Poster A89, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Age effects on ventral visual pathway representations: Evidence for dedifferentiation and hyperdifferentiation
Zachary Monge1, Erik Wing1, Benjamin Geib1, Lifu Deng1, Simon Davis1, Ziwei Zhang1, Roberto Cabeza1; 1Duke University
Activation patterns for different visual stimuli (e.g, faces vs. houses) in the ventral visual pathway (VVP) have been shown to be less differentiated (i.e., dedifferentiated) in older (OAs) than younger (YAs) adults. Here, we tested the hypothesis that age-related dedifferentiation would be greater for visual features (e.g., spatial frequency) in posterior VVP (e.g., V1) than for semantic features (e.g., meaningful associations) in anterior VVP (e.g., anterior temporal lobe [ATL]). During fMRI scanning, 21 YAs and 20 OAs viewed 96 scenes. We combined representational similarity analyses with a Deep convolutional Neural Network (DNN). DNNs can be trained to classify images with a high level of accuracy and accurately model the VVP. The scenes were submitted to a pre-trained DNN (16-layered VGG16 network), which, for each layer, yielded a stimulus representational dissimilarity matrix (RDM). The stimuli RDMs were then correlated with co-variance in activation patterns across the 96 scenes in multiple VVP regions. We used the second-order stimulus RDM-brain RDM correlation as our measure of differentiation. The results showed a clear cross-over in differentiation: (1) for visual features (early DNN layers), differentiation in posterior VVP (e.g., V1) was reduced in OAs (age-related dedifferentiation); however, (2) for semantic features (late DNN layers), differentiation in the anterior VVP (e.g., ATL), was greater in OAs (age-related hyperdifferentiation). In OAs, the anterior VVP hyperdifferentiation was associated with better performance on a perceptual discrimination task, suggesting compensation. In sum, we found age-related dedifferentiation of visual features in posterior VVP but hyperdifferentiation of semantic features in anterior VVP.
Topic Area: PERCEPTION & ACTION: Development & aging