Knowing where but not what: Impaired thematic roles and spatial language

Abstract

We describe case J.P. who, following a left inferior frontal lesion, made frequent role confusions in comprehension and production (e.g., saying “The boy kicks the girl” for a picture showing a girl kicking a boy). J.P.'s preserved ability to judge the grammaticality of sentences rules out a syntactic deficit as the primary cause of the role confusions. Thematic role assignment is also required with spatial prepositions such as in or above, and J.P.'s thematic role assignment was also severely impaired with spatial prepositions. We capitalized on prior linguistic analyses and behavioural studies to design accurate tests of the semantics of spatial terms, spatial relations, and critical features of objects. Fine-grain semantic tests revealed that the semantics of spatial terms and objects was intact. We hypothesize that J.P.'s role confusions reflected a failure to integrate objects within semantic representations that define the thematic roles. Our data suggest that properties of objects and thematic roles are specified by distinct semantic processes, which have different brain localizations. J.P.'s lesion further suggests that left inferior frontal regions are critical in thematic role assignment, thus contributing to the understanding of the linguistic functions of these regions.

Keywords:

• Spatial language
• Thematic roles
• Semantics
• Semantic impairment.

Acknowledgments

We would like to thank Argye Hillis for consulting on the location of brain damage, Gordy Rogers and Jeremiah Bertz for their assistance in both designing materials and testing the patient, and especially J.P. and his family for their warmth and curiosity. We also want to thank the reviewers for their valuable comments and suggestions. This investigation was supported by a National Institutes of Health (NIH) grant DC-006242.

Notes

¹ This is not to say that the meaning of in (or other locatives) does not exhibit a certain degree of complexity. The variety of spatial relations to which in applies or its extension to nonspatial domains—for example, in temporal expressions such as “in time” or “in an hour”—probably requires a meaning that entails more than cavities and partial inclusions (Hawkins, 1988). The point we want to make, however, is that the prototypical spatial meaning of in, as in sentences like “the milk is in the bowl” or “the flower is in the vase”, is semantically simpler than the meaning of most verbs.

² Wu et al. (2007) also observed dissociations in a small number of their patients, who showed impaired scores only when tested on the thematic roles of verbs or locatives. Data about semantic knowledge were only reported by Wu et al. for verbs. The patients who failed specifically with the thematic roles of verbs also obtained scores that were borderline or below controls' range in the verb semantic test, suggesting that the impaired performance with the thematic roles of verbs could have reflected a more general problem with the semantic of verbs. The patient reported by Wu et al. with a selective deficit for the thematic roles of locatives could have had a more general impairment with spatial relations, like the cases reported by Tranel and Kemmerer (2004).