The cortical localization of the lexicons. Positron emission tomography evidence

Positron emission tomography was used to investigate changes in regional cerebral blood flow (rCBF) in neurologically normal subjects during word reading and word repetition. The blood flow in these conditions was compared with control conditions where subjects were presented with stimuli of comparable auditory and visual complexity to real words and said the same word on presentation of each stimulus. The control condition for word repetition (hearing spoken words presented backwards) resulted in bilateral activation of the superior temporal gyrus. Word repetition caused a significant increase in rCBF over this control condition in the left superior and middle temporal gyri. The control condition for word reading (seeing stimuli written in 'false fonts', i.e. non-existent letter-like forms) resulted in significant changes in rCBF bilaterally in the striate and extrastriate cortex. Word reading caused a significant increase in blood flow relative to this control in the posterior part of the left middle temporal gyrus. The implications of these results are discussed, and it is argued that they are consistent with localization of a lexicon for spoken word recognition in the middle part of the left superior and middle temporal gyri, and a lexicon for written word recognition in the posterior part of the left middle temporal gyrus.

Localization of bronchial intraepithelial neoplastic lesions by fluorescence bronchoscopy

BACKGROUND

In the treatment of lung cancer, the best outcome is achieved when the lesion is discovered in the intraepithelial (preinvasive) stage. However, intraepithelial neoplastic lesions are difficult to localize by conventional white-light bronchoscopy (WLB).

OBJECTIVE

To determine if autofluorescence bronchoscopy, when used as an adjunct to WLB, could improve the bronchoscopist's ability to locate and remove biopsy specimens from areas suspicious of intraepithelial neoplasia as compared with WLB alone.

METHOD

A multicenter clinical trial was conducted in seven institutions in the United States and Canada. WLB followed by fluorescence examination with the light-induced fluorescence endoscopy (LIFE) device was performed in 173 subjects known or suspected to have lung cancer. Biopsy specimens were taken from all areas suspicious of moderate dysplasia or worse on WLB and/or LIFE examination. In addition, random biopsy specimens were also taken from other parts of the bronchial tree.

RESULTS

The relative sensitivity of WLB + LIFE vs WLB alone was 6.3 for intraepithelial neoplastic lesions and 2.71 when invasive carcinomas were also included. The positive predictive value was 0.33 and 0.39 and the negative predictive value was 0.89 and 0.83, respectively, for WLB+LIFE and WLB alone.

CONCLUSION

Autofluorescence bronchoscopy, when used as an adjunct to standard WLB, enhances the bronchoscopist's ability to localize small neoplastic lesions, especially intraepithelial lesions that may have significant implication in the management of lung cancer in the future.

Hearing and saying. The functional neuro-anatomy of auditory word processing

The neural systems involved in hearing and repeating single words were investigated in a series of experiments using PET. Neuropsychological and psycholinguistic studies implicate the involvement of posterior and anterior left perisylvian regions (Wernicke's and Broca's areas). Although previous functional neuroimaging studies have consistently shown activation of Wernicke's area, there has been only variable implication of Broca's area. This study demonstrates that Broca's area is involved in both auditory word perception and repetition but activation is dependent on task (greater during repetition than hearing) and stimulus presentation (greater when hearing words at a slow rate). The peak of frontal activation in response to hearing words is anterior to that associated with repeating words; the former is probably located in Brodmann's area 45, the latter in Brodmann's area 44 and the adjacent precentral sulcus. As Broca's area activation is more subtle and complex than that in Wernicke's area during these tasks, the likelihood of observing it is influenced by both the study design and the image analysis technique employed. As a secondary outcome from the study, the response of bilateral auditory association cortex to 'own voice' during repetition was shown to be the same as when listening to "other voice' from a prerecorded tape.

Brain activity during reading. The effects of exposure duration and task

Brain activity during reading tasks was investigated using PET. The aim was to account for differences in the results of two previous studies [those of Petersen et al. (Science 1990; 249: 1041-4) and Howard et al. (Brain 1992; 115: 1769-82)] by systematically varying the type of reading task and the exposure duration of the word stimuli. Both variables strongly influenced patterns of brain activity. There were three types of task: (i) reading aloud; (ii) reading silently; and (iii) lexical decision on visually presented words and pseudowords. Reading aloud and reading silently engaged the left middle and superior temporal regions, confirming the important role of these areas in visual word processing. The areas principally engaged during lexical decision were the left inferior and middle frontal cortices and the supplementary motor area; activity in these areas suggests that the subjects were using a phonological strategy to perform the task. There was also a significant effect of exposure duration, with activity being greater for short (150 ms) exposure durations than for long (1000 ms or 981 ms) exposure durations. We conclude that until we understand how subtle variations in experimental design influence brain activity during reading tasks, the association of specific processing functions with individual anatomical areas activated during reading is premature.

Frequency of lupus flare in pregnancy. The Hopkins Lupus Pregnancy Center experience

To determine whether pregnancy is associated with an increased rate of flare in patients with systemic lupus erythematosus (SLE), we prospectively studied 40 pregnancies in 37 women with SLE. The women were evaluated on a monthly basis in the Hopkins Lupus Pregnancy Center. Flare was designated using a previously developed quantitative definition, i.e., a change of greater than 1.0 in the physician's global assessment (scale of 0-3) since the preceding visit or during the last 93 days. Flare occurred in 24 (60%) of the pregnancies. Flares presented most commonly as constitutional symptoms, renal involvement, or involvement of skin or joints. Comparison of the rates of flare in the same patients after delivery and in nonpregnant SLE patients showed a significant increase in the rate of flare during pregnancy (P less than 0.001 and P less than 0.0001, respectively). We conclude that flare of lupus during pregnancy is common and occurs significantly more frequently than does flare in nonpregnant SLE patients or in the same patients after pregnancy.

Age of acquisition and imageability ratings for a large set of words, including verbs and function words

Age of acquisition and imageability ratings were collected for 2,645 words, including 892 verbs and 213 function words. Words that were ambiguous as to grammatical category were disambiguated: Verbs were shown in their infinitival form, and nouns (where appropriate) were preceded by the indefinite article (such as to crack and a crack). Subjects were speakers of British English selected from a wide age range, so that differences in the responses across age groups could be compared. Within the subset of early acquired noun/verb homonyms, the verb forms were rated as later acquired than the nouns, and the verb homonyms of high-imageability nouns were rated as significantly less imageable than their noun counterparts. A small number of words received significantly earlier or later age of acquisition ratings when the 20-40 years and 50-80 years age groups were compared. These tend to comprise words that have come to be used more frequently in recent years (either through technological advances or social change), or those that have fallen out of common usage. Regression analyses showed that although word length, familiarity, and concreteness make independent contributions to the age of acquisition measure, frequency and imageability are the most important predictors of rated age of acquisition.

Regional response differences within the human auditory cortex when listening to words

The relationship between activity within the human auditory cortices and the presentation rate of heard words was investigated by measuring changes in regional cerebral blood flow with positron emission tomography. We demonstrate that in the primary auditory cortices and middle regions of the superior temporal gyri there is a linear relationship between the rate of presentation of heard words and blood flow response. In contrast, the blood flow response in an area of the left posterior superior temporal gyrus (Wernicke's area) is primarily dependent on the occurrence of words irrespective of their rate of presentation. The primary auditory cortices are associated with the early processing of complex acoustic signals whereas Wernicke's area is associated with the comprehension of heard words. This study demonstrates for the first time that time dependent sensory signals (heard words) detected in the primary auditory cortices are transformed into a time invariant output which is channelled to a functionally specialised region--Wernicke's area. Wernicke's area is therefore distinguished from other areas of the auditory cortex by direct observation of signal transformation rather than by association with a specific behavioural task.

Occurrence of amyotrophic lateral sclerosis among Gulf War veterans

BACKGROUND

In response to Gulf War veterans' concerns of high rates of ALS, this investigation sought to determine if Gulf War veterans have an elevated rate of ALS.

METHODS

A nationwide epidemiologic case ascertainment study design was used to ascertain all occurrences of ALS for the 10-year period since August 1990 among active duty military and mobilized Reserves, including National Guard, who served during the Gulf War (August 2, 1990, through July 31, 1991). The diagnosis of ALS was confirmed by medical record review. Risk was assessed by the age-adjusted, average, annual 10-year cumulative incidence rate.

RESULTS

Among approximately 2.5 million eligible military personnel, 107 confirmed cases of ALS were identified for an overall occurrence of 0.43 per 100,000 persons per year. A significant elevated risk of ALS occurred among all deployed personnel (RR = 1.92; 95% CL = 1.29, 2.84), deployed active duty military (RR = 2.15, 95% CL = 1.38, 3.36), deployed Air Force (RR = 2.68, 95% CL = 1.24, 5.78), and deployed Army (RR = 2.04; 95% CL = 1.10, 3.77) personnel. Elevated, but nonsignificant, risks were observed for deployed Reserves and National Guard (RR = 2.50; 95% CL = 0.88, 7.07), deployed Navy (RR = 1.48, 95% CL = 0.62, 3.57), and deployed Marine Corps (RR = 1.13; 95% CL = 0.27, 4.79) personnel. Overall, the attributable risk associated with deployment was 18% (95% CL = 4.9%, 29.4%).

CONCLUSIONS

Military personnel who were deployed to the Gulf Region during the Gulf War period experienced a greater post-war risk of ALS than those who were not deployed to the Gulf.

Dilation of the influenza hemagglutinin fusion pore revealed by the kinetics of individual cell-cell fusion events

We have monitored kinetics of fusion between cell pairs consisting of a single influenza hemaglutinin (HA)-expressing cell and a single erythrocyte (RBC) that had been labeled with both a fluorescent lipid (Dil) in the membrane and a fluorescent solute (calcein) in the aqueous space. Initial fusion pore opening between the RBC and HA-expressing cell produced a change in RBC membrane potential (delta psi) that was monitored by a decrease in Dil fluorescence. This event was followed by two distinct stages of fusion pore dilation: the flux of fluorescent lipid (phi L) and the flux of a large aqueous fluorescent dye (phi s). We have analyzed the kinetics of events that occur as a result of transitions between a fusion pore (FP) and a solute permissive fusion pore (FPs). Our data are consistent with a fusion pore comprising six HA trimers.

Foot kinematics during walking measured using bone and surface mounted markers

The aim was to compare kinematic data from an experimental foot model comprising four segments ((i) heel, (ii) navicular/cuboid (iii) medial forefoot, (iv) lateral forefoot), to the kinematics of the individual bones comprising each segment. The foot model was represented using two different marker attachment protocols: (a) markers attached directly to the skin; (b) markers attached to rigid plates mounted on the skin. Bone data were collected for the tibia, talus, calcaneus, navicular, cuboid, medial cuneiform and first and fifth metatarsals (n=6). Based on the mean differences between the three data sets during stance, the differences between any two of the three kinematic protocols (i.e. bone vs skin, bone vs plate, skin vs plate) were >3 degrees in only 35% of the data and >5 degrees in only 3.5% of the data. However, the maximum difference between any two of the three protocols during stance was >3 degrees in 100% of the data, >5 degrees in 73% of the data and >8 degrees in 23% of the data. Differences were greatest for motion of the combined navicular/cuboid relative to the calcaneus and the medial forefoot segment relative to the navicular/cuboid. The differences between the data from the skin and plate protocols were consistently smaller than differences between either protocol and the kinematic data for each bone comprising the segment. The pattern of differences between skin and plate protocols and the actual bone motion showed no systematic pattern. It is unlikely that one rigid body foot model and marker attachment approach is always preferable over another.

Juvenile angiofibroma: the lessons of 20 years of modern imaging

Seventy-two patients with juvenile angiofibroma have been investigated by computerized tomography (CT) and/or magnetic resonance imaging (MRI) over a period of 20 years. The evidence from these studies indicates that angiofibroma takes origin in the pterygo-palatine fossa at the aperture of the pterygoid (vidian) canal. An important extension of the tumour is posteriorly along the pterygoid canal with invasion of the cancellous bone of the pterygoid base, and greater wing of the sphenoid (60 per cent of patients). Distinctive features of angiofibroma are the high recurrence rate, and the rapidity with which many tumours recur. It is postulated that the principal determinant of recurrence is a high tumour growth rate at the time of surgery coupled with incomplete surgical excision. The inability to remove the tumour in toto is principally due to deep invasion of the sphenoid, as described above. In this series 93 per cent of recurrences occurred with this type of tumour extension. A contributory cause in these patients is the use of pre-operative embolization. The treatment implications of these findings are examined.

Nicotine treatment of mild cognitive impairment: a 6-month double-blind pilot clinical trial

OBJECTIVE

To preliminarily assess the safety and efficacy of transdermal nicotine therapy on cognitive performance and clinical status in subjects with mild cognitive impairment (MCI).

METHODS

Nonsmoking subjects with amnestic MCI were randomized to transdermal nicotine (15 mg per day or placebo) for 6 months. Primary outcome variables were attentional improvement assessed with Connors Continuous Performance Test (CPT), clinical improvement as measured by clinical global impression, and safety measures. Secondary measures included computerized cognitive testing and patient and observer ratings.

RESULTS

Of 74 subjects enrolled, 39 were randomized to nicotine and 35 to placebo. 67 subjects completed (34 nicotine, 33 placebo). The primary cognitive outcome measure (CPT) showed a significant nicotine-induced improvement. There was no statistically significant effect on clinician-rated global improvement. The secondary outcome measures showed significant nicotine-associated improvements in attention, memory, and psychomotor speed, and improvements were seen in patient/informant ratings of cognitive impairment. Safety and tolerability for transdermal nicotine were excellent.

CONCLUSION

This study demonstrated that transdermal nicotine can be safely administered to nonsmoking subjects with MCI over 6 months with improvement in primary and secondary cognitive measures of attention, memory, and mental processing, but not in ratings of clinician-rated global impression. We conclude that this initial study provides evidence for nicotine-induced cognitive improvement in subjects with MCI; however, whether these effects are clinically important will require larger studies.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that 6 months of transdermal nicotine (15 mg/day) improves cognitive test performance, but not clinical global impression of change, in nonsmoking subjects with amnestic MCI.

The effect of maternal undernutrition on ovine fetal growth

Modifications in maternal nutrition during pregnancy can significantly disrupt fetal growth and subsequent post-natal health and survival. This study investigated the effects of undernutrition on fetal growth and the potential mechanisms involved. Tissue from pregnant ewes (n=27) was investigated on days 45, 90 and 135 of gestation (term = approximately 150 days). The thoracic girth (P<0.05) was greater in fetuses from nutrient restricted ewes on day 45 and there was also a trend towards an increased gut weight (P<0.08). By day 90, the fetal brain and thymus weight were lighter in underfed than in well-fed animals whilst the weight of the fetal ovaries was heavier (P<0.05). On day 135 the fetal heart, pancreas, thymus, gut and kidney weights were lighter in undernourished ewes (P<0.05). When expressed as a percentage of fetal body weight, significance was retained in the heart, pancreas and thymus (P<0.05). Bone growth was also affected. At day 90 the fetal femur and metatarsal were longer in underfed mothers (P<0.05). In contrast, the fetal humerus and scapula were shorter in underfed than in well-fed animals on day 135 (P<0.05) when the weight of the semitendinosus muscle (P<0.05) was also reduced. The fall in fetal glucose (P<0.1), insulin (P<0.01) and IGF-I (P<0.01) levels in underfed ewes on day 135 may have compromised fetal growth. Fetal plasma IGF binding protein-2 also increased between days 90 and 135 in underfed ewes (P<0.03), whilst levels were unaltered in well-fed animals. Although maternal and fetal plasma IGF-I levels increased with gestation (P<0.01) and the placentome morphology altered in all ewes (P<0.05), the fall in placental mass (P<0.05), amniotic and allantoic glucose concentrations (P<0.05) and maternal plasma glucose and insulin levels (P<0.05) in underfed ewes in late gestation may have compromised fetal substrate delivery. These perturbations in fetal development may have significant implications on adult health and carcass conformation, raising important health and economic issues in medical and agricultural sectors.

Aphasic naming: what matters?

This paper investigates the factors which affect naming performance for two groups of aphasic subjects. The effects of word age-of-acquisition, operativity, frequency, familiarity, imageability, concreteness, length and the visual complexity of the stimulus picture were examined. In contrast to previous studies, we found remarkably small effects of word frequency on naming performance; these studies, we argue, have failed to control sufficiently for the effects of variables which intercorrelate with frequency. However, many patients were significantly affected by age-of-acquisition even when any effects of frequency and familiarity had been accounted for. Operativity, imageability and word length were also predictive of naming performance for some of the patients investigated, unlike visual complexity. The applicability of conclusions drawn from groups of aphasics is again thrown into doubt, as these two groups showed different patterns of predictor variables, and the variables affecting the performance of individuals could be different from those affecting the group.

Noun imageability and the temporal lobes

We used positron emission tomography to investigate brain activity in response to hearing or reading nouns of varying imageability. Three experiments were performed. Activity increased with noun imageability in the left mid-fusiform gyrus, the lateral parahippocampal area in humans, and in the rostral medial temporal lobes close to or within perirhinal cortex. The left mid-fusiform activation has been observed in previous imaging studies of single word processing. Its functional significance was variously attributed to semantic processing, visual imagery, encoding episodic memories, or the integration of lexical inputs from different sensory modalities. These hypotheses are not mutually exclusive. The more rostral medial lobe response to noun imageability has not been observed previously. However, lesions in perirhinal cortex impair knowledge about objects in non-human primates, and bilateral rostral ventromedial temporal lobe potentials in response to object nouns were observed with human intracranial recordings. Imageable (object) nouns are learnt with reference to sensory experiences of living and non-living objects, whereas acquisition of the meaning of low imageable (abstract) nouns is more dependent on their context within sentences. Parahippocampal and perirhinal cortices are reciprocally connected with, respectively, second and third order sensory association cortices. We conclude that access to the representations of word meaning is dependent on heteromodal temporal lobe cortex, and that during the acquisition of object nouns one route is established through ventromedial temporal cortical regions that have reciprocal connections with all sensory association cortices.

Why is a verb like an inanimate object? Grammatical category and semantic category deficits

Semantic category effects, such as difficulties in naming animate things relative to inanimate objects, have been explained in terms of the relative weightings of perceptual and functional features within the semantic representations of these concepts. We argue that grammatical category deficits, such as difficulties in naming nouns relative to verbs, can be explained within the same framework. We hypothesize that verb concepts are richer in functional than sensory features and present a model of the semantic representations of animate nouns, inanimate nouns, and verbs. The model demonstrates that sensory feature damage results in a deficit for naming living things but spares verb naming, and functional feature damage results in a deficit for naming inanimate objects and verbs. We then report the assessment results of two patient groups. In accordance with the model's predictions, the "verb spared" patients were consistently worse at naming living things than inanimate objects, and their definitions of both living and nonliving items were lacking in sensory information. We conclude that damage to sensory features in semantic representations causes difficulties in naming concrete nouns relative to action verbs, and within the grammatical category of nouns, animate items will be more severely affected. Imageability was shown to be a strong predictor of naming performance in the "verb deficit" patients, and when this variable was controlled no class effect remained. Production of definitions revealed no differential damage to sensory or functional features, and no consistent effect of animacy in naming was shown. While the model suggests that verb deficits might occur in patients for whom functional features are damaged relative to sensory features, we conclude that the "verb deficit" shown in our patients (and potentially in many previously reported cases) was an artifact of the lower imageability of verbs in confrontation naming tasks.

MR imaging of levator ani muscle recovery following vaginal delivery

Our aim was to quantify the changes that occur in the levator ani muscles (LA) after vaginal delivery using magnetic resonance imaging. Fourteen women underwent MRI 1 day postpartum. Six of them were also scanned 1, 2, 6 weeks and 6 months after delivery. LA signal intensities and thickness, in areas of the urogenital and the levator hiatus were assessed in the transverse plane. Perineal body position was measured in the sagittal plane. One day postpartum a higher T2-signal intensity of the LA compared to the obturator internus muscle was found in all women and a lower T1-signal intensity in 8 of 12 women. By 6 months these differences were present in only 1 woman in the left LA. An elevation in perineal body position of 13.4 +/- 7.3 mm (P < 0.05), as well as a decrease in the area of the urogenital hiatus by 27% (P<0.05) and of the levator hiatus by 22% (P < 0.05) by 2 weeks postpartum suggest a return of normal LA geometry. LA thickness showed interindividual variations, and a complete loss of LA tissue was found in 1 woman. Changes in LA signal intensity, topography and thickness during the puerperium can be documented using MR imaging.

Semantic memory is impaired in both dementia with Lewy bodies and dementia of Alzheimer's type: a comparative neuropsychological study and literature review

OBJECTIVE

To test the hypothesis that semantic impairment is present in both patients with dementia with Lewy bodies (DLB) and those with dementia of Alzheimer's type (DAT).

METHODS

A comprehensive battery of neuropsychological tasks designed to assess semantic memory, visuoperceptual function, verbal fluency, and recognition memory was given to groups of patients with DLB (n=10), DAT (n=10) matched pairwise for age and mini mental state examination (MMSE), and age matched normal controls (n=15).

RESULTS

Both DLB and DAT groups exhibited impaired performance across the range of tasks designed to assess semantic memory. Whereas patients with DAT showed equivalent comprehension of written words and picture stimuli, patients with DLB demonstrated more severe semantic deficits for pictures than words. As in previous studies, patients with DLB but not those with DAT were found to have impaired visuoperceptual functioning. Letter and category fluency were equally reduced for the patients with DLB whereas performance on letter fluency was significantly better in the DAT group. Recognition memory for faces and words was impaired in both groups.

CONCLUSIONS

Semantic impairment is not limited to patients with DAT. Patients with DLB exhibit particular problems when required to access meaning from pictures that is most likely to arise from a combination of semantic and visuoperceptual impairments.

Probiotics-supplemented feeding in extremely low-birth-weight infants

OBJECTIVE

The objective of this trial was to test whether probiotic-supplemented feeding to extremely low-birth-weight (ELBW) infants will improve growth as determined by decreasing the percentage of infants with weight below the 10th percentile at 34 weeks postmenstrual age (PMA). Other important outcome measures, such as improving feeding tolerance determined by tolerating larger volume of feeding per day and reducing antimicrobial treatment days during the first 28 days from the initiation of feeding supplementation were also evaluated.

STUDY DESIGN

We conducted a multicenter randomized controlled double-blinded clinical study. The probiotics-supplementation (PS) group received Lactobacillus rhamnosus GG and Bifidobacterium infantis added to the first enteral feeding and continued once daily with feedings thereafter until discharge or until 34 weeks (PMA). The control (C) group received unsupplemented feedings. Infant weight and feeding volumes were recorded daily during the first 28 days of study period. Weights were also recorded at 34 weeks PMA.

RESULT

A total of 101 infants were enrolled (PS 50 versus C 51). There was no difference between the two groups in the percentage of infants with weight below the 10th percentile at 34 weeks PMA (PS group 58% versus C group 60%, (P value 0.83)) or in the average volume of feeding during 28 days after study entry (PS group 59  ml  kg(-1) versus C group 71  ml  kg(-1), (P value 0.11)). Calculated growth velocity was higher in the PS group compared with the C group (14.9 versus 12.6  g per day, (P value 0.05)). Incidences of necrotizing enterocolitis (NEC), as well as mortality were similar between the two groups.

CONCLUSION

Although probiotic-supplemented feedings improve growth velocity in ELBW infants, there was no improvement in the percentage of infants with growth delay at 34 weeks PMA. There were no probiotic-related adverse events reported.

The functional anatomy of the female pelvic floor and stress continence control system

This paper provides an overview of the functional anatomy of the structures responsible for controlling urinary continence under stress. The stress continence control system can be divided into two parts: the system responsible for bladder neck support, and the system responsible for sphincteric closure. Age- and injury-related changes in each of these systems are discussed. Understanding the pathophysiology of incontinence on the anatomical level will help to lead to identification of specific defects, thereby allowing better individualized treatment for the incontinent patient.

The uses of short-term memory: a case study

It has been widely claimed that the systems employed in tasks of immediate memory have a function in the comprehension of speech; these systems, it has been proposed, are used to hold a representation of the speech until a syntactic analysis and interpretation have been completed. Such a holding function is meant to be especially important where the sentences heard are long or complex. It has thus been predicted that subjects with impaired short-term memory performance would show deficits in comprehension of such materials.

In this study, one subject with impaired phonological processing and a severely reduced digit span was tested on a range of tasks requiring the syntactic analysis, memory and comprehension of long and complex material. She was found to be unimpaired on syntactic analysis and comprehension, but not on sentence repetition. The implications for models of short-term memory are discussed.

Phonological errors in aphasic naming: comprehension, monitoring and lexicality

This paper investigates the production of phonological errors in aphasic naming, examining the relationship between these errors and deficits in comprehension. The predictions of Dell and O'Seaghda's (1991) computational model of speech production were tested by lesioning. The set of lesioned models demonstrated a strong correlation between proportion of phonologically related errors in naming and comprehension accuracy. In contrast, no correlation between proportion of phonological errors in naming and comprehension accuracy was found for a group of fifteen aphasics. This paper also examines monitoring behaviours, such as the presence of self-corrections and interrupted responses, again finding no relationship with auditory comprehension. There was also no evidence for a lexical bias in the phonological errors for these aphasic subjects. Phonologically related errors were argued to be words only by chance; this was supported by the fact that they occurred more frequently on short words than long words, and that the proportion of real word errors was not significantly different to that observed in a pseudocorpus of errors. We conclude that a production-based monitor would be compatible with these results but that any comprehension-based monitor is not reliably employed by some or all of the aphasic subjects examined here. Additionally, these data are incompatible with models of language processing where speech input and output share the same processing components.

Predicting lower limb joint kinematics using wearable motion sensors

The aim of this study was to estimate sagittal plane ankle, knee and hip gait kinematics using 3D angular velocity and linear acceleration data from motion sensors on the foot and shank. We explored the accuracy of intra-subject predictions (i.e., where training and testing uses trials from the same subject) and inter-subject (where testing uses subjects different from the ones used for training) predictions, and the effect of loss of sensor data on prediction accuracy. Hip, knee and ankle kinematic data were collected using reflective markers. Simultaneously, foot and shank angular velocity and linear acceleration data were collected using small integrated accelerometers/gyroscope units. A generalised regression networks algorithm was used to predict the former from the latter. The best results were from intra-subject predictions, with very high correlations (0.93-0.99) and low mean absolute deviation (< or =2.3 degrees ) between measured kinematic joint angles and predicted angles. The inter-subject case produced poorer correlations (0.70-0.89) and larger absolute differences between measured and predicted angles, ranging from 4.91 degrees (left ankle) to 9.06 degrees (right hip). The angular velocity data added little to the accuracy of predictions and there was also minimal benefit to using sensor data from the shank. Thus, a wearable system based only on footwear mounted sensors and a simpler sensor set providing only acceleration data shows potential. Whilst predictions were generally stable when sensor data was lost, it remains to be seen whether the generalised regression networks algorithm is robust for other activities such as stair climbing.