Spike-accomodation in the hippocampus

William Calvin wcalvin at u.washington.edu
Mon Feb 21 18:58:25 EST 1994


kisley at spot.Colorado.EDU (Michael Kisley) writes:

>wcalvin at u.washington.edu (William Calvin) writes:

>>What you are looking for is generally called "adaptation" in spiking; 
>>"accommodation" is generally reserved for threshold changes to a slow 
>>depolarization.

>In response, I have two comments:  

>First of all, I have seen no such
>clear demarcation between "accomodation" and "adaptation" in the
>literature.  Guyton's "Textbook of Medical Physiology" does seem to favor
>your categorization, but the problem is this:  It seems to me that when
>people speak of "adaptation" they are usually using it to describe
>primary sensory receptors (ie. somatosensory and olfactory receptors)
>rather than, say, cortical pyramidal cells.  It is clear from the responses
>I received to this post that many researchers refer to decreased spiking
>in the hippocampus as accomodation.

The 1950-70s literature on spinal motorneurons is largely where the 
distinction arose.

>Secondly, I have seen no other attempt to explain "adaptation" by any other
>mechanism than exactly your definition of "accomodation" (which is the
>change of threshold due to depolarization).  In other words, as far as I
>know, the slow rise in threshold due to depolarization is exactly
>what causes spiking to decrease and eventually cease during a non-novel
>stimulus.  Therefore, accomodation of threshold is precisely what
>produces accomodation of spiking (or adaptation by your definition).
>Given this, I see no reason not to refer to "adaptation" as "accomodation
>of spiking".
  On the contrary, both spike rate adaptation and voltage threshold 
runaway accommodation are products of a number of causes.  The 
accommodation experiments with current ramps (see Koike et al, Exp Brain 
Research, early 70s) do confuse the issue a little, as the end point is 
the stimulus current at the time of first spike, not the voltage from 
which the upstroke of the impulse begins.  For an example of voltage 
thresholds in motorneurons, see W. H. Calvin & C. F. Stevens, J. 
Neurophysiol. 1968  and W. H. Calvin, Brain Research 1974.
    William H. Calvin   WCalvin at U.Washington.edu




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