Temporal processing and context dependency in C. elegans mechanosensation

A quantitative understanding of how sensory signals are transformed into motor outputs places useful constraints on brain function and helps reveal the brain's underlying computations. We investigate how the nematode C. elegans responds to time-varying mechanosensory signals using a high-throughput optogenetic assay and automated behavior quantification. In the prevailing picture of the touch circuit, the animal's behavior is determined by which neurons are stimulated and by the stimulus amplitude. In contrast, we find that the behavioral response is tuned to temporal properties of mechanosensory signals, like its integral and derivative, that extend over many seconds. Mechanosensory signals, even in the same neurons, can be tailored to elicit different behavioral responses. Moreover, we find that the animal's response also depends on its behavioral context. Most dramatically, the animal ignores all tested mechanosensory stimuli during turns. Finally, we present a linear-nonlinear model that predicts the animal's behavioral response to stimulus.Comment: 40 pages, 8 main figures, 19 supplementary figure

Net-Loss Reciprocation and the Context Dependency of Economic Choices

This paper proposes a novel explanation for the context dependency of individual choices in two-player games. Context dependency refers to the well-established phenomenon that a player, when choosing from a given opportunity set created by the other player’s strategy, chooses differently in different situations because of different alternatives to the other player’s strategy. The utility model used to explain this kind of context dependency incorporates a preference for net-loss reciprocation. Net-loss reciprocation means that a player’s willingness to impose a net loss (i.e., loss minus gain) on the other player increases in the net loss that he or she derives from the other player’s strategy. I show that net-loss reciprocation together with the method for calculating net losses developed in this paper explains the context dependencies in individual behaviour that have been documented in a number of experimental studies, whereas existing models of intention-based reciprocity fail to explain all the evidence

Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)

The escape trajectories animals take following a predatory attack appear to show high degrees of apparent 'randomness' - a property that has been described as 'protean behaviour'. Here we present a method of quantifying the escape trajectories of individual animals using a path complexity approach. When fish (Pseudomugil signifer) were attacked either on their own or in groups, we find that an individual's path rapidly increases in entropy (our measure of complexity) following the attack. For individuals on their own, this entropy remains elevated (indicating a more random path) for a sustained period (10 seconds) after the attack, whilst it falls more quickly for individuals in groups. The entropy of the path is context dependent. When attacks towards single fish come from greater distances, a fish's path shows less complexity compared to attacks that come from short range. This context dependency effect did not exist, however, when individuals were in groups. Nor did the path complexity of individuals in groups depend on a fish's local density of neighbours. We separate out the components of speed and direction changes to determine which of these components contributes to the overall increase in path complexity following an attack. We found that both speed and direction measures contribute similarly to an individual's path's complexity in absolute terms. Our work highlights the adaptive behavioural tactics that animals use to avoid predators and also provides a novel method for quantifying the escape trajectories of animals.Comment: 9 page

Scene Context Dependency of Pattern Constancy of Time Series Imagery

A fundamental element of future generic pattern recognition technology is the ability to extract similar patterns for the same scene despite wide ranging extraneous variables, including lighting, turbidity, sensor exposure variations, and signal noise. In the process of demonstrating pattern constancy of this kind for retinex/visual servo (RVS) image enhancement processing, we found that the pattern constancy performance depended somewhat on scene content. Most notably, the scene topography and, in particular, the scale and extent of the topography in an image, affects the pattern constancy the most. This paper will explore these effects in more depth and present experimental data from several time series tests. These results further quantify the impact of topography on pattern constancy. Despite this residual inconstancy, the results of overall pattern constancy testing support the idea that RVS image processing can be a universal front-end for generic visual pattern recognition. While the effects on pattern constancy were significant, the RVS processing still does achieve a high degree of pattern constancy over a wide spectrum of scene content diversity, and wide ranging extraneousness variations in lighting, turbidity, and sensor exposure

On the context-dependency of inequality aversion: Experimental evidence and a stylized model

We consider three-person envy games with a proposer, a responder, and a dummy player. In this class of games, the proposer, rather than allocating a constant pie, chooses the pie size which the responder can then accept or reject while the dummy player can only refuse his own share. While the agreement payoffs for the responder and the dummy are exogenously given, the proposer acts as the residual claimant who - in case of responder acceptance - receives whatever is left after the two exogenously given agreement payoffs have been deducted from the pie. Consistent with earlier findings from three-person generosity games, we find inequality aversion to be strongly context-dependent and affected by the (in)equality of exogenously given agreement payoffs. Motivated by these findings, we present a stylized model on context-dependent inequality aversion that accounts for the observed effects

Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)

The escape paths prey animals take following a predatory attack appear to be highly unpredictable - a property that has been described as ‘protean behaviour’. Here we present a method of quantifying the escape paths of individual animals using a path complexity approach. When individual fish (Pseudomugil signifer) were attacked, we found that a fish's movement path rapidly increased in complexity following the attack. This path complexity remained elevated (indicating a more unpredictable path) for a sustained period (at least 10 seconds) after the attack. The complexity of the path was context dependent; paths were more complex when attacks were made closer to the fish, suggesting that these responses are tailored to the perceived level of threat. We separated out the components of speed and turning rate changes to determine which of these components contributed to the overall increase in path complexity following an attack. We found that both speed and turning rate measures contributed similarly to an individual's path complexity in absolute terms. Overall, our work highlights the context dependent escape responses that animals use to avoid predators and also provides a method for quantifying the escape paths of animals