, a finding consistent with the prominent semantic demands made by many visual imagery tasks. We observed bilateral activation in several areas associated with the integration of eye movements and visual information, including the supplementary and cingulate eye fields (SCEFs) and the frontal eye fields (FEFs), suggesting that enactive processes are important in visual imagery. V1 was typically activated during visual imagery, even when participants have their eyes closed, consistent with influential depictive theories of visual imagery. Temporal lobe activation was restricted to area PH and regions of the fusiform gyrus, adjacent to the fusiform face complex (FFC). These results provide a secure foundation for future work to characterise in greater detail the functional contributions of specific areas to visual imagery.
Highlights
Imagination has attracted human interest for at least two thousand years (Hume, 1784; Mithen, 1998; Modrak, 1987; see MacKisack et al, 2016 for a recent review), was disavowed by much of the academic community in the first half of the 20th century (Watson, 1913), played a central role in the subsequent Cognitive Revolution (Neisser, 1967)
Our first calculation combined all of these results, and thereby identified the areas most consistently activated during visual imagery
The superior parietal lobule was consistently activated in all our comparisons, suggesting that attentional processes are an important aspect of visual imagery
Summary
Imagination has attracted human interest for at least two thousand years (Hume, 1784; Mithen, 1998; Modrak, 1987; see MacKisack et al, 2016 for a recent review), was disavowed by much of the academic community in the first half of the 20th century (Watson, 1913), played a central role in the subsequent Cognitive Revolution (Neisser, 1967). Most conceptual discussions have centred on whether the mental representations that mediate visual imagery are depictive, in that they arise from activity in a visual buffer with crucial spatial properties (Kosslyn, 1981, 2005), or propositional: one product amongst many of a syntactically structured system (Pylyshyn, 2003) These influential alternatives have been comprehensively evaluated (Thomas, 2014a; Tye, 1991); more recent enactive theories, which prioritise the role of attentional mechanisms and seem especially well-placed to explain phenomena such as perceptual and representational neglect (Bartolomeo, Bourgeois, Bourlon, & Migliaccio, 2013; Thomas, 2003), have so-far received considerably less consideration (Thomas, 2014b). Neural events within these periods are contrasted with the patterns of activity observed at baseline, such as those observed when participants judge whether a given number is even (Mazard, Laou, Joliot, & Mellet, 2005)
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