Abstract:

PURPOSE: Recent studies have shown that information from peripherally presented images can be obtained from foveal retinotopic cortex, presumably due to feedback signals. The current study is designed to investigate whether such a feedback processing is temporally ?exible.
METHODS: We investigated this potential feedback signal by presenting noise in fovea at di?erent object-noise SOAs while subjects performed a discrimination task on peripheral objects.
RESULTS: First, we found a selective impairment of performance when a foveal noise was presented around 250 ms following the onset of the peripheral presentation of objects. Then we tested whether foveal processing is automatically engaged as soon as peripheral object information reaches higher levels of cortex. If so, we would predict a rather fixed temporal window for the foveal noise to be effective (i.e., around 250 ms); however, when the two peripheral objects were oriented differently and mental rotation was required for the discrimination task, the engagement of foveal processing was delayed as revealed by a systematic shift of the effective temporal window of foveal noise.
CONCLUSIONS: During processing spatially detailed object information in the periphery, the foveal retinotopic cortex is engaged at a ?exible time point when ?ne detail information is needed.

Key words: feedback, fovea, object recognition, vision