Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Models, Neurological”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

An hypothesis on information, memory and perception.

It is generally held that a sensory receptor serves, in some way to "map" an external event (such as a light or sound signal) onto some internal or neural event (such as a volley of impulses moving along an axon toward the brain). Or schematically (external event leads to neural event). It is postulated in this paper that it is not the external event, but rather uncertainty about the nature of the external event, which produces the neural activity. In place of the traditional map it is hypothesized that we should substitute (rate of change of uncertainty about an external event leads to neural event). It follows from this revised mapping process that one perceives only those external events about which he was initially uncertain. One cannot perceive something about which he is perfectly certain. It is seen that various observed sensory phenomena, such as the process of adaptation and the fading of a fixed retinal image, issue directly from this new hypothesis.

Humans↗
PubMed1985

Selective attention and the brain: a hypothesis concerning the hippocampal--ventral striatal axis, the mediation of selective attention, and the pathogenesis of attentional disorders.

The mechanisms mediating selective attention are not currently known. Dysfunctional selective attention is a common and prominent finding in a variety of medical and psychiatric conditions. A hypothesis is developed that efferents from the hippocampal formation are the final common pathway of processes which determine the noteworthiness of both exteroceptive and interoceptive stimuli, and that dysfunction of these efferents is a common pathway for a variety of anatomical, electrophysiological, and neurochemical lesions. This hypothesis suggests that clinical syndromes of disordered attention may be caused by various lesions of efferent connections from hippocampal formation to nucleus accumbens. The hypothesis further addresses the possibility that the threshold of hippocampus to various classes of stimuli may change on a diurnal and phasic basis. Experimental evidence that bears on the hypothesis is reviewed and experimental implications of the hypothesis are explored.

Attention↗
PubMed1990

A brain mechanism for attention.

Attention is directed or focussed consciousness. Consciousness is a subjective sensation produced by the simultaneous activation of discrete neurophysiological systems. These are the alerting, awareness, affect, arousal, and attention systems. The process begins with the subcortical scanning of sensory stimuli for affect and significance via pleasure, pain and tension systems. The perceptions then pass to the Thalamus for further scanning and concentration into one sensory modality by Thalamic-Prefrontal-Thalamic reflex inhibition. The unimodal, significant perceptions then activate engrams in the Posterior Inferior Temporal Cortex, the Posterior Inferior Parietal Cortex, and the Posterior and Anterior Association Cortex. These areas project to the Prefrontal Association Cortex (PAC). The PAC inactivates sensory scanning systems causing fixation. The PAC also sends signals to the Hippocampus, which are gated by Septal and Hippocampal generated theta activity in the Hippocampus. This transiently interrupts the blanket inhibition of orientation, alertness, awareness, and arousal produced by the theta activity via the Hypothalamus. As a result of the above mechanisms, only one sensory stimulus activates the orientation, alerting, awareness, arousal, and cognitive systems and hence focussed attention occurs. Focussed attention can also be used to explain the initiation of voluntary movements.

Arousal↗
PubMed1991

Dissipative structure and the mind-body problem.

A theory explaining the link between mind and body is presented which depends upon viewing personal awareness as a figure against the ground of infinity. It is proposed that a tendency toward dissipation, in tension with an opposite tendency toward structural integrity, determines both the 'illumination' and specificity of awareness. Mind, as an aspect of the awareness bubble, is envisioned as influencing the body via a regressive discrepancy in relation to the current organization of the body mass - a conclusion derived from the fact that the origin of the tension between structure and its dissipation extends regressively back to the time when self was infinite or boundless, i.e., non-existent. This regressive discrepancy drives behavior in an expectable and therefore visible direction [corrected]. The entire thesis rests upon viewing reality as fundamentally personal, such that the linkage between a sensory field and neural activity can be explained on the basis of a simple gap between structure and its dissipation. The significance of this viewpoint for understanding the brain is briefly discussed.

Awareness↗
PubMed1993

Using neural networks to model personality development.

A neural network approach to modeling the development of personality traits through social learning is presented. From the more general model the special case of a network mapping four situation dimensions (input neurons) into seven dimensional personality traits (output neurons) is described. This network is allowed to learn with input/output sets representing conditions suspected of leading to a borderline personality disorder. The network's ability to learn these pattern pairs is demonstrated. The trained network is then presented with new input (situational) patterns and is shown to respond to these new situations with output patterns consistent with a borderline personality disorder. The neural network model is thus shown to have important advantages over other personality models in that it can predict what situations will produce shifts in personality traits, for example from active to passive. This model provides a quantitative and reproducible framework within which to discover and test theories of personality development. It is hoped that it will extend our ability to predict human behavior.

Humans↗
PubMed1993

Schizophrenic symptoms: a theory based on a neurophysiological model.

Under normal conditions, just a few mental subunits are simultaneously at a conscious level according to a previously presented model. The present paper explains how a somewhat increased number of simultaneously appearing subunits can cause the positive schizophrenic symptoms (thought disturbances, hallucinations, etc). Negative schizophrenic symptoms can develop when too few mental subunits are appearing at a time. Neuroleptic drugs are proposed to act by reducing the number of simultaneously appearing subunits.

Antipsychotic Agents↗
PubMed1993

Manodepressive disorders: a theory based on a neurophysiological model.

In a previously presented model, a column in the cerebral cortex has activity at two separate levels. A few columns are under normal conditions at the high level of activity at a time while the rest are kept at the low level. The effects of changes in the number of columns that are at the high level of activity simultaneously have been dealt with in previous papers. It has been concluded that a somewhat increased number results in positive schizophrenic symptoms, and that too few can give negative schizophrenic symptoms. In the present paper, the effects of changes in a second parameter are discussed. This parameter is the length of time during which a cerebral column is at the high level of activity. It is explained how too short duration causes the manic phase in manodepressive disorders, and too long duration the depressive phase.

Association↗
PubMed1993

Crick and Mitchison's theory of REM sleep and neural networks.

Crick and Mitchison proposed that a reverse learning mechanism in REM sleep removes certain undesirable modes of interaction in neural networks within the cerebral cortex. If their theory is correct then abnormalities of reverse learning might account for some aspects of schizophrenia, mania, and depression. The theory of reverse learning might lead to an understanding of why lithium salts terminate manic episodes.

Animals↗
PubMed1995

Felonious sex crime: the possibility of unilateral cerebral irradiation for the offenders.

Some felonious sex crimes might result from compulsions that the perpetrator finds impossible to control. Under judicial systems derived from British law, the court should be extraordinarily careful in mandating any medical procedure. However, if a rapist or child molester voluntarily asks a physician for help, then medical ethics might allow destruction of part of the patient's brain for the purpose of controlling compulsive behaviour. The part of the human brain primarily associated with volition might be near the anterior cingulate sulcus. Could unilateral irradiation of an area near the anterior cingulate sulcus partially destroy the patient's volition? By leaving intact the patient's will based on language and by partially destroying the patient's will based on intuition, could the physician diminish the patient's will to commit felonious sex crimes? Would some patients reject chemical castration but accept unilateral irradiation of an area near the anterior cingulate sulcus?

Adult↗
PubMed1995

A molecular model for bipolar affective disorder.

The biological basis of bipolar disorder is not known. Models for the illness have been proposed that were based on the neurobiological effects of pharmacological agents that affect mood. Although of great interest, these models have not adequately explained the striking clinical pattern of illness in which patients may experience either unipolar episodes or bipolar cycles of mania and depression. We now present a new model suggesting that the unique clinical heterogeneity found in patients with bipolar disorder could be explained by a defect in a 'downstream' portion of a signal transduction pathway that can regulate two or more neurotransmitter systems that have opposite effects on neuronal activity. This model may target specific candidate genes for involvement in bipolar disorder.

Bipolar Disorder↗
PubMed1995

The role of neuropeptides in learning and memory: possible mechanisms.

Endogenous neuropeptides such as vasopressin, adrenocorticotropin and opioids have significant effects on learning and memory. However, because of the complexity of behaviour, that is defined as 'learning' and 'memory' and, because of the limitation of current knowledge, it has been difficult to interpret these behavioural data, especially via neural mechanisms. The application of modern experimental techniques including molecular biology such as cloning and electrophysiology, such as patch-clamp, has had a significant impact upon the concepts about drugs, including neuropeptides action sites. This allows us to try to interpret some behavioural consequences influenced by neuropeptides. The data on effects of some neuropeptides on behaviours and their possible mechanisms are reviewed. Whatever the mechanisms, vasopressin, adrenocorticotropic hormone and endogenous opioids seem to have important effects upon learning and memory and these open up the possibility that drugs enhance cognitive functions or treat dementia via alteration of functions of neuropeptides. Some criteria are proposed for evaluating the validity of behavioural tests for neuropeptides.

Adrenocorticotropic Hormone↗
PubMed1995

Schizophrenia, suicide and the serotonin story.

In this paper, the relationship between schizophrenia, suicide and serotonin will be examined. Throughout, it will be argued that the fundamental problem does not lie with the neurotransmitter per se, but rather with uncontrolled fluctuations of brain glycaemic levels acting in conjunction with insulin resistance. It will be shown that the area of dopaminergic and serotonergic activity in the brain is intimately tied to the relative distribution of the central glucose transporters and, hence, to glucose metabolism and insulin activity. It will be argued that mania and positive schizophrenia represent a continuum of liability associated with hyperglycaemia, hyperdopaminergia, and hyperserotonergia. In contrast, depression and negative schizophrenia represent another continuum of liability involving hypoglycaemia, hypodopaminergia, and hyposerotonergia. This serves as a useful distinction in drawing together a large number of seemingly unrelated, diverse facts concerning both schizophrenia and suicide and, in particular, the possible relationship that obtains between cholesterol-lowering drugs, low serotonin and suicide. Essentially, this paper reaffirms a previously stated contention that mental illness, in its many guises, is a general manifestation of a diabetic brain state which has been termed 'cerebral diabetes'.

Animals↗
PubMed1995

Triplet code-independent programming of living systems organisation by DNA: the link with intelligence and memory.

Previous suggestions from this laboratory (3), (a) that within its molecular electronic structure, DNA houses a computer-analog program of immense complexity, operating independently of, but complementary to, triplet coding and (b) that, inter alia, this program is the driving force for organising and executing the construction of species individuals in three dimensions, are extended in the present communication. It is now concluded that the DNA program also embodies an 'intelligence' component, which extends its organising ability both qualitatively and quantitatively beyond any of the heavily circumscribed 'self-organising' attributes claimed to be associated with naturally occurring inanimate systems. Further, that as part of the developmental process, a program component organises the fabrication of mammalian central nervous systems, including that of human beings with the associated attributes of intelligence, creativity and constructional skills. It is further suggested that the sophisticated random access memory system associated with human beings in particular may be explicable in terms of an extension of the DNA programming system: basically this involves the latter operating as computer-type 'hardware' for the storage of long-term memory and interacting with, primarily, glial cell RNA, acting as 'software' and storing short term traces. Finally, it is suggested that such an interrelationship between DNA/RNA molecular electronic structures can provide the necessary memory storage capacity and flexibility and also facilitates random access to the long-term DNA memory store.

Animals↗
PubMed1995

Working memory networks and the origin of language areas in the human brain.

Temporoparietal-prefrontal working memory networks are proposed as fundamental in the evolutionary origin of the language regions. Having a primordial capacity to name objects or situations, primitive hominids may have strongly benefited from the possibility to recall past events from memory, in order to refer to them through vocal communication. Working memory cortical networks are related to these types of tasks, and are arranged quite similarly to the language networks in the brain. It is possible that the language areas and their connections arose as a local specialization of these large-scale cortical networks, that developed as neural strategies to recall past events to be shared in community. The origin of syntax may have taken place after these networks were sufficiently stabilized, and (at least originally) may have been related to aspects of vocal motor control, involving the progressive differentiation of the anterior language areas and their connections.

Biological Evolution↗
PubMed1988

Single-tone intensity discrimination based on auditory-nerve rate responses in backgrounds of quiet, noise, and with stimulation of the crossed olivocochlear bundle.

We use simple statistical models of the firing patterns of high, medium, and low spontaneous rate auditory-nerve fibers to study mechanisms which determine the overall dynamic range of the auditory periphery. The models relate experimentally measured rate response properties of fibers with best frequency (BF) near 8.0 kHz to their ability to encode changes in BF tone level by changes in discharge rate in backgrounds of quiet and noise, with and without electrical stimulation of the crossed olivocochlear bundle (COCB). Application of the models to the BF tone rate responses of auditory-nerve fibers in backgrounds of quiet shows that optimum processing of the rate responses of fibers with BF near 8.0 kHz yields performance in the intensity discrimination task meeting or exceeding that of human subjects over an 80 dB range of levels. By defining a statistical measure of dynamic range, we confirm the results of Costalupes et al. (1984) demonstrating that masking noise shifts the dynamic range of auditory-nerve fibers to higher stimulus levels, thus preventing rate saturation. However, model analysis shows that masking noise also produces large reductions of dynamic range as well as large increases in the minimum intensity difference that can be encoded by the rate responses of single and ensembles of fibers. Electrical stimulation of the COCB can restore auditory-nerve fiber dynamic range and sensitivity to changes in BF tone level in noise backgrounds, in some cases to roughly that observed in backgrounds of quiet.

Animals↗
PubMedDate not supplied

A mathematical model of performance on a simple reaction time test.

A nonlinear function with components for learning and fatigue was used to model individual performance on a simple reaction time test. The relationships between the parameters of the model and the mean and variance of the reaction times are discussed. The function is used to analyze data from a field study of agricultural workers exposed to organophosphate pesticides. Exposure had a significant effect on the relationships between education level and initial performance, age and fatigue rate, and age and performance variability. Parameter estimates from the model were able to distinguish between effects that the mean and standard deviation of the reaction times were unable to distinguish.

Adolescent↗