No abstract

The ability to learn is universal among animals; we investigate associative learning between odors and "tastants" in larval Drosophila melanogaster. As biologically important gustatory stimuli, like sugars, salts, or bitter substances have many behavioral functions, we investigate not only their reinforcing function, but also their response-modulating and response-releasing function. Concerning the response-releasing function, larvae are attracted by fructose and repelled by sodium chloride and quinine; also, fructose increases, but salt and quinine suppress feeding. However, none of these stimuli has a nonassociative, modulatory effect on olfactory choice behavior. Finally, only fructose but neither salt nor quinine has a reinforcing effect in associative olfactory learning. This implies that the response-releasing, response-modulating and reinforcing functions of these tastants are dissociated on the behavioral level. These results open the door to analyze how this dissociation is brought about on the cellular and molecular level; this should be facilitated by the cellular simplicity and genetic accessibility of the Drosophila larva.

No abstract

Accumulating evidence suggests that visual perception operates in an oscillatory fashion at an alpha frequency (around 10 Hz). Moreover, visual attention also seems to operate rhythmically, albeit at a theta frequency (around 5 Hz). Both rhythms are often associated to "perceptual snapshots" taken at the favorable phases of these rhythms. However, less is known about the unfavorable phases: do they constitute "blind gaps," requiring the observer to guess, or is information sampled with reduced precision insufficient for the task demands? As simple detection or discrimination tasks cannot distinguish these options, we applied a continuous report task by asking for the exact orientation of a Landolt ring's gap to estimate separate model parameters for precision and the amount of guessing. We embedded this task in a well‐established psychophysical protocol by densely sampling such reports across 20 cue‐target stimulus onset asynchronies in a Posner‐like cueing paradigm manipulating involuntary spatial attention. Testing the resulting time courses of the guessing and precision parameters for rhythmicities using a fast Fourier transform, we found an alpha rhythm (9.6 Hz) in precision for invalidly cued trials and a theta rhythm (4.8 Hz) in the guess rate across validity conditions. These results suggest distinct roles of the perceptual alpha and the attentional theta rhythm. We speculate that both rhythms result in environmental sampling characterized by fluctuating spatial resolution, speaking against a strict succession of blind gaps and perceptual snapshots.

Bivariate extremes, Pickands dependence function, Tail independence, Tail dependence parameter, Neyman–Pearson test, Kolmogorov–Smirnov test, Fisher’s κ, Chi-square goodness-of-fit test, Differentiable spectral neighborhood, Generalized Pareto distribution,