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Abstract:
Using fMRI, we examined the response in the "fusiform face
area" (FFA) and the "parahippocampal place area" (PPA) to the high
spatial frequency (HSF) and low spatial frequency (LSF) filtered
greyscale photographs of common objects, scenes and faces. The FFA
and PPA were defined functionally in 10 subjects using MR data
obtained during performance of a 1-back repetition detection task
on unfiltered versions of the same photographs. In the PPA, scenes
gave more activation than objects, and objects more then faces with
no effect of spatial frequency. In the FFA, faces gave more
activation than objects and scenes, and there were
stimulus-class-specific effects of spatial frequency: although
there was more activation for HSF than LSF faces, there was more
activation for LSF than HSF objects and scenes. These results were
found both when activation was measured as mean percent signal
change (relative to a fixation baseline) as well as when the signal
change was normalized by the standard error of the signal in each
voxel (mean t-value). The absence of spatial frequency effects in
the PPA indicates that the scene-selective response observed in
this region cannot be explained by spatial-frequency differences
between scenes and faces/objects. The interaction of spatial
frequencies and object category in the FFA is unlikely to be due to
stimulus properties since faces and objects were more similar in
their frequency spectra then the scenes. The effect could be due to
a difference in categorization level and/or in expertise; this will
be explored in follow-up ex
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