Recognition memory for Braille or spoken words: An fMRI study in early blind

Abstract

We examined cortical activity in early blind during word recognition memory. Nine participants were blind at birth and one by 1.5years. In an event-related design, we studied blood oxygen level-dependent responses to studied (“old”) compared to novel (“new”) words. Presentation mode was in Braille or spoken. Responses were larger for identified “new” words read with Braille in bilateral lower and higher tier visual areas and primary somatosensory cortex. Responses to spoken “new” words were larger in bilateral primary and accessory auditory cortex. Auditory cortex was unresponsive to Braille words and occipital cortex responded to spoken words but not differentially with “old”/“new” recognition. Left dorsolateral prefrontal cortex had larger responses to “old” words only with Braille. Larger occipital cortex responses to “new” Braille words suggested verbal memory based on the mechanism of recollection. A previous report in sighted noted larger responses for “new” words studied in association with pictures that created a distinctiveness heuristic source factor which enhanced recollection during remembering. Prior behavioral studies in early blind noted an exceptional ability to recall words. Utilization of this skill by participants in the current study possibly engendered recollection that augmented remembering “old” words. A larger response when identifying “new” words possibly resulted from exhaustive recollecting the sensory properties of “old” words in modality appropriate sensory cortices. The uniqueness of a memory role for occipital cortex is in its cross-modal responses to coding tactile properties of Braille. The latter possibly reflects a “sensory echo” that aids recollection.