Read the passage and answer the question given below by selecting the correct option:
A recent study by researchers from Basel University and Munich Technical University challenges prior beliefs about the influence of different light colours on the human body's internal clock and sleep-wake rhythm. Unlike a previous study conducted on mice, this one suggests, that light colour may be less critical for the internal clock than originally thought.
Vision involves a complex process of perceiving various light wavelengths as colours and brightness in the brain. Photoreceptors in the retina convert light into electrical impulses, transmitted to ganglion cells in the retina and to the visual cortex in the brain. Specialised ganglion cells play a significant role in the internal clock, being sensitive to short-wavelength light at around 490 nanometers, perceived as blue. When activated by short-wavelength light, these cells signal "it's daytime" to the internal clock.
To explore the influence of light colour on the internal clock, the researchers exposed 16 healthy volunteers to blueish or yellowish light stimuli for one hour in late evening with a white light stimulus as a control condition. The light stimuli were designed to selectively activate the colour- sensitive cones in the retina, while maintaining consistent stimulation of the light-sensitive ganglion cells in all conditions. This allowed the researchers to directly check effects of light on the respective cone stimulation and, the colour of the light.
Contrary to the findings in mice, the study suggests that the colour of light, as encoded by the cones, may not significantly influence the human internal clock and sleep-wake rhythm.The current research contradicts the earlier finding that yellowish light had a stronger influence on the internal clock than blueish light. The results, published in "Nature Human Behaviour", imply that while light intensity and exposure duration remain crucial factors, the colour of light may not play as significant a role in influencing sleep and circadian rhythms as previously believed.
Why were the light stimuli designed to differentially activate colour-sensitive cones in the retina?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → to check the effect of light on the cone stimulation
The light stimuli were designed to selectively activate the colour-sensitive cones while keeping the stimulation of the ganglion cells the same. "This allowed the researchers to directly check effects of light on the respective cone stimulation" and the colour of the light.
Why the Other Options are Incorrect?
Option 1: to study the circadian rhythms — Incorrect. Too broad: the circadian rhythm is the wider subject of the study; the particular design of the stimuli was meant to separate the effect of the cones.
Option 2: to maintain consistent stimulation of ganglion cells — Incorrect. Wrong reason: keeping the ganglion cells steady was a condition of the experiment, kept while the cones were activated; it was not the purpose of activating the cones.
Option 4: to explore vision complexity — Incorrect. Wrong focus: vision complexity is only background in the passage; the experiment was not about it.