Insular cortex and consummatory successive negative contrast in the rat

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Animal Models

Background:

• Successive negative contrast (SNC) is a phenomenon where reward devaluation leads to reduced responding.
• The insular cortex is implicated in processing reward value and aversion.
• Previous research suggests the insular cortex plays a role in behavioral contrast effects.

Purpose of the Study:

• To investigate the role of the insular cortex in successive negative contrast (SNC).
• To determine if insular cortex lesions abolish the SNC effect in rats.
• To explore potential mechanisms underlying SNC, such as novelty detection.

Main Methods:

• Rats underwent either insular cortex lesion (ICX) or a sham procedure.
• Rats were trained to consume high-value sucrose reward.
• Following training, rats were exposed to a reduced-value saccharin reward (postshift trials).
• Drinking behavior (intake) was measured before and after the reward downshift.

Main Results:

• Rats with insular cortex lesions (ICX) showed normal initial responses to both sucrose and saccharin.
• ICX rats did not display SNC; they did not reduce their intake of saccharin after the downshift.
• ICX rats consumed significantly more saccharin during downshift trials compared to control rats maintained on saccharin.

Conclusions:

• The insular cortex is critical for the expression of successive negative contrast (SNC).
• Lesions of the insular cortex may impair the ability to detect or respond to a decrease in reward value.
• Impaired novelty recognition of the less preferred stimulus may underlie the absence of SNC in ICX rats.