Sources of sentence constraint on lexical ambiguity resolution.

Results from a series of naming experiments demonstrated that major lexical categories of simple sentences can provide sources of constraint on the interpretation of ambiguous words (homonyms). Manipulation of verb (Experiment 1) or subject noun (Experiment 2) specificity produced contexts that were empirically rated as being strongly biased or ambiguous. Priming was demonstrated for target words related to both senses of a homonym following ambiguous sentences, but only contextually appropriate target words were primed following strongly biased dominant or subordinate sentences. Experiment 3 showed an increase in the magnitude of priming when multiple constraints on activation converged. Experiments 4 and 5 eliminated combinatorial intralexical priming as an alternative explanation. Instead, it was demonstrated that each constraint was influential only insofar as it contributed to the overall semantic representation of the sentence. When the multiple sources of constraint were retained but the sentence-level representation was changed (Experiment 4) or eliminated (Experiment 5), the results of Experiments 1, 2, and 3 and were not replicated. Experiment 6 examined the issue of homonym exposure duration by using an 80-msec stimulus onset asynchrony. The results replicated the previous experiments. The overall evidence indicates that a sentence context can be made strongly and immediately constraining by the inclusion of specific fillers for salient lexical categories. The results are discussed within a constraint-based, context-sensitive model of lexical ambiguity resolution.

Summation of activation: evidence from multiple primes that converge and diverge within semantic memory.

Six experiments addressed the combinatorial influence of multiple related primes in naming, lexical decision and relatedness judgment performance. Primes either converged on a single semantic representation (e.g., LION-STRIPES-TIGER) or diverged onto distinct semantic representations (e.g., KIDNEY-PIANO-ORGAN). The facilitatory influence of 2 related primes was well predicted by the sum of the influences from the single-related-prime conditions (a) for both convergent and divergent primes, (b) in lexical-decision and naming, (c) across varying prime-target stimulus onset asynchronies, and (d) under target-degradation conditions that increased the priming effects. The relatedness-judgment task yielded an additive pattern of priming for convergent prime conditions; however, an underadditive pattern of priming was found for divergent prime conditions. Discussion focuses on the role of attentional systems that modulate the type of information used to perform a given task.

Search for semantic inhibition failure during sentence comprehension by younger and older adults.

The present research examined recent evidence that inhibition failures do not contribute to age-related declines in on-line text comprehension. Evaluating naming performance over a time course revealed that processes serving to eliminate thematically irrelevant information from memory in young adults were apparently deficient for older adults. Experiment 2 generalized these findings to contexts that rely on later information to disambiguate ambiguous words. Under these conditions, older adults were as able as younger adults to use context to disambiguate words. Despite the apparent disagreement between the experimental outcomes, it is argued that the present studies together are consistent and support the view that inhibition failures unlikely contribute to age differences in on-line sentence comprehension (at least) when the contexts are semantically constraining (i.e., self-contained). It is proposed that the detection of age-related inhibition failures may depend on the extent to which adults must rely on internally generated processing constraints.

Effect of low fluoride dentifrices on microhardness of sound enamel. In vitro study.

The present study was undertaken to evaluate the effect of dentifrices containing low fluoride concentrations on microhardness of sound enamel in 50 healthy young premolar teeth. They were divided into five different groups according to the concentrations of fluoride in dentifrice used. The Vickers hardness of enamel was measured using a Zwick microhardness tester under 1000 g load and a Vickers indenter before and after the application of fluoride dentifrices. The results of the present study suggest that low fluoride concentration dentifrices are as effective as the higher concentrations in increasing the hardness of enamel.

Scope of word meaning activation during sentence processing by young and older adults.

In a naming experiment, we examined word meaning activation on-line during sentence processing by younger and older adults. Sentences were biased to either the most or least frequently used meaning of a sentence-final ambiguous word. In order to determine the scope of initial meaning activation, targets represented either high- or low-salient semantic relationships to a single sense of the ambiguous word in context. Both age groups evidenced context-dependent activation of word meaning. In addition, context activated a wide scope of meaning that included both high- and low-salience aspects of the ambiguous words. These results contradict predictions based on the inhibition deficit hypothesis (Hasher & Zacks, 1988). However, they are compatible with an interactive activation model of language comprehension that does not discriminate among age groups.

Prosthetic rehabilitation of a child with induced anodontia.

A case of prosthetic rehabilitation of a five and half year old child with induced anodontia is presented. Complete dentures were provided and patient was followed for a period of 20 months. As the permanent teeth erupt into the oral cavity, regular modifications have to be made on the denture base to facilitate their eruption.

Influence of contextual features on the activation of ambiguous word meanings.

Three studies examined whether initial meaning activation is sensitive to context. Experiment 1 demonstrated that contextually appropriate targets were activated more than inappropriate targets. Experiment 2 evaluated activation across intervals of 0, 300, and 600 ms. Constraining sentences activated contextually appropriate meanings over inappropriate meanings. This was maintained across the intervals for highly salient targets. Less-salient targets, although initially activated, were no longer activated 300 ms following the homograph. Experiment 3 converged on context-sensitive activation following a 50-ms exposure of the sentence-final homograph. Conclusions are (a) initial meaning activation can be sensitive to context, (b) when a homograph is instantiated, it is congruent with a broad scope of targets, and (c) less-salient targets receive less activation over the time course.

Beta-adrenergic receptors on canine coronary collateral vessels: characterization and function.

The present studies were performed to examine the role of beta-adrenergic receptors in modulating smooth muscle tone in mature coronary collaterals. To examine the beta-adrenergic receptor population present, radioligand binding-cover slip autoradiographic studies were performed on sections of native canine coronary vessels and sections of coronary collaterals developed after placement of Ameroid constrictors. Specific binding of the nonselective beta-adrenergic antagonist [125I]iodopindolol to vascular smooth muscle in segments of both collaterals and native coronary arteries was saturable and stereospecific. Maximal binding and the potency of beta-adrenergic subtype-selective antagonists were similar in all segments. Beta-adrenergic relaxation of native coronary vessels and collateral vessels were studied in isolated organ chambers after preconstriction with prostaglandin F2 alpha. Both native coronary arteries and collateral segments demonstrated beta-adrenergic-mediated relaxation with affinities for both agonists and antagonists compatible with a mixed population of beta 1- and beta 2-adrenergic receptors. These studies indicate that during development, the new collateral vascular smooth muscle expresses a functional population of beta-adrenergic receptors, comparable to that in native vessels.