PNN under Attack (IMAGE) University of Queensland Caption UQ researchers propose that when vitamin D levels drop, certain enzymes become unchecked and begin to break down perineuronal nets. Credit Nick Valmas, The University of Queensland Usage Restrictions Only to be used with attribution. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.