Visual mental imagery: what the head's eye tells the mind's eye.

The demonstration of an implication of attentional/eye gaze systems in visual mental imagery might help to understand why some patients with visual neglect, who suffer from severe attentional deficits, also show neglect for mental images. When normal participants generate mental images of previously explored visual scenes, their oculomotor behavior resembles that used during visual exploration. However, this could be a case of encoding specificity, whereby the probability of retrieving an event increases if some information encoded with the event (in this case its spatial location) is present at retrieval. In the present study, normal participants were invited to conjure up a mental image of the map of France and to say whether auditorily presented towns or regions were situated left or right of Paris. A perceptual version of the task was administered after the imaginal condition. Thus, in the imaginal condition participants had to retrieve information from long-term memory. Vocal response times and, unbeknownst to participants, also eye movements were recorded. Participants tended to produce similar eye movements on the imaginal and on the perceptual conditions of the task. We concluded that some mechanisms involved in spontaneous oculomotor behavior may be shared in exploration of visuospatial mental images. Deficits of these common processes participating in the oculomotor exploration might contribute to imaginal neglect.