Children's computation of complex linguistic forms: a study of frequency and imageability effects.

This study investigates the storage vs. composition of inflected forms in typically-developing children. Children aged 8-12 were tested on the production of regular and irregular past-tense forms. Storage (vs. composition) was examined by probing for past-tense frequency effects and imageability effects--both of which are diagnostic tests for storage--while controlling for a number of confounding factors. We also examined sex as a factor. Irregular inflected forms, which must depend on stored representations, always showed evidence of storage (frequency and/or imageability effects), not only across all children, but also separately in both sexes. In contrast, for regular forms, which could be either stored or composed, only girls showed evidence of storage. This pattern is similar to that found in previously-acquired adult data from the same task, with the notable exception that development affects which factors influence the storage of regulars in females: imageability plays a larger role in girls, and frequency in women. Overall, the results suggest that irregular inflected forms are always stored (in children and adults, and in both sexes), whereas regulars can be either composed or stored, with their storage a function of various item- and subject-level factors

The neurocognition of developmental disorders of language

Developmental disorders of language include developmental language disorder, motor-speech disorders such as articulation disorder and stuttering, and dyslexia. These disorders have been explained by various accounts, which generally focus on their behavioral rather than neural characteristics, their processing rather than learning impairments, and each disorder separately rather than together, despite their commonalities and comorbidities. Here we update and review a unifying neurocognitive account, the Procedural circuit Deficit Hypothesis (PDH). The PDH posits that abnormalities of brain structures underlying procedural memory (learning and memory that relies on the basal ganglia and associated circuitry) can explain numerous brain and behavioral characteristics, across learning and processing, in multiple disorders, including both commonalities and differences. We describe procedural memory, examine its role in multiple aspects of language, and then present the PDH and relevant evidence across language-related disorders. The PDH has substantial explanatory power, and both basic research and translational implications

The Auditory Comprehension of Unaccusative Verbs in Aphasia

Some persons with aphasia, particularly those diagnosed with a Broca’s aphasia, exhibit a delayed time course of lexical activation in canonically ordered S-V-O sentences (Ferrill et al., 2012) and delayed re-activation of displaced arguments in sentences that contain syntactic dependencies (Love et al., 2008). These patterns support the Delayed Lexical Activation (DLA) hypothesis: Lexical activation is delayed relative to the normal case, and thus lexical activation and syntactic operations are de-synchronized; that is, lexical access is too slow for normally fast-acting syntactic operations. This delay in lexical access leads to what appear to be syntactic comprehension deficits in aphasia. In the current study we further examined lexical activation during sentence comprehension in persons with aphasia by using unaccusative verbs. Unaccusative verbs are a type of intransitive verb with a single argument that is base generated in object position and displaced to the surface subject position, leaving behind a copy or trace (‘gap’) of the movement (see, for example, Burzio, 1986), as in: 1. The girl vanished Thus there is a syntactic dependency between the two positions. When encountering sentences that contain syntactic dependencies (e.g., object relatives, Wh-questions) neurologically unimpaired individuals immediately reactivate the displaced argument at the gap (Shapiro et al., 1999; Love et al., 2008). In contrast to this immediate reactivation, prior findings indicate that neurologically unimpaired individuals do not reactivate the displaced argument in similar sentences with unaccusative verbs until 750ms downstream from the gap (Friedmann et al., 2008). This built-in delay observed with unaccusative verbs in neurologically healthy participants provides a unique opportunity to further examine lexical delays in individuals with Broca’s aphasia. Importantly, individuals with Broca’s aphasia may have unaccusative verb deficits. Previous research has found that persons with aphasia have difficulty producing unaccusative verbs. Offline truth-value judgment tasks with intransitive sentences containing unaccusative verbs do not reveal comprehension deficits (Lee & Thompson, 2004). However, in a sentence-picture matching task, McAllister et al. (2009) found lower accuracy for intransitive sentences that contained unaccusative verbs than transitive sentences. We entertain the following hypothesis: The delayed lexical access routines better synchronize with the delay of reactivating the argument of unaccusatives, suggesting that individuals with Broca’s aphasia should evince a pattern like that of unimpaired individuals. Alternatively, participants with Broca’s aphasia might show activation even further downstream from the gap, given that in other sentence constructions containing syntactic dependencies they exhibit a delayed pattern of reactivation compared to neurologically unimpaired individuals

Comprehension of Who and Which-NP questions: Which Account do the Data Support?

This study investigated the comprehension of various types of Wh-questions in unimpaired adults and those with Broca’s aphasia. Using an eye tracking-while listening method, we examined four specific hypotheses. Our initial results for our healthy controls revealed offline support for a Word Order Hypothesis – object-extracted Who and Which-NP questions took longer to resolve than subject-extracted versions. Our results using eye gaze data, however, revealed support for a Retrieval Hypothesis – Which-NP questions that contain more specific information yielded fewer looks to the correct referent than their Who-question counterparts. These patterns set the stage for our ongoing aphasia study

Structure-function correspondences in Broca’s aphasia: Evidence from MRI and comprehension of verb phrase ellipsis constructions

We describe an effort to map lesion to behavior by studying the comprehension of complex VP-Ellipsis constructions (e.g., The policeman defended the child, and the dedicated fireman did___ too…) in participants with Broca‟s aphasia. We quantified the lesions of our individual participants using cytoarchitectonic probability maps of the human brain. We found that our Broca participants evinced delayed priming of the object in the ellipsis clause, while off-line comprehension was largely spared. Structure-function analyses revealed that lesions in both temporal and frontal areas participated in the behavioral outcomes, though each region seems to have played a distinct role

The Time-course of Lexical Reactivation of Unaccusative Verbs in Broca’s Aphasia

Individuals with Broca’s aphasia typically have difficulty understanding sentences containing syntactic dependencies (e.g., Wh-questions, as in “Which mailman did the policeman push___ yesterday afternoon”). Broca’s patients can compute these dependency relationships, though in a delayed fashion unlike their unimpaired counterparts (Love et al., 2008). The basis for the processing delay could be in lexical access (Ferrill et al., 2012); that is, lexical access is delayed, and so to is re-access of the displaced argument (e.g., Which mailman) at the gap. Based on these findings, we have argued for the Delayed Lexical Activation (DLA) hypothesis: lexical access is too slow for normally fast-acting syntactic operations, resulting in what appears to be syntactic comprehension deficits in participants with Broca’s aphasia. The current study investigates this issue by using sentences containing unaccusative verbs (UA). UAs are intransitive verbs, but their single argument is base generated in object position and displaced to subject position, leaving behind a gap (Burzio, 1986) and thus creating a syntactic dependency, as in: 1. The boy disappeared yesterday afternoon. Friedmann et al. (2008) demonstrated that unimpaired individuals do not immediately reactivate the displaced argument at verb offset (gap), but instead 750ms downstream. This inherent delay observed with UAs in neurologically healthy participants provides an opportunity to test listeners with Broca’s aphasia. Specifically, we ask whether these participants also evince such a delay (and thus show a normal pattern), or whether the delay is pushed even further ‘downstream’ because of their inherently slow lexical activation. Twelve adults who experienced a single unilateral left hemisphere stroke participated in the study; seven had a Broca’s aphasia with a comprehension deficit and the remaining five participants were considered LCVA controls. We used an on-line cross-modal picture priming task. Participants listened to 32 sentences that contained UAs as in (2) below. 2. The queen with the bad temper vanished[*1] during[*2] the[*3] spectacu[*4]lar fireworks show. During the uninterrupted temporal unfolding of each sentence, a picture representing the displaced NP (e.g., queen) or an unrelated control probe (e.g., surgeon) was briefly presented at one of four probe positions (as numbered above). Participants listened to sentences while also making a binary decision about the picture (animate/inanimate). Faster response times to the related as compared to the control probe indicate lexical priming/activation. Similar to Friedmann et al.’s (2008) findings of normally delayed re-access of the displaced argument, the results for all 12 participants (Fig.1) revealed priming only at the downstream probe position [*2], t(11)=3.08, p=.01. In a separate subgroup analysis, the same pattern was found for the Broca group, t(6)=4.77, p=.003. These results suggest that participants with Broca’s aphasia can take advantage of the inherent delay of unaccusatives and exhibit similar patterns of syntactic dependency linking as unimpaired individuals. We discuss these findings with reference to its generalizability across patient groups, the DLA, and the interaction between lexical and syntactic processes

Slowed Speech Input has a Differential Impact on On-line and Off-line Processing in Children’s Comprehension of Pronouns

The central question underlying this study revolves around how children process co-reference relationships—such as those evidenced by pronouns (him) and reflexives (himself)—and how a slowed rate of speech input may critically affect this process. Previous studies of child language processing have demonstrated that typical language developing (TLD) children as young as 4 years of age process co-reference relations in a manner similar to adults on-line. In contrast, off-line measures of pronoun comprehension suggest a developmental delay for pronouns (relative to reflexives). The present study examines dependency relations in TLD children (ages 5–13) and investigates how a slowed rate of speech input affects the unconscious (on-line) and conscious (off-line) parsing of these constructions. For the on-line investigations (using a cross-modal picture priming paradigm), results indicate that at a normal rate of speech TLD children demonstrate adult-like syntactic reflexes. At a slowed rate of speech the typical language developing children displayed a breakdown in automatic syntactic parsing (again, similar to the pattern seen in unimpaired adults). As demonstrated in the literature, our off-line investigations (sentence/picture matching task) revealed that these children performed much better on reflexives than on pronouns at a regular speech rate. However, at the slow speech rate, performance on pronouns was substantially improved, whereas performance on reflexives was not different than at the regular speech rate. We interpret these results in light of a distinction between fast automatic processes (relied upon for on-line processing in real time) and conscious reflective processes (relied upon for off-line processing), such that slowed speech input disrupts the former, yet improves the latter