Subcortical brain mechanisms in speech and language

This paper reviews current research and contemporary theories of subcortical participation in the motor control of speech production and language processing. As a necessary precursor to the discussion of the functional roles of the basal ganglia and thalamus, the neuroanatomy of the basal ganglial-thalamocortical circuitry is described. Contemporary models of hypokinetic and hyperkinetic movement disorders based on recent neuroanatomical descriptions of the multi-segmented circuits that characterise basal ganglion anatomy are described. Reported effects of surgically induced lesions in the globus pallidus and thalamus on speech production are reviewed. In addition, contemporary models proposed to explain the possible contribution of various subcortical structures to language processing are described and discussed in the context of evidence gained from observation of the effects of circumscribed surgically induced lesions in the basal ganglia and thalamus on language function. The potential of studies based on examination of the speech/language outcomes of patients undergoing pallidotomy and thalamotomy to further inform the debate relating to the role of subcortical structures in speech motor control and language processing is highlighted. Copyright (C) 2001 S. Karger AG, Basel.

Dynamic assessment of tongue function in children with dysarthria associated with acquired brain injury using electromagnetic articulography

The study to be presented is the first to use a new physiological device, the electromagnetic articulograph, to assess articulatory dysfunction in children with acquired brain injury. Two children with dysarthria subsequent to acquired brain injury participated in the study. One child, a female aged 12 years 9 months exhibited a mild-moderate ataxic dysarthria following traumatic head injury while the other, a male aged 13 years 10 months, demonstrated a moderate-severe flaccid-ataxic dysarthria also following traumatic head injury. The speed and accuracy of their tongue movements was assessed using the Carstens AG100 electromagnetic articulograph. Movement trajectories together with a range of quantitative kinematic parameters were estimated during performance of ten repetitions of the lingual consonants /t, s, k/ and consonant cluster /kl/ in the word initial position of single syllable words. A group of ten non-neurologically impaired children served as controls. Examination of the kinematic parameters, including movement trajectories, velocity, acceleration, deceleration, distance travelled and duration of movement, revealed differences in the speed and accuracy of the tongue movements in both children with acquired brain injury compared to those produced by the non-neurologically impaired controls. The results are discussed in relation to contemporary theories of the effects of acquired brain injury on neuromuscular function. The implications of the findings for the treatment of articulatory dysfunction in children with motor speech disorders associated with acquired brain injury are highlighted.

Quantitative analysis of the speed and accuracy of tongue movements in dysarthria subsequent to traumatic brain injury using electromagnetic articulography

It has been recognised that in order to study the displacement, timing and co-ordination of articulatory components (i.e., tongue. lips, jaw) in speech production it is desirable to obtain high-resolution movement data on multiple structures inside and outside the vocal tract. Until recently, with the exception of X-ray techniques such as cineradiography, the study 0. speech movements has been hindered by the inaccessibility of the oral cavity during speech. X-ray techniques are generally not used because of unacceptable radiation exposure. The aim of the present study was to demonstrate the use of a new physiological device, the electromagnetic articulograph, for assessing articulatory dysfunction subsequent to traumatic brain injury. The components of the device together with the measuring principle are described and data collected from a single case presented. A 19 year-old male who exhibited dysarthria subsequent to a traumatic brain injury was fitted wit 2 the electromagnetic articulograph (Carstens AG-100) and a kinematic analysis of his tongue movements during production of the lingual consonants it, s, k/ within single syllable words was performed. Examination of kinematic parameters including movemmt trajectories, velocity, and acceleration revealed differences in the speed and accuracy of his tongue movements compared to those produced by a non-neurologically impaired adult male. It was concluded that the articulograph is a useful device for diagnosing speed and accuracy disorders in tongue movements during speech and that the device has potential for incorporation into physiologically based rehabilitation programs as a real-time biofeedback instrument.

Rehabilitation outcomes for brain injured patients in Australia: functional status, length of stay and discharge destination

This study describes the rehabilitation length of stay (LOS), discharge destination and discharge functional status of 149 patients admitted with traumatic brain injury (TBI) to an Australian hospital over a 5-year period. Hospital charts of patients admitted between 1993-1998 were reviewed. Average LOS over the 5-year time period was 61.8 days and only decreased nominally over this time. Longer LOS was predicted by lower admission motor FIM scores and presence of comorbidities. Mean admission and discharge motor FIM scores were 58 and 79, which represented a gain of 21 points. Higher discharge motor FIM scores were predicted by higher admission motor FIM scores and younger age. FIM gain was predicted by cognitive status and age. Most patients, 88%, were discharged back to the community, with 30% changing their living setting or situation. Changing living status was predicted by living alone and having poorer functional status on admission.

A test of the ash-free dry weight technique on the developmental stages of Patiriella spp. (Echinodermata : Asteroidea)

Determination of the ash-free dry weight (AFDW) of marine specimens requires samples to be rinsed, soaked, and centrifuged. Problems associated with this technique were examined with the developmental stages of seastar species (Patiriella) with different modes of development. The influence of three rinsing solutions (ammonium formate [AF], filtered seawater [FSW], and reverse osmosis water [RO]) was assessed. The hypothesis that the AFDW technique is a measure of organic material was addressed by drying inorganic salts. Developmental stages of Patiriella calcar rinsed in FSW were twice as heavy as those rinsed in RO or AE indicating that samples should be rinsed in RO or AF before weighing. Soaking treatments had a significant effect on the AFDW of samples of P. calcar (planktonic developer), indicating that the rinsing period should be brief. Zygotes of Patiriella re gularis (planktonic developer) were significantly heavier than ova or gastrulae, regardless of treatment. In contrast, there were no significant differences in the AFDW of any stages or treatments of Patiriella exigua (benthic developer). This may be due to the presence of a modified fertilization envelope, which protects these benthic embryos. Inorganic salts with water of crystallization and FSW lost 20-75% and 14% of their dry weight, respectively, after ashing. We propose that salt ions may retain water, which does not evaporate during drying but is lost during ashing, resulting in the overestimation of sample AFDW. If a similar process occurs in the developmental stages of marine invertebrates, changes in the intracellular ionic composition through development may result in inaccurate estimates of biomass.

Brain activity during the encoding, retention, and retrieval of stimulus representations

Studies of delayed nonmatching-to-sample (DNMS) performance following lesions of the monkey cortex have revealed a critical circuit of brain regions involved in forming memories and retaining and retrieving stimulus representations. Using event-related functional magnetic resonance imaging (fMRI), we measured brain activity in 10 healthy human participants during performance of a trial-unique visual DNMS task using novel barcode stimuli. The event-related design enabled the identification of activity during the different phases of the task (encoding, retention, and retrieval). Several brain regions identified by monkey studies as being important for successful DNMS performance showed selective activity during the different phases, including the mediodorsal thalamic nucleus (encoding), ventrolateral prefrontal cortex (retention), and perirhinal cortex (retrieval). Regions showing sustained activity within trials included the ventromedial and dorsal prefrontal cortices and occipital cortex. The present study shows the utility of investigating performance on tasks derived from animal models to assist in the identification of brain regions involved in human recognition memory.

The influence of age on weight-bearing joint reposition sense of the knee

Knee joint-position sensitivity has been shown to decline with increasing age, with much of the research reported in the literature investigating this age effect in non-weight-bearing (NWB) conditions. However, little data is available in the more functional position of weight-bearing conditions. The objective of this study was to identify the influence of age on the accuracy and nature of knee joint-position sense (JPS) in both full weight-bearing (FWB) and partial weight-bearing (PWB) conditions and to determine the effect of lower-extremity dominance on knee JPS. Sixty healthy subjects from three age groups (young: 20-35 years old, middle-aged: 40-55 years, and older: 60-75 years) were assessed. Tests were conducted on both the right and left legs to examine the ability of subjects to correctly reproduce knee angles in an active criterion-active repositioning paradigm. Knee angles were measured in degrees using an electromagnetic tracking device, Polhemus 3Space Fastrak, that detected positions of sensors placed on the test limb. Errors in FWB knee joint repositioning did not increase with age, but significant age-related increases in knee joint-repositioning error were found in PWB. It was found that elderly subjects tended to overshoot the criterion angle more often than subjects from the young and middle-aged groups. Subjects in all three age groups performed better in FWB than in PWB. Differences between the stance-dominant (STD) and skill-dominant (SKD) legs did not reach significance. Results demonstrated that for, normal pain-free individuals, there is no age-related decline in knee JPS in FWB, although an age effect does exist in PWB. This outcome challenges the current view that a generalised decline in knee joint proprioception occurs with age. In addition, lower-limb dominance is not a factor in acuity of knee JPS.

Sonographic estimation of fetal weight in macrosomic fetuses: diabetic versus non-diabetic pregnancies

The objective of this study is to compare the accuracy of sonographic estimation of fetal weight of macrosomic babies in diabetic vs non-diabetic pregnancies. Ali babies weighing 4000 g or more at birth, and who had ultrasound scans performed within one week of delivery were included in this retrospective study. Pregnancies with diabetes mellitus were compared to those without diabetes mellitus. The mean simple error (actual birthweight - estimated fetal weight); mean standardised absolute error (absolute value of simple error (g)/actual birthweight (kg)); and the percentage of estimated birthweight falling within 15% of the actual birthweight between the two groups were compared. There were 9516 deliveries during the study period. Of this total 1211 (12.7 %) babies weighed 4000 g or more. A total of 56 non-diabetic pregnancies and 19 diabetic pregnancies were compared. The average sonographic estimation of fetal weight in diabetic pregnancies was 8 % less than the actual birthweight, compared to 0.2 % in the non-diabetic group (p < 0.01). The estimated fetal weight was within 15% of the birthweight in 74 % of the diabetic pregnancies, compared to 93 % of the non-diabetic pregnancies (p < 0.05). In the diabetic group, 26.3 % of the birthweights were underestimated by more than 15 %, compared to 5.4 % in the non-diabetic group (p < 0.05). In conclusion, the prediction accuracy of fetal weight estimation using standard formulae in macrosomic fetuses is significantly worse in diabetic pregnancies compared to non-diabetic pregnancies. When sonographic fetal weight estimation is used to influence the mode of delivery for diabetic women, a more conservative cut-off needs to be considered.

Brain natriuretic peptide: Disease marker or more in cardiovascular medicine?

Brain natriuretic peptide (BNP) is predominantly a cardiac ventricular hormone that promotes natriuresis and diuresis, inhibits the renin-anglotensin-aldosterone axis, and is a vasodilator. Plasma BNP levels are raised in essential hypertension, and more so in left ventricular (LV) hypertrophy and heart failure. Plasma BNP levels are also elevated in ischemic heart disease. Attempts have been made to use plasma BNP levels as a marker of LV dysfunction, but these have shown that plasma BNP levels are probably not sensitive enough to replace echocardiography in the diagnosis of LV dysfunction. Pericardial BNP or N-BNP may be more suitable markers of LV dysfunction. Plasma BNP levels are also elevated in right ventricular dysfunction, pregnancy-induced hypertension, aortic stenosis, age, subarachnoid hemorrhage, cardiac allograft rejection and cavopulmonary connection, and BNP may have an important pathophysiological role in some or all of these conditions. Clinical trials have demonstrated the natriuretic, diuretic and vasodilator effects, as well as inhibitory effects on renin and aldosterone of infused synthetic human BNP (nesiritide) in healthy humans. BNP infusion improves LV function in patients with congestive heart failure via a vasodilating and a prominent natriuretic effect. BNP infusion is useful for the treatment of decompensated congestive heart failure requiring hospitalization. The clinical potential of BNP is limited as it is a peptide and requires infusion. Drugs that modify the effects of BNP are furthering our understanding of the pathophysiological role and clinical potential of BNP. Increasing the effects of BNP may be a useful therapeutic approach in heart failure involving LV dysfunction. The levels of plasma BNP are increased by blockers, cardiac glycosides and vasopeptidase inhibitors, and this may contribute to the usefulness of these agents in heart failure. (C) 2001 Prous Science. All rights reserved.

Self-awareness of Prospective Memory Failure in Adults with Traumatic Brain Injury

The frequency of prospective memory failure in individuals with severe traumatic brain injury (TBI) was investigated by comparison with a non-brain-injured control group. Self-awareness of prospective memory function was also assessed by comparing self-ratings with ratings by significant others. Study participants included 33 individuals with severe TBI and 29 non-brain-injured persons. Each participant nominated a close friend or relative who completed the informant's version of the questionnaire. Participants and their significant others both rated the participants' frequency of prospective memory lapses using the Comprehensive Assessment of Prospective Memory (CAPM). An independent groups design was adopted to compare the TBI and control groups. No significant difference was found between the TBI and control participants' self-ratings of frequency of prospective memory failure, but ratings by significant others were significantly different. The TBI group demonstrated less self-awareness (i.e. underestimated the frequency of prospective memory failure compared to significant others) than the control group.

Acute characteristics of pediatric dysphagia subsequent to traumatic brain injury: Videofluoroscopic assessment

Objective: To document the acute characteristics of swallowing impairment in a group of children post moderate/severe traumatic brain injury (TBI) by means of videofluoroscopy. Participants: Eighteen children with moderate/severe TBI. Main Outcome Measure: Videofluoroscopy at an average of 27.7 days post-injury. Results: Subjects demonstrated a range of dysphagia severity levels: mild-moderate (n = 8), moderate (n = 6), moderate-severe (n = 3), and severe (n = 1) and had a combination of oral and pharyngeal phase characteristics. More specifically; observable features or physiological impairments that were identified included reduced lingual control, hesitancy of tongue movement, repetitive tongue pumping, the presence of aspiration (including silent aspiration), delayed swallow reflex trigger, reduced laryngeal elevation and closure, and reduced peristalsis. Conclusions: These data highlight the diversity of swallowing deficits and dysphagia severity levels in children following TBI and suggest that the former are consistent with a pattern of oropharyngeal impairments.