Duration-Dependent fMRI Adaptation and Distributed Viewer-Centered Face Representation in Human Visual Cortex

Fang Fang, Scott O. Murray, Sheng He
Cerebral Cortex June 2007;17:1402--1411 doi:10.1093/cercor/bhl053

Two functional magnetic resonance imaging (fMRI) face viewpoint
adaptation experiments were conducted to investigate whether
fMRI adaptation in high-level visual cortex depends on the duration
of adaptation and how different views of a face are represented in
the human visual system. We found adaptation effects in multiple
face-selective areas, which suggest a distributed, viewer-centered
representation of faces in the human visual system. However, the
nature of the adaptation effects was dependent on the length of adaptation.
With long adaptation durations, face-selective areas along
the hierarchy of the visual system gradually exhibited viewpointtuned
adaptation. As the angular difference between the adapter
and test stimulus increased, the blood oxygen level--dependent
(BOLD) signal evoked by the test stimulus gradually increased as
a function of the amount of 3-dimensional (3D) rotation. With short
adaptation durations, however, face-selective areas in the ventral
pathway, including the lateral occipital cortex and right fusiform
area, exhibited viewpoint-sensitive adaptation. These areas showed
an increase in the BOLD signal with a 3D rotation, but this signal
increase was independent of the amount of rotation. Further, the
right superior temporal sulcus showed little or very weak viewpoint
adaptation with short adaptation durations. Our findings suggest
that long- and short-term fMRI adaptations may reflect selective
properties of different neuronal mechanisms.