Lisa H. Milman

Neural correlates of covert and overt production of tense and agreement morphology: Evidence from fMRI.

Most neuroimaging studies examining verb morphology have focused on verb tense, with fewer examining agreement morphology, and no previous fMRI studies have investigated distinctions between past and present tense inflection. However, models of language representation and processing suggest differences in where these inflections are instantiated in the phrase structure as well as differences in the linguistic functions they serve, suggesting unique neural networks for these forms. In addition, results of available neuroimaging studies of grammatical morphology vary considerably due to methodological differences. Some studies have used overt production tasks, whereas others have used covert tasks. In the present study we examined brain activation associated with past tense and present tense/agreement morphology under overt and covert production conditions in 13 healthy adults using an event-related functional magnetic resonance imaging (fMRI) design. Production of verbs inflected for past tense (V + -ed) and present tense/agreement (V -s) was elicited using temporal adverbs (i.e. Yesterday, Nowadays). Results showed that in healthy adults inflecting both past tense and agreement morphology (compared to a verb stem production condition) recruited not only left inferior frontal structures, but also motor and premotor cortices, and posterior parietal regions. Activation also was observed in the basal ganglia, thalamus, and the cingulate gyrus. Past tense and present tense/agreement recruited partially overlapping tissue in these regions, with distinctions observed for the two forms in frontal and parietal brain areas. We also found that activation varied with task demands, with more extensive frontal activation noted in the overt compared to the covert verb inflection task. These results are consistent with the hypothesis that the neural signatures for verb inflection differ from that for verb stems alone and involve a distributed frontal and parietal network of brain regions. Further, the neural tissue recruited for instantiation of past tense versus present tense/agreement morphology is distinct, supporting linguistic theories that differentiate the two forms.

Functional category production in agrammatism: Treatment and generalization effects

Department of Neurology, Northwestern University, USAAccepted 6 July 2006IntroductionThe complexity account of treatment efficacy (CATE; Thompson,Shapiro, Kiran, & Sobecks, 2003) predicts that training complex languagestructures in agrammatism will result in generalize to less complex struc-tures, but only when they share similar derivations. For instance, trainingcomplex sentences derived by ‘wh’ movement, such as object clefts (e.g., Itwas the coach who the skater chased) results in generalization to less com-plex ‘wh’ movement structures such as object-extracted wh questions (Whodid the skater chase?), but not to ‘NP’ movement structures (e.g. passivevoice: The coach was chased by the skater). To date, CATE has been testedwith noncanonical sentence structures, which are particularly difficult foragrammatic speakers. In this paper, we examined the generalization pat-terns that result from training functional morphology in basic canonicalsentences. Specifically, we examined patterns of acquisition and general-ization of:(1) Complementizers: They wonder if the cat is following the mouse.(2) Past tense inflections: Yesterday the cat followed the mouse.(3) Presentagreement inflections: Nowadaysthe cat follows the mouse.While all three morphemes are considered functional category mem-bers, complementizers and tense/agreement are not equivalent with respectto their structural position in the syntactic tree. Complementizers are ele-ments generated in the complementizer phrase (CP); while tense and agree-ment inflections are both elements licensed by the inflection phrase (IP).Therefore, based on CATE, we predicted generalization between tense(2) and agreement (3), but NOT between complementizers (1) and tense(2) or between complementizers (1) and agreement (3), since they arelicensed by distinct functional projections.In contrast to CATE,the Tree pruninghypothesis (TPH; FriedmannG Thompson, 2005), and spontaneouslanguage patterns. Participants were between 36–68 years old, and hadbetween 12–20 years of education.Design and analysisA single subject multiple baseline design across behaviors and partici-pants was used. Pre- and post-testing measures included the Westernaphasia battery (WAB; Kertesz, 1982), the Verb Inflection Test (VIT;Bastiaanse & Thompson, 2005), and two neuroimaging (fMRI) tasksdesigned to examine neural patterns associated with production and com-prehension of the target morphemes. Baseline probes were also adminis-tered to assess production of all target morpheme using picture stimuli(line drawings).During each treatment session participants were asked to produce 15sentences containing the target morpheme. Three types of sentences weretrained: those with complementizers (1), past tense (2), and present tense(3). Training included: (a) thematic role training, (b) placement of writtensentence constituent cards in their surface structure position, (c) readingtarget sentences, (d) reassembly of scrambled written sentence constituentcards, and (d) re-reading sentences. Prior to each session probes, identicalto baseline, were administered to evaluate learning and generalizationpatterns.doi:10.1016/j.bandl.2006.06.049

Perception of functional morphology in agrammatic Broca's aphasia

Individuals with agrammatic Broca’s aphasia show marked deficits in production of functional morphemes such as complementizers (like that and if) and tense and agreement markers (like –ed and –s). Furthermore, production of complementizers appears to be more impaired in many aphasic individuals than production of verbal morphology (Friedmann Hagiwara, 1995; & Grodzinky, 1997; Milman, Dickey, & Thompson, 2004). Some accounts, in particular the Tree-Pruning Hypothesis (Friedmann & Grodzinky, 1997), have linked this production deficit to the hierarchical syntactic structure associated with these morphemes. Specifically, morphemes associated with higher functional projections (e.g., complementizers) are more impaired than those associated with lower projections (e.g., verbal inflections). This paper presents the results of two grammaticality judgment experiments examining the perception of complementizers and verb inflections by English speakers with Broca’s aphasia. If perception patterns with production, perception of complementizers is expected to be more impaired than perception of verbal morphology, particularly under the Tree-Pruning Hypothesis.