Encoding and decoding bursts by NMDA spikes in basal dendrites of layer 5 pyramidal neurons.
Bursts of action potentials are important information-bearing signals in the brain, although the neuronal specializations underlying burst generation and detection are only partially understood. In apical dendrites of neocortical pyramidal neurons, calcium spikes are known to contribute to burst generation, but a comparable understanding of basal dendritic mechanisms is lacking. Here we show that NMDA spikes in basal dendrites mediate both detection and generation of bursts through a postsynaptic mechanism. High-frequency inputs to basal dendrites markedly facilitated NMDA spike initiation compared with low-frequency activation or single inputs. Unlike conventional temporal summation effects based on voltage, however, NMDA spike facilitation depended mainly on residual glutamate bound to NMDA receptors from previous activations. Once triggered by an input burst, we found that NMDA spikes in turn reliably trigger output bursts under in vivo-like stimulus conditions. Through their unique biophysical properties, NMDA spikes are thus ideally suited to promote the propagation of bursts through the cortical network.
Department of Physiology, Technion Medical School, Haifa, Israel.
Alon
A
Polsky
Bartlett
B
Mel
Jackie
J
Schiller
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D003198:Computer Simulation; D003712:Dendrites / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D016202:N-Methylaspartate / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D002121:Calcium Channel Blockers; C120997:NR2A NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D026941:Sodium Channel Blockers; D018698:Glutamic Acid; D016202:N-Methylaspartate