Aleman et al. (2001)
From Psy3241
Activation of the Striate Cortex in the absence of visual stimulation: an fMRI Study of Synesthesia- Presented by Hayley Devlin and Rachel Kimchi
Shadowed by Lauren Malonson
Overview of Article:
The purpose of this study was to find out if the primary visual cortex is activated without direct external input to the visual system. In other words, the question is, does the primary visual cortex play a functional role in internally generated visual perception? To determine this, an fMRI scan was conducted on a woman with color-word synesthesia (when she heard a word, she involuntarily saw a color) during two verbal tasks and control conditions. In the first task (passive listening), the participant was auditorily presented with 14 words, and in the next (verbal fluency), she was presented with one letter at a time and asked to generate as many words as possible starting with that letter. In the control conditions, tones were presented and the participant pressed a button when the frequency changed. All fMRI results were compared against those of normal participants.
Results showed that V1 was activated in both the passive listening and the verbal fluency tasks in the participant with color-word synesthesia. The normal subjects did not show activation of V1 in any condition. These results are significant for several reasons: first, while previous studies have tested the role of V1 in the presence of visual perception (in the absence of visual stimulation), those studies had mixed results; additionally, the previous studies focused on conscious visual perception, whereas this one focused on involuntarily generated perception; next, these results, as suggested in the study, may have important implications regarding other types of visualization that are uncontrolled by the experiencer (such as hallucinations); and finally, the results provide significant evidence that feedback connections into V1 may “mediate processes such as perceptual organization, attention and awareness,” and that those connections play a major role in “associative and primary visual areas in visual experience” in the absence of direct visual stimulation.
