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Medial prefrontal cortex and pavlovian conditioning: trace versus delay conditioning
Joselyn McLaughlin1, Helen Skaggs, John Churchwell
1Shirley L. Buchanan Neuroscience Laboratory, Veterans Affairs Medical Center, Columbia, South Carolina 29209-1639, USA.
Abstract:
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.
Insights
Medial prefrontal cortex lesions impaired trace eyeblink conditioning in rabbits, especially with longer stimuli. Delay conditioning and anterior cingulate cortex lesions showed no significant effects on this learning.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Cognitive Neuroscience
Background:
- Pavlovian conditioning is a fundamental learning process.
- The medial prefrontal cortex (mPFC) plays a role in complex cognitive functions, including learning and memory.
- Specific subregions of the mPFC, like the prelimbic cortex, are implicated in different aspects of conditioning.
Purpose of the Study:
- To investigate the role of the medial prefrontal cortex (mPFC), specifically the prelimbic cortex, in trace and delay eyeblink (EB) conditioning.
- To examine the effect of mPFC lesions on different phases of Pavlovian conditioning.
- To determine if lesion effects are dependent on conditioned stimulus (CS) duration.
Main Methods:
- Rabbits (Oryctolagus cuniculus) underwent either trace or delay eyeblink conditioning.
- Surgical lesions were made in the medial prefrontal cortex (prelimbic cortex, Area 32) or anterior cingulate cortex (Area 24), with sham lesion controls.
- Behavioral responses (eyeblink) and autonomic responses (heart rate slowing) to the conditioned stimulus were measured.
Main Results:
- Medial prefrontal cortex lesions significantly retarded trace eyeblink conditioning, particularly when the conditioned stimulus duration was 500 ms compared to 100 ms.
- No significant impairment in delay eyeblink conditioning was observed following mPFC lesions.
- Lesions of the anterior cingulate cortex did not affect trace eyeblink conditioning.
- mPFC lesions attenuated conditioned stimulus-evoked heart rate slowing, though not always significantly.
Conclusions:
- The prelimbic cortex of the medial prefrontal cortex is crucial for trace eyeblink conditioning, but not delay conditioning.
- The duration of the conditioned stimulus influences the impact of mPFC lesions on trace conditioning.
- The mPFC's role in eyeblink conditioning may involve modulating autonomic responses alongside motor learning.