By manipulating the amount of money on offer in each situation, Cohen and his collaborators could watch this neural tug of war unfold. Our ultimate decision - to save for the future or to indulge in the present - was largely determined by whichever region showed greater activation.
The human brain consists of about one billion neurons. Each neuron forms about 1,000 connections to other neurons, amounting to more than a trillion connections. If each neuron could only help store a single memory, running out of space would be a problem.