Distinct and convergent visual processing of high and low spatial frequency information in faces

We tested for differential brain response to distinct spatialfrequency (SF) components in faces. During a functional magneticresonance imaging experiment, participants were presented with"hybrid" faces containing superimposed low and high SF informationfrom different identities. We used a repetition paradigm wherefaces at either SF range were independently repeated or changedacross consecutive trials. In addition, we manipulated whichSF band was attended. Our results suggest that repetition andattention affected partly overlapping occipitotemporal regionsbut did not interact. Changes of high SF faces increased responsesof the right inferior occipital gyrus (IOG) and left inferiortemporal gyrus (ITG), with the latter response being also modulatedadditively by attention. In contrast, the bilateral middle occipitalgyrus (MOG) responded to repetition and attention manipulationsof low SF. A common effect of high and low SF repetition wasobserved in the right fusiform gyrus (FFG). Follow-up connectivityanalyses suggested direct influence of the MOG (low SF), IOG,and ITG (high SF) on the FFG responses. Our results reveal thatdifferent regions within occipitotemporal cortex extract distinctvisual cues at different SF ranges in faces and that the outputsfrom these separate processes project forward to the right FFG,where the different visual cues may converge.