  In the domain of face recognition, there exists a puzzling timing discrepancy
between results from macaque neurophysiology on the one hand and human
electrophysiology on the other. Single unit recordings in macaques have
demonstrated face identity specific responses in extra-striate visual cortex
within 100 milliseconds of stimulus onset. In EEG and MEG experiments with
humans, however, a consistent distinction between neural activity corresponding
to unfamiliar and familiar faces has been reported to emerge around 250 ms.
This points to the possibility that there may be a hitherto undiscovered early
correlate of face familiarity perception in human electrophysiological traces.
We report here a successful search for such a correlate in dense MEG recordings
using pattern classification techniques. Our analyses reveal markers of face
familiarity as early as 85 ms after stimulus onset. Low-level attributes of the
images, such as luminance and color distributions, are unable to account for
this early emerging response difference. These results help reconcile human and
macaque data, and provide clues regarding neural mechanisms underlying familiar
face perception.
