Dissociable Neural Mechanisms For Iconic Memory : fMRI study

Hyun-Jung Cho and Kyoung-Min Lee

Abstract

Visual stimuli remain visible for some time after the visual array disappears and information extracted from the visual stimulus persists. These phenomena is called “iconic memory". Despite the ubiquity of iconic memory, little is yet known about the neural substrates of these phenomena. Here we investigated the neural substrates for iconic memory using functional magnetic resonance imaging through colored number stimuli. Subjects were instructed to identify either color or number stimuli which were preceded(precue condition) or followed(postcue condition) by a cue; such cueing paradigm allowed the subjects to utilize selective attention. We found that iconic memory for number decayed much faster than that for color. The results showed that patterns of neural activity associated with iconic memory for color and number are different. Results from our fMRI data revealed that different types of stimuli, i.e. color or number, induced distinct brain activation patterns in ventral occipital cortex, fusiform gyrus, and lingual gyrus. We also found different bilateral activation patterns in the ventral occipital cortex for precue and postcue trials and significant feature specific modulatory effects in the fusiform gyrus and lingual gyrus. These neuroimaging data suggest that some distinct neural mechanisms underlie iconic memory for color and number.