Reactive and effortful processes in the organization of temperament

Self-organization can be approached in terms of developmental processes occurring within and between component systems of temperament. Within-system organization involves progressive shaping of cortical representations by subcortical motivational systems. As cortical representations develop, they feed back to provide motivational systems with enhanced detection and guidance capabilities. These reciprocal influences may amplify the underlying motivational functions and promote excessive impulsivity or anxiety. However, these processes also depend upon interactions arising between motivational and attentional systems. We discuss these between-system effects by considering the regulation of approach motivation by reactive attentional processes related to fear and by more voluntary processes related to effortful control. It is suggested than anxious and impulsive psychopathology may reflect limitations in these dual means of control, which can take the form of overregulation as well as underregulation.     

Tuberculosis 2000: problems and solutions

The incidence of tuberculosis is expected to increase, from 8.8 million cases in 1995, to 10.2 million cases by the year 2000 and 11.9 million by 2005. Three million deaths due to tuberculosis occurred in 1995, and 3.5 million can be expected in the year 2000. The most important causes of the world-wide increase in tuberculosis are: 1) non-compliance with control programmes; 2) inadequate diagnosis and treatment; 3) migration; 4) endemic human immunodeficiency virus (HIV); 5) ambulatory and self-administered treatment. In the 1970s it was stated that treatment needed to be supervised-a recommendation that went unheeded. A number of fundamental changes should be introduced in order to make treatment effective, to cure patients and thus to arrest the transmission of the disease: 1) supervision during the whole period antituberculosis drugs are taken, and 2) hospitalization during the initial treatment stage for all groups at risk. It is already 50 years since the first antituberculosis drugs were discovered; effective treatments capable of curing all patients in 6 months have been available for the last 25 years, and the result is failure plus a growing mortality curve at the beginning of the twenty-first century. If we wish to alter this trend, we need trained doctors all over the world who possess enough clinical knowledge of tuberculosis; hospitalization for specific groups of tuberculosis patients; true supervision during the whole treatment period; fixed-dose combinations of drugs; and prophylaxis or preventive treatment whenever possible. We also need to take into account other factors such as drug resistance, endemic HIV, and migration.     

The spectral-correlational analysis of the electrical activity of the rabbit brain in the organization of a goal-directed blinking reaction

At organization of the blinking reaction directed to a cessation of the motivational hunger dominant the spectral power of biopotentials of the frontal, sensorimotor cortical areas and the blinking cortical centres of both eyes, VMH and LH increases in the range of the delta- and theta-frequencies. Coherence (Coh) of electrical activity of the frontal and sensorimotor cortical areas increases, Coh between potentials of the swallowing cortical area and the blinking cortical zones corresponding to the trained and non-trained eyes is being asymmetrically reconstructed. Coh function of the electrical activity of the LH, VMH and potentials of different cortical areas changes uniformly. Coh of electrical activity of the VMH and LH, NIII and MPO increases in the whole analysed frequency range, Coh between potentials of the MPO and LPO, LPO and VMH increases in the delta- and decreases in the theta- and alpha-frequency ranges. It is suggested that in the process of preparation of the goal-directed reaction all the cerebral cortex areas and subcortical structures under study related to alimentary motivation and the blinking function are involved into the dominant constellation.     

Distribution and organization of odontoblast processes in human dentin

The distribution and organization of odontoblast processes in young human dentin was examined with a scanning electron microscope. By applying the HCl-collagenase method, the extracellular matrix of dentin was almost completely removed, thereby exposing the odontoblast processes and their branches to direct observation. The odontoblast processes are located close to the dentinoenamel junction. In the middle and outer zones of dentin the processes bear numerous branches. Some of these appeared to bridge the space between the processes and connect them.     

Sensations and brain processes

A hypothesis on the physiological conditions of consciousness is presented. It is assumed that the occurrence of states of consciousness causally depends on the formation of complex representational structures. Cortical neural networks that exhibit a high representational activity develop higher-order, self-referential representations as a result of self-organizing processes. The occurrence of such states is identical with the appearance of states of consciousness. The underlying physiological processes can be identified. It is assumed that neural assemblies instantiate mental representations; hence consciousness depends on the rate at which large active assemblies are generated. The formation of assemblies involves the activation of the N-methyl-D-aspartate receptor channel complex which controls different forms of synaptic plasticity including rapid changes of the connection strengths. The various causes of unconsciousness (e.g., anaesthetics or brain stem lesions) have a common denominator: they directly or indirectly inhibit the formation of assemblies.     

Spatial organization of distractors in visual search.

This paper investigates visual search in displays in which distractors are spatially grouped. The effect on detection of target position within a spatially grouped 2-dimensional display containing 2 distractor types were examined. The authors compared detection in grouped displays with detection in 2 kinds of control display, homogeneous (one distractor type) and ungrouped (2 distractor types), to determine whether detection in grouped displays would be more similar to efficient detection in homogeneous displays than to inefficient detection in ungrouped displays. Findings show relatively efficient detection in group displays. Detection of targets at the border of two regions where distractors are coherent is easier than can be predicted by models that do not take spatial organization into account. Thus, models of visual search need to incorporate effects of spatial organization in addition to bottom-up difference calculations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Figure-ground organization and object recognition processes: An interactive account.

Traditional bottom-up models of visual processing assume that figure-ground organization precedes object recognition. This assumption seems logically necessary: How can object recognition occur before a region is labeled as figure? However, some behavioral studies find that familiar regions are more likely to be labeled figure than less familiar regions, a problematic finding for bottom-up models. An interactive account is proposed in which figure-ground processes receive top-down input from object representations in a hierarchical system. A graded, interactive computational model is presented that accounts for behavioral results in which familiarity effects are found. The interactive model offers an alternative conception of visual processing to bottom-up models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial electrical patterns in simulated neuronal dendrites

Steady state longitudinal distributions of (a) the density of channels conducting an inward transmembrane current of cations, (b) the submembrane concentrations of these cations, and (c) the resting membrane potential, were investigated in a phenomenological model of a cylinder-shaped dendritic process of the neuron. It was found that spatially non-uniform patterns of these distributions occur only if one of the following conditions held (i) an increase in the intracellular concentration of cations conducting an inward passive transmembrane current amplified the active efflux of those cations by the pump and attenuated their passive influx through the voltage dependent channels, with amplification of the efflux lower than attenuation of the influx; (ii) molecules of mobile channels bore a negative electrophoretic charge exposed to the intracellular space and were subject to lateral electrodiffusion in the membrane; (iii) the cations induced a further release of cations from intracellular stores. Numerical simulation studies of the membrane with Na and K channels and Na/K pumps with conditions (i) and (ii) have demonstrated the possibility of the creation of inhomogeneous patterns in the neurites. These inhomogeneous patterns are dissipative structures (DSs), and they can be spatially periodic.     

Current problems in the standardisation of medical electrical equipment

The progress towards a coherent policy of international standardisation of electrical equipment used in medical practice is reviewed against the background to existing legislation in Western Europe. The work of the International Electrotechnical Commission and the implications of the EEC in this context are discussed, as well as the general philosophy of the safety of medical electrical equipment in relation to standardisation.     

Encoding processes and memory organization: A model of the von Restorff effect.

The mechanisms underlying the improved recall of isolated events (von Restorff effect) were investigated. Participants studied lists of stimuli containing a physical and a semantic isolate while performing a physical task or a lexical decision task. The physical-task group showed a physical but not a semantic isolation effect (IE) in free recall, whereas the lexical-decision group displayed both types of IEs. The recall of the isolates was independent of that of the other words, and isolates were usually reported separately from other words in the list. Event-related potentials recorded at encoding predicted the recall of both types of isolates. In recognition tests, the IE was obtained only when the encoding context was reinstated. These results are consistent with a model of the IE that stresses the role of the encoding processes immediately following the presentation of distinctive events, and that postulates interactions between these processes and subsequent elaboration of the stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial resolution of cochlear implants: the electrical field and excitation of auditory afferents

This paper investigates the spatial resolution of electrical intracochlear stimulation in order to enable further refinement of cochlear implants. For this purpose electrical potential distributions around a conventional human intracochlear electrode (NUCLEUS-22) were measured in a tank, in cat cadaver cochleae and in living cat cochleae. Potential gradients were calculated where of importance. The values were compared to spatial tuning curves from cat primary auditory afferents in electrical mono-, bi-, and various tripolar stimulation modes. Finally, a lumped element model was developed to elucidate the single fiber data. Tank potential measurements show the principal features of the different stimulation modes but are not sufficient to explain all the features of experimental data from single fibers. Intracochlear potential measurements indicate an increase in spatial resolution in an apical direction. The single fiber data also confirm that a tripolar stimulus configuration provides significantly better spatial resolution than any other stimulation mode presently in use.     

Spatial organization and plasticity of the primary and secondary olfactory projections in goldfish

Crystals of the lipophilic tracer DiI were applied to discrete regions of the olfactory epithelium of goldfish to trace the primary sensory projection to the olfactory bulb. Receptors from the anterior half of the sensory sheet project primarily to glomeruli in the medial half of the bulb and receptors in the posterior half terminate mainly within the lateral half of the bulb. This pattern disappeared following ablation of selected, discrete epithelial regions. In order to investigate reorganization of secondary olfactory projections, unoperated control and unilaterally bulbectomized animals received injections of [3H]proline into the right olfactory bulb. Densities of silver grains per unit area were determined within six different forebrain nuclei in both the right and left hemispheres of each animal. Of the six areas examined, three demonstrated a significantly greater density of afferent innervation from the ipsilateral versus contralateral bulb; a difference which disappeared in two of these three regions after bulbectomy. Thus, for at least two forebrain nuclei, bulb removal caused a change in the afferent input from the spared olfactory bulb to those regions. We conclude that both primary and secondary olfactory projections in goldfish are capable of some degree of reorganization following insult.     

Bipedicle flaps: simple solutions for difficult problems in the extremities

Bipedicle flaps have been used to provide good quality soft tissue cover for defects in many anatomical sites. The indications for the use of this flap have not been well defined and with the advent of more complex modes of tissue transfer this simple technique is often overlooked. We have found it to be a safe and expedient method of providing cover for difficult defects on the extremities. We present a series of 9 flaps raised on 7 patients over a 12-month period and discuss the indications and refinements in flap design.