Hippocampal function is required for feedback control of an internal clock's criterion

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Cognitive Neuroscience

Background:

• The hippocampus plays a crucial role in memory and temporal processing.
• Understanding the neural mechanisms of interval timing is essential for cognitive neuroscience.

Purpose of the Study:

• To investigate the effects of hippocampal fimbria-fornix lesions on the control of an internal clock's criterion in rats.
• To determine how hippocampal damage impacts temporal memory and working memory related to timing.

Main Methods:

• A discrete-trial peak-interval procedure was employed.
• Rats underwent either fimbria-fornix lesions or sham operations.
• Following surgery, rats were trained and tested on 20-s and 10-s peak-interval procedures.

Main Results:

• Sham-operated rats exhibited peak responding at the reinforcement time (10 or 20 s), showing feedback control.
• Fimbria-fornix lesioned rats responded approximately 20% earlier than the reinforcement time (8 or 16 s).
• Lesioned rats failed to demonstrate control over successive peak-time values.

Conclusions:

• Fimbria-fornix lesions impair the memory of reinforcement timing (reference memory).
• Hippocampal damage interferes with the internal control of temporal criteria (working memory).
• These lesions do not affect stimulus duration sensitivity or learning new temporal criteria.