The neurology of enteric disease.
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Dietary Supplements↗
Biomedical subjects
A J Wills
Publications and source records attributed to A J Wills.
Why are artificial polymorphous concepts so hard for birds to learn?
Stimulus sets defined in terms of artificial polymorphous concepts have frequently been used in experiments to investigate the mechanisms of discrimination of natural concepts, both in humans and in other animals. However, such stimulus sets are frequently difficult for either animals or humans to discriminate. Properties of artificial polymorphous stimulus sets that might explain this difficulty include the complexity of the individual stimuli, the unreliable reinforcement of individual positive features, attentional load, difficulties in discriminating some stimulus dimensions, memory load, and a lack of the correlation between features that characterizes natural concepts. An experiment using chickens as subjects and complex artificial visual stimulus sets investigated these hypotheses by training the birds in discriminations that were not polymorphous but did have some of the properties listed above. Discriminations that involved unreliable reinforcement or high attentional load were found to approach the difficulty of polymorphous concept discriminations, and these two factors together were sufficient to account for the entire difficulty. The usual kind of artificial polymorphous concept may not be a good model for natural concepts as they are perceived and discriminated by birds. A RULEX account of natural concept learning may be preferable.
Animals↗
Oculopharyngeal muscular dystrophy: a point mutation which mimics the effect of the PABPN1 gene triplet repeat expansion mutation.
BACKGROUND: Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant late onset neuromuscular disease characterised by proximal muscle weakness, ptosis, and swallowing difficulty. The only causative mutation described to date is a triplet repeat expansion consisting of two to seven additional base triplets in a repeat sequence in exon 1 of the polyadenine binding protein nuclear 1 (PABPN1) gene. This results in an increase in length of a polyalanine tract in the PABPN1 protein from 10 to 12-17 residues. OBJECTIVE: Description of another mutation in a case of OPMD. METHODS: Sequence analysis of exon 1 of the PABPN1 gene was undertaken on 202 patients referred for a possible diagnosis of OPMD but negative for the triplet repeat expansion mutation. RESULTS: A case was identified with typical symptoms of OPMD, negative for the repeat expansion mutation but with a missense mutation in PABPN1 close to the 3' end of the normal polyalanine codon repeat sequence. CONCLUSIONS: The single base mutation changes a glycine codon to an alanine codon and results in an increase in the number of contiguous polyalanine codons. This mimics the effect of the common triplet repeat expansion mutation and represents a previously undescribed mechanism of mutation.
Aged↗
Respiratory involvement in inherited primary muscle conditions.
Patients with inherited muscle disorders can develop respiratory muscle weakness leading to ventilatory failure. Predicting the extent of respiratory involvement in the different types of inherited muscle disorders is important, as it allows clinicians to impart prognostic information and offers an opportunity for early interventional management strategies. The approach to respiratory assessment in patients with muscle disorders, the current knowledge of respiratory impairment in different muscle disorders and advice on the management of respiratory complications are summarised.
Humans↗
Tubular aggregate myopathy presenting with acute type II respiratory failure and severe orthopnoea.
Acute hypercapnic respiratory failure (AHRF) is a common reason for hospital admission. Most patients have an underlying chronic lung disease such as chronic obstructive pulmonary disease. We report the case of a man who presented with AHRF secondary to tubular aggregate myopathy.
Dyspnea↗
Formation of category representations.
Many formal models of categorization assume, implicitly or explicitly, that categorization results in the formation of direct associations from representations of the presented stimuli to representations of the experimentally provided category labels. In three categorization experiments employing a polymorphous classification structure (Dennis, Hampton, & Lea, 1973) and a partial reversal, optional shift procedure (Kendler, Kendler, & Wells, 1960), we provide evidence consistent with the hypothesis that learning a new classification problem results in the creation of category representations that mediate between representations of the stimulus and the label. This hypothesis can be instantiated through the AMBRY model (Kruschke, 1996).
Adult↗
Thymectomy in myasthenia gravis: comparison of outcome in Santiago, Cuba and Nottingham, UK.
OBJECTIVES: We compared the outcome of thymectomy for myasthenia gravis (MG) in two healthcare systems. In Nottingham, UK, thymectomy is performed for thymic enlargement and considered in acetylcholine receptor (AchR) antibody positive patients. In Santiago, Cuba, thymectomy is considered in all generalised MG patients irrespective of their radiological findings or AchR antibodies. METHOD: 22 MG patients in Nottingham and 75 in Santiago who had a thymectomy were identified and their notes reviewed. We compared the median age, stage of disease, thymic histology and clinical outcome at two years post-thymectomy. RESULTS: The median ages for the Cuban and Nottingham patients were 25 and 35 years respectively. The median stage of disease was IIa by Osserman's classification in both. In Nottingham, 59% (13/22) showed an improvement compared with 88 % (66/75) in Santiago (p < 0.01). There were significantly more cases of thymoma in Nottingham whereas thymic hyperplasia and atrophy were a more frequent finding in Cuban patients. The majority of cases who improved post-thymectomy had thymic hyperplasia on histology in both Nottingham (46%) and Cuban (61%) patients. CONCLUSION: Selecting MG patients based on thymic enlargement alone or AchR antibody positivity may be inadequate and thymectomy should perhaps be considered in all patients with generalised myasthenia.
Adult↗
Nonsense mutations in mitochondrial DNA associated with myalgia and exercise intolerance.
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Codon, Nonsense↗
The outcome specificity of learned predictiveness effects: parallels between human causal learning and animal conditioning.
Two experiments examined the outcome specificity of a learned predictiveness effect in human causal learning. Experiment 1 indicated that prior experience of a cue-outcome relation modulates learning about that cue with respect to a different outcome from the same affective class but not with respect to an outcome from a different affective class. Experiment 2 ruled out an interpretation of this effect in terms of context specificity. These results indicate that learned predictiveness effects in human causal learning index an associability that is specific to a particular class of outcomes. Moreover, they mirror demonstrations of the reinforcer specificity of analogous effects in animal conditioning, supporting the suggestion that, under some circumstances, human causal learning and animal conditioning reflect the operation of common associative mechanisms.
Adolescent↗
Significance of Beevor's sign in facioscapulohumeral dystrophy and other neuromuscular diseases.
An atypical presentation of facioscapulohumeral dystrophy (FSH) is described, where the presence of a positive Beevor's sign led to genetic testing and subsequent probable diagnostic confirmation. This prompted evaluation of a further 68 patients for the presence of Beevor's sign. Among these, 19/20 patients with FSH had a positive Beevor's sign, compared with 2/28 with other muscle diseases, and 0/20 in a neurological control group. Beevor's sign should be considered as an additional criterion for the diagnosis of FSH.
Aged↗
Ataxia, peripheral neuropathy, and anti-gliadin antibody. Guilt by association?
Some authors contend that patients with idiopathic neurological disease who are also anti-gliadin antibody seropositive are gluten sensitive. However, anti-gliadin antibodies lack disease specificity being found in 10% of healthy blood donors. We report a study comparing anti-gliadin antibody with other food antibodies in patients with idiopathic ataxia (20), hereditary ataxias (seven), or idiopathic peripheral neuropathy (32). Patients were HLA typed. IgA anti-tissue transglutaminase antibodies (tTG) were measured. No case was positive for IgA anti-tTG making occult coeliac disease unlikely. HLA DQ2 and HLA DQ8 were found distributed equally across all patient groups and unrelated to gliadin antibody status. HLA DQ2 expressing, anti-gliadin antibody positive cases (so called "gluten ataxia") were rare in our clinics (four cases in 2 years from a population of 2 million). We conclude that coeliac disease per se is not commonly associated with either idiopathic ataxia or idiopathic peripheral neuropathy. Our study also casts doubt on the nosological status of "gluten ataxia" as a discreet disease entity. All food antibodies tested, particularly IgG, were a common finding in both ataxia and peripheral neuropathy groups. No particular food antibody was associated with any patient group. Food antibodies were equally common in hereditary ataxias. We conclude they are a non-specific finding.
Adult↗
The influence of stimulus properties on category construction.
It has been demonstrated that when people free classify stimuli presented simultaneously in an array, they have a preference to categorize by a single dimension. However, when people are encouraged to categorize items sequentially, they sort by "family resemblance," grouping by overall similarity. The present studies extended this research, producing 3 main findings. First, the sequential procedure introduced by G. Regehr and L. R. Brooks (1995) does not always produce a preference for family resemblance sorts. Second, sort strategy in a sequential procedure is sensitive to subtle variations in stimulus properties. Third, spatially separable stimuli evoked more family resemblance sons than stimuli of greater spatial integration. It is suggested that the family resemblance sorting observed is due to an analytic strategy.
Association Learning↗
Brief communication: the role of category structure in determining the effects of stimulus preexposure on categorization accuracy.
What are the effects of preexposure of stimuli on participants' subsequent ability to categorize them accurately? An experiment employing artificial, abstract, visual stimuli confirms that, for adult humans, the effect of preexposure is dependent upon category structure. Whether preexposure has beneficial or detrimental effects is shown to be dependent on the way category examples are generated from the category base patterns. The results are predicted by salience reduction accounts of perceptual learning but may be problematic for stimulus differentiation accounts.
Adolescent↗
Global-feature classification can be acquired more rapidly than local-feature classification in both humans and pigeons.
When humans process visual stimuli, global information often takes precedence over local information. In contrast, some recent studies have pointed to a local precedence effect in both pigeons and nonhuman primates. In the experiment reported here, we compared the speed of acquisition of two different categorizations of the same four geometric figures. One categorization was on the basis of a local feature, the other on the basis of a readily apparent global feature. For both humans and pigeons, the global-feature categorization was acquired more rapidly. This result reinforces the conclusion that local information does not always take precedence over global information in nonhuman animals.
Adult↗
Urgent 2-week referrals for CNS/brain tumours: a retrospective audit.
OBJECTIVE: To assess the effectiveness of the 2-week referral system for CNS/brain tumours and to contrast this with the number of patients with neurological cancers identified independently of this system. METHOD: Retrospective casenote review of patients referred to emergency neurology clinics pre-implementation of the 2-week referral system. Retrospective review of GP referral letters via this system and comparison to Department of Health referral guidelines. Review of corresponding casenotes to determine the actual neurological diagnosis. Identification of patients with CNS/brain tumours diagnosed independently of this system from a local CNS cancer register. RESULTS: Over a 3-month period pre-implementation of the referral system, of 12 patients referred as emergencies, none had CNS/brain cancer. Forty-three patients were referred via this system over a 9-month period to neurology departments of a teaching hospital and a district general hospital. Thirty per cent of the referrals did not follow the Department of Health guidelines. Only 9% actually had CNS tumours (two astrocytomas, two cerebral metastases). The remainder were diagnosed with chronic daily headache (10), epilepsy (5), migraine (3), demyelination (2), essential tremor (2), other (17). During this period at least 69 neurological cancers were identified independently of the 2-week system. CONCLUSION: These guidelines may increase diagnostic precision if adhered to rigidly. Inappropriate referrals have extended already lengthy outpatient waiting times in other specialities. We suggest early re-consideration of these guidelines and further study for earlier identification of CNS cancer.
Central Nervous System Neoplasms↗
Dermatitis herpetiformis and neurological dysfunction.
Dermatitis herpetiformis and coeliac disease are gluten sensitive diseases, which have common immunopathological and genetic mechanisms. Neuropsychiatric complications have been reported in up to 26% of patients with coeliac disease. This is probably an overestimate, because of the chance associations with some common neurological conditions such as epilepsy. The pathogenesis is speculative but it has been postulated that gluten is neurotoxic possibly via immune mechanisms. The frequency of neurological dysfunction in patients with dermatitis herpetiformis has not been characterised. Patients with dermatitis herpetiformis might be expected to be particularly susceptible to neuronal damage as some continue to consume gluten when their dermatological symptoms are controlled by dapsone. Thirty five patients were recruited with dermatitis herpetiformis from dermatology clinics at St Mary's Hospital, London and Queen's Medical Centre, Nottingham and investigated for evidence of neurological abnormality. All patients underwent a full neurological examination and were asked about their neurological and general medical history by means of a structured questionnaire. Serum samples were taken and screened for the presence of anti-neuronal antibodies (anti-Hu and Yo) as well as anti-gliadin (IgA and G) anti-endomysial (IgA), and anti-tissue transglutaminase (IgA) antibodies. Neurophysiological tests were carried out where appropriate. Only two patients were identified with unexplained neurological abnormalities (one essential tremor, and one chorea). Two other patients had a history of migraine. The patient with chorea also had borderline/equivocally positive anti-Hu antibodies by immunofluorescence assay. All other samples were negative for anti-neuronal antibodies. Fifteen patients were positive for anti-gliadin antibodies (IgA and/or IgG), four for anti-endomysial antibodies (monkey oesophagus or umbilical cord), and six for anti-tissue transglutaminase antibodies. The presence of these antibodies did not correlate with the presence of neurological abnormalities. No cases of "gluten ataxia" were identified. In conclusion, there was no convincing evidence for immune mediated neurological damage in this pilot study of dermatitis herpetiformis.
Adolescent↗
Superficial siderosis associated with anterior horn cell dysfunction.
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Cerebellar Ataxia↗