Loss of brain signal points to difference between visual imagery and perception
In a recent brain imaging study published in Neuron, Amedi and colleagues demonstrates that visual imagery deactivates areas in the auditory brain system and other “deeper” areas. This seems to suggest that normal visual perception requires a merging of information from many senses. In this sense, it seems that other sensory areas such as hearing […]
In a recent brain imaging study published in Neuron, Amedi and colleagues demonstrates that visual imagery deactivates areas in the auditory brain system and other “deeper” areas. This seems to suggest that normal visual perception requires a merging of information from many senses. In this sense, it seems that other sensory areas such as hearing can modulate the visual system. In visual imagery, this dynamic process is halted. Instead, visual imagery is the result of isolated processing in the visual cortices and a blocking of input from other sensory areas.
Negative BOLD Differentiates Visual Imagery and Perception
Amir Amedi et al. (2005), Neuron 48 (5)
Summary
Recent studies emphasize the overlap between the neural substrates of visual perception and visual imagery. However, the subjective experiences of imagining and seeing are clearly different. Here we demonstrate that deactivation of auditory cortex (and to some extent of somatosensory and subcortical visual structures) as measured by BOLD functional magnetic resonance imaging unequivocally differentiates visual imagery from visual perception. During visual imagery, auditory cortex deactivation negatively correlates with activation in visual cortex and with the score in the subjective vividness of visual imagery questionnaire (VVIQ). Perception of the world requires the merging of multisensory information so that, during seeing, information from other sensory systems modifies visual cortical activity and shapes experience. We suggest that pure visual imagery corresponds to the isolated activation of visual cortical areas with concurrent deactivation of “irrelevant” sensory processing that could disrupt the image created by our “mind’s eye.”
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