Eye position signals modulate early dorsal and ventral visual areas.

An internal sense of eye position is necessary to maintain the constancy of the visual world in spite of movements of the eyes. Neuroimaging studies have localized human homologs of monkey visual motion processing areas in MT/MST and also in the collateral sulcus (V4), an area that codes features within objects. We show that these two areas have a baseline fMRI signal that is modulated by eye position and that the preferred direction of the eye position signal is different in the two areas; increasing for ipsiversive eye positions in MT/MST and increasing for contraversive eye positions within the collateral sulcus. This baseline modulation is a true eye position signal; one that is present in the absence of visual motion stimuli. The difference in the preferred direction of the eye position signal may reflect the different transformations in these two areas; a transformation from a retinotopic (eye-centered) to an egocentric coordinate frame necessary for guiding action and to an object-centered frame for object recognition.