A Cognitive Psychometric Investigation of Word Production and Phonological Error Rates in Logopenic Progressive Aphasia.

Purpose This study investigated the relationship between word production rates (WPRs) and phonological error rates (PERs) in generative and responsive tasks in logopenic progressive aphasia (lvPPA). We examined whether a portion of the reduced WPR during generative tasks related directly to phonological impairments affecting PER on all tasks, irrespective of other task differences that contributed to WPR. Method Two cognitive psychometric models were hypothesized and fit to the total number of words produced and the number of phonological errors produced by 22 participants on 10 tasks. Bayesian inference was used to construct posterior distributions of participant ability and task difficulty parameters. Model fit statistics were compared. Association strengths for average generative WPR and average responsive PER were also evaluated with linear least-squares regression. Results Average generative WPR and average responsive PER were significantly associated (r = -.77, p = .00002). A cognitive psychometric model that assumed reduced WPR on generative tasks reflects a portion of general phonological impairment yielded better fit than a model that ignored performance differences between generative and responsive tasks. Generative fluency tasks that elicited few phonological errors still reflected phonological impairment, via suppression. Individual participants were estimated to suppress between 62% and 93% of phonological errors on generative tasks that would have emerged on responsive tasks. Conclusions Suppression of phonological errors may present as decreased WPR on generative tasks in lvPPA. Failure to account for this suppression tendency may lead to overestimation of phonological ability. The findings indicate the need to account for task demands in assessing lvPPA.

Neuroanatomical correlates of phonologic errors in logopenic progressive aphasia.

While phonologic errors may be one of the salient features of the logopenic variant of primary progressive aphasia (lvPPA), sparse data are available on their neuroimaging correlates. The purpose of this study was to identify brain regions associated with different types of phonologic errors across several tasks for participants with lvPPA. Correlational analyses between phonologic errors across tasks most likely to elicit such errors and specific left hemisphere gray matter volume regions were conducted for 20 participants. Findings point to the inferior parietal lobe and supramarginal gyrus as being the most relevant correlates. Atrophy in these regions may increase the likelihood of making phonologic errors in lvPPA, particularly substitution error types. Our results provide support for neuroanatomical correlates of phonologic errors in the parietal region, which is consistent with previous findings of temporoparietal cortex involvement/atrophy in lvPPA.

Effect of Number of Graphic Symbols, Levels, and Listening Conditions on Symbol Identification and Latency in Persons with Aphasia.

This study investigated the ability of persons with aphasia to complete a series of experimental tasks involving single symbol and subject-verb-object sentence identification on a speech-generating device (SGD) in the presence/absence of competing stimuli. In all, 10 persons with Broca's aphasia and 10 persons in the control group were compared on accuracy and response latency of symbol identification across three listening conditions. Persons with aphasia identified fewer symbols accurately and had longer response latencies than persons in the control group. Number of symbols on the screen and location level had a significant effect on accuracy and latency for both groups. Persons with aphasia perceived tasks to be more difficult than persons in the control group. Results indicate that effective use of SGDs by persons with aphasia may depend on several message organization factors including location and number of symbols per screen.