Decoupling the Effects of Collagen Alignment and Bioceramic Incorporation on Osteoblast Proliferation, Differentiation, and Mineralization.

Biomimetic scaffolds provide the essential biophysical (e.g., surface topography, stiffness) and biochemical cues (e.g., composition) to guide cell morphology, proliferation, and differentiation. Although the effects of biomaterial-directed cues on cell response have been widely reported, few studies have sought to decouple these effects to better understand the interplay between the different physicochemical factors on tissue-specific cell function. Herein, beta-tricalcium phosphate (ß-TCP) was incorporated into electrochemically aligned collagen (ELAC) and random collagen threads, and the individual and interactive effects of collagen alignment (i.e., biophysical) and bioceramic incorporation (i.e., biochemical) on osteoblast cell morphology, proliferation, differentiation, and mineralization were investigated. Results showed that collagen alignment in ELAC threads was retained upon ß-TCP incorporation. Collagen alignment significantly improved (p < 0.05) the swelling capacity and stability of collagen threads, while ß-TCP incorporation showed no such effects. Tensile tests revealed that ß-TCP incorporation significantly decreased (p < 0.05) the strength and stiffness of ELAC threads. Significant increase (p < 0.05) in Saos-2 cell orientation and alkaline phosphatase (ALP) activity was observed on ELAC compared to random collagen threads indicating that aligned collagen serves as a key driving factor for osteogenesis. ß-TCP incorporation into random collagen threads had no effect on Saos-2 cell function. On the other hand, presence of ß-TCP significantly augmented (p < 0.05) Saos-2 cell metabolic activity, differentiation, and mineralization on ELAC threads. Together, these findings suggest that combining collagen alignment and ß-TCP incorporation can create robust tissue-mimicking scaffolds for bone regeneration applications.

Resolving Conflicts in Natural and Grammatical Gender Agreement: Evidence from Eye Movements.

The present research investigated the attraction phenomenon, which commonly occurs in the domain of production but is also apparent in comprehension. It particularly focused on its accessibility to conceptual influence, in analogy to previous findings in production in Hebrew (Deutsch and Dank, J Mem Lang, 60:112-143, 2009). The experiments made use of the contrast between grammatical and natural gender in Hebrew, using complex subject noun phrases containing head nouns and prepositional phrases with local nouns. Noun phrases were manipulated to produce (a) matches and mismatches in grammatical gender between heads and local nouns; and (b) inanimate nouns and animate nouns with natural gender that served either as head or as local nouns. These noun phrases were the subjects of sentences that ended with predicates agreeing in gender with the head noun, with the local noun, or both. The ungrammatical sentences were those in which the gender of the predicate and the head noun did not match. To assess the impact of conflicts in grammatical and natural gender on the time course of reading, participants' eye movements were monitored. The results revealed clear disruptions in reading the predicate due to grammatical-gender mismatches with head and local nouns, in analogy to attraction in production. When the head nouns conveyed natural gender these effects were amplified, but variations in the natural gender of local nouns had negligible consequences. The results imply that comprehension and production are similarly sensitive to the control of grammatical agreement by grammatical and natural gender in subject noun phrases.

On the parity of structural persistence in language production and comprehension.

Structural priming creates structural persistence. That is, differences in experience with syntax can change subsequent language performance, and the changes can be observed in both language production and comprehension. However, the effects in comprehension and production appear to differ. In comprehension, persistence is typically found when the verbs are the same in primes and targets; in production, persistence occurs without verb overlap. The contrast suggests a theoretically important hypothesis: parsing in comprehension is lexically driven while formulation in production is structurally driven. A major weakness in this hypothesis about comprehension-production differences is that its empirical motivation rests on the outcomes of experiments in which the priming manipulations differ, the primed sentence structures differ, and the measures of priming differ. To sharpen the comparison, we examined structural persistence with and without verb overlap in both reading comprehension and spoken production, using the same prime presentation procedure, the same syntactic structures, the same sentences, and the same participants. These methods yielded abstract structural persistence in comprehension as well as production. A measure of the strength of persistence revealed significant effects of priming and verb overlap without significant comprehension-production differences. This argues for uniformity in the structural mechanisms of language processing.

What counts in grammatical number agreement?

Both notional and grammatical number affect agreement during language production. To explore their workings, we investigated how semantic integration, a type of conceptual relatedness, produces variations in agreement (Solomon & Pearlmutter, 2004). These agreement variations are open to competing notional and lexical-grammatical number accounts. The notional hypothesis is that changes in number agreement reflect differences in referential coherence: More coherence yields more singularity. The lexical-grammatical hypothesis is that changes in agreement arise from competition between nouns differing in grammatical number: More competition yields more plurality. These hypotheses make opposing predictions about semantic integration. On the notional hypothesis, semantic integration promotes singular agreement. On the lexical-grammatical hypothesis, semantic integration promotes plural agreement. We tested these hypotheses with agreement elicitation tasks in two experiments. Both experiments supported the notional hypothesis, with semantic integration creating faster and more frequent singular agreement. This implies that referential coherence mediates the effect of semantic integration on number agreement.

Reversing the hands of time: changing the mapping from seeing to saying.

To describe a scene, speakers must map visual information to a linguistic plan. Eye movements capture features of this linkage in a tendency for speakers to fixate referents just before they are mentioned. The current experiment examined whether and how this pattern changes when speakers create atypical mappings. Eye movements were monitored as participants told the time from analog clocks. Half of the participants did this in the usual manner. For the other participants, the denotations of the clock hands were reversed, making the big hand the hour and the little hand the minute. Eye movements revealed that it was not the visual features or configuration of the hands that determined gaze patterns, but rather top-down control from upcoming referring expressions. Differences in eye-voice spans further suggested a process in which scene elements are relationally structured before a linguistic plan is executed. This provides evidence for structural rather than lexical incrementality in planning and supports a "seeing-for-saying" hypothesis in which the visual system is harnessed to the linguistic demands of an upcoming utterance.

Driving impairs talking.

It is well known that conversation (e.g., on a cell phone) impairs driving. We demonstrate that the reverse is also true: Language production and comprehension, and the encoding of the products of comprehension into memory, are less accurate when one is driving. Ninety-six pairs of drivers and conversation partners engaged in a story-retelling task in a driving simulator. Half of the pairs were older adults. Each pair completed one dual-task block (driving during the retelling task) and two single-task control blocks. The results showed a decline in the accuracy of the drivers' storytelling and of their memory for stories that were told to them by their nondriving partners. Speech production suffered an additional cost when the difficulty of driving increased. Measures of driving performance suggested that the drivers gave priority to the driving task when they were conversing. As a result, their linguistic performance suffered.

A purple giraffe is faster than a purple elephant: inconsistent phonology affects determiner selection in English.

The form of a determiner is dependent on different contextual factors: in some languages grammatical number and grammatical gender determine the choice of a determiner variant. In other languages, the phonological onset of the element immediately following the determiner affects selection, too. Previous work has shown that the activation of opposing determiner forms by a noun's grammatical properties leads to slower naming latencies in a picture naming task, as does the activation of opposing forms by the interaction between a noun's gender and the phonological context. The present paper addresses the question of whether phonological context alone is sufficient to evoke competition between determiner forms. Participants produced English phrases in which a noun phrase's phonology required a determiner that was the same as or differed from the determiner required by the noun itself (e.g., apurple giraffe; an orange giraffe). Naming latencies were slower when the phrase-initial determiner differed from the determiner required by the noun in isolation than when the phrase-initial determiner matched the isolated-noun determiner. This was true both for definite and indefinite determiners. The data show that during the production of a determiner-noun phrase, nouns automatically activate the phonological forms of their determiners, which can compete with the phonological forms that are generated by an assimilation rule.

Lexical or syntactic control of sentence formulation? Structural generalizations from idiom production.

To compare abstract structural and lexicalist accounts of syntactic processes in sentence formulation, we examined the effectiveness of nonidiomatic and idiomatic phrasal verbs in inducing structural generalizations. Three experiments made use of a syntactic priming paradigm in which participants recalled sentences they had read in rapid serial visual presentation. Prime and target sentences contained phrasal verbs with particles directly following the verb (pull off a sweatshirt) or following the direct object (pull a sweatshirt off). Idiomatic primes used verbs whose figurative meaning cannot be straightforwardly derived from the literal meaning of the main verb (e.g., pull off a robbery) and are commonly treated as stored lexical units. Particle placement in sentences was primed by both nonidiomatic and idiomatic verbs. Experiment 1 showed that the syntax of idiomatic and nonidiomatic phrasal verbs is amenable to priming, and Experiments 2 and 3 compared the priming patterns created by idiomatic and nonidiomatic primes. Despite differences in idiomaticity and structural flexibility, both types of phrasal verbs induced structural generalizations and differed little in their ability to do so. The findings are interpreted in terms of the role of abstract structural processes in language production.

Memory for syntax despite amnesia.

Syntactic persistence is a tendency for speakers to reproduce sentence structures independently of accompanying meanings, words, or sounds. The memory mechanisms behind syntactic persistence are not fully understood. Although some properties of syntactic persistence suggest a role for procedural memory, current evidence suggests that procedural memory (unlike declarative memory) does not maintain the abstract, relational features that are inherent to syntactic structures. In a study evaluating the contribution of procedural memory to syntactic persistence, patients with anterograde amnesia and matched control speakers reproduced prime sentences with different syntactic structures; reproduced 0, 1, 6, or 10 neutral sentences; then spontaneously described pictures that elicited the primed structures; and finally made recognition judgments for the prime sentences. Amnesic and control speakers showed significant and equivalent syntactic persistence, despite the amnesic speakers' profoundly impaired recognition memory for the primes. Thus, syntax is maintained by procedural-memory mechanisms. This result reveals that procedural memory is capable of supporting abstract, relational knowledge.

Prototypicality in sentence production.

Three cued-recall experiments examined the effect of category typicality on the ordering of words in sentence production. Past research has found that typical items tend to be mentioned before atypical items in a phrase--a pattern usually associated with lexical variables (like word frequency), and yet typicality is a conceptual variable. Experiment 1 revealed that an appropriate conceptual framework was necessary to yield the typicality effect. Experiment 2 tested ad hoc categories that do not have prior representations in long-term memory and yielded no typicality effect. Experiment 3 used carefully matched sentences in which two category members appeared in the same or in different phrases. Typicality affected word order only when the two words appeared in the same phrase. These results are consistent with an account in which typicality has its origin in conceptual structure, which leads to differences in lexical accessibility in appropriate contexts.

Persistent structural priming from language comprehension to language production.

To examine the relationship between syntactic processes in language comprehension and language production, we compared structural persistence from sentence primes that speakers heard to persistence from primes that speakers produced. [Bock, J. K., & Griffin, Z. M. (2000). The persistence of structural priming: transient activation or implicit learning? Journal of Experimental Psychology: General, 129, 177-192.] showed that the production of target priming structures increased the probability of spontaneously using the same structures to describe events in subsequent pictures that were semantically unrelated to the primes. These priming effects persisted across as many as ten intervening filler trials. The present studies replicated these results using auditorily presented primes to which participants only listened. The results indicated persistence of priming across all lags, with relative magnitudes of priming as large as those observed by Bock and Griffin. The implication is that structural priming is persistent regardless of the modality in which language structures are experienced, underscoring the power of priming as an implicit learning mechanism.

Becoming syntactic.

Psycholinguistic research has shown that the influence of abstract syntactic knowledge on performance is shaped by particular sentences that have been experienced. To explore this idea, the authors applied a connectionist model of sentence production to the development and use of abstract syntax. The model makes use of (a) error-based learning to acquire and adapt sequencing mechanisms and (b) meaning-form mappings to derive syntactic representations. The model is able to account for most of what is known about structural priming in adult speakers, as well as key findings in preferential looking and elicited production studies of language acquisition. The model suggests how abstract knowledge and concrete experience are balanced in the development and use of syntax.

The functions of structural priming.

Structural priming refers to speakers' tendency to produce sentences with previously heard or produced syntactic structures. We review arguments and evidence for three common accounts of the functions of structural priming. One is that structural priming enhances fluency. Only some (reaction time and fluency measure) evidence supports this view. A second account argues that structural priming stems from implicit learning of how features of meaning are linked to syntactic configurations. We describe evidence suggesting that structural priming exhibits effects characteristic of both learning and implicitness. A third account claims that structural priming is an aspect of coordination or alignment among interlocutors. Consistent with this, some evidence shows that structural priming involves a shorter-term component that is broadly sensitive to repeated bindings of wide-ranging types of knowledge. Together, these observations suggest that structural priming is likely a multifaceted force that reflects implicit learning and, possibly independently, alignment among interlocutors.

Making syntax of sense: number agreement in sentence production.

Grammatical agreement flags the parts of sentences that belong together regardless of whether the parts appear together. In English, the major agreement controller is the sentence subject, the major agreement targets are verbs and pronouns, and the major agreement category is number. The authors expand an account of number agreement whose tenets are that pronouns acquire number lexically, whereas verbs acquire it syntactically but with similar contributions from number meaning and from the number morphology of agreement controllers. These tenets were instantiated in a model using existing verb agreement data. The model was then fit to a new, more extensive set of verb data and tested with a parallel set of pronoun data. The theory was supported by the model's outcomes. The results have implications for the integration of words and structures, for the workings of agreement categories, and for the nature of the transition from thought to language.

Notional number agreement in English.

To investigate the contested role of notional number in English subject-verb agreement, we used a sentence completion task to examine agreement with minimally different subject noun-phrases, such as the gang on the motorcycles and the gang near the motorcycles. These contrasting phrases biased different notional construals of collective nouns, such as gang, which are normally ambiguous between plural (distributed) and singular (collected) construals. With subjects biased toward spatial distribution, such as gang on motorcycles, more plural verbs occurred in speakers' sentence completions than in sentence completions with a bias toward spatial collection, such as gang near motorcycles. This offers strong evidence regarding both the existence and the magnitude of notional effects on subject-verb number agreement in English.

Can thematic roles leave traces of their places?

An important question in the study of language production is the nature of the semantic information that speakers use to create syntactic structures. A common answer to this question assumes that thematic roles help to mediate the mapping from messages to syntax. However, research using structural priming has suggested that the construction of syntactic frames may be insensitive to variations in thematic roles within messages (Cognition 35 (1990) 1; Psychological Review 99 (1992) 150). Because these studies involved structural alternations whose syntax covaries with the order of thematic roles, it is difficult to assess any independent contribution that role information may make to the positioning of phrases. In this study, we primed the order of the roles without changing the syntactic structure of the sentences produced, and found that the order of the roles was influenced by the priming manipulation. This implies that thematic roles or the features that differentiate them are active within the mapping between messages and sentence structures.

Morphophonological influences on the construction of subject-verb agreement.

In three experiments, we investigated whether the production of subject-verb number agreement is affected by the phonological realization of grammatical information. Speakers repeated and completed German or Dutch noun phrases along the lines of The position against the demonstrations. We varied the number of the subject noun (position) and the local noun (demonstrations), as well as the number ambiguity of the subject noun's determiner and the case ambiguity of the local noun phrase. Sentence completions more often contained a verb of the wrong number if the subject and the local nouns mismatched in number than if they matched. Experiments 1 and 2, in German, showed a stronger number mismatch effect if the local noun phrase was ambiguous between the nominative and the accusative cases. Experiment 3, in Dutch, showed a stronger mismatch effect if the subject noun's determiner was ambiguous in number. We conclude that morphophonological factors affect the implementation of agreement during grammatical encoding.