When abstract becomes concrete:

Victor Kewenig, Gabriella Vigliocco, and Jeremy I Skipper

Abstract

Most of what we know about the neurobiology of conceptual processing comes from experiments presenting individuals with isolated words and asking them to carry out artificial tasks to activate associated concepts. These studies have identified fixed sets of regions for concepts that do not have a physical referent (abstract) and those that do (concrete). Yet, in natural environments we are exposed to a range of dynamic, multimodal contextual information other than speech, like faces, bodies, objects, etc. Behavioral data suggests that conceptual processing is modulated by such context. However, no study has assessed to what extent this is the case for the underlying neurobiological organization. 

We investigate processing of a large set of words in naturalistic settings with rich context (watching a movie). Brain activity was estimated using a deconvolution, deriving the brain response function rather than assuming its shape. We predicted the following: (1) neural encodings of concepts are based on meaning-related experiential information processed in a set of corresponding brain regions. To address this, we used an automated web-based meta-analysis as well as a reverse correlation (“Peaks and Valleys Analysis”). (2) There are no fixed sets of regions for abstract and concrete concepts. Instead, activation dynamically changes depending on visual context. Specifically, if abstract concepts are highly embedded (e.g. “science” in the setting of a chemistry experiment), they activate concrete-like structures and vice versa. To test this, we added a “contextual embeddedness” regressor to our model, based on semantic similarity (measured with GloVe) between labels of visual objects present (obtained through automated feature extraction) and verbally produced concepts. 

Group analysis using linear mixed effect models revealed activation for abstract words in anterior cingulate cortex, thalamus, insula, bilateral medial prefrontal areas and anterior temporal lobe (ATL). Results from the meta-analysis and the reverse correlation showed that these regions were correlated with processing valence, interoception and social based information. Concrete words activated motor and premotor areas, right hemisphere prefrontal areas, visual cortex, precuneus, right inferior frontal gyrus and the bilateral superior temporal lobe (STL). These regions were correlated with processing information about body parts and motion. Overlap was found in STL, ATL and visual cortex. Activation in these regions was related to language in general. Results from the second model revealed that contextual embeddedness modulated activity in regions corresponding to the default mode network (DMN). A comparison between abstract and concrete concepts in high vs low context and the brain maps obtained from (1) showed that in low context conditions, the neurobiological organization of concrete concepts resembled more that of abstract concepts and vice versa. 

Our results indicate that during real-world conceptual processing, habitual experiences are encoded in a set of related brain regions. However, this underlying neurobiological organization is not fixed. Instead, activation depends on the dynamics of situational context. This conclusion emphasizes the need for incorporating experiential information into models of word meaning. It also suggests a new challenge for reaching more human-like representations in computational language processing: understanding and modelling the dynamic influences of multimodal contextual information.