Figure 10.

Dendritic spines allow the pyramidal neuron to function as a complex multiunit processing system. (A): representation of a pyramidal neuron with multiple spine units. (B): representation of the pyramidal neuron with multiple sites for coincidence detection (A, B) in its spines and distal dendritic branches, with spread to summation points by passive or active mechanisms (C), further spread boosted by active membrane and synaptic inputs) (D), similar mechanisms in the basal dendrites (E), and final summation at the ell body and axon hillock (F). Modulation occurs through excitation or inhibition at successive stages by layer-targeted inputs. Excitatory synapses indicated by open arrows; inhibitory synapses by filled arrows. (C): Examples of interconnections between point neurons that could implement OR (left), AND (middle), or more complex logic operations (right), as represented by McCulloch and Pitts (1943). From Shepherd (1994).