A-Z Index...
How does a paramecium move and process information?

Rebounding reaction of Paramecia towards external stimulus.

(1-3) short-lasting ciliary reversal; (3-5) pivoting and circling; (6) swimming in new direction...

"If we are to believe that neurons are the only things that control the sophisticated actions of animals, then the humble paramecium presents us with a profound problem. For she swims about her pond with her numerous tiny hairlike legs - the cilia - darting in the direction of bacterial food which she senses using a variety of mechanisms, or retreating at the prospect of danger, ready to swim off in another direction. She can also negotiate obstructions by swimming around them. Moreover, she can apparently even learn from her past experiences - though this most remarkable of her apparent faculties has been disputed by some. How is this achieved by an animal without a single neuron or synapse? Indeed, being but a single cell, and not being a neuron herself, she has no place to accomodate such accessories.

Yet there must indeed be a complicated control system governing the behavior of a paramecium - or indeed other one-celled animals like amoebas - but it is not a nervous system. The structure responsible is apparently part of what is refrerred to as the cytoskeleton..."

Roger Penrose Shadows of the Mind