Abstract
Humans can both estimate the age of people from their faces and recognize the same individual at different times of life. This indicates an ability to perceive age-related characteristics that generalize across identity, and also an ability to derive age-invariant representations of facial identity. We investigated the degree to which either or both of these abilities reflected the operation of processes within the fusiform face areas (FFA), of the left and right hemispheres, through the use of an fMRI adaptation paradigm. Our stimuli were 3D avatar faces created with FaceGen software. Ten different individual male faces were chosen with the aim of maximizing the perceived differences between faces. We created images of each face at 10 different ages ranging from 20 to 60 years. Eleven healthy subjects participated in this study. First, an FFA in both the right and left hemisphere was identified in each individual using a functional localizer that contrasted blocks of viewed objects with blocks of viewed faces. Following the localizer, subjects underwent a block-design adaptation run consisting of three experimental conditions; blocks of avatar faces which differed in both identity and age, blocks of avatar faces which differed in identity but all of the same age, and blocks of the same avatar face at different ages. We found that adaptation for identity regardless of variations in age occurred most strongly in the left FFA (p[[lt]]0.00003), with a trend to a similar effect in the right FFA (p= 0.09). Neither the left or right FFA showed adaptation effects for age. We conclude that age-invariant representations for face identity may be encoded within the FFA, possibly predominantly within the left hemisphere, and that representations of age-related characteristics of faces may be encoded elsewhere in the face-processing network.
This work was supported by an operating grant from the CIHR (MOP-77615). CJF was supported by a CIHR Canada Graduate Scholarship Doctoral Research Award and a Michael Smith Foundation for Health Research Senior Graduate Studentship. GI was supported by the Alzheimer Society of Canada and the Michael Smith Foundation for Health Research. JJSB was supported by a Canada Research Chair and a Senior Scholarship from the Michael Smith Foundation for Health Research.