Giordano Ramos-Traslosheros

Bio: Giordano Ramos-Traslosheros is an academic researcher from University of Mainz. The author has contributed to research in topics: Population & Motion (physics). The author has an hindex of 2, co-authored 5 publications receiving 21 citations. Previous affiliations of Giordano Ramos-Traslosheros include University of Göttingen.

Populations of local direction–selective cells encode global motion patterns generated by self-motion

Abstract: Self-motion generates visual patterns on the eye that are important for navigation. These optic flow patterns are encoded by the population of local direction–selective cells in the mouse retina, whereas in flies, local direction–selective T4/T5 cells are thought to be uniformly tuned. How complex global motion patterns can be computed downstream is unclear. We show that the population of T4/T5 cells in Drosophila encodes global motion patterns. Whereas the mouse retina encodes four types of optic flow, the fly visual system encodes six. This matches the larger number of degrees of freedom and the increased complexity of translational and rotational motion patterns during flight. The four uniformly tuned T4/T5 subtypes described previously represent a local subset of the population. Thus, a population code for global motion patterns appears to be a general coding principle of visual systems that matches local motion responses to modes of the animal’s movement.

Motion detection: cells, circuits and algorithms

Abstract: Abstract Many animals use visual motion cues to inform different behaviors. The basis for motion detection is the comparison of light signals over space and time. How a nervous system performs such spatiotemporal correlations has long been considered a paradigmatic neural computation. Here, we will first describe classical models of motion detection and introduce core motion detecting circuits in Drosophila. Direct measurements of the response properties of the first direction-selective cells in the Drosophila visual system have revealed new insights about the implementation of motion detection algorithms. Recent data suggest a combination of two mechanisms, a nonlinear enhancement of signals moving into the preferred direction, as well as a suppression of signals moving into the opposite direction. These findings as well as a functional analysis of the circuit components have shown that the microcircuits that process elementary motion are more complex than anticipated. Building on this, we have the opportunity to understand detailed properties of elementary, yet intricate microcircuits.

The physiological basis for contrast opponency in motion computation in Drosophila.

Abstract: In Drosophila, direction-selective neurons implement a mechanism of motion computation similar to cortical neurons, using contrast-opponent receptive fields with ON and OFF subfields. It is not clear how the presynaptic circuitry of direction-selective neurons in the OFF pathway supports this computation if all major inputs are OFF-rectified neurons. Here, we reveal the biological substrate for motion computation in the OFF pathway. Three interneurons, Tm2, Tm9 and CT1, provide information about ON stimuli to the OFF direction-selective neuron T5 across its receptive field, supporting a contrast-opponent receptive field organization. Consistent with its prominent role in motion detection, variability in Tm9 receptive field properties transfers to T5, and calcium decrements in Tm9 in response to ON stimuli persist across behavioral states, while spatial tuning is sharpened by active behavior. Together, our work shows how a key neuronal computation is implemented by its constituent neuronal circuit elements to ensure direction selectivity. The Drosophila visual system first computes motion in the dendrites of T4 and T5 neurons via a linear mechanism that uses ON and OFF information. Here, the authors show that the Tm9, Tm2, and CT1 neurons provide both ON and OFF information to direction-selective T5 cells in the OFF pathway.

An optimal population code for global motion estimation in local direction-selective cells

Abstract: Nervous systems allocate computational resources to match stimulus statistics. However, the physical information that needs to be processed depends on the animal’s own behavior. For example, visual motion patterns induced by self-motion provide essential information for navigation. How behavioral constraints affect neural processing is not known. Here we show that, at the population level, local direction-selective T4/T5 neurons in Drosophila represent optic flow fields generated by self-motion, reminiscent to a population code in retinal ganglion cells in vertebrates. Whereas in vertebrates four different cell types encode different optic flow fields, the four uniformly tuned T4/T5 subtypes described previously represent a local snapshot. As a population, six T4/T5 subtypes encode different axes of self-motion. This representation might serve to efficiently encode more complex flow fields generated during flight. Thus, a population code for optic flow appears to be a general coding principle of visual systems, but matching the animal’s individual ethological constraints.

Populations of local direction–selective cells encode global motion patterns generated by self-motion

Abstract: Self-motion generates visual patterns on the eye that are important for navigation. These optic flow patterns are encoded by the population of local direction–selective cells in the mouse retina, whereas in flies, local direction–selective T4/T5 cells are thought to be uniformly tuned. How complex global motion patterns can be computed downstream is unclear. We show that the population of T4/T5 cells in Drosophila encodes global motion patterns. Whereas the mouse retina encodes four types of optic flow, the fly visual system encodes six. This matches the larger number of degrees of freedom and the increased complexity of translational and rotational motion patterns during flight. The four uniformly tuned T4/T5 subtypes described previously represent a local subset of the population. Thus, a population code for global motion patterns appears to be a general coding principle of visual systems that matches local motion responses to modes of the animal’s movement.

Eye-tracking Support for Architects, Conservators, and Museologists. Anastylosis as Pretext for Research and Discussion

Abstract: Conservators, museologists, and architects make extremely complex decisions capable of affecting the way people perceive monuments. One might give this idea deeper consideration while pondering anastylosis. One of the things a designer should do when selecting a method of merging together parts of a damaged monument is answer the question whether the chosen method will facilitate the interest of onlookers in the presented object. In which case will the observers spend most of their time looking at the authentic relic fragments and distinguishing between the old and the new parts? The definitions in force do not explain how to approach this topic. By using eye-tracking research, we can learn how observers look at historical objects that have been reassembled again. By combining the observation of visual behaviours with a survey of people looking at such objects, it is possible to see how the process of classifying what is new and old actually works. This knowledge allows for more conscious approach to heritage management processes. In future, results of eye-tracking experiments should help experts plan sustainable conservation projects. Thanks to knowing the reactions of regular people, one will be able to establish conservation programmes in which the material preservation of a monument will reflect the way in which this object affects contemporary onlookers. Such an approach ought to result in real social and economic benefits.