Vision in dynamically changing environments

Visual systems need to be capable of extracting relevant visual information from the constantly changing environment and process this information in order to assure appropriate behavioral responses and thus animal survival. Many visual systems are well suited to function at daylight, dusk and dawn, as well as in rapidly changing environments. This is possible due to photoreceptor adaptation, which ensures that photoreceptors compute contrast irrespective of the background illumination. However, visual perception is challenged when adaptation is not fast enough to deal with sudden declines in overall illumination, for example, when a gaze follows a moving object from bright sunlight into a shaded area. Thus, contrast computation alone is insufficient to explain robust behavioral responses under rapidly changing light conditions, arguing for the need of a corrective signal that scales contrast-sensitive responses when light levels suddenly decline. This corrective signal is luminance information. Just downstream of the photoreceptor cells, there are distinct visual pathway inputs in the fly visual system, L2 and L3, which encode luminance and contrast, respectively. The luminance-sensitive pathway L3 is required for visual processing in rapidly changing light conditions. This ensures contrast constancy when pure contrast sensitivity underestimates a stimulus.

Downstream of these contrast and luminance-sensitive neurons, luminance and contrast signals must ultimately be combined to control motion-guided behaviors. Several synapses downstream of these inputs, the so-called descending neurons carry sensory information from the brain to motor regions of the ventral nerve cord. Descending neurons connect 100,000 neurons in the brain with the 30,000 neurons in the ventral nerve cord. There are only around 1100 descending neurons, making them a critical bottleneck in the flow of sensory information along the sensory-motor pathway. Therefore, anatomical and physiological characterization of individual descending neurons is crucial in our understanding of visual motion processing and motor control. In addition, understanding the connectivity or wiring of those neurons is an important step to our understanding of how the nervous system controls behavior.

Short Bio

Katja Sporar Klinge completed her PhD in 2019, at the Goerg-August University Göttingen, Germany, in Marion Silies’ group. During her PhD Katja uncovered a luminance-sensitive pathway in the Drosophila visual system, which allows for accurate image processing under dynamically changing light conditions.
Following a short post doc in the Silies lab, Katja joined the Motion Vision group at Flinders University, led by Professor Karin Nordström. Katja is continuing her work on insect motion vision and is now focusing on reconstructing neuronal morphology, which will enable us to understand the input mechanisms and connectivity of different types of descending neurons.

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