Talking while you sleep? Dream on!

QUESTION Is it impossible to read or tell the time in dreams?

LANGUAGE-RELATED functions such as reading, writing and deciphering symbols are very difficult to carry out while dreaming.

During rapid eye movement sleep, which is associated with dreaming, certain parts of the brain are inactive – crucially, these include the Broca’s and Wernicke’s areas, which are in the dominant left side of the brain.

The Broca’s area is associated with speech and articulation, while the Wernicke’s area is primarily for speech comprehension. Stringing a coherent sentence together is practically impossible when the Wernicke’s area is asleep.

Most dreamers also lose the ability to read or comprehend signs.

However, those with a great facility for language, such as poets, are able to formulate complex language in their sleep. Samuel Taylor Coleridge wrote his classic poem Kubla Khan after ‘seeing’ it in a dream. Conrad Smith, St Andrews, Fife.

QUESTION How closely

related are sweet potatoes to potatoes? Which is better for us? FURTHER to the earlier answer, when I worked in Uganda in the 1990s, children living in the African country would often have protein deficiency (kwashiorkor) and rotten teeth because they ate mainly maize, sugar cane and sweet potatoes.

An important difference between the Irish potato, as they called it in Uganda, and sweet potato is the protein content.

Sweet potato contains very little, but the Irish potato is 15% protein, which made a significant difference to their nutrition. Dr Steve Brennan, Hope Valley, Derbys.