How does the brain process concepts such as 'peaceful' or 'diurnal'? As concepts have been regarded to be propositional in nature, their neural representation has been difficult to grasp. But some authors have argued that concepts are grounded in motor and sensory processes, leading to the prediction that the neural processing of concepts might activate specific motor and sensory areas. In support of this idea, a recent paper reports that auditory and action-related conceptual features that have been linked to specific visual stimuli lead to the activation of brain areas that respond to auditory and action-related sensory stimuli, respectively.

Examples of the visual stimuli used by James and Gauthier. Images courtesy of M. J. Tarr (Brown University, Providence, Rhode Island).

James and Gauthier trained people to associate a visual stimulus with words of a given knowledge type that could not be linked to the stimulus on the basis of its pure static appearance. For example, one visual stimulus might be associated with auditory features (squeals, howls, sings), and another one with action-related features (digs, climbs, walks). As auditory and motion-related features activate specific regions of the brain (the superior temporal gyrus and the posterior superior temporal sulcus, respectively), the key question was whether these regions were activated during a visual task that did not require the explicit retrieval of the associations. Indeed, the authors found this to be the case, supporting the idea that concepts are grounded in perception. But in addition, the data of James and Gauthier indicate that semantic knowledge might be stored in sensory- and motor-specific brain systems, instead of in a global, amodal system, as previously proposed.