Cortisol reduces plasticity in the kitten visual cortex

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Animal Models

Background:

• Cortisol, a stress hormone, plays a role in brain development and function.
• Visual cortex plasticity is crucial for normal visual system development.
• The critical period for visual plasticity is a sensitive window for developmental changes.

Purpose of the Study:

• To investigate the impact of elevated cortisol on visual cortex plasticity in cats.
• To determine if cortisol affects ocular dominance shifts during monocular deprivation.
• To explore the relationship between natural cortisol levels and the decline of the critical period.

Main Methods:

• Cats received daily cortisol injections starting around 35 days of age.
• Monocular deprivation was implemented for 10 days, followed by visual cortex recordings.
• Ocular dominance histograms were constructed and compared between cortisol-treated and control groups.
• Plasma cortisol levels were measured in normal cats of various ages.

Main Results:

• Cortisol administration significantly reduced the ocular dominance shift in a dose-dependent manner.
• The effect of cortisol on plasticity was observed even when administered before light exposure and outside the peak critical period.
• Natural cortisol levels in cats remained relatively constant during the critical period for plasticity, suggesting it's not the primary driver for its decline.

Conclusions:

• Elevated cortisol levels substantially impact visual cortex plasticity in cats.
• Cortisol's influence on plasticity is present throughout the sensitive developmental window, not just at its peak.
• The natural rise in cortisol levels does not appear to be the cause for the closure of the critical period for visual plasticity.