Biomedical subjects

B E Murdoch

Publications and source records attributed to B E Murdoch.

At least 19 recordsLinked to original sources

PubMed2005

Kinematic analysis of jaw function in children following traumatic brain injury.

PRIMARY OBJECTIVE: To investigate jaw movements in children following traumatic brain injury (TBI) during speech using electromagnetic articulography (EMA). METHODS AND PROCEDURES: Jaw movements of two non-dysarthric children (aged 12.75 and 13.08 years) who had sustained a TBI were recorded using the AG-100 EMA system (Carstens Medizineletronik) during word-initial consonant productions. Mean quantitative kinematic parameters and coefficient of variation (variability) values were calculated and individually compared to the mean values obtained by a group of six control children (mean age 12.57 years, SD 1.52). MAIN OUTCOMES AND RESULTS: The two children with TBI exhibited word-initial consonant jaw movement durations that were comparable to the control children, with sub-clinical reductions in speed being offset by reduced distances. Differences were observed between the two children in jaw kinematic variability, with one child exhibiting increased variability, while the other child demonstrated reduced or comparable variability compared to the control group. CONCLUSIONS: Possible sub-clinical impairments of jaw movement for speech were exhibited by two children who had sustained a TBI, providing insight into the consequences of TBI on speech motor control development.

Adolescent↗

PubMed2003

Dysarthria and dysphagia following treatment for a fourth ventricle choroid plexus papilloma.

The present case report describes the presence of a persistent dysarthria and dysphagia as a consequence of surgical intervention for a choroid plexus papilloma (CPP). WM was a nine year ten month old male who at the time of the present study was seven years post-surgery. A comprehensive perceptual and instrumental test battery was used to document the nature of the dysarthria incorporating all components of speech production including respiration, phonation, resonance, articulation, and prosody. The nature of the dysphagia was evaluated through the use of videofluoroscopic evaluation of swallowing (VFS). Assessments confirmed the presence of a LMN dysarthria, marked by deficits in phonation, respiration, and prosody. Dysphagia assessment revealed deficits in oral preparatory, oral and pharyngeal stages of the swallow. The presence of persistent dysarthria and dysphagia in this case has a number of important implications for the management of children undergoing surgery for fourth ventricle CPPs, in particular the need for appropriate treatment, as well as counselling prior to surgery of the possible negative outcomes related to speech and swallowing.

Child↗

PubMed2003

Defining a role for the subthalamic nucleus within operative theoretical models of subcortical participation in language.

OBJECTIVE: To investigate the effects of bilateral, surgically induced functional inhibition of the subthalamic nucleus (STN) on general language, high level linguistic abilities, and semantic processing skills in a group of patients with Parkinson's disease. METHODS: Comprehensive linguistic profiles were obtained up to one month before and three months after bilateral implantation of electrodes in the STN during active deep brain stimulation (DBS) in five subjects with Parkinson's disease (mean age, 63.2 years). Equivalent linguistic profiles were generated over a three month period for a non-surgical control cohort of 16 subjects with Parkinson's disease (NSPD) (mean age, 64.4 years). Education and disease duration were similar in the two groups. Initial assessment and three month follow up performance profiles were compared within subjects by paired t tests. Reliability change indices (RCI), representing clinically significant alterations in performance over time, were calculated for each of the assessment scores achieved by the five STN-DBS cases and the 16 NSPD controls, relative to performance variability within a group of 16 non-neurologically impaired adults (mean age, 61.9 years). Proportions of reliable change were then compared between the STN-DBS and NSPD groups. RESULTS: Paired comparisons within the STN-DBS group showed prolonged postoperative semantic processing reaction times for a range of word types coded for meanings and meaning relatedness. Case by case analyses of reliable change across language assessments and groups revealed differences in proportions of change over time within the STN-DBS and NSPD groups in the domains of high level linguistics and semantic processing. Specifically, when compared with the NSPD group, the STN-DBS group showed a proportionally significant (p<0.05) reliable improvement in postoperative scores achieved on the word test-revised (TWT-R), as well as a reliable decline (p<0.01) in the accuracy of lexical decisions about words with many meanings and a high degree of relatedness between meanings. CONCLUSIONS: Bilateral STN-DBS affects certain aspects of linguistic functioning, supporting a potential role for the STN in the mediation of language processes.

Aged↗

PubMed2001

Semantic priming in Parkinson's disease: evidence for delayed spreading activation.

Nineteen persons with Parkinson's disease (PD) and 19 matched control participants completed a battery of online lexical decision tasks designed to isolate the automatic and attentional aspects of semantic activation within the semantic priming paradigm. Results highlighted key processing abnormalities in PD. Specifically, persons with PD exhibited a delayed time course of semantic activation. In addition, results suggest that experimental participants were unable to implicitly process prime information and, therefore, failed to engage strategic processing mechanisms in response to manipulations of the relatedness proportion. Results are discussed in terms of the 'Gain/Decay' hypothesis (Milberg, McGlinchey-Berroth, Duncan, & Higgins, 1999) and the dopaminergic modulation of signal to noise ratios in semantic networks.

Aged↗

PubMed2001

Discourse priming of homophones in individuals with dominant nonthalamic subcortical lesions, cortical lesions and Parkinson's disease.

An on-line priming experiment was used to investigate discourse-level processing in four matched groups of subjects: individuals with nonthalamic subcortical lesions (NSL) (n = 10), normal control subjects (n = 10), subjects with Parkinson's disease (PD) (n = 10), and subjects with cortical lesions (n = 10). Subjects listened to paragraphs that ended in lexical ambiguities, and then made speeded lexical decisions on visual letter strings that were: nonwords, matched control words, contextually appropriate associates of the lexical ambiguity, contextually inappropriate associates of the ambiguity, and inferences (representing information which could be drawn from the paragraphs but was not explicitly stated). Targets were presented at an interstimulus interval (ISI) of 0 or 1000 ms. NSL and PD subjects demonstrated priming for appropriate and inappropriate associates at the short ISI, similar to control subjects and cortical lesion subjects, but were unable to demonstrate selective priming of the appropriate associate and inference words at the long ISI. These results imply intact automatic lexical processing and a breakdown in discourse-based meaning selection and inference development via attentional/strategic mechanisms.

Aged↗

PubMed2001

Tongue-to-palate contact patterns and variability of four English consonants in an /i/ vowel environment.

Minimal data exist describing tongue-to-palate contact patterns and their variability in normal speakers of English. Consequently, the aims of the present study were to examine, using a comprehensive profile of data analysis, tongue-to-palate contact patterns and their variability in a group of ten normal speakers of English using the Reading Electropalatography3 (EPG3) system. Each speaker produced ten repetitions of the target words tea, leap, sea, and key following the carrier phrase 'I saw a ...'. Results revealed that the contact patterns produced exhibited similar characteristics to those described in earlier research. Additionally, the lateral approximant /i/ exhibited the highest degree of intra-subject variability with the alveolar fricative /s/ exhibiting the least. The results of this study are discussed in relation to existing normative data.

Humans↗

PubMed2001

Physiological assessment of tongue function in dysarthria following traumatic brain injury.

A tongue pressure transducer system was used to assess tongue strength, endurance, fine pressure control and rate of repetitive movement in a group of 20 individuals, aged 17 to 60 years, with dysarthria following severe traumatic brain injury (TBI). Comparison of the TBI group's results against data obtained from a group of 20 age and sex matched control subjects revealed reductions in tongue endurance and rate of repetitive movement. Tongue strength and fine pressure control, however, were found not to differ significantly from the control group. Pearson's product-moment correlations indicated there to be only weak correlations between the physiological nonspeech tongue parameters and the deviant perceptual articulatory features exhibited by the TBI group. Further analysis of the results on an individual subject basis revealed no clear relationships between the physiological and perceptual parameters suggesting that the TBI subjects may have been compensating in different ways for the physiological impairments.

Adolescent↗

PubMed2000

How thick is thick? Multicenter study of the rheological and material property characteristics of mealtime fluids and videofluoroscopy fluids.

Objective rheological assessment of fluids given to dysphagic patients at mealtime and during videofluoroscopy was carried out using a multicenter format. Thin, quarter-thick, half-thick and full-thick fluids were examined for the degree of correlation between mealtime fluids and their allegedly matched videofluoroscopy counterparts. The study was carried out to determine whether perceived subjective differences between mealtime fluids and videofluoroscopy fluids could be quantified using the rheological parameters of viscosity, density, and yield stress. The results showed poor correlation between mealtime fluids and videofluoroscopy fluids over all parameters. In general, the videofluoroscopy fluids were more viscous, more dense, and showed higher yield stress values than their mealtime counterparts. Given these results, it is reasonable to assume that the fluids used during videofluoroscopy do not provide an accurate indication of swallowing ability at mealtime. Therefore, it is suggested that clinicians use objective methods to rheologically match videofluoroscopy fluids to mealtime fluids.

Beverages↗

PubMed2000

Understanding ambiguous words in biased sentences: evidence of transient contextual effects in individuals with nonthalamic subcortical lesions and Parkinson's disease.

A cross-modal priming experiment was used to investigate lexical ambiguity resolution during sentence processing in individuals with nonthalamic subcortical lesions (NSL) (n = 10), compared to matched normal controls (n = 10), and individuals with cortical lesions (CL) (n = 10) and Parkinson's disease (PD) (n = 10). Critical sentences biased towards the dominant or subordinate meaning of a sentence-final lexical ambiguity were presented auditorily, followed after a short interstimulus-interval (ISI) (0 msec) or a long ISI (1000 msec), by the presentation of a visual target which was related to the dominant or subordinate meaning, or was an unrelated control word. Subjects made speeded lexical decisions on the targets. At the short ISI, lexical activation for the neurological patient groups appeared influenced by contextual information to a greater extent than in normal controls, which may indicate delayed lexical decision making or disturbed automatic lexical activation. At the long ISI, only the PD and NSL individuals failed to selectively activate the contextually appropriate meaning, suggesting a breakdown in the attention-based control of semantic activation through contextual integration. This finding may implicate disruptions to proposed frontal-striatal mechanisms which mediate attentional allocation and strategy formation.

Aged↗

PubMed2000

Processing lexical ambiguities in word triplets: evidence of lexical-semantic deficits following dominant nonthalamic subcortical lesions.

Lexical-semantic function was investigated in 10 participants with lesions of the dominant nonthalamic subcortical (NS) region and a matched normal control group. Participants performed speeded lexical decisions on the 3rd member of auditorily presented word triplets. The 4 critical triplet conditions were concordant (coin-bank-money), discordant (river-bank-money), neutral (day-bank-money), and unrelated (river-day-money). When the interstimulus interval (ISI) between the words in the triplets was 100 ms, patients with NS lesions obtained priming that indicated nonselective lexical access; at 1,250-ms ISI, however, there was no significant priming effect. This pattern of results is consistent with the view that patients with NS lesions can automatically access lexical-semantic information but may be unable to sustain lexical activation through controlled or attentional forms of processing.

Aged↗

PubMed2000

Which one of these is not like the others? An inter-hospital study of the viscosity of thickened fluids.

This investigation examined the rheological (viscosity and yield stress) and material property (density) characteristics of the thickened meal-time and videofluorscopy fluids provided by 10 major metropolitan hospitals. Differences in the thickness of thickened fluids were considered as a source of variability and potential hazard for inter-hospital transfers of dysphagic patients. The results indicated considerable differences in the viscosity, density, and yield stress of both meal-time and videofluoroscopy fluids. In theory, the results suggest that dysphagic patients transferred between hospitals could be placed on inappropriate levels of fluid thickness because of inherent differences in the rheology and material property characteristics of the fluids provided by different hospitals. Slowed improvement or medical complications are potential worst-case scenarios for dysphagic patients if the difference between the thick fluids offered by 2 hospitals are extreme. The investigation outlines the most appropriate way to assess the rheological and material property characteristics of thickened fluids. In addition, it suggests a plan of quality improvement to reduce the variability of the thickness of fluids offered at different hospitals.

Deglutition Disorders↗

PubMed2000

Kinematic analysis of tongue movements in dysarthria following traumatic brain injury using electromagnetic articulography.

Electromagnetic articulography (EMA), a technique that uses alternating magnetic fields to track the movement of miniature receiver coils affixed to the articulators, was used to assess the speed and accuracy of tongue movements exhibited by an individual with dysarthria following severe traumatic brain injury (TBI). Three receiver coils were attached to the TBI subject's tongue and the movements of these coils were recorded during five productions of three single syllable real words consisting of the lingual consonants /t, s, k/ in the word-initial position. A non-neurologically impaired adult male served as a control subject. A range of kinematic parameters was analysed from the consonant productions including the movement trajectories, velocity, acceleration, distance, and duration of tongue movements. Examination of the complex interactions between the kinematic parameters recorded for the TBI subject revealed a disturbance in the 'control' of tongue speed rather than a disturbance in speed per se, as it was found that the TBI subject exhibited difficulty in decelerating his tongue movements appropriately on the approach up to the palate during consonant production. The difficulty noted in deceleration resulted in inaccurate tongue movements that overshot the point of intent (in the case of /t/) and may have been instrumental in reducing the length of time that the tongue remained at the palate (in the case of /s/ and /k/) in comparison to the control subject. The disturbances identified in the kinematic parameters recorded provided objective insights into the nature of the articulatory disturbances responsible for the deviant speech feature, consonant imprecision, perceived in the TBI subject's speech. The study stresses the importance of examining a range of kinematic parameters and the interactions between these parameters in attempting to determine the nature of articulatory disturbances exhibited by individuals with dysarthria following TBI.

Adult↗

PubMed2000

Interpretation and comprehension of linguistic humour by adolescents with head injury: a group analysis.

The aim of the present study was to determine the ability of adolescents with a head injury to interpret and comprehend linguistic humour. Nine adolescents with head injury aged between 12 years 1 month and 15 years 4 months, and nine individually matched adolescents aged between 12 years 1 month and 16 years 1 month were administered a humour test, a standard language battery, the CELF-3, and the Self-Esteem Index. The test of humour abilities required each subject to recognize and select an explanation from a group of three, as to what made each item funny. Items were based on morphological, semantic and syntactic humour elements. Comparison at a group level demonstrated that adolescents with head injury performed significantly poorer in the interpretation and comprehension of linguistic humour than a group of individually matched peers. Contrary to expectations, a relationship between the level of self-esteem and humour comprehension did not exist. The findings of the present study suggest that further research into the effects of head injury on linguistic humour in adolescents is warranted, particularly from a case-by-case perspective.

Adolescent↗

PubMed1999

Interpretation and comprehension of linguistic humour by adolescents with head injury: a case-by-case analysis.

The aim of the present study was to examine the linguistic humour abilities of a group of adolescents with head injury on a case-by-case basis. Nine adolescents with head injury aged between 12 years 1 month and 15 years 4 months, and nine individually matched adolescents aged between 12 years 1 month and 16 years 1 month were administered a humour test, a standard language battery, the CELF-3, and the Self-Esteem Index. The test of humour abilities required each subject to recognize and select an explanation from a group of three, as to what made each item funny. Items were based on morphological, semantic and syntactic humour elements. Examination of the individual profiles of each subject with head injury illustrated the existence of variability between subjects representing three language abilities in the presence of mild head injury; and impaired humour ability with concurrent language skills that are within normal limits. This third pattern supports previous studies, which have documented the occurrence of high-level language impairment while language abilities are intact. The present study emphasized the importance of investigating the abilities of individuals who have had a head injury in childhood, within a developmental framework. This perspective serves to highlight the context of contributing aspects that impact on future language development and recovery of injury, such as the time that the injury occurred in a child's development, in addition to injury severity and main trends: reduced humour abilities together with below average language skills; intact humour and the time that has elapsed post-injury.

Adolescent↗

PubMed1998

The physiologic cause of swallowing sounds: answers from heart sounds and vocal tract acoustics.

A hypothetical discussion of the cause of swallowing sounds is presented. It is suggested that the pharynx contains a number of valves and pumps that produce reverberations within the pharynx to generate swallowing sounds. As heart sounds are propagated via vibration of muscles and valves, it is further suggested that an analogy exists between the generation of heart sounds and swallowing sounds. This new theory is known as the cardiac analogy hypothesis. The inability of the current literature to explain the cause of swallowing sounds is seen to limit the diagnostic potential of cervical auscultation for dysphagia assessment. Future investigators are encouraged to prove or disprove the cardiac analogy hypothesis.

Acoustics↗

PubMed1998

Voice changes in women treated for endometriosis and related conditions: the need for comprehensive vocal assessment.

Hormonal treatments which have an androgenic effect have the potential to cause vocal changes. The changes in vocal fold structure and voice quality are considered to be irreversible. To date, studies have documented subjective vocal changes or documented single cases without detailed, baseline voice assessments. The impact on laryngeal function of women taking these androgenic treatments requires further detailed, objective assessment. The need for increased awareness of the actions of androgenic hormones on womens' voices, and the benefits of a thorough voice assessment are discussed.

Danazol↗

PubMed1998

Cognitive-linguistic subgroups in closed-head injury.

This study examined variability in the interrelationship between language skill and neuropsychological function within a group of 25 severe closed head injury (CHI) subjects and 23 matched controls. All subjects underwent a battery of standardized language and neuropsychological tests. Cluster analyses were conducted to determine whether the CHI sample was universally or differentially impaired. Further subgroup analysis using a Q-type factor analysis outlined the differences in performance profiles within the group of CHI subjects. Results support the hypothesis that while some deficits were common to all CHI subjects, impairments delineated by whole group analysis do not necessarily represent universal impairments. In particular, ability to perform tasks involving auditory comprehension, naming, verbal memory, visual memory and visuospatial skills appeared to be important components in group differentiation. The cognitive-linguistic impairments which were common to all CHI subjects and considered to be the 'cardinal' cognitive-linguistic deficits following severe CHI were deficits in lexical-semantic and sentential semantic skills, verbal fluency, complex auditory comprehension, and attentional operations. Profile analysis revealed the existence of a double dissociation between performances on naming and verbal memory tasks and performances on visually related cognitive tasks. Results are discussed with reference to findings on previous studies of subgroups in the CHI population.

Adolescent↗

PubMed1998

Towards a conceptualization of language and cognitive impairment in closed-head injury: use of clinical measures.

Language deficits following closed-head injury (CHI) are widely considered as impairments secondary to the cognitive disruptions common to closed-head injury. In addition, the use of standardized measures to assess the functioning of the language system in closed-head injury has mostly been limited to aphasia test batteries which examine primary language functions only. This has resulted in generalizations as to the integrity of the language system following closed-head injury, and as a consequence, consideration of the contribution of the language system to the achievement of communicative competence in this population has been minimized. This paper presents a framework in which the functional language system is identified as a hierarchical system containing primary and higher-order language processes involved in reciprocal relationships with cognitive functions at each level. A group of 25 closed-head injury subjects and 23 demographically matched control subjects were examined for linguistic proficiency using a battery of standardized tests which investigated the language system across a hierarchy of complexity, structure and predictability. In addition, 23 of the closed-head subjects were administered a comprehensive neuropsychological test battery in order to determine the nature and extent of concomitant impairments in cognitive processes and their relationship with impairments in the language system. The language battery was found to consistently discriminate between the control and clinical groups indicating that the linguistic system is significantly impaired following CHI, with the lexical-semantic system being the most vulnerable to disruption. A strong influential relationship between language and cognitive processes was statistically confirmed and the nature of the relationship between aspects of language and cognition further delineated.

Adolescent↗