described Trace Conditioned Reflexes, or sometimes in other literature: Trace Conditioned Responses
as the response caused by conditioning which presented the US
, then stopped the US
and paused for a time, before presenting the CS
Depending on the relative period of the pause, seconds (called: short-trace), or minutes (called: long-trace), this conditioning produced different forms of recall-results. Pavlov
apparently referred to this as "Trace conditioned reflex" because it did not rely on simultaneous stimulation of the CS
, but instead relied on a "trace" of the US
remaining in the brain after the unconditioned stimulus
had been removed from the animal.
. . . . . . . . . . .
"Trace Reflex" is NOT equal to "Periodicity Reflex"
Immediately following his discussion of the trace reflex in his third lecture Pavlov
described, but failed to name, another "agent" which could be used as a CS.
Because it came right on the heels of the discussion about trace reflexes, and because he never named it, it is sometimes conflated with trace reflex. Trace Reflex is NOT the same thing as the periodicity reflex which was described (but not named) in a discussion immediately following the discussion of trace reflexes. See Periodicity Conditioned Reflex
for more information on this.
There is considerable confusion regarding the term Trace Reflex, which, as far as I can tell originates with Pavlov's third lecture, or with its translation into English. In the English translation of his book, Pavlov spoke of long- and short-trace reflexes
Internal trace was his term for a trace of the US that remained in the brain after the US had been removed. Conditioned reflexes that relied on this "trace" were referred to as: "Trace Conditioned Reflexes". To avoid this I will attempt to use the term "after effect" to refer to the internal trace (Pavlov noted this term as being common in the literature of his time).
The term trace conditioning has taken on a slightly different definition in Internet based circles. There, it is thought of as conditioning in which, the US
is turned off for some period of time prior to the CS
being introduced (during conditioning). Pavlov distinguished this as a short-term trace reflex (that is, a reflex which is caused by conditioning that presents the CS
within a second or two after the US
). The resulting CR is indistinguishable from a CR produced by simultaneous stimuli.
In the first version of Netlab, applying the CS
after the US
had ceased was referred to as temporal-associative learning, or association across the temporal-domain.