Processing of audiovisual stimuli in aphasic and non-brain-damaged listeners

Abstract

We report the case of a 65-year-old monolingual right-handed man with 5 years of schooling who, after partial recovery of Wernicke's aphasia due to a left temporoparietal lesion, was affected by a second stroke involving the homologous regions in the right hemisphere. The clinical picture after the second stroke was characterized by a severe ‘glossolalic’ jargon: auditory comprehension was only moderately impaired. This case supports the association of severe, disinhibited jargon production with bihemispheric lesions. Furthermore, it indicates that partially preserved auditory comprehension can be found in a patient with bilateral temporal lesions involving Wernicke's area and its mirror region in the right hemisphere.     

Immediate repetition and learning of a series of words by 30 aphasic subjects]

Report and discussion of the results obtained with 4 groups of aphasics in a test of immediate repetition and in a learning test of word series.     

Effects of category learning on neural sensitivity to non-native phonetic categories

Categorical perception, an increased sensitivity to between- compared with within-category contrasts, is a stable property of native speech perception that emerges as language matures. Although recent research suggests that categorical responses to speech sounds can be found in left prefrontal as well as temporo-parietal areas, it is unclear how the neural system develops heightened sensitivity to between-category contrasts. In the current study, two groups of adult participants were trained to categorize speech sounds taken from a dental/retroflex/velar continuum according to two different boundary locations. Behavioral results suggest that for successful learners, categorization training led to increased discrimination accuracy for between-category contrasts with no concomitant increase for within-category contrasts. Neural responses to the learned category schemes were measured using a short-interval habituation design during fMRI scanning. Whereas both inferior frontal and temporal regions showed sensitivity to phonetic contrasts sampled from the continuum, only the bilateral middle frontal gyri exhibited a pattern consistent with encoding of the learned category scheme. Taken together, these results support a view in which top-down information about category membership may reshape perceptual sensitivities via attention or executive mechanisms in the frontal lobes.     

Effects of receptive and expressive training of category labels on generalized learning by severely mentally retarded children

The effects of receptive vs. expressive training of category labels on the acquisition of generalized referential labels by prelinguistic severely mentally retarded children were investigated. A crossover design was used, in which each subject received the two conditions successively; order of presentation of conditions was counterbalanced across subjects. The data indicated that receptive training resulted in more accurate generalization to novel category members than did expressive training. Further, generalization was above chance levels following receptive training but not following expressive training. The importance of these results for designing and evaluating generalized labeling instruction for severely retarded children was considered.     

Proactive interference in short-term recall by aphasic,brain-damaged nonaphasic and normal subjects

Aphasic, brain-damaged nonaphasic and normal subjects performed a short-term recall task, and groups were compared with regard to (1) the amount of proactive interference occurring in short-term memory and (2) amount of proactive interference release occurring in short-term memory as a result of changing stimulus material. The aphasic subjects had, in general, mild communication problems. Results were that groups demonstrated approximately the same degrees of proactive interference and proactive interference release. However, the aphasic subjects were able to recall fewer items than the other subjects. The relatively poor recall by the aphasic subjects appeared due to factors operating within trials during the recall task.     

The effects of multimodality stimulation on hemispheric alpha asymmetries of aphasic and normal subjects

Abstract

Hemispheric alpha asymmetries of normal males, normal females, and male aphasics were observed from anterior and posterior placement sites for recall and recognition of multimodality (auditory and visual) presented high and low imagery words and during resting conditions. No significant differences were observed during the resting condition between groups. Males were not found to have hemispheric asymmetries for any of the stimulus or task conditions. Females showed lower alpha power for the low imagery words compared to the high imagery words. Aphasic males were found to have significantly less alpha power in the right compared to the left hemisphere across conditions and tasks. A significant group × hemisphere × imagery interaction revealed significantly less alpha power in the left hemisphere (although not as low as the right) for low imagery words compared to the high imagery words for the aphasic subjects. This finding suggests greater involvement of the left hemisphere in processing multimodality information in aphasics that has not been reported for unimodality information (Moore 1989a, Moore and Lux 1987). Behavioural responses were found to be effected by group classification, task condition, and imagery value.     

Effects of age on retrieval cue processing as revealed by ERPs

The electrophysiological correlates of retrieval cue processing were investigated in healthy young (18-30 years) and older (63-75 years) subjects (n = 16 per group). Retrieval orientation--the differential processing of cues according to the form of the sought-for information--and retrieval difficulty were manipulated in a factorial design. In separate study-test cycles, subjects studied either words or pictures, and performed a yes/no recognition memory task with words as the test items. ERPs elicited by correctly classified new words differed markedly according to study material in the young subjects, replicating previous findings. In the older subjects, this effect was smaller than in the young, and had a later onset and earlier offset. The scalp topography of the effect was however statistically indistinguishable in the two groups. These age-related ERP differences were unmodulated by task difficulty, and remained reliable when recognition performance was matched across the groups. By contrast, the magnitude and timing of ERP difficulty effects were unaffected by age. The findings suggest that older subjects are less able than young individuals to vary their processing of retrieval cues in response to different retrieval demands.     

Age- and education-corrected,standardized short form of the category test

Abstract

A 128-item short form of the Category Test is described. The advantage of this form over earlier forms is that the user has a choice of interpretation methods. The user can estimate the total Category Test score or obtain a standardized score corrected for age and education. This standardized score can be compared to a normative sample of 109 non-brain-damaged subjects.     

Effects of cue exposure on the subjective perception of alcohol dependents with different types of cue reactivity

Summary. Thirty male alcohol-patients were divided into 3 subgroups with increased, unchanged, or reduced craving. Despite no significant difference at baseline, after cue-exposure, the increased craving subgroup showed significantly more confusion, insecurity, and anxiety, nevertheless, stronger beliefs in the positive effects of alcohol compared to the unchanged craving subgroup.     

The assessment of limb apraxia: Relationship between performances on single- and multiple-object tasks by left hemisphere damaged aphasic subjects

Two types of object manipulation tests, commonly advocated for the assessment of limb apraxia, were administered to 30 left hemisphere damaged aphasic (LHD) adults and 10 non-neurologically impaired control subjects. The tests were a multiple-object (MOT), requiring the manipulation of several related objects (e.g., lighting a candle when given a candle, a handle holder, and a match), and a single-object test (SOT) (e.g., lighting a match). Each of the subject's responses was assigned to one of six response categories: Standard (in which the response met all criteria for a faultless response) and five Nonstandard categories (Clumsy, Mislocation, Object Misuse, Perplexity, Omission). The results on comparing performances on the two tests showed that the SOT was “harder” than the MOT. Also, analyses of the relationship between MOT and SOT performances for the LHD subjects resulted in strong correlations between tests, loadings on the same two factors, and no evidence of double dissociations between the two tests for individual subjects. The two factors were interpreted to be a “conceptual/semantic” and a “motor execution” factor. The strong relationship and absence of double dissociations between response categories across the SOT and MOT suggest that both tasks are mediated by the same two neuropsychological processes. Clinical and theoretical implications of the findings are discussed.     

Changing patterns of brain activation during category learning revealed by functional MRI

Functional magnetic resonance imaging (fMRI) was used to investigate neural changes as a function of category learning in normals (n=8). Subjects were trained to classify patterns of dots into four categories over 4 consecutive days. fMRI monitored the changes that occurred during learning prior to training and then following each training session. During fMRI, subjects determined whether two patterns of dots were members of the same category. The behavioral changes that occurred as a result of the training were observed as increases in response accuracy within shortened response times. fMRI illustrated initial increases in volumes of activation distributed across the known visuospatial processing networks. The regions affected by learning were identified as those involved in the planning and execution of eye movements (frontal and supplementary eye fields, FEF and SEF), spatial attention (superior and inferior parietal lobules, SPL and IPL) and visual processing (primary, secondary, and tertiary visual cortices). The volumes of activation then decreased as training progressed further. Of the two proposed mechanisms for learning, that of strengthened connectivity on a given network and that of selection of different networks, our data supports the former.     

Effects of age on the neural correlates of retrieval cue processing are modulated by task demands

The electrophysiological correlates of retrieval orientation--the differential processing of retrieval cues according to the nature of the sought-for information--were investigated in healthy young (18-20 years old) and older (63-77 years old) adults. In one pair of study-test cycles, subjects studied either words or pictures presented in one of two visually distinct contexts, and then performed a yes/no recognition task with words as test items. In another pair of study-test cycles, subjects again made recognition judgments, but were required, in addition, to signal the study context for each item judged "old." Young subjects' event-related potentials (ERPs) for new (unstudied) test items were more negative-going when the study material was pictures rather than words, and this effect varied little between the two retrieval tasks. Replicating a previous report [Morcom, A. M., & Rugg, M. D. Effects of age on retrieval cue processing as revealed by ERPs. Neuropsychologia, 42, 1525-1542, 2004], the effects of study material on the ERPs of the older subjects were attenuated and statistically nonsignificant in the recognition task. In the source retrieval task, however, material effects in the older group were comparable in both onset latency and magnitude with those of the young subjects. Thus, the failure of older adults to demonstrate differential cue processing in tests of recognition memory likely reflects the adoption of a specific retrieval strategy rather than the incapacity to process retrieval cues in a goal-directed manner.     

Paired associate learning of Morse code and Braille letter names by dyslexic and normal children.

Twenty dyslexic and twenty normal children, matched for age and sex and with the same mean I.Q. were tested on their ability to learn letter names of Braille configurations presented visually or tactually and to Morse Code signals presented aurally. The dyslexic Ss learned fewer letters in all three modalities although for both groups the visual-verbal method was easiest. The deficits were not attributable to specific modality dysfunction nor to a failure of intersensory integration. More general encoding and retrieval difficulties appear to be implicated.     

Dissociation between the procedural learning of letter names and motor sequences in developmental dyslexia

Motor sequence learning has been studied extensively in Developmental dyslexia (DD). The purpose of the present research was to examine procedural learning of letter names and motor sequences in individuals with DD and control groups. Both groups completed the Serial Search Task which enabled the assessment of learning of letter names and motor sequences independently of each other. Control participants learned both the letter names as well as the motor sequence. In contrast, individuals with DD were impaired in learning of the letter names sequence and showed a reliable transfer of the motor sequence. Previous studies proved that motor sequence learning is impaired in DD. The present study demonstrated that this deficit is more pronounced when the task to be learned involves linguistic units. This result implies that the procedural learning system of language is more deficient than the motor procedural learning system in individuals with DD. The dissociation between motor and letter names sequence learning in those with DD also implies that the systems underlying these two tasks are separable.     

Effects of modified response elaboration training with apraxic and aphasic speakers

Response Elaboration Training (Kearns 1997) was modified for use with aphasic speakers with moderate to severe apraxia of speech. The modifications included additional clinician modelling, use of integral stimulation, and repeated practice of elaborated utterances. The acquisition, response generalization, stimulus generalization, and maintenance effects of treatment were examined with three chronic, apraxic-aphasic speakers. Increases in the number of CIUs produced in response to picture stimuli and in a personal recount task were found for all speakers. However, the magnitude of change varied greatly across speakers. Treatment was sequentially extended to the personal recount condition and additional positive changes were observed.     

The application of errorless learning to aphasic disorders: A review of theory and practice

Recently, there has been great interest in errorless learning as a new intervention technique. This may be because there are data from both basic neuroscience and clinical application that suggest it is superior to more traditional trial and error methods. In the contemporary literature the most prominent investigations of errorless learning are those designed for rehabilitation of memory impairments. These studies include numerous demonstrations of effective amelioration of word finding difficulties using errorless intervention. The aphasic literature contains no examples of purely errorless learning methods, however, some studies have successfully treated anomia using error reducing techniques. This suggests that errorless learning could be advantageous for treating aphasic disorders, in particular anomia. To explore this idea, we discuss previous research and review two current theories of errorless learning. We provide our own framework for thinking about errorless and errorful learning. In addition, a review of the anomia treatment literature (from 1985 to the present) is presented and conclusions drawn on the methods of treating the word finding difficulties of patients with aphasia.     

Effects of low,autoreceptor selective doses of dopamine agonists on the discriminative cue and locomotor hyperactivity produced by d-amphetamine

Summary The ability of low doses of the dopamine (DA) agonists quinpirole and (+)-3-PPP to reduce the discriminative stimulus properties and locomotor hyperactivity produced by d-amphetamine (0.5 mg/kg) was assessed in two groups of rats. Quinpirole (0.0125–0.05mg/kg) and (+)-3-PPP (1.0–2.0 mg/kg) completely antagonized d-amphetamine-induced locomotor hyperactivity. In contrast, only single doses of quinpirole (0.025 mg/kg) and (+)-3-PPP (2.0 mg/ kg) were effective in the drug discrimination paradigm; the antagonisms were small (18–47%), but significant. The inhibitory effects of quinpirole and (+)-3-PPP in these behavioural models are probably due to their ability to selectively stimulate DA autoreceptors in the nucleus accumbens and reduce the increase in DA release produced by d-amphetamine. It is suggested that the much weaker effects of the drugs in the discrimination paradigm are due to changes produced by the long-term periodic administration of d-amphetamine to these animals, such as a down-regulation in the sensitivity of DA autoreceptors.