MARCH 2006 



Learning to 

 Find Your Way 



The biochemical pathways underlying spatial memory 

 in the brain are giving up their secrets. 



By Eric R. Kandel 



For all living creatures, knowledge of the 

 surrounding environment and their posi- 

 tion within it is key to behavior and critical 

 to survival. At the simplest level spatial "knowl- 

 edge" may encompass no more than the ability to 

 orient toward or away from a stimulus. In complex 

 organisms, though, the representation of space is a 

 cognitive process, in which inputs from several 

 senses — sight, hearing, the sensations of motion 

 and posture provided by the inner ear and muscle 

 tension — are bound together. Such binding is a 

 function of the brain. How is it accomplished? 



The brain represents information about space in 

 many of its areas and in many different ways. For 

 some purposes the brain represents space with 



egocentric coordinates, that is, from the point of 

 view of the sensing organism. For example, the 

 brain encodes where a light is relative to the fovea 

 of the retina, or where an odor or touch comes 

 from with respect to the body For other kinds of 

 behavior the brain encodes the organism's position 

 with respect to the outside world, and the relations 

 of external objects with respect to one another. 

 Such position coordinates, which are centered on 

 the world, are known as allocentric coordinates. 



The eighteenth-century German philosopher 

 Emmanuel Kant, one of the forefathers of cogni- 

 tive psychology, argued that the ability to repre- 

 sent space allocentrically is built into the mind. 

 People, in Kant's view, were born with principles 



NATURAL HISTORY March 2006 



