The ventral dentate gyrus mediates pattern separation for reward value.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Behavioral Neuroscience

Background:

• The hippocampus, particularly the dentate gyrus (DG), is implicated in memory and spatial navigation.
• The ventral DG subregion's specific role in reward processing and decision-making remains less understood.

Purpose of the Study:

• To investigate the role of the ventral dentate gyrus (DG) in pattern separation related to reward value.
• To determine if lesions to the ventral DG affect behavioral responses to changes in reward magnitude.

Main Methods:

• Rats with ventral DG lesions, sham lesions, and controls were trained on a runway task with a 20-pellet reward.
• After reaching asymptotic running speed, reward size was reduced to 1, 9, or 17 pellets.
• Running velocities were measured to assess behavioral adjustments.

Main Results:

• Control and sham-lesioned rats showed a graded decrease in running speed corresponding to reduced reward values, indicating pattern separation.
• Ventral DG-lesioned rats maintained high running speeds irrespective of reward magnitude changes.
• These deficits were not attributed to hyperactivity and suggest a role in reward prediction.

Conclusions:

• The ventral DG is essential for processing reward value and adjusting behavior accordingly.
• Lesions in the ventral DG disrupt decision-making processes related to goal-relevant outcomes.
• Findings support the ventral DG's involvement in a neural circuit for predicting reward outcomes.