Neural correlates of visual mental imagery vividness : A systematic review of fMRI studies

Sammanfattning

Visual mental imagery (VMI) refers to the ability to generate visual representations in the absence of external stimuli, where vividness reflects how clear and intense these images are. Previous research has identified neural correlates of imagery; however, the mechanisms underlying the vividness of visual imagery remain unclear. Earlier theories have suggested that vividness primarily depends on the early visual cortex, but this has increasingly been questioned. This study aimed to examine how different levels of vividness of visual imagery relate to neural activity across different brain regions and networks. A systematic search was conducted through Medline, PubMed, and Web of Science. Studies were required to assess functional magnetic resonance imaging (fMRI) and vividness using the Vividness of Visual Imagery Questionnaire (VVIQ). After screening, based on predefined inclusion criteria, 17 studies were included. The results showed that vividness was not consistently associated with activity in the early visual cortex. Instead, more consistent associations were observed in higher-order cognitive regions, including parietal and frontal cortices, as well as large-scale brain networks. Vividness was linked to patterns of functional connectivity, particularly involving the fusiform gyrus, insula, and occipital networks. In addition, the overlap between imagery and perception is discussed, although imagery relied more strongly on top-down processes. Evidence from aphantasia further demonstrated a dissociation between neural representations and subjective vividness. In conclusion, vividness of visual imagery is supported by distributed neural processes rather than a single region. Vividness appears to emerge from interactions between sensory, cognitive, and network-level mechanisms, noting the importance of individual differences in imagery.