Fine Dendrites Fire Differently

Science Signaling  11 Aug 2009:
Vol. 2, Issue 83, pp. ec270
DOI: 10.1126/scisignal.283ec270

The pyramidal neuron is the basic computational unit in the brain cortex. Its distal tuft dendrite is heavily innervated by horizontal fibers coursing through cortical layer 1, providing long-range corticocortical and thalamocortical associational input. Larkum et al. investigated whether the apical tuft dendrites of layer 5 neocortical pyramidal neurons, like basal dendrites, generate N-methyl-D-aspartate (NMDA) spikes using two-photon–guided direct dendritic recording, glutamate uncaging, and modeling. NMDA spikes could be evoked in the distal tuft dendrites, whereas Ca2+ spikes could be triggered at the bifurcation points. Block of the hyperpolarization-activated current enhanced these NMDA spikes. Thus, the generation of NMDA spikes is a general principle of thin, basal, and tuft dendrites.

M. E. Larkum, T. Nevian, M. Sandler, A. Polsky, J. Schiller, Synaptic integration in tuft dendrites of layer 5 pyramidal neurons: A new unifying principle. Science 325, 756–760 (2009). [Abstract] [Full Text]