The modulation of simple reaction time by the spatial probability of a visual stimulus

Simple reaction time (SRT) in response to visual stimuli can be influenced by many stimulus features. The speed and accuracy with which observers respond to a visual stimulus may be improved by prior knowledge about the stimulus location, which can be obtained by manipulating the spatial probability of the stimulus. However, when higher spatial probability is achieved by holding constant the stimulus location throughout successive trials, the resulting improvement in performance can also be due to local sensory facilitation caused by the recurrent spatial location of a visual target (position priming). The main objective of the present investigation was to quantitatively evaluate the modulation of SRT by the spatial probability structure of a visual stimulus. In two experiments the volunteers had to respond as quickly as possible to the visual target presented on a computer screen by pressing an optic key with the index finger of the dominant hand. Experiment 1 (N = 14) investigated how SRT changed as a function of both the different levels of spatial probability and the subject's explicit knowledge about the precise probability structure of visual stimulation. We found a gradual decrease in SRT with increasing spatial probability of a visual target regardless of the observer's previous knowledge concerning the spatial probability of the stimulus. Error rates, below 2%, were independent of the spatial probability structure of the visual stimulus, suggesting the absence of a speed-accuracy trade-off. Experiment 2 (N = 12) examined whether changes in SRT in response to a spatially recurrent visual target might be accounted for simply by sensory and temporally local facilitation. The findings indicated that the decrease in SRT brought about by a spatially recurrent target was associated with its spatial predictability, and could not be accounted for solely in terms of sensory priming.

Synaptic vesicle pool size, release probability and synaptic depression are sensitive to Ca2+ buffering capacity in the developing rat calyx of Held

The calyx of Held, a specialized synaptic terminal in the medial nucleus of the trapezoid body, undergoes a series of changes during postnatal development that prepares this synapse for reliable high frequency firing. These changes reduce short-term synaptic depression during tetanic stimulation and thereby prevent action potential failures during a stimulus train. We measured presynaptic membrane capacitance changes in calyces from young postnatal day 5-7 (p5-7) or older (p10-12) rat pups to examine the effect of calcium buffer capacity on vesicle pool size and the efficiency of exocytosis. Vesicle pool size was sensitive to the choice and concentration of exogenous Ca2+ buffer, and this sensitivity was much stronger in younger animals. Pool size and exocytosis efficiency in p5-7 calyces were depressed by 0.2 mM EGTA to a greater extent than with 0.05 mM BAPTA, even though BAPTA is a 100-fold faster Ca2+ buffer. However, this was not the case for p10-12 calyces. With 5 mM EGTA, exocytosis efficiency was reduced to a much larger extent in young calyces compared to older calyces. Depression of exocytosis using pairs of 10-ms depolarizations was reduced by 0.2 mM EGTA compared to 0.05 mM BAPTA to a similar extent in both age groups. These results indicate a developmentally regulated heterogeneity in the sensitivity of different vesicle pools to Ca2+ buffer capacity. We propose that, during development, a population of vesicles that are tightly coupled to Ca2+ channels expands at the expense of vesicles more distant from Ca2+ channels.

Etat général des dettes de l'Etat à la mort du feu Roy Louis XIV . Arrivée le premier septembre 1715. Leur réduction & payement. Avec la suppression & extinction d'un grand nombre d'offices & droits, à la décharge des peuples, jusqu'au premier septembre 1720

[Acte. 1720]

Manuscrits de la bibliothèque de l'Arsenal. Archives de la Bastille. DEUXIÈME SECTION — PRISONNIERS DOSSIERS INDIVIDUELS ET DOCUMENTS BIOGRAPHIQUES (1). AFFAIRE DU DUC ET DE LA DUCHESSE DU MAINE. Correspondance contre les intérêts de l'État avec la cour d'Espagne, par l'entremise du prince de Cellamare, ambassadeur d'Espagne à Paris, et complot contre le Régent, pour les droits à la couronne de France, des princes légitimés, en cas d'extinction de la maison royale, et pour rétablir le duc du Maine dans le pouvoir que le testament de Louis XIV lui avait donné. Dossiers particuliers et notes.

Contient : Dossiers particuliers de Boisdavy, de l'abbé Brigault, de Dadvisard, de La Jonquière, de l'abbé Lecamus et de l'abbé Thouvenin, comprenant leur correspondance des années 1716-1719 ; Notes prises par Duval, secrétaire de la Lieutenance de police, et ses commis, et par les commissaires des papiers de la B. nommés en 1789, sur les dossiers de l'affaire du duc du Maine