Gray or White? – The Contribution of Gray Matter in a Glioma to Language Deficits

Abstract

Symptoms of a glioma include not only headaches and seizures, but cognitive deficits including aphasia. One of the most important regions for aphasia is the anterior speech area, the damage of which causes Broca’s aphasia, marked by effortful, distorted articulation, reduced speech output, and agrammatic syntax. These patients show relatively good comprehension of single words and simple sentences, but show trouble understanding sentences with more complex syntactic structures, such as passive sentences and sentences with object relative clauses (Schwartz et al., 1980; Caplan et al., 1985; Grodzinsky, 2000); this aspect of Broca’s aphasia is called agrammatic comprehension (Goodglass & Menn, 1985; Menn and Obler, 1990; Pulvermuller, 1995). However, methodological problems have been raised (Badecker & Caramazza, 1985), and general processes of short-term memory or decision-making have been proposed to be disrupted in agrammatic comprehension (Just & Carpenter, 1992; Cupples & Inglis, 1993; Dick et al., 2001). Thus, for appropriately assessing a coginitive deficit, it is crucial to use an experimental task in which general cognitive demands such as the memory load are stricly controlled. In our recent functional magnetic resonance imaging (fMRI) study with a picture-sentence matching task, we examined the effect of sentence structures strictly controlling general cognitive demands such as the memory load (Kinno et al., 2008), where a sentence was visually presented with a picture representing an action (Fig. 1; the same task and stimuli were used in the present study). The participants indicated whether or not the meaning of each sentence matched the action depicted by the corresponding picture. There were three main conditions with different sentence types: canonical / subject-initial active sentences (AS) (e.g., “ ∆-ga ○-o hiiteru”, “ ∆ pulls ○”), noncanonical / subject-initial passive sentences (PS) (e.g., “ ○-ga ∆-ni hikareru”, “ ○ is affected by ∆'s pulling it”; see Kinno et al. (2008) for ni direct passive form), and noncanonical / object-initial scrambled sentences (SS) (e.g., “ ○-o ∆-ga hiireru”, “as for □, ○ pulling it”; this form is allowed not only in Japanese but in German, Finnish, and other languages). Under these conditions, each sentence had a