1. Cognitive impairments in multiple domains
Language and mathematics
Simultaneous rehabilitation of cognitive functions in several domains Language deficits can be caused by impairments in memory or memory operation due to brain damage. Recent studies found that Broca's area support both syntactic structure building in natural language and a similar hierarchical operation in arithmetic (Makuuchi et al., 2012). These findings imply that impairments in speech and calculation can be treated in a same training technique. Indeed, recent studies reported that training on symbol operation improve sentence processing of natural language (e.g., Dominey et al., 2009). Based on these findings, we pursue a language rehabilitation program using symbol operation.
Language and executive function
Persons with higher brain dysfunctions often show disorders of executive function (also known as cognitive control). Executive function (or cognitive control) is a term in cognitive neuroscience that refers to the mental ability to coordinate thoughts and actions flexibly in order to accomplish internal goals, including inhibition of irrelevant information, manipulation of working memory contents, switching of internal goals, etc. Recent studies have indicated that sentence comprehension entails executive function or cognitive control (Novick et al., 2010). In addition, it is known that Broca's area is involved not only in sentence processing (Sakai, Hashimoto, & Homae, 2001), but also in the processing of hierarchically organized sequence (Koechlin & Jubault, 2006) or executive function (January et al., 2009). Because a sentence is hierarchically organized sequence of words, the analysis of hierarchical structure is crucial for sentence processing. We focus on the functional role of Broca's area, and aim to clarify the relationship between executive function and the processing of hierarchical sentence structure by using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS). Based on the insights gained through this study, furthermore, we try to develop effective rehabilitation techniques or training methods.