Our visual world consists of an immense number of unique objects and yet, we are easily able to identify, distinguish, and reason about the things we see within a few hundred milliseconds. Here, we used a large-scale and comprehensively sampled stimulus set and developed an analysis approach to capture how rich, multidimensional object representations unfold over time in the human brain. We modelled time-resolved MEG signals of four humans (2 females and 2 males) viewing single presentations of tens of thousands of object images based on millions of behavioral judgments. Extracting behavior-derived object dimensions from similarity judgments, we developed a data-driven approach to guide our understanding of the neural representation of the object space and found that every dimension is reflected in the neural signal. Studying the temporal profiles for different object dimensions we found that the time courses fell into two broad types, with either a distinct and early peak (∼125 ms) or a slow rise to a late peak (∼300 ms). Further, early effects were stable across participants, in contrast to later effects which showed more variability, suggesting that early peaks may carry stimulus-specific and later peaks more participant-specific information. Dimensions with early peaks appeared to be primarily visual dimensions and those with later peaks more conceptual, suggesting that conceptual representations are more variable across people. Together, these data provide a comprehensive account of how behavior-derived object properties unfold in the human brain and form the basis for the rich nature of object vision. Significance Statement Humans are excellent at identifying, distinguishing, and reasoning about a huge number of objects — all of which requires comparing visual information to internal representations and assign what we see to object categories. Simultaneously, we also process properties relevant to behavior. Seeing a cat, for instance, involves recognizing both its physical properties (fur, size, ears, claws) and many other types of properties (living, moving, playful) that add up to our idea of 'cat.' In our study, we investigated the time course of the neural response using MEG neuroimaging. We found that a diverse array of object properties relevant to behavior contributes to the neural signal and reveal how such rich object representations unfold over time in the human brain.
Teichmann et al. (Mon,) studied this question.