fMRI (IMAGE) University of Arizona College of Engineering Caption fMRI scans show 'hot spots' of human brain activity as subjects perform memory tasks. The brain contains 100 billion nerve cells, or neurons, with 100 trillion connections, or synapses. Credit Courtesy of the Walter Reed National Military Medical Center Usage Restrictions None 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.