The present study was designed to compare lexical decision latencies in visual and auditory modalities to three word types: (a) words that are inconsistent with two information sources, orthography and semantics (i.e., heterographic homophones such as bite/byte), (b) words that are inconsistent with one information source, semantics (i.e., homographic homophones such as bat), and (c) control words that are not inconsistent with any information source. Participants (N = 76) were randomly assigned to either the visual or auditory condition in which they judged the lexical status (word or nonword) of 180 words (60 heterographic homophones, 60 homographic homophones, and 60 control words) and 180 pronounceable nonsense word foils. Results differed significantly in the visual and auditory modalities. In visual lexical decision, homographic homophones were responded to faster than heterographic homophones or control words, which did not differ significantly. In auditory lexical decision, both homographic homophones and heterographic homophones were responded to faster than control words. Results are used to propose potential modifications to the Cooperative Division of Labor Model of Word Recognition (Harm & Seidenberg, 2004) to enable it to encompass both the visual and auditory modalities and account for the present results.

Based predominantly on semantic priming studies with divided visual field (DVF) presentation, current models of hemispheric differences in word semantic processing converge on a proposal that left hemisphere (LH) processes focus word meanings to their core by inhibiting less related meanings, whereas right hemisphere (RH) processes keep less related meanings active. The inhibition process supported by LH processing is assumed to apply to two distinct semantic processes: (a) narrowing of a single word meaning (inhibition of less related features and words), and (b) elimination of incompatible/ conflicting meanings of an ambiguous word. Semantic priming studies investigating hemispheric differences in these two processes have relied on associated prime-target pairs, which might have been problematic for two reasons. First, association might reflect lexical co-occurrence of word forms rather than effects of semantic relatedness; therefore, these studies might have confounded lexical and semantic priming effects. Second, in studies of ambiguous words dominant items were strongly associated whereas subordinate items were weakly associated; therefore, these studies confounded dominance and degree of relatedness. To address these confounds, this study conducted two semantic priming experiments with central prime presentation, DVF presentations for targets, and a 750 ms SOA. Experiment 1 investigated the effect of degree of semantic similarity on priming, using non-associated, prime-target pairs that were controlled for lexical co-occurrence. Experiment 2 investigated effects of meaning dominance on priming with non-associated prime-target pairs. Results are consistent with high-similarity priming for left visual field (lvf) and possibly for right visual field (rvf) targets, and with high-dominance priming for rvf and lvf targets, suggesting that LH (and RH) processes mediate effects of semantic similarity and dominance. However, priming effects in both experiments were very small. Thus, priming effects might have reflected that prime-target relatedness was less than expected, indicating that LH processing does not inhibit less related meanings, which is consistent with other studies using central primes. Additionally/ alternatively, larger priming effects in other studies might derive mainly from association rather than semantic similarity. Finally, the small priming effects could be due to some aspect of the experimental procedure that might have made these experiments less sensitive to semantic priming.

Although it is generally acknowledged that sensory feedback is required to fine tune movement patterns, its role in coordinative dynamics has received less attention. Experiment 1 investigated the role of visual and auditory feedback on 0º and 180º relative phase patterns at increasing frequency of oscillation for a bimanual limb task. The dependent variables were mean error of relative phase and standard deviation of relative phase. Results indicated that the visual and auditory feedback conditions did not influence the accuracy and the variability in performance of the 2 relative phase patterns, whereas increasing frequency influenced the performance of the 180º relative phase pattern, but not the 0º relative phase pattern. Experiment 2 investigated the role of auditory feedback on breathy, normal, and pressed voice qualities at increasing fundamental frequency for a voice coordination task. The dependent variables were mean of laryngeal resistance (cmH2O/l/s) and standard deviation of laryngeal resistance (cmH2O/l/s). Results indicated that the masked auditory feedback condition significantly increased variability in performance across all 3 voice qualities and specifically, the masked auditory feedback condition facilitated significantly higher mean laryngeal resistance values for the pressed voice quality but not for the breathy and the normal voice qualities. As a potential explanation of the current findings in Experiment 1, it is hypothesized that the bimanual coordination task did not rely on visual and auditory feedback because the task was governed by proprioceptive feedback, which was not controlled in the present study. For Experiment 2, sensory feedback may be relevant for voice patterns that have a shallow basin of attraction (i.e., pressed voice), but irrelevant for voice patterns that have a steep basin of attraction (i.e., breathy and normal voice). Perhaps the breathy and normal voice qualities were governed by voice coordination dynamics, while the pressed voice quality was partly influenced by auditory feedback connections. In addition, level of expertise may also play a role in the coordination dynamics of a voice task. The influence of auditory feedback on voice coordination dynamics suggests an expanded view of dynamic systems theory and supports the role of auditory feedback in vocal rehabilitation.

The kinetics of the rate-limiting genes of the molecular DNA repair pathways of nucleotide excision repair (NER) were quantified from the inner ear as a function of cis-diamminedichloroplatinum-II (cisplatin) treatment. The distribution of the post-translational products of these genes was evaluated among neurons and sensory hair cells of the inner ear following cisplatin treatment. These NER factors (genes & post-translational products) are only potentiated by DNA damage and are particularly sensitive to cisplatin induced DNA damage. A 2 x 3 x 2 factorial design, consisting of two treatment conditions (saline and cisplatin treated Fischer344 rats), three survival times and two molecular analysis methods (polymerase chain reaction and immunohistochemistry) was employed in this dissertation. The results revealed at least five important findings. First, it revealed for the first time that complex DNA repair molecular pathways such as NER exist in the inner ear. Second, it revealed for the first time that molecules used by advanced tumor cells to detect and repair damaged DNA from cisplatin genotoxicity also generalize to the inner ear and are stimulated by even small sub-toxic doses of cisplatin. Third, it revealed for the first time that NER proteins reside in the cytoplasm of neurons under normal conditions and translocate to the nucleus under conditions of genomic stress. Fourth, it revealed for the first time that the basal coil of the mammalian cochlea differs from the apical coil in the magnitude and latency in which NER molecules translocate from the cytoplasm to the nucleus under conditions of genomic stress. Fifth, the current work provides the bases for a new line of hearing research focused on molecular mechanisms of inner ear DNA repair.

The purpose of this study was to determine the point at which a minimally complex well-trained nonspeech task transfers to other nonspeech tasks of varying complexity. Participants included ten normal adult speakers. The nonspeech training task included bilabial production of a single intraoral pressure peak at either 7 or 15 cm H2O. Participants received random training on the two pressure targets, with Knowledge of Results provided on 50% of the trials. Complexity of the transfer tasks was manipulated by varying both the number of intraoral pressure peaks and the consistency of pressure targets. Only 4 participants demonstrated learning of the single peak task. For these four participants, transfer occurred from the training task to the more complex transfer tasks at roughly the same time. Findings suggest that there was no difference in complexity between number of pressure peaks and the consistency of the pressure targets.

Recent theories suggest that speech disfluencies result from a disruption in the time-dependent processes of phonological and phonetic encoding (Howell & Au-Yeung, 2002; Karniol, 1995; Perkins, Kent, & Curlee, 1991; Postma & Kolk, 1993; Wingate, 1988). The purpose of this study was to examine the relationship between phonological complexity and disfluencies in the speech of preschool-age children. It was predicted that speech disfluencies would be more likely to occur in utterances with a higher degree of phonological complexity than in utterances with a lower degree of phonological complexity. Participants in this study were 12 monolingual English-speaking preschool-age children who stutter. Other than the diagnosis of stuttering, all 12 children exhibited normal speech, language, and hearing function. Each child was videotaped with a parent or guardian while engaged in a 30 minute free-play conversational interaction. Each of the participants utterances was examined to identify the presence of speech disfluencies. The presence of word-initial late-emerging consonants and consonant strings (LECi/CSi; Howell, Au-Yeung, & Sackin, 2000; Shriberg, 1993; Throneburg, Yairi, & Paden, 1994) and the Index of Phonetic Complexity (IPC; Jakielski, 2000) were utilized as metrics to identify a relationship between speech disfluencies and phonological complexity. Logistic regression was employed to determine the relationship between phonological complexity and disfluency for each child individually and to determine if a similar relationship existed for the group as a whole. While the results of initial analyses suggested that an utterance with a higher phonological complexity score was more likely to be disfluent than an utterance with a lower phonological complexity score, post-hoc analyses did not support this initial conclusion. The results of post-hoc analyses suggested that the initial results were confounded by the effect of utterance length. The best fit to the logistic regression model was achieved by utterance length (in number of words). The addition of phonological complexity did not add significantly to the regression model. The results of this study do not offer support to the contention that speech disfluency in young children is influenced by the phonological complexity of the utterance being produced (Howell et al., 2000; Weiss & Jakielski, 2001).

The view that impairments of attention may constitute an important factor underlying impaired language performance in aphasia has gained support in recent years. Aphasiologists taking this view have generally proceeded from resource allocation models of attention, with little or no attention given to alternative models. One alternative model of dual-task performance is the central bottleneck model, which proposes a single-channel limit at response selection or other central processing stages. The first purpose of the present experiments was to further examine the effects on word production of lexical frequency in the context of the psychological refractory period (PRP) dual-task method. The second purpose was to examine whether the reaction time (RT) patterns obtained under conditions promoting equal task emphasis are more consistent with the central bottleneck or central resource models. Three dual-task experiments were conducted using speeded picture naming and tone identification tasks presented at varying timulus onset asynchronies (SOAs). In experiment 1, lexical frequency affected primary-task naming and secondary-task tone identification RTs approximately equally. In experiment 2, lexical frequency affected secondary-task naming RTs similarly at all levels of SOA, after potentially confounding variables were taken into account. It was concluded that frequency-sensitive lexical processing in picture-naming participates in the central processing stage of the dual-task models under study. In the third experiment, the two tasks were presented in variable order and subjects were instructed to give equal attention to both. On tone-primary trials, tone RTs increased with decreasing SOA, a result consistent with the central resource model and inconsistent with the central bottleneck model, unless augmented by the assumption that particpants grouped responses on short SOA trials. Also, additional analyses restricted to those participants demonstrating a lexical frequency effect on the secondary naming task found that lexical frequency and SOA interacted on primary-task tone RTs such that tone responses preceding low-frequency naming responses were slower than those preceding high-frequency names. This further suggests that these subjects allocated more central processing capacity to the naming task on low-frequency trials. Comparison of results across the three experiments suggested that participants in Experiment 3 demonstrated less dual-task interference than predicted by either model.

While many speech errors can be generated at either a linguistic or motoric level of production, phonetically well formed sound-level serial order errors are generally assumed to result from disruption of phonologic encoding (PE) processes. An influential model of PE (Dell, 1986; Dell, Burger & Svec, 1997) predicts that speaking rate should affect the relative proportion of these serial order sound errors (anticipations, perseverations, exchanges). These predictions have been extended to, and have special relevance for persons with aphasia (PWA) because of the increased frequency with which speech errors occur and because their localization within the functional linguistic architecture may help in treatment management. Supporting evidence regarding the effect of speaking rate on phonological encoding has been provided by studies using young normal language (NL) speakers and computer simulations. Limited data exist at present for older NL users and no group data exist for PWA. The purpose of this study was to examine the effects of speech rate on the ratio of phonological sequencing errors (anticipation/exchange (AE), anticipation/perseveration) (AP)) and other error types (vocal reaction time and distortion) in non-brain-damaged individuals and in persons with aphasia who were without concomitant motor speech disorders. Sixteen NL users and 16 PWA performed a phonologically challenging (tongue twister) speech production task at their typical and two faster speaking rates. A significant effect of rate was obtained for the AP ratio but not for the other comparisons. Contrary to the predictions of the model, the AP ratio increased with faster speaking rates. There was also a significant effect of rate and group for the VRT measure. The results for the serial order error ratios did not provide support for the model derived predictions regarding the direction of change for error type proportions. However, the significant effect of rate for the AP ratio provided support that changes in speaking rate did affect phonological encoding. Additionally, the results suggest that the relationships among slow post-selection inhibition and normal residual activation functions postulated to create an increase in perseverations relative to anticipation serial order errors, needs to be reconsidered within the Dell, et al. (1997) model.

Language samples from 10 adults using an augmentative and alternative communication (AAC) system were analyzed for gender differences in performance measures. Participants (5 female; 5 male) were matched on device, access method, software, experience, age, and education. Each participant was asked to describe the "cookie theft" picture from the Boston Diagnostic Aphasia Examination (BDAE; Goodglass & Kaplan, 1983). The language samples were analyzed on the following two dependent variables: frequency of Semantic Compaction™ language representation use and average communication rate. A dependent samples t-test and the equivalent non-parametric matched-pair Wilcoxon tests were conduced on both variables. The effect size and the power were also calculated and used to support the following results. There was not a significant difference in the Semantic Compaction™ dependent variable, however there was a large effect size (d=1.11). A power analysis indicated a sample size consisting of 9 pairs (4 more males and 4 more females) would increase the power to 82%. Further research with an increased sample size of 9 pairs of participants may provide more support for the current finding in relation to the use of Semantic Compaction™. No significant difference was found between the average communication rates of the genders; however the presence of a female outlier was concluded to influence these results. A dependent samples t-test was conducted on the data excluding the pair containing the outlier. The results of the dependent samples t-test indicated a significant difference between the genders in the average communication rates. Overall, for both dependent variables, the majority of males were higher on the performance measures than their paired female participants. These observations support a need for future research addressing gender differences in individuals who use AAC. Clinical implications suggest that future research is needed to determine if intervention strategies need to accommodate for differences between genders in their ability to effectively use their device to communicate as fast as they are able. Caution needs to be used when interpreting and applying these results to this population due to the limitations (i.e., small sample size and lack of control of extraneous variable) of the current study.

Background: In 1990, Hough conducted a study investigating the role of theme organization on discourse comprehension in adults with right hemisphere brain damage (RHD). She reported that participants with RHD performed significantly worse when the theme of a narrative was delayed until the end, compared to when the theme was at the beginning. RHD participants also performed significantly worse on these tasks compared to participants with left hemisphere brain damage and normal controls. However, manipulations to delay the theme also resulted in narratives that lacked coherence and violated the rules of narrative structure. Aims: The current study examined if controlling for differences in coherence between original and delayed-theme narratives would eliminate discrepancies in comprehension in the two conditions. Methods & Procedures: Participants were 10 adults with unilateral RHD and five without brain damage. Participants listened to experimental and filler narratives. Experimental narratives consisted of original-theme narratives and delayed-theme narratives that were manipulated to delay the theme while maintaining story coherence. Filler narratives consisted of original-theme narratives and delayed-theme narratives that were not controlled for coherence. All narratives were followed by three yes/no questions pertaining to main ideas and details. Several ancillary tasks were also included to further classify participants and to analyze alternative explanations for performance. Outcomes & Results: Accuracy data revealed that as predicted, there was no significant difference in performance on experimental original-theme and delayed-theme narratives for the RHD group. There was a trend towards poorer comprehension of filler delayed-theme narratives compared to original-theme narratives. These results support the hypothesis that poor comprehension on delayed-theme narratives in Houghs study was a result of differences in coherence rather than theme organization. However, analysis of ancillary tasks revealed a significant correlation between estimated capacity for auditory working memory and performance on delayed-theme narratives. These results imply that even with coherence accounted for, delaying the theme of a narrative is more taxing on mental processing, thus decreasing comprehension in RHD participants with particularly low working memory capacity.