Why are the experiences of visual perception and visual imagery different?
Poster Presentation

Amir Amedi
Center for Non-Invasive Magnetic Brain Stimulation, Dept. of Neurology, BIDMC, Harvard Medical School

Rafael Malach
Department of Neurobiology, Weizmann Institute of Science, Israel.

Alvaro Pascual-Leone
Center for Non-Invasive Magnetic Brain Stimulation, Dept. of Neurology, BIDMC, Harvard Medical School

     Abstract ID Number: 157
     Full text: Not available
     Last modified: March 21, 2005

Abstract
Seeing an object is clearly a different experience than imagining it. In fact, when experiential boundaries between perceiving and imagining blur, we speak of psychosis and hallucinations. Nevertheless, recent studies emphasize the large overlap in neural substrates supporting visual perception and visual imagery. So, why is our experience is so different? Here we demonstrate that deactivation of the auditory cortex unequivocally differentiates visual imagery from visual perception. In fact, the vividness of the visual imagery is stronger correlated with the magnitude of auditory cortex deactivation than with the activation of any visual cortical region. Finally we report of a patient with bilateral lesions in the auditory cortex, who shows supra-normal vividness visual imagery (5 S.D. above the average in the vividness of visual imagery questionnaire). Perception of the world requires merging of multi-sensory information so that seeing is inextricably associated with processing of other sensory modalities that modify visual cortical activity and shape experience. By contrast, we suggest that pure visual imagery is the isolated activation of visual cortical areas with concurrent suppression of sensory inputs that could disrupt the image created by our ‘mind’s eye’.