"Where is the sun" for hemi-neglect patients?

Human observers use prior constraints to disambiguate a scene; in particular, light is preferentially seen as coming from above but also slightly from the left. One explanation of this lateral bias could be a cerebral hemispheric difference. The aim of the present study was to determine the preferred light source position for neglect patients. For this purpose, we used the ambiguous shaded "Polo Mint" stimulus, a ring divided into eight equal sectors. All sectors but one were the same shape, convex or concave, as determined by the light source position. Participants had to report the side (left or right) of the odd sector or, in a separate experiment, to report its shape (convex or concave). Eight patients with spatial neglect (left neglect N=7, right neglect N=1) after a right or left temporo-parietal or thalamic lesion and 14 control participants ran the experiment. Left neglect patients showed a significantly different light bias from the bias observed for controls and for the right neglect patient (i.e., a reduction of the left bias or a right bias rather than a left bias). We conclude that some disabilities presented by patients with spatial neglect may be due to difficulties processing information that is not present in the visual field or imagined in the representational scene.

Deficit of preparatory attention in children with frontal lobe epilepsy.

We compared the performance of a sustained attention task by children with epilepsy in either the frontal or temporal lobe. In a new simple task that specifically measures preparatory attention, developed recently by LaBerge, Auclair, and Siéroff [LaBerge, D., Auclair, L., & Siéroff, E. (2000). Preparatory attention: Experiment and theory. Consciousness and Cognition, 9, 396-434], patients responded to a target presented in the centre of the display and ignored a distracter presented at locations to the right or the left side of the target. The distracter was presented prior to the onset of the target and the relative frequency of the distracter to target was varied within a block of trials (from 0% to 67%). Children with frontal lobe epilepsy showed a higher mean slope of response time to the target as a function of distracter probability compared to children with temporal lobe epilepsy or compared to the response time slope of control subjects. The response time slope of children with temporal lobe epilepsy did not differ from that of control subjects. These results indicate that the presence of frontal lobe epilepsy selectively affects the capacity of these patients to resist the interference a distracter.

Is the optimal viewing position in reading influenced by familiarity of the letter string?

An optimal viewing position (OVP) for word recognition has been proposed by several authors. The location of this position would be located at the center of the word or just left of it. Several hypotheses ranging from perceptual to hemispheric factors have been proposed to explain this phenomenon. In the experiment presented here, the effect of the nature of the stimulus was tested: word, pseudo-word, or nonword on the existence and location of this position. Little research has investigated this issue. Five-letter words, pseudo-words, and non-words were presented, with the subject fixating initially on one of the five possible letter positions. The number of letters correctly identified and reading performance were recorded for each stimulus. Results show that an initial fixation on the third letter entails better letter identification for all kinds of stimuli. However, in terms of reading, only word reading benefit from a fixation on the third letter. These results are discussed in relation to the different hypotheses of OVP in reading. These are (1) hemispheric specialization, (2) reading habits, and (3) lexical constraints.

Randomized trial of a noninvasive strategy to reduce hospital stay for patients with low-risk myocardial infarction.

OBJECTIVES: This study evaluated the feasibility, pertinence and psychosocial repercussions of a noninvasive reduced hospital stay strategy (three days) for low-risk patients with acute myocardial infarction using simple clinical criteria and predischarge 24-h ambulatory ST-segment ischemic monitoring. BACKGROUND: Previous studies evaluating shorter stays for uncomplicated myocardial infarction have been limited by retrospective or nonrandomized design and overdependence on invasive cardiac procedures. METHODS: One-hundred twenty consecutive patients admitted with an acute myocardial infarction fulfilling low-risk criteria were randomized 2:1 to a short hospital stay (80 patients) or standard stay (40 patients). Short-stay patients with no ischemia on ST-segment monitoring were discharged on day 3, returning for exercise testing a week later. All analyses were on an intention-to-treat basis. RESULTS: Forty-one percent of all screened patients with acute myocardial infarction would have been medically eligible for the short-stay strategy. Seventeen patients (21%) were not discharged early because of ischemia on ST-monitoring or angina. Median initial hospital stay was halved from 6.9 days in the standard stay to 3.5 days in the short-stay group. At six months, median total days hospitalized were 7.5 in the standard stay and 3.6 in the short-stay group (p < 0.0001). Adverse events and readmissions were low and not significantly different, and there were 25% fewer invasive cardiac procedures in the short-stay group. Psychosocial outcomes, risk factor changes and exercise test results were similar in the two groups. CONCLUSIONS: This reduced hospital stay strategy for low-risk patients with acute myocardial infarction is feasible and worthwhile, resulting in a substantial and sustained reduction in days hospitalized. It is without unfavorable psychosocial consequences, appears safe and does not increase the number of invasive cardiac procedures.

Preparatory attention: experiment and theory.

This study investigated attention to a spatial location using a new spatial preparation task. Participants responded to a target dot presented in the center of a display and ignored a distractor dot presented to the right or left of the center. In an attempt to vary the level of preparatory attention directed to the target, the distractor dot was presented prior to the onset time of the target and the relative frequency of distractor dots to target dots within a block of trials was varied. The results from the first three experiments showed that when instructions induce weak preparatory attention to the target location, response times to a target on target-only trials increase substantially as the percentage of trials containing a distractor increases from 0 to 75%. In Experiments 2 and 3, instructions and display saliency were used to induce strong preparatory attention to the target location, resulting in almost constant response times across distractor percentages. Experiment 4 varied percentage of target trials in the absence of distractors, with the result that response times decreased as target trial percentage increased. Accounts of these data by early "activity-based" and late "criterion-based" attention theories are compared, and the early theory is given a more detailed description within the context of a cognitive neuroscience theory of attention.

Effect of mycobacterium bovis (BCG) infection on the kinetics of the mononuclear cell response within the lung.

Specific pathogen-free LBN rats were parabiotically linked and the monocyte donor animal was labeled with multiple pulses of tritiated thymidine (1 microCi/g body weight). The right-hand (recipient) rat lungs were infected with 10(5) viable Mycobacterium bovis (BCG) Pasteur by the intravenous, aerogenic, or intratracheal routes. Control animals received heat-killed BCG or saline only, given intratracheally. The BCG infection resulted in a ten-fold increase in the number of heavily labeled, blood-derived monocytes recovered 24 hr later in the lung lavage fluid. The percentage of labeled cells peaked on day 3 and then declined slowly. Introduction of heat-killed BCG into the lung produced a smaller mononuclear cell influx but a marked polymorphonuclear phagocyte response that persisted for several days. The labeled monocyte counts for the infected recipient rat lung washouts were five to ten times those for the uninfected donor parabiont, except when the aerogenic infection route was used, when both donor and recipient rats were equally infected and both showed substantial increases in labeled monocytes in the lung washouts.

The effect of combined chemotherapy on suppressor T-cell activity in Mycobacterium simiae-infected mice.

Specific pathogen-free B6D2 mice were infected with 10(6) or 10(8) viable Mycobacterium bovis (BCG Pasteur) or Mycobacterium simiae and the in vivo growth curves were correlated with the levels of delayed hypersensitivity developed against a cytoplasmic protein antigen (CPA) injected into a hind footpad at increasing time intervals after infection. Half of the heavily infected, anergic mice were placed on a regimen of 10 mg of rifampin, 5 mg of amikacin and 2 mg of clofazimine per 100 ml of drinking water 2 or 8 weeks into the infection. The number of viable mycobacteria recovered from the lungs and spleens of the treated mice (compared with the corresponding drug-free controls) were reduced by up to 10,000-fold over a 3-month treatment period. Spleen cells were harvested at increasing time intervals from the drug-treated and control mice and T-cell enriched suspensions were tested for blastogenic responsiveness to phytohaemagglutinin (PHA) and to the specific CPA mitogen. The early (day 14) peak in tritiated thymidine ([3H]-TdR) uptake was followed by a sharp drop to near background levels. Cell-mixing experiments demonstrated the presence of a suppressor T-cell population in the heavily infected spleens of the M. simiae-infected mice. The suppressor-cell effect was substantially reduced following combined drug therapy although the specific CPA-mediated response was less affected than the non-specific PHA-mediated response.

Mycobacterium bovis (BCG) infection of the lymph nodes of normal, immune, and cortisone-treated guinea pigs.

Strain-2 inbred guinea pigs were infected intradermally with 10(5)-10(7) viable BCG (Pasteur) organisms by means of multiple scarifications of shaven midflank skin. The spread of the BCG to the draining lymph nodes and on to the spleen was followed quantitatively for 28 days. The population of bacilli at the inoculation site increased as much as tenfold the first 14 days. The number of viable BCG organisms recovered from the primary draining superficial dorsal axillary and inguinal lymph nodes varied from 0.1 to 1.0% of the inoculum, with a further tenfold to 100-fold drop in counts for the secondary subclavian and lumbar lymph nodes. The bacterial counts for the various nodes increased substantially the first 14 days. By 28 days, as many as 1,000 viable bacilli were recovered from the spleen. Increasing the inoculum size or the number of inoculation sites increased the primary node counts and promoted a more extensive and rapid spread by the BCG population to the secondary lymph nodes and spleen. Prior vaccination of the host with living BCG decreased the spread of the BCG inoculum from the scarification site to the various draining lymph nodes. Multiple injections of cortisone tended to reverse this effect.

Effect of T-cell depletion on the growth of BCG in the mouse footpad.

The growth of Mycobacterium bovis (BCG Montreal) and M. tuberculosis Erdman was determined in normal and T-cell depleted (THXB) mice when injected subcutaneously into a hind footpad. The bacilli multiplied only to a limited extent within the footpad itself but the infection quickly spread to the draining popliteal lymph node to eventually reach the liver, spleen and lung. The amount of systemic growth seen in the THXB mice was 10-100 times greater than in the normal controls, all of which developed a tuberculin hypersensitivity and an immune response in 14-18 days. T-cell depletion completely inhibited the expression of tuberculin sensitivity by the infected host as well as ablating the antituberculous response against both the vaccinating BCG population and a superinfecting Erdman challenge inoculum. Incorporation studies in the THXB mice indicated a striking reduction in cell division within the draining lymph node but there was an unexpected elevation in the level of incorporation by the lung cells as the BCG infection progressed. The significance of these findings is discussed in relation to the possible use of the BCG footpad model for studies of leprosy immunity.