PubMed Health⌕ Search

Biomedical subjects

M Stead

Publications and source records attributed to M Stead.

9 recordsLinked to original sources
PubMed2001

"It's as if you're locked in": qualitative explanations for area effects on smoking in disadvantaged communities.

Evidence suggests that place of residence may be associated with smoking independently of individual poverty and socio-economic status. Qualitative research undertaken in disadvantaged communities in Glasgow explored possible pathways which might explain this 'area effect'. A poorly resourced and stressful environment, strong community norms, isolation from wider social norms, and limited opportunities for respite and recreation appear to combine not only to foster smoking but also to discourage or undermine cessation. Even the more positive aspects of life, such as support networks and identity, seem to encourage rather than challenge smoking. Policy and intervention responses need to tackle not only individual but also environmental disadvantage.

Adaptation, Psychological↗
PubMed1999

Automated collection of quality-of-life data: a comparison of paper and computer touch-screen questionnaires.

PURPOSE: To evaluate alternative automated methods of collecting data on quality of life (QOL) in cancer patients. After initial evaluation of a range of technologies, we compared computer touch-screen questionnaires with paper questionnaires scanned by optical reading systems in terms of patients' acceptance, data quality, and reliability. PATIENTS AND METHODS: In a randomized cross-over trial, 149 cancer patients completed the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30, version 2.0 (EORTC QLQ-C30), and the Hospital Anxiety and Depression Scale (HADS) on paper and on a touch screen. In a further test-retest study, 81 patients completed the electronic version of the questionnaires twice, with a time interval of 3 hours between questionnaires. RESULTS: Fifty-two percent of the patients preferred the touch screen to paper; 24% had no preference. The quality of the data collected with the touch-screen system was good, with no missed responses. At the group level, the differences between scores obtained with the two modes of administration of the instruments were small, suggesting equivalence for most of the QOL scales, with the possible exception of the emotional, fatigue, and nausea/vomiting scales and the appetite item, where patients tended to give more positive responses on the touch screen. At the individual patient level, the agreement was good, with a kappa coefficient from 0.57 to 0.77 and percent global agreement from 61% to 97%. The electronic questionnaire had good test-retest reliability, with correlation coefficients between the two administrations from 0.78 to 0.95, kappa coefficients of agreement from 0.55 to 0.90, and percent global agreement from 56% to 100%. CONCLUSION: Computer touch-screen QOL questionnaires were well accepted by cancer patients, with good data quality and reliability.

Adult↗
PubMed1996

Hippocampal place cells connected by Hebbian synapses can solve spatial problems.

We propose that a cognitive map can be stored in the synapses between the pyramidal cells of CA3 in the form of the pattern of synaptic strengths connecting them. The model requires only that there are place cells in CA3 and that the connections between them are modifiable in a Hebbian manner. Given these suppositions, the synaptic strengths must evolve to represent the distance between firing centers of synaptically connected place cells. We argue that this arrangement of synaptic weights embodies all the formal properties of a map. We demonstrate that the information stored in such a structure is sufficient to solve several classic spatial problems including finding shortest paths, and negotiating detours. It is clear that much of the physiology and anatomy necessary to more precisely characterize the model is not known at this time. Nevertheless the model is robust under a variety of cell and connection densities. It also performs well under several different functions relating distance to synaptic strength. What is most remarkable in the model is that it is a logical consequence of the several key anatomical and physiological properties of the CA3 region of rats. Whether this information is used by the rat is difficult to assess at this time. Regardless of the outcome of this question, the model has promising applications to the field of robot navigation.

Animals↗
PubMed1996

The hippocampus as a cognitive graph.

A theory of cognitive mapping is developed that depends only on accepted properties of hippocampal function, namely, long-term potentiation, the place cell phenomenon, and the associative or recurrent connections made among CA3 pyramidal cells. It is proposed that the distance between the firing fields of connected pairs of CA3 place cells is encoded as synaptic resistance (reciprocal synaptic strength). The encoding occurs because pairs of cells with coincident or overlapping fields will tend to fire together in time, thereby causing a decrease in synaptic resistance via long-term potentiation; in contrast, cells with widely separated fields will tend never to fire together, causing no change or perhaps (via long-term depression) an increase in synaptic resistance. A network whose connection pattern mimics that of CA3 and whose connection weights are proportional to synaptic resistance can be formally treated as a weighted, directed graph. In such a graph, a "node" is assigned to each CA3 cell and two nodes are connected by a "directed edge" if and only if the two corresponding cells are connected by a synapse. Weighted, directed graphs can be searched for an optimal path between any pair of nodes with standard algorithms. Here, we are interested in finding the path along which the sum of the synaptic resistances from one cell to another is minimal. Since each cell is a place cell, such a path also corresponds to a path in two-dimensional space. Our basic finding is that minimizing the sum of the synaptic resistances along a path in neural space yields the shortest (optimal) path in unobstructed two-dimensional space, so long as the connectivity of the network is great enough. In addition to being able to find geodesics in unobstructed space, the same network enables solutions to the "detour" and "shortcut" problems, in which it is necessary to find an optimal path around a newly introduced barrier and to take a shorter path through a hole opened up in a preexisting barrier, respectively. We argue that the ability to solve such problems qualifies the proposed hippocampal object as a cognitive map. Graph theory thus provides a sort of existence proof demonstrating that the hippocampus contains the necessary information to function as a map, in the sense postulated by others (O'Keefe, J., and L. Nadel. 1978. The Hippocampus as a Cognitive Map. Clarendon Press, Oxford, UK). It is also possible that the cognitive mapping functions of the hippocampus are carried out by parallel graph searching algorithms implemented as neural processes. This possibility has the great attraction that the hippocampus could then operate in much the same way to find paths in general problem space; it would only be necessary for pyramidal cells to exhibit a strong nonpositional firing correlate.

Animals↗