Anxiety induces long-term memory forgetting in the crayfish.

Area of Science:

• Animal behavior
• Neuroscience
• Neuroendocrinology

Background:

• Crayfish establish dominance hierarchies through agonistic encounters.
• A 'winner effect' enhances future performance but can be overcome by experienced smaller individuals.
• Anxiety in mammals is linked to impaired learning and memory loss.

Purpose of the Study:

• To investigate if anxiety-like states, induced by electrical shocks or serotonin, affect the 'winner effect' in crayfish.
• To explore the role of serotonin in mediating anxiety and memory forgetting in crayfish.

Main Methods:

• Dominant crayfish were subjected to electrical shocks or serotonin injections after establishing a win.
• Subsequent pairings with naive opponents assessed the persistence of the 'winner effect'.
• Mianserin (a serotonin antagonist) was used to confirm serotonin's role.

Main Results:

• Electrical shocks impaired the 'winner effect', making dominant crayfish lose to larger naive opponents.
• Serotonin injections (0.5 µM) mimicked the effect of electrical shocks, causing memory forgetting.
• Higher serotonin concentrations (1.0 µM) and mianserin treatment did not affect the 'winner effect'.

Conclusions:

• Anxiety, mediated by low-concentration serotonin, can erase the 'winner effect' in crayfish.
• This suggests a conserved mechanism linking anxiety, serotonin, and memory impairment across species.
• The findings provide insights into the neurobiological basis of social memory and stress responses.