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Linear summation of excitatory inputs by CA1 pyramidal neurons.

A fundamental problem in neurobiology is understanding the arithmetic that dendrites use to integrate inputs. The impact of dendritic morphology and active conductances on input summation is still unknown. To study this, we use glutamate iontophoresis and synaptic stimulation to position pairs of excitatory inputs throughout the apical, oblique, and basal dendrites of CA1 pyramidal neurons in rat hippocampal slices. Under a variety of stimulation regimes, we find a linear summation of most input combinations that is implemented by a surprising balance of boosting and shunting mechanisms. Active conductances in dendrites paradoxically serve to make summation linear. This "active linearity" can reconcile predictions from cable theory with the observed linear summation in vivo and suggests that a simple arithmetic is used by apparently complex dendritic trees.

Pubmed ID: 10069343


  • Cash S
  • Yuste R



Publication Data

February 30, 1999

Associated Grants

  • Agency: NEI NIH HHS, Id: EY 111787-01A1

Mesh Terms

  • Action Potentials
  • Afferent Pathways
  • Aging
  • Animals
  • Cell Membrane
  • Dendrites
  • Electric Conductivity
  • Excitatory Postsynaptic Potentials
  • Glutamic Acid
  • Hippocampus
  • In Vitro Techniques
  • Intracellular Membranes
  • Iontophoresis
  • Potassium
  • Pyramidal Cells
  • Rats
  • Rats, Sprague-Dawley