A neural model of binocular integration and rivalry based on the coordination of action-potential timing in primary visual cortex

In normal vision, the inputs from the two eyes are integrated into a single percept. When dissimilar images are presented to the two eyes, however, they compete for perceptual dominance, so that one eye's view suppresses that of the other. Recent evidence suggests that this phenomenon, known as binocular rivalry, arises through competition between alternative stimulus interpretations in extrastriate cortex. Because eye-specific information appears to be lost at this stage, it remains unclear how the stimulus conditions that yield binocular rivalry are distinguished from those that produce stable single vision. Using a neural network that models the mammalian early visual system, I investigate here the hypothesis that congruent and conflicting stimuli are distinguished by their different effects on the relative timing of action potentials in primary visual cortex (V1), where monocular inputs are first combined. In the model, congruent stimulation of both eyes results in synchronization of discharges among binocular neurons in V1. By contrast, conflicting stimulation of the two eyes results in neuronal asynchrony in this area. This asynchrony then produces rivalrous response suppression at later stages in the visual pathway. Synchronization of firing in V1, however, prevents such competition, thereby ensuring non-rivalrous responses. These novel effects of spike timing on competition emerge naturally from the network dynamics. The results suggest that input-related differences in relative spike timing at an early stage of visual processing may play an important part in the phenomena both of binocular integration and rivalry; furthermore, they indicate that the temporal patterning of cortical activity may be a fundamental mechanism of selection among competing stimulus representations.      

Managing to care: the importance of using existing information to guide service provision for informal carers

All managerial deciions are taken on the basis of the information. It is important that managers use appropriate information to base their decisions upon about service provision to ensure erhcient use or resources. This basic premise serves as a framework for examining how quantitative and qualitative information can be of help to nurse managers in taking these decisions in the context of developing services for informal carers. The current emphasis on surveys as a means of assessing client need is questioned, and it is suggested that a wealth of evidence, relating to the experience of carers, already exists. Examples of accounts which express the needs of informal carers are presented and their utility, in terms of highlighting the carers' perspective, is discussed to reinforce the importance of utilizing this information. The paper concludes that nurse managers can use these sources as a basis for decision-making in the area of service provision and this may result in a more effective use of resources through a needs-based approach.     

Managing nurses and nursing: short courses as role development

This paper describes the development over a 3-year-period of short management courses for registered nurses offered as part of a professional development educational programme by Oxfordshire Health Authority (OHA) Clinical Education and Practice Team (OXCEPT). The courses were seen as role development for staff nurses, team leaders, sisters, charge nurses and senior sisters, and the content and length of courses were altered, extended and developed in response to evaluation of the courses by tutors and participants. The emphasis is on integrating participants' clinical, managerial and educational roles, as professional practitioners managing nurses and nursing.