Temporal dynamics of neural adaptation effect in the human visual ventral stream

When the same visual stimulus is repeatedly presented with a brief interval, the brain's responses to that stimulus are attenuated relative to those at first presentation (neural adaptation, NA). Although this effect has been widely observed in various regions of human brain, its temporal dynamics as a neuronal population has been mostly unclear. In the present study, we used a magnetoencephalography (MEG) and conducted a rnacrolevel investigation of the temporal profiles of the NA occurring in the human visual ventral stream. We dissociated three dimensions of the NA: activation strength, peak latency, and temporal duration of neural response. The results revealed that visual responses to the repeated as compared with novel stimulus showed a significant reduction in both activation strength and peak latency but not in the duration of neural processing. These results indicate that (i) the NA involves brain response changes in the temporal domain as well as the response attenuation reported previously, and (ii) this temporal change is mainly observed as a rapid rising of 'what' responses rather than a temporal shortening of neural response curves within the visual ventral stream as previously considered. (c) 2004 Elsevier B.V. All rights reserved.