The sensory systems of living organisms have evolved to detect changes rather than absolute sensory stimuli. This means that, for example, we may forget the glasses we hold against our nose, but we will definitely feel an insect resting on our skin.
The vision works in the same way, it is adaptable and designed to respond to the changes in the environment. The vision is also based on the perception of contrastIn fact, when lighting conditions change, the eye needs a certain amount of time to adapt and restore its ability to correctly estimate contrast. In this sense, the retinal photoreceptors play a key role by ensuring that contrast is detected regardless of background brightness. This retinal adaptation cannot, however, explain the mechanism that is established when faced with sudden changes, where the background brightness can change in milliseconds.
Researchers at the Johannes Gutenberg University Mainz (JGU) studied the mechanism implemented by Drosophila melanogaster (fruit fly) the correct perception of contrast even in suddenly changing light conditions. The study, recently published in Current Biology, investigated processes occurring in the nervous system, downstream of photoreceptors, paying particular attention to pathways involving lamina neurons specialised in detecting an increase or decrease in contrast.
Scholars have identified a new mechanism which explains how correct image processing takes place in rapidly changing light conditions, demonstrating that brightness information act as a corrective signal which intervenes when light suddenly dims. Contrast sensitivity alone is therefore not sufficient to explain behavioural responses to visual stimuli, brightness information is needed to accurately recognise contrasts.
The study concludes that the intensity of the light, the primary input signal for the visual system, it is also a crucial factor in correctly controlling behavioural responses to visual stimuli, proposing that this is a strategy of visual processing probably also used by the human eye.
Source:
Dr. Carmelo Chines
Direttore responsabile
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