Information Processing in Dendritic Spines
Dendritic spines are small twigs on the dendrites of a very large class of neurons in the central nervous system. There are between 10 (3) and 10 (5) spines per neuron, each one including at least one synapse, i.e. a connection with other neurons. Thus, spines are usually associated with an important feature of neurons ??eir high degree of connectivity ??e of the most obvious differences between present computers and brains. We have analysed the electrical properties of a cortical (spiny) pyramidal cell on the basis of passive cable theory, from measurements made on histological material, using the solution of the cable equation for an arbitrary branched dendritic tree. As postulated by Rall, we found that the somatic potential induced by firing synapse on a spine is a very sensitive function of the dimension of the spine. This observation leads to several hypotheses concerning the electrical functions of spines, especially with respect to their role in memory.