VISUAL-IMAGERY FACILITATES VISUAL-PERCEPTION - PSYCHOPHYSICAL EVIDENCE

Visual imagery is the invention or recreation of a perceptual experien ce in the absence of retinal input. The degree to which the same neura l representations are involved in both visual imagery and visual perce ption is unclear. Previous studies have shown that visual imagery inte rferes with perception (Perky effect). We report here psychophysical d ata showing a direct facilitatory effect of visual imagery on visual p erception. Using a lateral masking detection paradigm of a Gabor targe t, flanked by peripheral Gabor masks, observers performed imagery task s that were preceded by perceptual, tasks. We found that both perceive d and imaginary flanking masks can reduce contrast detection threshold . At short target-to-mask distances imagery induced a threshold reduct ion of 50% as compared with perception, while at long target-to-mask d istances imagery and perception had similar facilitatory effect. The i magery-induced facilitation was specific to the orientation of the sti mulus, as well as to the eye used in the task. These data indicate the existence of a stimulus-specific short-term memory system that stores the sensory trace and enables reactivation of quasi-pictorial represe ntations by top-down processes. We suggest that stimulus parameters do minate the imagery-induced facilitation at short target-to-mask distan ces, yet the top-down component contributes to the effect at long targ et-to-mask distances.