OTHERS

Question Corner

Blinking eyes

QUESTION: Why do we blink our eyes ?

P.V. Srinivasan, Chennai

ANSWER: The object of blinking of our eyelids is to keep the front of the eyeball clean. Blinking is done by means of muscles in the eye lids and the cleansing by tears. The tears are secreted in a little gland and carried along to the eye and whwn our eyelids open and close the teasrs are poured over the front of the eye and they wash away any particles of dust or any other harmful substances. Some animals like the snake for example, do not have eye lids and hence cannot blink. But there is a hard film or scale over the eyes to protect them from dust and injury.

N.Dharmeshwaran, Chennai

Dreamtime

QUESTION: Do people who were born blind dream? And if they do, how do they ``see" in their dreams?

ANSWER: People who were born blind certainly do dream. However, people who are born blind or become blind before the age of five do not ``see" in their dreams, though their dreams are as rich in narrative and detail as those of sighted people. People who lose thier sight after the age of seven can still have very vivid visual imagery in their dreams 20 to 30 years after the loss of vision. Between the ages of five and seven there is a bit of a grey area. Rapid eye movements, or REM's - a series of jerky movements of the sleeper's eyes - accompany dreaming sleep. The eyes move as if the sleeper is watching the scenes about which they are dreaming. However, people with congenital blindness, and those who lose their sight before the age of five, may lack REM's, or if they have them they are generally of low amplitude. Those who lose their sight after the age of seven continue to have REMs during dreaming.

As one might expect, congenitally blind dreamers report auditory imagery as being more vivid than sighted dreamers do. Interestingly, deaf people dream in sign language and report more vivid colours in their dreams than hearing individuals. Finally blind people tend to dream more about familiar situations and less about novel ones than do sighted people.

New Scientist

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G.R.K. Murthy, Mysore

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