Swathi Kiran

Effects of pitch-shift velocity on voice F0 responses

Previous studies have shown that voice fundamental frequency (F0) is modified by changes in the pitch of vocal feedback and have demonstrated that the audio-vocal control system has both open- and closed-loop control properties. However, the extent to which this system operates in closed-loop fashion may have been underestimated in previous work. Because the step-type stimuli used were very rapid, and people are physically unable to change their voice F0 as rapidly as the stimuli, feedback responses might have been reduced or suppressed. In the present study, pitch-shift stimuli, consisting of a disparity between voice F0 and feedback pitch of varying ramp onset velocities, were presented to subjects vocalizing a steady /ah/ sound to examine the effect of stimulus onset on voice F0 responses. Results showed that response velocity covaried with stimulus velocity. Response latency and time of the peak response decreased with increases in stimulus velocity, while response magnitude decreased. A simple feedback model reproduced most features of these responses. These results strongly support previous suggestions that the audio-vocal system monitors auditory feedback and, through closed-loop negative feedback, adjusts voice F0 so as to cancel low-level fluctuations in F0.

Effect of Verb Network Strengthening Treatment (VNeST) on lexical retrieval of content words in sentences in persons with aphasia

Background: Verb Network Strengthening Treatment (VNeST) is a semantic treatment that aims to improve lexical retrieval of content words in sentence context by promoting systematic retrieval of verbs (e.g., measure) and their thematic roles—i.e., agent (doer of the action, e.g., carpenter, chef) and patient (receiver of the action, e.g., lumber, sugar). VNeST is influenced by Loverso and colleagues (e.g., Loverso, Selinger, & Prescott, 1979) who used “verb as core” treatment to improve sentence production with encouraging results, and McRae and colleagues who showed that verbs prime typical agents (e.g., pray–nun) and patients (arrest–criminal) (Ferretti, McRae, & Hatherell, 2001) and vice‐versa (McRae, Hare, Elman, & Ferretti, 2005). Aims: There are four specific questions in this study. Does training a set of verbs using VNeST generalise to the ability to produce (1) an agent (carpenter), trained verb (measure), and patient (stairs) in response to novel picture stimuli and (2) an agent (nurse), untrained semantically related verb (weigh), and patient (baby) in response to novel picture stimuli? (3) Are generalisation effects maintained? (4) Does VNeST generalise to the ability to retrieve nouns and verbs not directly related to treatment items in single word naming, picture description, and connected speech tasks? Methods & Procedures: Four participants with aphasia participated. Participants received VNeST, which involves retrieval of agent–patient pairs (e.g., chef/sugar, surveyor/land) related to trained verbs (e.g., measure), twice per week. A single‐participant, repeated probe, multiple baseline experimental design was used. Generalisation to sentence production for sentences containing trained verbs and untrained semantically related verbs was tested weekly. Outcomes & Results: Results demonstrated generalisation to lexical retrieval of content words in sentences with trained and untrained verbs across participants. Additionally, pre‐ to post‐treatment generalisation was observed on single verb and noun naming and lexical retrieval in sentences across a variety of tasks across participants. Generalisation to connected speech was observed for three of four participants. Conclusions: Although preliminary, these results indicate that VNeST may be effective in promoting generalisation from single word naming to connected speech in persons with moderate aphasia. A number of clinical implications related to treatment efficiency are discussed. The authors would first like to thank the four individuals who participated in this study. Additional thanks go Laura K. Allred for creating the artwork for developed stimuli, and Michela Palmieri and Adam Jacks for assistance with reliability.

Effect of typicality on online category verification of animate category exemplars in aphasia

Normal young, elderly, Brocas aphasic, and Wernickes aphasic individuals participated in an online category verification task where primes were superordinate category labels while targets were either typical or atypical examples of animate categories or nonmembers belonging to inanimate categories. The reaction time to judge whether the target belonged to the preceding category label was measured. Results indicated that all four groups made significantly greater errors on atypical examples compared to typical examples. Young and elderly individuals, and Brocas aphasic patients performed similarly on the verification task; these groups demonstrated faster reaction times on typical examples than atypical examples. Wernickes aphasic patients made the most errors on the task and were slowest to respond than any other participant group. Also, these participants were not significantly faster at accepting correct typical examples compared to correct atypical examples. The results from the four groups are discussed with relevance to prototype/family resemblance models of typicality.

Comparison of voice F0 responses to pitch-shift onset and offset conditions

In order to maintain a steady voice fundamental frequency (F0), it is assumed that people compare their auditory feedback pitch with an internal (memory) or external (acoustic) referent. In the present study we examined whether the internal referent is fixed or variable by comparing voice F0 responses to incorrect auditory feedback in two timing conditions. In one condition, the incorrect pitch was introduced during vocalization (ON condition). In the second, the incorrect auditory feedback pitch was presented before vocal onset and then removed during vocalization (OFF condition). These conditions were examined with pitch-shift stimuli of ±25, 100, and 200 cents. There were no differences in response latency or magnitude between the two timing conditions, indicating that for a sustained-pitch vocalization task, the internal referent is not fixed. Several alternative types of referencing are discussed, which include use of a pitch relative to that which existed at the onset of vocalization (a sample and h...

Semantic feature analysis treatment in Spanish–English and French–English bilingual aphasia

Background: Edmonds and Kiran (2006) reported that training lexical retrieval in one language resulted in within‐language and cross‐language generalisation in three bilingual (English–Spanish) patients with aphasia. Aims: The present experiment continues this line of research, repeating a similar procedure with new patients and examining a broader range of factors that may affect generalisation patterns. Methods & Procedures: Four participants (two Spanish–English and two French–English speakers) with anomia post CVA received a semantic feature‐based treatment aimed at improving naming of English or Spanish/French nouns. Using a multiple baseline design, generalisation to untrained semantically related and unrelated items in each language was measured during periods of therapy first in one language, then in the other. Outcomes & Results: All patients improved their naming of the trained items in the trained language, although to varying degrees. Within‐language generalisation to semantically related items occurred in two Spanish–English patients and one French–English patient. Cross‐language generalisation to translations and semantically related items occurred only for one French–English patient. Conclusions: The impact of the intervention is very clear. The semantic feature‐based practice is linked to the gains made, and accounts for the predominance of semantic naming errors after treatment. Possible explanations for the different patterns of generalisation are considered in terms of the various factors including each patients pre‐stroke language proficiency, age of acquisition of each language, post‐stroke level of language impairment, and type and severity of aphasia.

Neuroimaging in aphasia treatment research: Consensus and practical guidelines for data analysis

Functional magnetic resonance imaging is the most widely used imaging technique to study treatment-induced recovery in post-stroke aphasia. The longitudinal design of such studies adds to the challenges researchers face when studying patient populations with brain damage in cross-sectional settings. The present review focuses on issues specifically relevant to neuroimaging data analysis in aphasia treatment research identified in discussions among international researchers at the Neuroimaging in Aphasia Treatment Research Workshop held at Northwestern University (Evanston, Illinois, USA). In particular, we aim to provide the reader with a critical review of unique problems related to the pre-processing, statistical modeling and interpretation of such data sets. Despite the fact that data analysis procedures critically depend on specific design features of a given study, we aim to discuss and communicate a basic set of practical guidelines that should be applicable to a wide range of studies and useful as a reference for researchers pursuing this line of research.

What Is the Nature of Poststroke Language Recovery and Reorganization

This review focuses on three main topics related to the nature of poststroke language recovery and reorganization. The first topic pertains to the nature of anatomical and physiological substrates in the infarcted hemisphere in poststroke aphasia, including the nature of the hemodynamic response in patients with poststroke aphasia, the nature of the peri-infarct tissue, and the neuronal plasticity potential in the infarcted hemisphere. The second section of the paper reviews the current neuroimaging evidence for language recovery in the acute, subacute, and chronic stages of recovery. The third and final section examines changes in connectivity as a function of recovery in poststroke aphasia, specifically in terms of changes in white matter connectivity, changes in functional effective connectivity, and changes in resting state connectivity after stroke. While much progress has been made in our understanding of language recovery, more work needs to be done. Future studies will need to examine whether reorganization of language in poststroke aphasia corresponds to a tighter, more coherent, and efficient network of residual and new regions in the brain. Answering these questions will go a long way towards being able to predict which patients are likely to recover and may benefit from future rehabilitation.

Meta-analysis of the neural representation of first language and second language

This study reports an activation likelihood estimation meta-analysis of published functional neuroimaging studies of bilingualism. Four parallel meta-analyses were conducted by taking into account the proficiency of participants reported in the studies. The results of the meta-analyses suggest differences in the probabilities of activation patterns between high proficiency and moderate/low proficiency bilinguals. The Talairach coordinates of activation in first language processing were very similar to that of second language processing in the high proficient bilinguals. However, in the low proficient group, the activation clusters were generally smaller and distributed over wider areas in both the hemispheres than the clusters identified in the ALE maps from the high proficient group. These findings draw attention to the importance of language proficiency in bilingual neural representation.

Evaluating the Effectiveness of Semantic-Based Treatment for Naming Deficits in Aphasia: What Works?

This article reviews the basic principles and evidence for the effectiveness of a semantic-based treatment for naming deficits in aphasia. This article focuses on three aspects of semantic-based treatment. First, the theoretical basis for semantic treatment approaches to alleviate naming deficits is explained. Second, the different types of semantic treatment approaches (i.e., substitutive and restitutive treatments) are reviewed. More attention is provided to restitutive treatment approaches, and some ideas regarding why these treatments may be effective are discussed. We argue that strengthening access to impaired semantic and phonologic representations and facilitating generalization to untrained but related targets are two factors determining the success of a restitutive-based semantic treatment. Finally, in the third section of the article, the effect of semantic treatment on the overall communicative effectiveness and suggestions for future research in this field are discussed.

Training phoneme to grapheme conversion for patients with written and oral production deficits: A model‐based approach

Background: A previous study (Kiran, Thompson, & Hashimoto, 2001) investigated the effect of training sublexical conversion on improving oral reading of regular words in two individuals with aphasia. Results revealed that training grapheme to phoneme conversion improved acquisition of trained items and facilitated generalisation to trained and untrained stimuli during oral naming, written naming, and writing to dictation as well. Aims: The aim of the present study was to extend this work to investigate if training phoneme to grapheme conversion would result in improvement of writing to dictation of trained items and facilitate generalisation to untrained stimuli and untrained tasks. Methods & procedures: Using a single subject experimental design across three participants with aphasia, the effects of phoneme to grapheme conversion treatment were evaluated by periodic probing of both trained and untrained regular words across lexical tasks: writing to dictation, written naming, oral spelling, and oral naming. Outcomes & Results: Results indicated that training phoneme to grapheme conversion resulted in improved writing to dictation of trained and untrained words in two out of three patients. In addition, improved written naming and oral spelling of trained words was observed. Marginal improvements were observed for untrained stimuli on written naming, oral spelling, and oral naming. Conclusions: The results of this experiment demonstrate the effectiveness of training sublexical conversion to improve written production deficits and to facilitate generalisation to untrained stimuli and untrained tasks. These results also complement findings of our previous study to suggest a more efficient method of improving single word production deficits than training each modality successively.