2,3-Cyclooctadienone (IX) is not an intermediate in these reactions. We have prepared this interesting cyclic allenone by reaction of 3-bromo-3-cyclooctenone (X) with base; it reacts with 1,3-diphenylisobenzofuran to give the two epimers of the expected Diels-Alder adduct XI, but none of VII.The literature is rich with uses of conjugated acetylenic carbonyl compounds. Nucleophilic additions to the triple bond are of particular value. Most such reactions give trans-added products.6 For example, the acetylenic ketone III reacts with sodium thiophenoxide in aqueous solvents to give the trans-f3-thiophenoxy ,/3-unsaturated ketone XII. It has been reported that primary and secondary amines add cis to activated triple bonds; it has been proposed that the proton carried into the reaction by the amine is transferred specifically to the -vinyl carbon.7 We have found, however, that cis addition to conjugated acetylenic carbonyl systems is not restricted to the addition of amines. The base-catalyzed addition of methanol to the acetylenic ketones we have studied takes the same course.For example, reaction of compound III with aqueous methanolic potassium carbonate gives only (by nmr) the c/s-added m-methoxy ,/3-unsaturated ketone XIII. This is known to be the kinetically controlled product as the trans isomer of XIII is not isomerized under the reaction conditions. Much remains to be done before the factors that control the (6) E.

No abstract

In many situations, such as pedestrians crossing a busy street or prey evading predators, rapid decisions based on limited perceptual information are critical for survival. The brevity of these perceptual judgments constrains how neuronal signals are integrated or pooled over time because the underlying sequence of processes, from sensation to perceptual evaluation to motor planning and execution, all occur within several hundred milliseconds. Because most previous physiological studies of these processes have relied on tasks requiring considerably longer temporal integration, the neuronal basis of such rapid decisions remains largely unexplored. In this study, we examine the temporal precision of neuronal activity associated with a rapid perceptual judgment. We find that the activity of individual neurons over tens of milliseconds can reliably convey information about sensory events and was well correlated with the animals' judgments. There was a strong correlation between sensory reliability and the correlation with behavioral choice, suggesting that rapid decisions were preferentially based on the most reliable sensory signals. We also find that a simple model in which the responses of a small number of individual neurons (<5) are summed can completely explain behavioral performance. These results suggest that neuronal circuits are sufficiently precise to allow for cognitive decisions to be based on small numbers of action potentials from highly reliable neurons.

94304)Summary 1, 10-Bis(tripheny1methoxy)decane forms stable threaded compounds with macrocyclic hydrocarbons in the range C25-C29 only.STATISTICAL and directed syntheses of compounds consisting of macrocycles threaded by methylene chains bearing large end groups, such as (9), have been describedl previously. Described here is the application of the statistical method to the determination of the effect of macrocycle ring size on the formation and stability of threaded compounds.

No abstract

No abstract

No abstract

Subjects naturally form and use expectations to solve familiar tasks, but the accuracy of these expectations, and the neuronal mechanisms by which these expectations enhance behavior, are unclear. We trained animals (Macaca mulatta) in a challenging perceptual task in which the likelihood of a very brief pulse of motion was consistently modulated over time and space. Pulse likelihood had dramatic effects on behavior: unexpected pulses were nearly invisible to the animals. To examine the neuronal basis of such inattention blindness, we recorded from single neurons in the middle temporal (MT) area, an area related to motion perception. Fluctuations in how reliably MT neurons both signaled stimulus events and predicted behavioral choices were highly correlated with changes in performance over the course of individual trials. A simple neuronal pooling model reveals the dramatic behavioral effects of attention in this task can be completely explained by changes in the reliability of a small number of MT neurons.