Mapping conditioned taste aversion associations using c-Fos reveals a dynamic role for insular cortex

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Learning and Memory

Background:

• Novel tastes are more effective conditioned stimuli (CSs) in taste aversion learning compared to familiar tastes.
• Novel CS-unconditioned stimulus (US) pairings elicit stronger Fos-like immunoreactivity (FLI) in the insular cortex (IC), amygdala, and brainstem than familiar pairings, indicating broader neural recruitment for novel taste acquisition.

Purpose of the Study:

• To elucidate the specific role of the insular cortex (IC) in taste aversion learning, particularly concerning novelty detection and memory formation.
• To differentiate the functions of the IC in the acquisition of novel taste aversion versus the consolidation of familiar taste safety.

Main Methods:

• Immunostaining was combined with targeted lesions or reversible inactivation of the insular cortex (IC).
• Fos-like immunoreactivity (FLI) was measured in the IC, amygdala, and brainstem following novel and familiar taste-US pairings.
• Taste preexposure followed by reversible inactivation was used to assess the formation of 'safe' taste memories.

Main Results:

• IC lesions abolished FLI increases in the amygdala during novel taste pairings, suggesting a role for the IC in novelty detection.
• Reversible inactivation of the IC during taste preexposure led to increased FLI in the amygdala and brainstem during familiar taste pairings.
• Temporary inactivation disrupted the establishment of 'safe' taste memory, unlike permanent lesions.

Conclusions:

• The insular cortex (IC) plays a critical, dual role in taste learning: it is essential for novelty detection during acquisition and involved in forming memories of safe tastes.
• These findings highlight the complex neural circuitry underlying taste aversion learning and the specific contributions of the IC to different phases of the learning process.