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ref: -0 tags: microstim ICMS axons soma Nowak NMDA date: 01-27-2012 23:30 gmt revision:1 [0] [head]

PMID-9504843 Axons, but not cell bodies, are activated by electrical stimulation in cortical gray matter. I. Evidence from chronaxie measurements.

  • Slice experiments / in vitro.
  • The chronaxie for orthodromic activation was similar to that for axonal activation, but was 40 times smaller than the chronaxie for direct cell body activation. This suggests that, whenever a postsynaptic response is elicited after electrical stimulation of the cortical gray matter, axons (either axonal branches or axon initial segments), but not cell bodies, are the neuronal elements activated.

PMID-9504844 Axons, but not cell bodies, are activated by electrical stimulation in cortical gray matter. II. Evidence from selective inactivation of cell bodies and axon initial segments.

  • Blocked soma and proximal axons / dendrites from firing AP through iontophoresis of NMDA.
  • When the NMDA-induced depolarization block was performed at the site of electrical stimulation, an unexpected increase in the amplitude of the orthodromic (backwards, into the white matter) responses was observed.
    • Possibly due to an increase in axonal excitability (?)
    • Superexitability eventually washed out, leading to responses that was 15-20% lower than before NMDA soma / proximal axon block.
  • "Since the neocortex is organised as a network of local and long-range reciprocal connections, great attention must be paid to the interpretation of data obtained with electrical stimulation."