Filtering of distractors during visual search studied by positron emission tomography.

We investigated the sensitivity of brain areas to the presence of filtering operations during overt visual search in crowded displays. Task conditions involved either visual search or predetermined simple eye movements for the detection of target digits. Furthermore, visual displays either contained letter foils that required filtering or contained only target digits. Brain imaging using positron emission tomography showed extensive overlap between areas involved in overt visual search and eye movements. Selective filtering of foils affected visual processing in ventral areas associated with object recognition and in primary visual cortex.

The dynamics of shifting visuospatial attention revealed by event-related potentials.

We developed a behavioral task for spatial orienting of attention in which the same physical stimulus cued covert peripheral shifts of attention to either the left or the right visual fields in different conditions. The design enabled us to record the brain activity engaged during spatial shifts of covert attention that was independent from the physical characteristics of the cueing stimulus using event-related potentials (ERPs). ERPs elicited by foveal cues differed according to the predicted target location starting ca. 160 ms, and differences persisted until the occurrence of the target stimuli. Multiple processes were linked to shifting spatial attention during the cue-target interval. The earliest effects consisted of enhanced negative potentials over the posterior scalp contralateral to the cued location. Later effects were concentrated over the right anterior scalp sites, where activity associated with shifts to the right visual field elicited larger positive potentials. The results extend our understanding of the neural system that orients spatial attention by providing valuable information about the temporal dynamics and hemispheric asymmetries of activity within its posterior and anterior regions.

Functional localization of the system for visuospatial attention using positron emission tomography.

PET was used to image the neural system underlying visuospatial attention. Analysis of data at both the group and individual-subject level provided anatomical resolution superior to that described to date. Six right-handed male subjects were selected from a pilot behavioural study in which behavioural responses and eye movements were recorded. The attention tasks involved covert shifts of attention, where peripheral cues indicated the location of subsequent target stimuli to be discriminated. One attention condition emphasized reflexive aspects of spatial orientation, while the other required controlled shifts of attention. PET activations agreed closely with the cortical regions recently proposed to form the core of a neural network for spatial attention. The two attention tasks evoked largely overlapping patterns of neural activation, supporting the existence of a general neural system for visuospatial attention with regional functional specialization. Specifically, neocortical activations were observed in the right anterior cingulate gyrus (Brodmann area 24), in the intraparietal sulcus of right posterior parietal cortex, and in the mesial and lateral premotor cortices (Brodmann area 6).

Face recognition as a function of social attention in non-human primates: an ERP study.

Epidural event related potentials (ERPs) were recorded from four squirrel monkeys (Saimiri sciureus) during the presentation of pictoral stimuli that comprised real human and monkey faces. Subjects viewed tachistoscopically presented stimuli belonging to four different categories: familiar and unfamiliar human faces, and familiar and unfamiliar monkey faces. Familiar faces were subcategorized into top, middle and bottom according to the perceived individual's dominance ranking in a social hierarchy, as rated by human judges observing the group's social behavior. Waveform peak components to monkey and human faces showed similarities in their spatial distribution. However, larger amplitude N1 and N2 components were elicited in response to monkey compared to human faces, particularly over lateral temporo-parietal sites. A similar trend was observed for the P3 component, with maximal differences along midline electrode site. Responses to familiar and unfamiliar monkey faces showed larger N1s to familiar monkey faces and larger P3s to unfamiliar monkey faces. N1 and P3 components elicited by human faces showed no significant differences between conditions. N2 amplitudes were larger over posterior sites for top-ranked monkeys and larger over frontal sites for middle- and bottom-ranked monkeys. Top-ranked human faces elicited the largest N2 components, middle-ranked faces the next largest, and bottom-ranked faces the smallest. N1, N2, and P3 latencies were similarly sensitive to the ranking of human but not monkey faces. These data suggest that non-human primates exhibit evoked potentials to conspecific and non-conspecific faces that are similar in morphology but different in function. Larger amplitude responses to monkey faces suggests increased processing for that category of stimuli. Additionally, monkey ERPs reflect familiarity with conspecifics but not with human faces. Finally, the social status of the perceived individual, or at least the perceived threat posed by an individual, affects the latencies and magnitudes of ERP components produced by the viewer. These data are consistent with social attention hypotheses which propose that higher status (i.e. more dominant or socially meaningful) members of a group receive more attention than lower status individuals.

[Determination of fibrinopeptide A (FpA): comparison of an enzymatic method and isotopic method with reference to ventilation-perfusion scintigraphy]. / Dosage du fibrinopeptide A (FpA): comparaison d'une méthode enzymatique et d'une méthode isotopique, en référence à la scintigraphie de ventilation-perfusion.

Fibrinopeptide A becomes free after thrombolysis of fibrinogen in thrombo-embolic situation. In view to quantify this molecule, the authors have compared two different methodologies (enzymatic and isotopic). Isotopic scintigraphy of lung (ventilation-perfusion) served as reference in this study for pulmonary thrombosis.

[Detection of anti-DNA antibodies using I125-protein A]. / Mise en évidence des anticorps anti-DNA par la protéine A-125I.

Our purpose is to detect and dose anti-DNA antibodies in sera with analytical interferences in compatibility tests. This method seems with interest to clear transfusional reactions or incompatibilities in the laboratory tests. With 122 sera presenting a minor and isolated incompatibility with bromelin, we've found 21 positive results correlated or not (18/26) with the IF. The exposed methodology, simple, fast and reproducible seems to be a useful tool to resolve some transfusional situations.

[Determination of anti-tetanus antibodies using protein A labeled with iodine 125]. / Dosage des anticorps antitétaniques avec la protéine "A" marquée à l'iode 125.

We present a quantitative measurement of specific antitetanic IgG immunoglobulins with protein "A" labeled with I125. The Laurell's immunoelectrophoresis was the reference method. After having fixed optimum conditions of duration and temperature of de reaction, we studied the different concentrations of the coated antigen and also the different dilution of serum. We can so eliminate the most aspecific effects of the antigen-antibody reaction. The correlation between the two methods of measurement is more than 98%.

Investigation of the interaction between Probon and indomethacin in rats.

The toxic side-effects and anti-inflammatory activity of combination treatment of Sprague-Dawley rats with indomethacin and Probon, a new type of analgesic, were investigated. Following four weeks of treatment with a combination of these two drugs, the characteristic gastrointestinal side-effect of indomethacin was markedly reduced. Mortality resulting from administration of the drug combination was significantly lower than that resulting from indomethacin treatment alone. The reduced toxicity of indomethacin in combination with Probon is probably due to a change in metabolism produced by the hepatic microsomal enzyme inducer, Probon. The anti-inflammatory effect was also investigated using a contact thermographic method following one, three or seven days pretreatment. The advantage of this combination is that, using a higher dose of indomethacin in combination with the minor analgesic, we could achieve a more reliable anti-inflammatory effect together with a pain-killing action.

Influencing of resorption and side-effects of salicylic acid by complexing with beta-cyclodextrin.

After oral administration of 14C-labelled salicylic acid and its beta-cyclodextrin complex to rats, the blood radioactivity-level increases in the first 2 h than decreases. The blood level obtained with the inclusion complex is somewhat but not significantly lower than with free acid. Since the resorption of cyclodextrin is a considerably slower process, it is very likely that the resorption of salicylic acid take place in the form of free acid after dissociation of the complex. The urinary excretion cumulative curves show that the free salicylic acid is completely excreted, while about 10% of the salicylic acid administered in the form of complex is lost. The cyclodextrin complex formation increases the pK value of all hydroxy-benzoic acids. Direct observations reveals that complex formation decreases the stomach-irritating effect of salicylic acid. The ratio of radioactivity was nearly the same in the organs of animals treated by both free salicylic and cyclodextrin complex.

Effect of CH-123 on vascular cholesterol deposition in experimental atherosclerosis of rabbits.

The effect of CH-123, a new antiarteriosclerotic pyrido-1,2a-pyramide derivate was checked in experimental atherosclerosis of rabbits. Cholesterol deposition was found to continue after 4-week cholesterol feeding even after the cholesterol level had returned to normal. This allowed to study the action of drugs in a phase dominated by lipid apposition to the vascular wall. In the experiments, clofibrate was used for reference. As judged by the lipid values in serum and aortic wall, CH-123 reduced substantially the deposition of lipids, mainly of cholesterol, into the aortic wall.