Reward maximization assessed using a sequential patch depletion task in a large sample of heterogeneous stock rats

Area of Science:

• Behavioral neuroscience
• Animal behavior
• Decision-making

Background:

• Choice behavior involves evaluating immediate and long-term consequences.
• Impulsive choice is often studied using delay discounting (DD), contrasting immediate smaller rewards with larger delayed rewards.

Purpose of the Study:

• To investigate if reward maximization measures overlap with traditional delay discounting models.
• To compare male and female rat performance in a sequential patch depletion task versus traditional DD tasks.

Main Methods:

• A large sample of Heterogeneous Stock (HS) male and female rats (n=896 males, n=898 females) were tested.
• A Sequential Patch Depletion procedure was used, offering choices between two water patches with decreasing rewards.
• Traditional delay discounting measures and patch utilization metrics were analyzed.

Main Results:

• No significant sex differences were found in traditional delay discounting measures (e.g., delay gradient, AUC).
• Females exhibited fewer patch changes and longer patch residence times compared to males.
• Females showed a greater deviation from reward maximization, but had a higher normalized rate of reinforcement when controlling for body weight.

Conclusions:

• Measures of reward maximization were only weakly associated with traditional DD measures, suggesting distinct underlying processes.
• The patch depletion model was more sensitive to sex differences in decision-making than traditional DD measures.
• Female rats demonstrated different reward maximization strategies compared to males, not captured by standard delay discounting paradigms.