Posterior cingulate cortical lesions eliminate learning-related unit activity in the anterior cingulate cortex

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Learning and Memory

Background:

• Neuronal firing in the cingulate cortex (Brodmann's Area 24 and 29) changes during discriminative avoidance conditioning.
• The dorsal subiculum's influence on these cortical areas is crucial, but its projection pathways are not fully understood.

Purpose of the Study:

• To investigate the pathway through which the dorsal subiculum influences Area 24 during avoidance learning.
• To test the hypothesis that Area 29 acts as a synaptic relay for subicular input to Area 24.

Main Methods:

• Discriminative avoidance conditioning in rabbits.
• Bilateral electrolytic and aspirative lesions of the dorsal subicular complex and Area 29.
• Electrophysiological recordings of multi-unit neuronal firing and macropotentials in Areas 24 and 29.

Main Results:

• Lesions of the dorsal subicular complex abolished training-induced excitatory responses in both Area 24 and Area 29.
• Lesions of Area 29 eliminated training-induced neuronal responses in Area 24.
• Lesions in both the subiculum and Area 29 increased macropotential amplitude in Area 24.

Conclusions:

• The dorsal subiculum influences Area 24's neuronal activity during avoidance learning.
• Area 29 appears to serve as a critical synaptic relay for subicular projections to Area 24.
• These findings contribute to understanding the neural circuitry of learning involving the cingulate cortex, hippocampus, and limbic thalamus.