Our neuropsychology of language work mainly focuses on how unilateral brain-injured patients comprehend and use language, the role of gestures in these processes, and the brain lesion correlate with these processes. We follow a cross-linguistic approach and examine speakers of different languages. Below are the some of our projects in this area:
Spatial/causal language and compensatory gestures: To understand neural correlates of different levels of event representations (verbal and gestural), we use a voxel-lesion symptom mapping analysis in stroke patients who have unilateral focal brain injury. In a series of studies, we are examining how brain injury relates to naming relational terms when they are shown static and dynamic scenes (i.e., prepositions and verbs) and whether impaired lexicalization is compensated by gesture production. Even though gesture production compensated for the lexical retrieval problems for prepositions, the tendency to compensate for speech with gestures was impaired – particularly when patients had lesions to the dorsolateral prefrontal cortex. These patients did not display global impairments in lexical access, because they could name objects and actions. There might, therefore, be a core deficit in representing spatial relations that lead to deficits in both lexical retrieval and gestural production of these relations. Yet, for patients who only have damage to the anterior superior temporal gyrus, gesture can compensate what is missing in spatial language use. These studies have been done in collaboration with Prof. Anjan Chatterjee from University of Pennsylvania (http://ccn.upenn.edu/chatterjee/). In our current work, we examine these research questions, focusing on other languages such as Persian and Turkish. For Persian studies, we collaborate with Asst. Prof. Nazbanou Nozari from Johns Hopkins University (http://www.nazbanou.net/index.html). We are also in the processes of founding a crosslinguistic patient database in collaboration with Asst. Prof. Simon Fischer-Baum from Rice University (https://sites.google.com/site/simonfischerbaum/).
Spontaneous narratives: In this work, we investigate the focal brain injured patients’ narrative production by addressing both micro- and macro-linguistic levels. In particular, we analyze the informativeness of patients’ narratives and social aspects of their narration as measured by production of evaluative devices that represent the narrator’s interpretation of events. Additionally, we examine dynamic spatial relations in spontaneous narratives, focusing on patients’ speech and gesture use mainly in Frog Story narratives.
The role of gestures in speech impairment: In another project with Prof. Anjan Chatterjee, we directly investigate patients’ use of gesture as compensation to speech problems. One way to do is to restrict people’s gesture use in various tasks (e.g., describing a direction on a map, story telling, and describing spatial relations) and to examine how their speech changes. We also administer various control tasks for tapping into the patients’ spatial representations. This allows us to understand whether there is a core deficit in representing spatial relations or whether there is a problem only with lexical access/speech that could be compensated with spontaneous gestures.