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Frontiers in Behavioral Neuroscience (1)
Health affairs (Project Hope) (1)
PLoS ONE (1)
Kress, Daniel (3)
Egelhaaf, Martin (2)
Bischof, Hans-Joachim (1)
Eckmeier, Dennis (1)
Geurten, Bart R. H. (1)
Kern, Roland (1)
Mertes, Marcel (1)
Ruger, Jennifer Prah (1)
Year of Publication
Impact of stride-coupled gaze shifts of walking blowflies on the neuronal representation of visual targets
Frontiers in Behavioral Neuroscience
During locomotion animals rely heavily on visual cues gained from the environment to guide their behavior. Examples are basic behaviors like collision avoidance or the approach to a goal. The saccadic gaze strategy of flying flies, which separates translational from rotational phases of locomotion, has been suggested to facilitate the extraction of environmental information, because only image flow evoked by translational self-motion contains relevant distance information about the surrounding world. In contrast to the translational phases of flight during which gaze direction is kept largely constant, walking flies experience continuous rotational image flow that is coupled to their stride-cycle. The consequences of these self-produced image shifts for the extraction of environmental information are still unclear. To assess the impact of stride-coupled image shifts on visual information processing, we performed electrophysiological recordings from the HSE cell, a motion sensitive wide-field neuron in the blowfly visual system. This cell has been concluded to play a key role in mediating optomotor behavior, self-motion estimation and spatial information processing. We used visual stimuli that were based on the visual input experienced by walking blowflies while approaching a black vertical bar. The response of HSE to these stimuli was dominated by periodic membrane potential fluctuations evoked by stride-coupled image shifts. Nevertheless, during the approach the cell’s response contained information about the bar and its background. The response components evoked by the bar were larger than the responses to its background, especially during the last phase of the approach. However, as revealed by targeted modifications of the visual input during walking, the extraction of distance information on the basis of HSE responses is much impaired by stride-coupled retinal image shifts. Possible mechanisms that may cope with these stride-coupled responses are discussed.
spatial vision; blowfly; head movements; goal-directed; walking; fixation
Health Financing And Insurance Reform In Morocco
Ruger, Jennifer Prah
Health affairs (Project Hope)
The government of Morocco approved two reforms in 2005 to expand health insurance coverage. The first is a payroll-based mandatory health insurance plan for public-and formal private–sector employees to extend coverage from the current 16 percent of the population to 30 percent. The second creates a publicly financed fund to cover services for the poor. Both reforms aim to improve access to high-quality care and reduce disparities in access and financing between income groups and between rural and urban dwellers. In this paper we analyze these reforms: the pre-reform debate, benefits covered, financing, administration, and oversight. We also examine prospects and future challenges for implementing the reforms.
Gaze Strategy in the Free Flying Zebra Finch (Taeniopygia guttata)
Geurten, Bart R. H.
Fast moving animals depend on cues derived from the optic flow on their retina. Optic flow from translational locomotion includes information about the three-dimensional composition of the environment, while optic flow experienced during a rotational self motion does not. Thus, a saccadic gaze strategy that segregates rotations from translational movements during locomotion will facilitate extraction of spatial information from the visual input. We analysed whether birds use such a strategy by highspeed video recording zebra finches from two directions during an obstacle avoidance task. Each frame of the recording was examined to derive position and orientation of the beak in three-dimensional space. The data show that in all flights the head orientation was shifted in a saccadic fashion and was kept straight between saccades. Therefore, birds use a gaze strategy that actively stabilizes their gaze during translation to simplify optic flow based navigation. This is the first evidence of birds actively optimizing optic flow during flight.
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