Biomedical subjects

H E Moss

Publications and source records attributed to H E Moss.

At least 19 recordsLinked to original sources

PubMed2001

The neural representation of nouns and verbs: PET studies.

Neuropsychological studies of patients with selective deficits for nouns or verbs have been taken as evidence for the neural specialization of different word classes. Noun deficits are associated with lesions in anterior temporal regions while verb deficits arise from left inferior frontal lesions. However, neuroimaging studies do not unequivocally support this account, with only some studies supporting claims for regional specialization. We carried out two PET studies to determine whether there is any regional specialization for the processing of nouns and verbs. One study used the lexical decision task and the other used a more semantically demanding task, i.e. semantic categorization. We found robust activation of a semantic network extending from left inferior frontal cortex into the inferior temporal lobe, but no differences as a function of word class. We interpret these data within the framework of cognitive accounts in which conceptual knowledge is represented within a non-differentiated distributed system.

Adolescent↗

PubMed2000

Conceptual structure and the structure of concepts: a distributed account of category-specific deficits.

We present a new account of the fine-grained structure of semantic categories derived from neuropsychological, behavioral, and developmental data. The account places theoretical emphasis on the functions of the referents of concepts. We claim (i) that the distinctiveness of functional features correlated with perceptual features varies across semantic domains; and (ii) that category structure emerges from the complex interaction of these variables. The representational assumptions that follow from these claims make strong predictions about what types of semantic information are preserved in patients showing category-specific deficits following brain damage. These claims are illustrated with a connectionist simulation which, when damaged, shows patterns of preservation of distinctive and shared functional and perceptual information which varies across semantic domains. The data model both dissociations between knowledge for artifacts and for living things and recent neuropsychological evidence concerning the robustness of functional information in the representation of concepts.

Brain↗

PubMed2000

Susceptibility-induced loss of signal: comparing PET and fMRI on a semantic task.

Functional magnetic resonance imaging (fMRI) has become a popular tool for investigations into the neural correlates of cognitive activity. One limitation of fMRI, however, is that it has difficulty imaging regions near tissue interfaces due to distortions from macroscopic susceptibility effects which become more severe at higher magnetic field strengths. This difficulty can be particularly problematic for language tasks that engage regions of the temporal lobes near the air-filled sinuses. This paper investigates susceptibility-induced signal loss in the temporal lobes and proposes that by defining a priori regions of interest and using the small-volume statistical correction of K. J. Worsley, S. Marrett, P. Neelin, A. C. Vandal, K. J. Friston, and A. C. Evans (1996, Hum. Brain Mapp. 4: 58-83), activations in these areas can sometimes be detected by increasing the statistical power of the analysis. We conducted two experiments, one with PET and the other with fMRI, using almost identical semantic categorization paradigms and comparable methods of analysis. There were areas of overlap as well as differences between the PET and fMRI results. One anticipated difference was a lack of activation in two regions in the temporal lobe on initial analyses in the fMRI data set. With a specific region of interest, however, activation in one of the regions was detected. These experiments demonstrate three points: first, even for almost identical cognitive tasks such as those in this study, PET and fMRI may not produce identical results; second, differences between the two methods due to macroscopic susceptibility artifacts in fMRI can be overcome with appropriate statistical corrections, but only partially; and third, new data acquisition paradigms are necessary to fully deal with susceptibility-induced signal loss if the sensitivity of the fMRI experiment to temporal lobe activations is to be enhanced.

Adult↗

PubMed2000

A progressive category-specific semantic deficit for non-living things.

We report a longitudinal study of a patient, ES, with a progressive degenerative disorder resulting from generalised cerebral atrophy. Across a range of tasks, ES showed a greater difficulty in recognising and naming artifacts than living things. This deficit for artifacts emerged over time, as she became more severely impaired. In one task, picture naming, there was a crossover from an initial deficit for living things to the later artifact deficit. All materials were carefully controlled to rule out potential confounding factors such as concept familiarity or age of acquisition. There was no evidence that ES's deficit for artifacts was associated with a greater loss of functional than visual information. The pattern of results are consistent with a recently proposed distributed connectionist model, in which a deficit for artifact concepts can emerge as the result of severe, general damage to semantic memory.

Aged↗

PubMed2000

The interaction of meaning and sound in spoken word recognition.

Models of spoken word recognition vary in the ways in which they capture the relationship between speech input and meaning. Modular accounts prohibit a word's meaning from affecting the computation of its form-based representation, whereas interactive models allow activation at the semantic level to affect phonological processing. We tested these competing hypotheses by manipulating word familiarity and imageability, using lexical decision and repetition tasks. Responses to high-imageability words were significantly faster than those to low-imageability words. Repetition latencies were also analyzed as a function of cohort variables, revealing a significant imageability effect only for words that were members of large cohorts, suggesting that when the mapping from phonology to semantics is difficult, semantic information can help the discrimination process. Thus, these data support interactive models of spoken word recognition.

Adult↗

PubMed1998

Going, going, gone...? Implicit and explicit test of conceptual knowledge in a longitudinal study of semantic dementia.

Patients suffering from semantic dementia provide important constraints on theories of the structure and organisation of semantic memory. In this article we report one such patient, AM, whose progressive deterioration of semantics enables us to address the much-debated issue of whether conceptual structure is hierarchically organised. The hierarchical account predicts that brain damage should impair lower levels of the hierarchy (property information) before affecting higher level (category) information (Warrington and Shallice, Q. J. Exp. Psychol. 1975, 27, 635-657). We evaluate this prediction by repeated testing of AM in two studies--a semantic priming task and a verification task--over an 18 month period, contrasting the progressive deterioration of properties (functional and perceptual) and category relations (category co-ordinates and category labels). Properties were preserved longer than category information, arguing against a hierarchical account of semantic memory. In addition, functional properties were most robust to brain damage, supporting our claim that functional information plays a special role in semantic representations (Durrant-Peatfield et al., Proc. 19th Ann. Conf. of the Cognitive Science Society. Erlbaum, Mahwah, NJ, 1997. pp. 193-198. Tyler et al., Cognitive Neuropsychol. 1997, 14, 511-545).

Anomia↗

PubMed1998

Category-specific semantic deficits: the role of familiarity and property type reexamined.

Category-specific deficits for living things have been explained variously as an artifact due to differences in the familiarity of concepts in different categories (E. Funnell & J. Sheridan, 1992) or as the result of an underlying impairment to sensory knowledge (E. K. Warrington & T. Shallice, 1984). Efforts to test these hypotheses empirically have been hindered by the shortcomings of currently available stimulus materials. A new set of stimuli are described that the authors developed to overcome the limitations of existing sets. The set consists of color photographs, matched across categories for familiarity and visual complexity. This set was used to test the semantic knowledge of a classic patient, J.B.R. (E. K. Warrington & T. Shallice, 1984). The results suggest that J.B.R.'s deficit for living things cannot be explained in terms of familiarity effects and that the most severely affected categories are those whose identification is most dependent on sensory information.

Adult↗

PubMed1997

The gradual deterioration of syntax and semantics in a patient with progressive aphasia.

FM is a progressive aphasic patient whose language comprehension we studied over a 4-year period. We developed a variety of implicit and explicit tasks to chart progressive changes in the representation of linguistic knowledge (in particular, syntax and semantics) and the automatic and controlled processes which operate on that knowledge. The representation of FM's semantic knowledge remained essentially intact over the years, but she became increasingly impaired at combining the meanings of words. She also showed progressive impairments in the processes of syntactic combination. Thus, FM's disease resulted in a progressive inability to engage in those combinatorial processes necessary for the normal comprehension of a spoken utterance. This is not a selective deficit in the traditional sense of the term, since aspects of both syntax and semantics are implicated; but it is selective in the sense that other aspects of language comprehension remain intact.

Aphasia↗

PubMed1996

Perceptual distance and competition in lexical access.

Two experiments use rhyme priming techniques to explore the decision space for lexical access. The 1st experiment, using intramodal (auditory-auditory) priming, covaried the phonological distance of a spoken rhyme prime (e.g., pomato) from its source word (e.g., tomato) with the presence or absence of close lexical competitors. The results showed strong effects of phonological distance and no significant effects of competitor environment. The 2nd experiment, using ambiguous rhyme primes in a cross-modal (auditory-visual) priming task, showed that phonetically ambiguous primes could fully match their source words, but only in the appropriate lexical environment. The results support a view of lexical access in which the listener's perceptual experience is based on strict requirements for a bottom-up match with the speech input, and in which competitor environment does not directly modulate the on-line goodness-of-fit computation.

Decision Making↗

PubMed1995

Automatic access of lexical information in Broca's aphasics: against the automaticity hypothesis.

A number of recent articles have claimed that the language comprehension impairments of so-called agrammatic patients can be characterized as being due to problems with the automatic access of semantic and/or syntactic information from the lexicon. We describe three experiments, all using tasks which probe the immediate and automatic access of lexical information and compare the performance of agrammatic patients with that of an anomic and a fluent patient. We find no evidence in support of the automaticity hypothesis as an explanatory account of the language deficits of agrammatic aphasics. Further, we argue that current research does not lend itself to a single-explanation account of agrammatic comprehension problems, and that in-depth analyses of individual patients are more likely to be fruitful in terms of understanding the nature of comprehension deficits.

Aged↗

PubMed1993

Access to word meanings during spoken language comprehension: effects of sentential semantic context.

In 3 cross-modal priming experiments, we investigated whether access to a word's meaning is affected by the semantic context in which it is heard or is exhaustive and context-independent. We probed access of nonassociated semantic properties and normatively associated words before and after prime offset. Whereas associated targets were primed context-independently, access to semantic property targets was affected by the sentential context. Semantic property targets showed greater priming in a sentence biasing to a specific semantic property than in a neutral condition, even when this bias made the target property irrelevant rather than relevant. These results cannot be accounted for by current exhaustive access or context-dependency theories of lexical access.

Adolescent↗

PubMed1992

Loss of sensory neuropeptides in the obstructed human bladder.

This is the first investigation of alterations in the innervation of the obstructed human bladder by nerves containing neuropeptides. The patient groups studied were those with stable detrusor function, those with unstable detrusor function, and those presenting with acute retention of urine. Specimens of bladder tissue were taken from the lateral wall of the bladder below the peritoneal reflection. A total of 23 patients was studied (control, n = 4; acute retention, n = 5; stable obstruction, n = 5; unstable obstruction, n = 9). Substance P, calcitonin gene-related peptide and vasoactive intestinal polypeptide levels in the bladder were quantified by immunoassay. The density of innervation of the bladder detrusor by nerves containing these neurotransmitters and by those containing neuropeptide Y and somatostatin was assessed using both semiquantitative and quantitative immunohistochemical techniques. A reduction in the density of innervation by vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and somatostatin-immunoreactive but not neuropeptide Y-immunoreactive nerve fibres was shown in the obstructed bladder. These findings, combined with the significant reduction in substance P content of the obstructed bladder and in particular of the acute retention bladder, indicate that there may be an afferent nerve dysfunction resulting from prostatic bladder outflow obstruction.

Aged↗

PubMed1991

Patients with lower motor spinal cord lesion: a decrease of vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P, but not neuropeptide Y and somatostatin-immunoreactive nerves in the detrusor muscle of the bladder.

Specimens of the detrusor muscle of the bladder from four patients with lower motor neurone lesion and three patients with carcinoma of the bladder used as "controls", were studied immunohistochemically for vasoactive intestinal polypeptide, neuropeptide Y, calcitonin-gene related peptide, substance P and somatostatin. The greatest density of nerves in the bladder from "control" patients contained neuropeptide Y, followed in a decreasing order by vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and somatostatin. Neuropeptide Y- and vasoactive intestinal polypeptide-immunoreactive nerves were found throughout the smooth muscle and the base of the mucosa, while calcitonin gene-related peptide-, substance P- and somatostatin-immunoreactive nerves were found predominantly in nerve bundles with a few single fibres at the base of the mucosa. Vasoactive intestinal polypeptide-, neuropeptide Y- and calcitonin gene-related peptide-immunoreactive nerves were also located around blood vessels. In patients with lower motor neurone lesion, there was a decrease in the density of vasoactive intestinal polypeptide-, calcitonin gene-related peptide- and substance P-immunoreactive nerves, but there was little change in neuropeptide Y- or somatostatin-immunoreactive nerves. Urinary retention, bladder areflexia and deficient sensation may be directly linked to neuropeptide neuropathy in patients with lower motor neurone lesion.

Adult↗

PubMed1990

Neuropeptide immunoreactivity and choline acetyltransferase activity in the mouse urinary bladder following inoculation with Semliki Forest Virus.

The effect of Semliki Forest Virus, a known central demyelinating agent and a proposed model for multiple sclerosis, on the innervation of the mouse urinary bladder has been examined 3, 6, 9 and 12 weeks after inoculation. Three weeks after Semliki Forest Virus inoculation, vasoactive intestinal polypeptide content of the bladder was reduced and the density of vasoactive intestinal polypeptide-immunoreactive nerves was decreased in the smooth muscle, but not in the mucosa. Choline acetyltransferase activity and neuropeptide Y and substance P content was normal, as was the pattern of innervation by acetylcholinesterase-containing and neuropeptide Y- and substance P-immunoreactive nerve fibres. Six weeks after Semliki Forest Virus inoculation, the choline acetyltransferase activity was significantly reduced. Between 6 and 9 weeks the level of vasoactive intestinal polypeptide in the bladder of Semliki Forest Virus-infected mice significantly increased, so that at 9 weeks it was higher than the control value. However, by 12 weeks both choline acetyltransferase activity and vasoactive intestinal polypeptide content were normal. At this time, the substantial age-related increase in substance P content of the bladder was more pronounced in the Semliki Forest Virus-treated animals. Thus there are transitory changes in the innervation of the mouse bladder by vasoactive intestinal polypeptide-containing and cholinergic nerve fibres after exposure to a central demyelinating agent which may reflect changes in bladder dysfunction seen in multiple sclerosis patients.

Animals↗

PubMed1990

The effects of granisetron, ICS 205-930 and ondansetron on the visceral pain reflex induced by duodenal distension.

1. Distension of the duodenum in anaesthetized rats, by rapid application of intraluminal pressures (10-75 cmH2O), evoked falls in diastolic blood pressure and intragastric pressure. 2. The distension-induced responses were blocked by pretreatment with morphine (20 mg kg-1, s.c.), an action reversible by injection of naloxone (5 mg kg-1, i.v.). 3. Bilateral cervical vagotomy reduced the distension-evoked fall in intragastric pressure but had no effect on the corresponding fall in blood pressure. 4. Granisetron or ICS 205-930 (1-1000 micrograms kg-1, i.v.) had no effects on duodenal intraluminal pressure, but reduced the responses to distension with a bell-shaped dose-response relationship. Ondansetron (1-1000 micrograms kg-1, i.v.) did not reduce the reflex responses. 5. These results show that the 5-HT3 receptor antagonists used exerted different effects on the reflex responses to duodenal distension.

Animals↗

PubMed1989

Abnormalities of responses to autonomic stimulation in the mouse urinary bladder associated with Semliki Forest virus-induced demyelination.

The responses to autonomic stimulation of the urinary bladder were studied in mice infected with Semliki Forest Virus, which has been proposed as an animal model for multiple sclerosis. Mice infected with Semliki Forest Virus showed a decreased body weight when compared with control animals, although their bladders were proportionately heavier. The pharmacological results indicated a selective change in purinergic transmission in the bladders of mice infected with Semliki Forest Virus, while cholinergic transmission remained unchanged. This was demonstrated by a significant increase in the contractile response to beta,gamma-methylene ATP accompanied by an increase in the proportion of the nerve-mediated response blocked by alpha,beta-methylene ATP. In contrast, the contractile response to acetylcholine and the atropine-sensitive component of the neurogenic response were not significantly different between the two groups of animals. Active length-tension curves were also unchanged in the mice infected with Semliki Forest Virus when compared with controls. The results are discussed in relation to those obtained from models of urinary bladder dysfunction associated with hypertrophy; whether the alteration of atropine-resistant (purinergic) function reported here is a general secondary feature of this type of bladder dysfunction or a change specific to the Semliki Forest Virus model of multiple sclerosis is not resolved. This study provides evidence that peripheral changes as well as central nervous system demyelination occur in the Semliki Forest Virus-infected mouse.

Acetylcholine↗

PubMed1987

The seminal vesicle in eight and 16 week streptozotocin-induced diabetic rats: adrenergic, cholinergic and peptidergic innervation.

The autonomic innervation of the seminal vesicle from 8 and 16 week streptozotocin-induced diabetic rats and age-matched controls was studied by pharmacological, histochemical and immunohistochemical methods. Contractions in response to electrical field stimulation, which were abolished using prazosin (2 microM) or tetrodotoxin (one to 1.6 microM), and to noradrenaline were significantly increased in both eight and 16 week diabetic animals. The contractile response to acetylcholine was significantly increased in the 16 week diabetic rats only, when compared with controls. Although these responses were significantly increased, no difference was found in ED50 and EF50 values between control and diabetic rats. Vasoactive intestinal polypeptide (0.3 microM) had no effect on resting tension or nerve-mediated responses. In seminal vesicles from control animals, both vasoactive intestinal polypeptide-immunoreactive and acetylcholinesterase-containing nerves were localised around the folds of the columnar epithelium of secretory cells, in contrast to neuropeptide Y-immunoreactive and catecholamine-containing nerves which were found in the smooth muscle layers. In seminal vesicles from both eight and 16 week diabetic animals no difference was seen in distribution or density of acetylcholinesterase-containing nerves; there was an increase in density and fluorescence intensity of vasoactive intestinal polypeptide- and neuropeptide Y-immunoreactive nerves and a decrease in catecholamine-containing nerves compared with controls. The results are discussed in relation to autonomic neuropathy in diabetes.

Acetylcholine↗

PubMed1987

A study of bladder dysfunction during streptozotocin-induced diabetes in the rat using an in vitro whole bladder preparation.

An in vitro whole bladder preparation has been used in this study to examine the effects of eight and 16 week streptozotocin-induced diabetes on detrusor function in the rat. In eight week animals cystometric recordings showed an increase in bladder capacity associated with a decrease in intraluminal pressure. Concentration-response curves revealed a significant increase in sensitivity of the detrusor to beta,gamma-methylene ATP, a potent purinergic agonist, and a trend towards subsensitivity to acetylcholine in bladders from eight week diabetic rats when compared to controls. The atropine-resistant (purinergic) response to neurogenic stimulation was increased over the frequency range two to 30 Hz and was significantly greater at two Hz. In 16 week animals the cystometrogram had partially recovered; capacity had decreased compared to eight week diabetics and intraluminal pressure was within the normal range. Concentration-response curves revealed no significant difference in the response to acetylcholine and a greatly reduced response to beta,gamma-methylene ATP in the 16 week diabetics compared to controls. The atropine-resistant neurogenic response was slightly, but not significantly reduced. The results are discussed in relation to clinical urodynamic measurements of human detrusor dysfunction in diabetes.

Acetylcholine↗