FIGURE 1.

Methodology for searching the functional neural correlates of synesthesia. The letter A may trigger the experience of red for a synesthete but not a control subject (A). In order to isolate the neural correlates (represented as the brain icon of the CerCo lab logo) of this experience, one may compare the brain activations of synesthetes and controls to this stimulus (B). To ensure that any observed difference is due to the synesthetic experience, one may compare the same subjects for similar activations that do not trigger any synesthetic experience, like pseudo-letters or false fonts (C). In such a control experiment, the stimuli are therefore “similar” to those triggering the synesthetic experience, but the phenomenal experience is “different” than the synesthetic experience. One may also compare the activation by synesthetic and real colors (D).