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At least 433 records · Page 24Linked to original sources
PubMed1988

Principles of odor coding and a neural network for odor discrimination.

A concept of olfactory coding is proposed. It describes the stimulus responses of all receptor cells by the use of vector spaces. The morphological convergence pattern between receptor cells and glomeruli is given in the same vector space as the receptor cell activities. The overall input of a glomerulus follows as the scalar product of the receptor cell activity vector and the vector of the glomerulus' convergence pattern. The proposed coding concept shows how the network of the olfactory bulb succeeds in discriminating odors with high selectivity. It is concluded that sets of mitral cells coding similar odors work very much in the way of mutually inhibited matched filters. This solves one main problem both in olfaction as well as real-time odor detection by an artificial nose, i.e., how the fairly low degree of selectivity of receptor cells or sensors is overcome by the neural network following the receptor stage. The formal description of olfactory coding suggests that quality perception which is invariant under concentration shifts is accomplished by an associative memory in the olfactory bulb.

Animals↗
PubMedDate not supplied

Eating disorders with and without substance use disorders: a comparative study of inpatients.

We assessed the co-occurrence of DSM-III-R axis I and II disorders and self-reported psychologic distress in inpatients with eating disorders with and without substance use disorders (ED-SUD and ED groups, respectively) and in a matched comparison sample with substance use disorders but no eating disorder (SUD group). The three groups showed similar distributions of axis I disorders but differed in the distribution of axis II disorders. Cluster B personality disorders were diagnosed more frequently in SUD and ED-SUD groups than in the ED group. In contrast, cluster C personality disorders were diagnosed more frequently in the ED group than in SUD and ED-SUD groups. The SUD group reported greater psychologic distress than ED and ED-SUD groups. Possible implications of the observed group differences for psychologic models of why these disorders may be associated are considered.

Adolescent↗
PubMedDate not supplied

Underconstrained perception: a theoretical approach to the nature and function of verbal hallucinations.

We do not see the world as it is. Perception forms a subjective image of the world in a language that has proven to be adaptive to our interaction with the external world. Perception is mainly determined by current needs of the organism and goals of behavior. Sensory processing itself does not culminate in perception and is not essential for perception, since perception derives from representations of internal symbols and their features. The current stimulation of sensory organs does, however, constrain our perception. Perception might be less constrained by the external world in cases of (1) increased attention, (2) decreased sensory stimulation, or (3) facilitated formation of cortical associations between representations of expectations and internal symbols. Hallucinations are perceptions that are underconstrained by external sensory stimulation. Verbal hallucinations that allow the patient to infer about his self-image might constitute the core psychopathology in a subset of schizophrenia. Commenting and discussing voices might be perceived under the pressure of increased attention to environmental factors that relate to the patient's social fears and wishes. Secondarily, delusions about the possession of thoughts and disorders of self-experience may develop.

Association↗
PubMedDate not supplied

The cycloid type and its differentiation from core schizophrenia: a phenomenological approach.

The heterogeneity within schizophrenia or the group of schizophrenias remains a vexing and limiting problem. An alternative to the "classic" explanatory construct of a schizophrenic unitary psychosis is the current concept of a positive/negative dichotomy with or without mixed type. However, the validation by findings from brain imaging, specificity, and prognostic validity of these multiple-entity approaches are still uncertain. Psychopathology is challenged to identify discrete types as homogenous as possible, providing closer relationship to distinct disease processes. Such types are to be defined by one or more axial syndromes, syndromes in an essential, not correlative, sense. One of these types is embraced by the term cycloid psychosis, implying a good prognosis. Using an integrative phenomenological methodology, the present study is able to show the specific quality of phenomena occurring in this type to pinpoint their "inner" relationships and to demonstrate cycloid syndromes as axial syndromes in the phenomenological sense. Thus, it is shown that positive symptoms in the cycloid type are different from those in core schizophrenia. In addition to the quality and inner coherence of the constituent elements, the absence of structural deformations of (1) emotional expression and affect, (2) thought, and (3) movement impulses and sequences is the decisive specificity feature that allows differentiation of the cycloid type from poor-prognosis core schizophrenia. These syndromes of structural deformations are the axial syndromes of core schizophrenia, occurring with or without "productive" (positive) phenomena. Its conceptualization makes a contribution to the actual negative-symptom discussion shifting the perspective from a low specific level (e.g., abulia) to phenomena of higher specificity. On the basis of a precise definition of cycloid axial syndromes, previous operationalization suggestions are reviewed and evaluated, and an alternative approach is outlined. Finally, it is hypothesized that the cycloid type may be a primary neurotransmitter disease, while core schizophrenia seems closer to the pathophysiological mechanisms described in Stevens' theory.

Affective Symptoms↗
PubMed2003

New graduate perception of clinical competence: testing a causal model.

The purpose of this study was to test relationships among variables hypothesized to affect new graduate perceptions of clinical competence. The proposed model was developed based on several theories in sociology, education and nursing. Seven variables were selected for their potential contributions to graduates' perceptions of clinical competence. The sample included 468 new graduates from six baccalaureate nursing programs in Thailand. Path analysis indicated that student effort, perception of clinical learning environment (CLE) and program grade point average had direct effects on perception of clinical competence whereas hardiness had an indirect effect on the outcome variables through its impacts on student effort, perception of CLE and perception of student-faculty relationship. The model explained 8-12% of variance in the subscales of clinical competence.

Adult↗
PubMed1999

Impulsive and premeditated aggression: a factor analysis of self-reported acts.

Although aggression research in general has been hampered by a lack of objective measurements of aggressive acts, two types of aggressive acts, impulsive vs. premeditated, have been studied extensively in recent years. These two types of aggression have been primarily measured by structured or semi-structured interviews. The current study was designed to assess the construct validity of these two types of aggression using a self-report questionnaire which included items gleaned from the content of interviews used in past studies. For this study, 216 college students assessed their own aggressive acts rather than answering general questions about aggression. The students were not significantly different from normative sample groups on self-report measures of impulsiveness, aggression, and anger/hostility. A PCA factor analysis with a promax rotation of the items on the self-report questionnaire identified four factors: impulsive aggression; mood on the day the act occurred; premeditated aggression; and agitation. Thus, impulsive and premeditated aggression are independent constructs which exist in varying degrees among these 'normal' persons in a non-clinical sample. Impulsive aggression was characterized in part by feelings of remorse following the acts and by thought confusion. Premeditated aggression was related to social gain and dominance.

Adult↗
PubMed2002

Regression modeling of rodent locomotion data.

We present the case for a model-based approach to the statistical analysis of rodent locomotion data for which previous research has established that the time course of behavioral change follows a specified parametric form. Inadequacies of statistical methods commonly applied to such data are described. Regression models can reveal time-dependent aspects of response that might escape more elementary analyses, as we illustrate with experimental data regarding the locomotion response to amphetamine. Inter-individual variation in response profiles is incorporated through the use of random coefficients (i.e. mixed effects models). These models provide an effective means of quantifying the extent of individual differences in behavioral response to stimulant drugs not attributable to treatment. The need to adjust for multiple comparisons when searching for regions of significant difference is discussed. We present specific models that we have found useful for characterizing responses to low doses of amphetamine or cocaine (the log-logistic random effects model) and higher or repetitive doses of amphetamine or cocaine (the polynomial random effects model). Code for performing these analyses with standard statistical software is provided.

Algorithms↗
PubMed2002

A lifetime portfolio of risky and risk-free sexual behaviour and the prevalence of AIDS.

A lifetime portfolio of risky and risk-free sexual activities is conceptually constructed in this paper. People's time allocation between risky and risk-free sexual activities affects, and is affected by, the prevalence of AIDS. A small satisfaction differential between risky and risk-free sex can lead to a significant prevalence of AIDS. Numerical simulations suggest that the reduction in the prevalence of AIDS generated by a 1% improvement in the sensual quality of freely distributed condoms can be 0.855% when the initial satisfaction differential between risky and risk-free sex is 50% or 0.464% when the initial satisfaction differential is 100%.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Depression with anosognosia following a left subcortical stroke.

Controversy exists about whether depression following stroke represents a biologically mediated change or a psychological reaction to the deficits. We present a patient with an acute isolated personality change and depression following a lacunar infarct of the left internal capsule, who was unaware of his affective change. His anosognosia for the depression, which was abrupt and not accompanied by cognitive impairments, suggests that post stroke depression, at least in this case, is better explained by a biological than a psychological model.

Aged↗
PubMed1999

Perception of future health risks in mid-aged women: estimates with and without behavioural changes and hormone replacement therapy.

Cardiovascular disease (CVD) and cancer are major causes of death for women, and osteoporosis negatively impacts upon the health and quality of life of many older women. There is evidence that risk of developing these diseases is partially determined by lifestyle factors, such as physical activity, diet and smoking, as well as being influenced by hormonal changes during the menopause. Participation in preventive strategies will be influenced by women's perceptions of the relative risks of developing these diseases, and beliefs about the effectiveness of the particular strategy. In this study, 103 mid-aged women were asked about their health and health behaviours and to estimate: (1) their future likelihood of developing CVD, osteoporosis and breast cancer; and (2) their future likelihood of developing diseases (a) if they improved their health behaviours, and (b) if they used hormone replacement therapy (HRT) for 5 years. Women believed that improving their health behaviours (diet, physical activity, smoking) would reduce their risks of CVD and osteoporosis, although modest reductions were expected. Breast cancer was not seen as significantly modifiable by lifestyle changes. They believed that taking HRT would significantly reduce their risk of osteoporosis, increase their risk of breast cancer, but not alter their risk of developing CVD. The findings are considered in the context of health psychology models of behaviour change and have implications for health promotion for mid-aged women.

Attitude to Health↗
PubMed2001

Social effects in simple computer model of aging.

A simple evolutionary model for biological aging is modified such that it requires a minimum population for survival, like in human society. This social effect leads to a transition between extinction and survival of the species.

Aging↗
PubMedDate not supplied

Anxiety sensitivity, state and trait anxiety, and perception of change in sympathetic nervous system arousal.

The psychological models of panic disorder predict that persons with this condition may demonstrate enhanced acuity for somatic stimuli, but research to date has produced conflicting results. Most studies have investigated acuity for cardiovascular responses such as heart rate. which may represent an inadequate test of this hypothesis because they would be unlikely to detect persons who respond maximally to panic through other physiological systems. The present study investigated the detection of changes in pulse transit time (PTT), as a reliable and omnibus measure of sympathetic nervous system activity, with 36 healthy volunteers. We found that accurate perception of changes in PTT was consistently related to higher levels of trait anxiety and anxiety sensitivity, both of which are risk factors for the development of anxiety disorders in general. and panic disorder in particular. served.

Adult↗
PubMed1999

A rating scale for psychotic symptoms (RSPS) part I: theoretical principles and subscale 1: perception symptoms (illusions and hallucinations).

The authors present a new rating scale for the psychotic symptoms of schizophrenia and related psychoses. The scale links specific symptoms of psychopathology to dysfunction and overactivity of dopaminergic mechanisms underlying the processes of reward and selective attention. The Rating Scale for Psychotic Symptoms (RSPS) is a 44-item rating instrument with a seven-point severity scale for each item. Psychotic symptoms are classified into three groups: Pathological amplification of mental images (perception symptoms) (subscale 1), Distraction symptoms (including catatonia and passivity experiences) (subscale 2), and Delusions (subscale 3). A dimensional, rather than a categorical, conceptualization of psychosis is assumed. Rating is accomplished through a manual and a semi-structured interview (SSCI-RSPS). In this first of two papers, general issues about the construction of the scale and the derivation of symptom groups are discussed. Dopamine-mediated modification of cortico-striatal synapses is seen as being of critical importance in all three groups of symptoms. In this first paper, we present subscale I (perception symptoms), which includes both amplified perceptual images (illusions) and hallucinations. A total of seven illusions and 11 hallucinations are rated as individual items.

Behavioral Symptoms↗
PubMed1989

Dynamic behavioural models and contraceptive choice.

Dynamic models of contraceptive use fill a theoretical gap. They bring behavioural content to the mathematically elegant Markov models of family building. They meet the criterion that Bulatao (1989) advances that method use, discontinuation and switching be considered not in isolation, but with reference to individual reproductive goals. Dynamic models help to link the literature on method choice with the literature on method effectiveness. These theoretical advantages are, at present, counter-balanced by empirical limitations. This article explores the theoretical and empirical underpinnings of dynamic contraceptive choice models.

Abortion, Legal↗
PubMed1997

Diagnostic boundaries, reasoning and depressive disorder, I. Development of a probabilistic morbidity model for public health psychiatry.

BACKGROUND: In recent years diagnostic practice in psychiatry has become increasingly structured in an attempt to standardize definitions of disorders and improve reliability. At the same time there has been an increasing recognition of the need to take account of uncertainty in the process of diagnostic decision making. For the most part, diagnosis is still represented by a binary outcome while this is known to entail a substantial loss of information. Many diagnostic schemes involve, in part, taking thresholds on the numbers of symptoms required from symptom lists. METHODS: A model is proposed here, using ideas derived from latent class analysis to permit generalization from these schemes through moving from a binary to a probabilistic measure of psychiatric case status and replacing thresholds with smoothed transitions. RESULTS: An outcome measure is produced where disorder status is expressed in terms of probabilities without changing the meaning of the original measure. Prevalence estimates (using ICD-10 Depressive Episode criteria) are more stable and can be given with increased precision. CONCLUSIONS: Disorder status when expressed in this way retains more diagnostic information and provides a useful extension to traditional binary analyses when looking at prevalence and risk factor estimation.

Bayes Theorem↗
PubMed2000

Is auditory imagery defective in patients with auditory hallucinations?

BACKGROUND: A variant of the 'inner speech' theory of auditory verbal hallucinations in schizophrenia suggests that there is an abnormality of the relationship between the 'inner voice' and 'inner ear', such that hallucinators are unable to distinguish inner 'imagined' speech from real external speech, and so misrecognize inner speech as alien. METHODS: Five experiments were carried out comparing 12 schizophrenic patients who were highly prone to hallucinate, with seven patients who were not, on a series of auditory imagery tasks that are differentially dependent on inner voice/inner ear partnership for successful performance: parsing meaningful letter/number strings; the verbal transformation effect; phoneme judgements; pitch judgements, and homophony and rhyme judgements. RESULTS: Contrary to our hypothesis, there was no evidence that the group with the propensity to hallucinate were impaired on tasks requiring normal inner ear/inner voice partnership. CONCLUSIONS: Together with previous work indicating no impairment of the phonological loop in patients who hallucinate, these results suggest that inner speech and auditory verbal hallucinations are not connected in a simplistic or direct way. Indeed, a reappraisal of psychological models of hallucinations in general may be warranted.

Adolescent↗
PubMedDate not supplied

The use of patient-level outcomes to inform treatment.

OBJECTIVE: The assessment of outcome for any purpose is not undertaken routinely in European mental health services. This paper discusses the merits of using outcome data to inform the planning of mental health care for individual patients, and provides practical advice to support the implementation of this new approach to working. METHOD: The use of outcomes in North America and Europe is briefly reviewed. A conceptual basis is proposed for routine outcome assessment--the ongoing measurement and use of outcome data to inform decisions about whether to continue, change or curtail treatment. A cognitive psychology model is developed which indicates that the routine use of outcomes will improve mental health care. Perceived problems with routine outcome assessment are discussed, and principles for implementation are identified. RESULTS: Outcomes are used mainly for generating local-level (rather than patient-level) data in North America, and rarely used in Europe. The use of outcome data routinely may facilitate reflective clinical practice, a model of decision-making which leads to a higher quality of clinical care than automated problem-solving. One issue relates to the use of standardised assessments designed for research purposes in clinical settings, and this is being addressed through the development of a new generation of outcome measures which are explicitly designed for clinical use. However, most clinicians remain unconvinced of the benefits of routine outcome assessment, and relevant research is currently underway across Europe which will address this concern. Scientific principles to maximise quality and pragmatic principles to maximise the chances of successful implementation are identified. CONCLUSIONS: The routine use of outcomes will become increasingly prominent in European mental health services. This provides clinicians with an opportunity to improve the quality of clinical care offered to patients.

Clinical Trials as Topic↗