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Biomedical subjects

L D Jacobson

Publications and source records attributed to L D Jacobson.

At least 19 recordsLinked to original sources
PubMed2000

Teenagers' views on general practice consultations and other medical advice. The Adolescent Working Group, RCGP.

BACKGROUND: The provision of health services for teenagers is of current interest in relation to primary care. OBJECTIVES: The main objective of the study was to look at satisfaction with the teenager's last consultation and any reasons for dissatisfaction. A further objective was to look at common teenage health concerns to identify how many teenagers had been concerned about them, where they sought advice, and to look at ratings of this advice. METHOD: Questionnaires were completed as part of a continuing evaluation of a novel sex education programme in 38 schools in 1997 and provided the data. The particular items reported in this study were related to satisfaction with the last GP consultation and reasons for dissatisfaction, health concerns and who (if anybody) was approached to address these concerns, and comments on services used. 5152 teenagers (51.8% male and 47.8% female) completed the questionnaires in a school lesson under conditions of complete confidentiality. RESULTS: Over 86% of adolescents were apparently satisfied with their last consultation with a GP, although several possible reasons were identified for any dissatisfaction. Health concerns were identified and sources of help were considered and compared; no obvious levels of relative dissatisfaction with services were noted. A large number of teenagers identified apparent concerns but did not seek help for these concerns. CONCLUSIONS: Adolescents are largely satisfied with the services available in primary care. A number of teenagers do not seek help for their own individual concerns. Encouraging teenagers to attend when they perceive a health problem may help provide a more sensitive primary care service.

Adolescent↗
PubMed1998

Challenges in evaluating primary health care for teenagers. Research Sub-Committee of the Adolescent Working Party of the Royal College of General Practitioners, London, UK.

This paper concerns the evaluation of health care for teenagers and examines the role of primary care and its interaction with the teenage users of this service. It recognizes that the majority of health care for teenagers takes place within general practice. The challenge posed is to identify and put in place suitable evaluation tools. There are government targets to improve the health of teenagers by reducing teenage pregnancy, drug use, smoking rates and suicides. It is an assumption of this paper that improvements in experiences of primary care will lead to improvements in more population-based outcomes of care, although this link needs investigation. The paper shows that there are few measures of generic outcome which are available for use in experiments to assess teenage health care as a baseline now. This has implications for conducting future research projects. Such measures are important and it is a necessary feature of research into teenage health that these measures are devised, tested and validated as a priority.

Adolescent↗
PubMed1997

Evidence-based medicine and general practice.

Evidence-based medicine (EBM) aids clinical decision making in all fields of medicine, including primary care. General practice is characterized by particular emphasis on the doctor-patient relationship and on biomedical, personal and contextual perspectives in diagnosis. Most evidence available to general practitioners (GPs) addresses only the bio-medical perspective and is often not directly applicable to primary care, as it derives from secondary or tertiary care. Emphasis on the biomedical domain and the randomized controlled trial (RCT) alone reflects a reductionist approach that fails to do justice to the philosophy of general practice. The art of medicine is founded on context, anecdote, patient stories of illness and personal experience, and we should continue to blend this with good quality and appropriate research findings in patient care.

Evidence-Based Medicine↗
PubMed1997

Teenagers' views on the general practice consultation and provision of contraception. The Adolescent Working Group.

BACKGROUND: The rate of unwanted pregnancies in adolescents in the United Kingdom (UK) is one of the highest in Europe and is a major reason for the RCGP's concern at the under-use of general practitioners' (GPs') contraceptive services by young people. AIM: To discover the attitudes of 15- to 16-year-olds to the GP consultation and contraceptive services. METHOD: Questionnaires were completed as part of an evaluation of a novel sex education programme in 30 schools in 1994, and provided the data for this study. A total of 4481 teenagers (51.6% male and 48.4% female completed the questionnaires in their classrooms under conditions of complete confidentiality. RESULTS: The median consulting rate per year was two for males and three for females. Over 60% of adolescents attended the consultation with a parent. Of the males, 27.5% 'felt that the discussion with their GP could be relayed to their parents against their wishes', as did 25.1% of the females. Other difficulties with GP appointments were identified as embarrassment (63% of females and 46% of males), difficulty getting a quick appointment (44% of both males and females), and an unsympathetic GP (32% of females and 20.5% of males). CONCLUSIONS: Adolescents identify significant factors blocking them from easy access to consultation with their GP. These included lack of trust in confidentiality, lack of staff friendliness, and delay in appointment. Consideration of how these blocks can be removed will assist in providing improved contraceptive services in primary care. General practices need to consider the above factors when providing contraceptive and other services to their teenage patients.

Adolescent↗
PubMed1995

Dust suppression in swine feed using soybean oil.

Dust generation from swine feed (corn-soybean meal diet) treated with soybean oil was investigated using a cement mixer in a plywood box. Airborne total dust concentrations in the box were measured gravimetrically using a vacuum pump and filters while 12-kg feed samples were constantly mixed. The treatment factors were soybean oil concentration (0, 1, and 3%), corn bulk density (normal, 730 kg/m3 and low, 600 kg/m3), time of oil addition (before vs after grinding the corn), and storage time (0, 7, and 14 d). The feed was a mixture of soybean meal, base mix, and adjusted amounts of ground corn and soybean oil. Adding soybean oil after grinding at 1 and 3% levels to feed made with normal-bulk density corn suppressed total dust generation (3.39 and .99 mg/m3, respectively) (P < .001) compared with the no oil treatment (29.1 mg/m3). The 3% soybean oil treatment suppressed dust generation (.99 mg/m3) more than the 1% soybean oil treatment (3.39 mg/m3) (P < .001). Adding soybean oil after grinding the corn suppressed dust generation more than adding the oil to the corn before grinding for every oil level (P < .001). More dust was generated by feed made from low-bulk density corn than by feed made with normal-bulk density corn at every oil level (P < .001). There was no evidence of any storage time or treatment x storage time interactions.

Animal Feed↗
PubMed1994

Is the potential of teenage consultations being missed?: a study of consultation times in primary care.

There is a paucity of knowledge regarding teenage health even though it features as one of the priority areas in the government's health plans. There have been few reports of adolescent contacts with primary care teams, although there are impressions of a suboptimal service. As a prelude to understanding more about communication between general practitioners and teenage patients, this study aimed to look at the time spent on teenage consultations, which can be used as one method of describing the quality of care provided to teenage patients. Nine-hundred consultations involving six doctors in one surgery were timed over a 3 month period by one observer using a validated method. One-hundred and nineteen consultations with patients aged 11-19 were compared with the 781 consultations for other age groups and showed a statistically significant mean shortfall of nearly 2 minutes (23%). This trend was confirmed for all six doctors, despite a broad range of average consulting times. The study also demonstrated some other characteristics of teenage consultations. Several implications of these results are discussed as well as possible reasons for these findings. The study emphasizes the need for further research in this area.

Adolescent↗
PubMed1994

Review of teenage health: time for a new direction.

Teenagers represent a large proportion of the population and have the potential for considerable morbidity because of high smoking rates and unwanted teenage pregnancy. The government intends to reduce the incidence of this important morbidity, but there is no coherent strategy for attaining these improvements. Research in this area is limited in the United Kingdom, but research from elsewhere has clarified teenagers' attitudes. There have also been some intervention studies resulting in improvements in specific aspects of teenage health. A worrying theme which emerges from this research is of a new inverse care law. Teenagers with low self-esteem and less hope for their own future are more likely to lead lifestyles which put them at risk and are less likely to ask for advice in relation to their health or lifestyle. Thus, it may be more difficult to alter behaviour in these patients; overall population based improvements may be difficult to achieve. Teenagers' own concerns appear to be at variance with the goals dictated by government and health professionals. It is suggested that the only method of meeting the needs of teenagers and at the same time aiming to reduce morbidity in this age group is to foster an atmosphere of patient centredness in dealings with adolescent patients and for further ther research in this important health gain area.

Adolescent↗
PubMed1993

Cross-correlation analyses of nonlinear systems with spatiotemporal inputs.

Methods are presented for analyzing the low-order stimulus-response cross-correlation functions (or kernels) of visual neurons studied with spatiotemporal white noise. In particular, formulas are derived that relate the low-order kernels of a cell to its responses to single-drifting, double-drifting, and counterphase gratings. The harmonic response terms contributed by the low-order kernels include a mean response term, first- and second-harmonic terms, and sum- and difference-harmonic terms. Using the formulas in this paper, one can obtain kernel-based predictions for the spatiotemporal-frequency tuning of each harmonic. These kernel-based predictions can then be compared with harmonic tuning data obtained in experiments with real grating stimuli. The methods are illustrated using data recorded from one simple and one complex cell from the primary visual cortex of the monkey. The approach of transforming low-order kernels into predicted harmonic tuning functions provides a useful data reduction technique as well as providing insight into the interpretation of kernels.

Animals↗
PubMed1992

Interneuronal interaction between members of quadrature phase and anti-phase pairs in the cat's visual cortex.

Interactions between adjacent simple cells recorded simultaneously from the same microelectrode placement were studied by correlational analysis. The receptive fields of pairs of such cells exhibit either 90 degrees (quadrature phase) or 180 degrees (anti-phase) phase relationships. We now show that the majority of quadrature phase pair members do not receive common input from the immediately precedent stage along the visual pathway, nor do these cells interact with each other. The anti-phase pairs show relatively strong mutual inhibition. These results suggest that each of the physically adjacent phase-related simple cells receives excitatory input from a distinct group of pre-cortical cells, and that mutual inhibitions between members of anti-phase pairs are used to construct the inhibitory subzones of these cells. We propose a model which incorporates these new results and provides a parsimonious explanation for the construction of both quadrature phase and anti-phase pairs.

Animals↗
PubMed1990

Structural classification of multi-input nonlinear systems.

We present new structural classification and parameter estimation results that are applicable to multi-input nonlinear systems. The mathematical relationships between the self- and cross-(Volterra and Wiener) kernels are derived for a basic two-input nonlinear structure. These results are then used to develop classification methods for more complicated two-input structures. Algorithms for estimating the parameters (linear and nonlinear subsystems) of these structures are also presented.

Cybernetics↗
PubMed1988

Spatial and temporal frequency selectivity of neurons in visual cortical area V3A of the macaque monkey.

Response properties of neurons in V3A were studied at a retinal eccentricity of 2-4 deg. The distributions of spatial frequency bandwidths and orientation bandwidths were similar to those of neurons in V1. Peaks of spatial frequency tuning curves ranged from 0.35 to 8.0 c/deg with a mean of 1.75 c/deg. Most V3A cells showed lowpass or, less often, broad bandpass temporal frequency selectivity. The mean direction selectivity index was 0.41. The response properties of cells in V3A differed most from those in V1 with respect to the larger receptive field widths in V3A averaging about 4 deg, the consequent larger number of cycles of the preferred grating that fall within the receptive field, and the previously reported profound response suppression incurred when patches of the preferred grating are extended both within and beyond the classical receptive field. The response properties of cells in V3A differed most from those in V3 in that V3A neurons are much less selective to the speed and direction of stimulus motion than are neurons in V3. The overall response properties of cells in V3A are consistent with anatomical evidence that places this cortical area in the visual pathway from V3A to V4 and then to IT.

Animals↗
PubMed1988

Responses of simple and complex cells to compound sine-wave gratings.

We have studied the responses of simple and complex cells in the primary visual cortex of the cat to rigidly drifting compound sine-wave gratings as a function of the phase offset between fundamental and harmonic frequencies that both fell within the passband of the cell. Simple cells show phase-dependent increases and decreases in peak and mean response which are predictable on the basis of a cell's line weighting function. However, the amplitudes and phases of the base and harmonic frequencies in the response are, in general, not well predicted by the relationships of these same components in the compound grating stimuli. These distortions are shown to be largely a consequence of the rectification that follows linear summation at the simple cell stage. Such distortions are, in principle, correctable when the responses of a second simple cell, as part of a 180 deg phase pair, are taken into account. Complex cells typically showed a strong nonlinear response component at the difference frequency of drifting compound gratings. This was sometimes accompanied by a linear response component at one, or both, of the separate stimulus frequencies. Information about the absolute phases of the frequency components of a compound grating is not preserved in the nonlinear response of complex cells; however, information about the local phase difference between the gratings is preserved. In effect, the nonlinear component of the complex cell response is proportional to the time-varying signal envelope that results from the mutual interference of stimulus frequencies that fall in the cell's spatial receptive field and frequency passband.

Animals↗
PubMed1987

Response suppression by extending sine-wave gratings within the receptive fields of neurons in visual cortical area V3A of the macaque monkey.

Even though there are many more cycles of the "optimal" grating extending across the receptive fields of cells in V3A than of cells in V1 and V2, the spatial frequency bandwidths in V3A are no narrower than in V1 or V2. Thus, the inputs to V3A cells are not combined in a phase coherent manner across the entire receptive field. Moreover, the defined receptive fields of cells in V3A are generally surrounded by suppressive regions which are, on average, much stronger than those found for neurons in V1 and V2. Even within the classical receptive field, most neurons in V3A respond far more vigorously to a limited patch of a few cycles of a grating at the preferred spatial frequency than to wider grating stimuli. This intra-receptive field suppression demonstrates a new level of response complexity, and suggests that V3A cells may antagonistically combine nonlinear mechanisms that themselves encode stimulus energy over a restricted region of space and spatial-frequency.

Animals↗
PubMedDate not supplied

Structural testing of multi-input linear-nonlinear cascade models for cells in macaque striate cortex.

Structural testing methods based on experimental white noise stimulus-response data were used to evaluate multi-input linear-nonlinear (LN) cascade models for simple and complex cells in macaque striate cortex. An LN structural test index, based on white noise stimulation, was developed and found to be suitable for classifying cells as simple vs complex. In particular, classification results based on the LN structural test index were similar to classification results based on a traditional modulation index derived from cell responses to drifting sinewave gratings. Judging from their structural test indices, complex cells deviated more strongly from LN behavior than did simple cells. Yet, even with simple cells, on average, only about 60% of the first- and second-order white noise stimulus-response relation was consistent with LN behavior. Just two of thirteen simple cells studied had an LN consistency level that exceeded 80%. Similar results were found in tests for consistency with an LNL model which includes an additional linear post-filter. We conclude that a conventional multi-input LN network model may be a useful approximation to the response behavior of some simple cells. However, even during steady state stimulus conditions, subcortical and/or cortical nonlinearities other than a static output nonlinearity play a very significant role in shaping the responses of most simple cells in the macaque striate cortex.

Animals↗