Medial prefrontal cortex and pavlovian conditioning: trace versus delay conditioning.

Pavlovian eyeblink (EB) conditioning was studied in both trace and delay paradigms in rabbits (Oryctolagus cuniculus) with either medial prefrontal cortex (mPFC) lesions or sham lesions. mPFC lesions of prelimbic cortex (Brodmann's Area 32) retarded EB conditioning in the trace but not the delay paradigm. However, this effect was significant only when the conditioned stimulus (CS) was 500 rather than 100 ms in duration. Lesions of the anterior cingulate cortex (Area 24) did not affect EB conditioning in a trace paradigm. Accompanying CS-evoked heart rate slowing was attenuated under all conditions by the mPFC lesions, although this result was not always statistically significant.