Commonality of neural representations of words and pictures.

In this work we explore whether the patterns of brain activity associated with thinking about concrete objects are dependent on stimulus presentation format, whether an object is referred to by a written or pictorial form. Multi-voxel pattern analysis methods were applied to brain imaging (fMRI) data to identify the item category associated with brief viewings of each of 10 words (naming 5 tools and 5 dwellings) and, separately, with brief viewings of each of 10 pictures (line drawings) of the objects named by the words. These methods were able to identify the category of the picture the participant was viewing, based on neural activation patterns observed during word-viewing, and identify the category of the word the participant was viewing, based on neural activation patterns observed during picture-viewing, using data from only that participant or only from other participants. These results provide an empirical demonstration of object category identification across stimulus formats and across participants. In addition, we were able to identify the category of the word that the participant was viewing based on the patterns of neural activation generated during word-viewing by that participant or by all other participants. Similarly, we were able to identify with even higher accuracy the category of the picture the participant was viewing, based on the patterns of neural activation demonstrated during picture-viewing by that participant or by all other participants. The brain locations that were important for category identification were similar across participants and were distributed throughout the cortex where various object properties might be neurally represented. These findings indicate consistent triggering of semantic representations using different stimulus formats and suggest the presence of stable, distributed, and identifiable neural states that are common to pictorial and verbal input referring to object categories.