Ghrelin modulates encoding-related brain function without enhancing memory formation in humans.

Area of Science:

• Neuroscience
• Endocrinology
• Cognitive Psychology

Background:

• Ghrelin is known to regulate energy homeostasis and enhance memory in animal models.
• The impact of ghrelin on human cognitive functions, particularly memory, remains largely uncharacterized.

Purpose of the Study:

• To investigate the acute effects of ghrelin administration on memory formation and related brain activity in healthy human participants.
• To determine if ghrelin administration enhances cognitive performance in tasks involving memory encoding and recall.

Main Methods:

• A double-blind, randomized, crossover study involving 21 healthy young male participants.
• Functional magnetic resonance imaging (fMRI) was used to record brain activity during a word memorization task.
• Participants underwent memory recall tests and a cognitive test battery on separate days following ghrelin or placebo administration.

Main Results:

• Ghrelin administration led to decreased resting-state functional connectivity between the caudate nucleus and other brain regions (insula, amygdala, orbitofrontal cortex) post-encoding.
• Brain activity associated with subsequent memory performance was modulated by ghrelin, but this modulation did not correlate with actual memory recall.
• No significant differences in free word recall, cued location-word association recall, or performance on a comprehensive cognitive test battery were observed between ghrelin and placebo conditions.

Conclusions:

• Acute ghrelin administration does not enhance memory formation or overall cognitive function in healthy young men.
• Contrary to findings in animal models, ghrelin does not appear to act as a short-term cognitive enhancer in humans.
• The observed alterations in brain activity and functional connectivity by ghrelin were not associated with improved memory performance.