Representation of event and object concepts in ventral anterior temporal lobe and angular gyrus

Abstract

Semantic knowledge includes understanding of objects and their features and also understanding of the characteristics of events. The hub-and-spoke theory holds that these conceptual representations rely on multiple information sources that are integrated in a central hub in the ventral anterior temporal lobes. The dual-hub theory expands this framework with the claim that the ventral anterior temporal lobe hub is specialized for object representation, while a second hub in angular gyrus is specialized for event representation. To test these ideas, we used representational similarity analysis, univariate and psychophysiological interaction analyses of fMRI data collected while participants processed object and event concepts (e.g. "an apple," "a wedding") presented as images and written words. Representational similarity analysis showed that angular gyrus encoded event concept similarity more than object similarity, although the left angular gyrus also encoded object similarity. Bilateral ventral anterior temporal lobes encoded both object and event concept structure, and left ventral anterior temporal lobe exhibited stronger coding for events. Psychophysiological interaction analysis revealed greater connectivity between left ventral anterior temporal lobe and right pMTG, and between right angular gyrus and bilateral ITG and middle occipital gyrus, for event concepts compared to object concepts. These findings support the specialization of angular gyrus for event semantics, though with some involvement in object coding, but do not support ventral anterior temporal lobe specialization for object concepts.

Keywords: angular gyrus; anterior temporal lobe; event semantics; object semantics; semantic representation.

Fig. 1

Experimental design. (A) Examples of object and event stimuli. (B) Experimental procedure, showing one trial followed by a catch question. (C) Semantic similarities for event concepts (left) and object concepts (right).

Fig. 2

Univariate effects of event concepts versus object concepts, FWE corrected (P < 0.05).

Fig. 3

Activation to events and objects in ROIs. Bars show 1 standard error of the mean.

Fig. 4

(A).Representational similarity maps for each concept type, showing regions where neural similarity is significantly correlated with semantic similarity (corrected P < 0.05); (B). The difference of representational similarities between event and object concepts (corrected P < 0.05). In (A) and (B), low-level visual features are controlled by covarying visual similarities measured with Hmax. Color scale shows the correlation strength.

Fig. 5

Representational similarity effects in ROIs. Bars show 1 standard error of the mean.

Fig. 6

(A). For events > objects, regions showing increased connectivity with left vATL. (B). For events > objects, regions showing increased connectivity with right AG. Surface render (cluster corrected P < 0.05). Seed regions are shown as colored circles.