PER3 and Tay-Sachs disease: The study was conducted in a sample of 36 healthy men and women, stratified on the basis of a variable-number (4 or 5) tandem-repeat polymorphism (rs57875989) in the coding region of the clock gene PERIOD3 (PER3) [28] which in previous behavioural [29] and fMRI studies [30], has been identified as a bio-marker for the “trait-like” susceptibility to effects of acute TSD on Working Memory performance with a high executive load when assessed in the morning hours.