Visualizing Desire (Brian Knutson, Stanford University)

Establish that desire is not merely philosophical but a scientific question with neural substrates. Present the classic self-stimulation experiment from 1954 where rats with brain electrodes repeatedly pressed a lever for direct brain stimulation.

Describe functional magnetic resonance imaging (fMRI) developed in 1993, highlighting its temporal resolution (seconds), spatial resolution (1-2mm voxels), and depth resolution to visualize subcortical brain circuits. Show structural brain imaging with activation maps.

Present the fMRI experimental design where subjects view cue signals, anticipate money gain or loss outcomes, and press a button when targets appear. Explain the trial structure that separates anticipatory phase from outcome phase.

Show fMRI results demonstrating increased nucleus accumbens activation when subjects anticipate monetary gain, with activation correlating to anticipated reward amount. Plot activation over time to show heightened response during anticipatory phase before button press.

Demonstrate that nucleus accumbens activation varies by individual subjective value of rewards, showing that the same monetary amount produces different activation levels depending on personal preference and wealth.

Apply brain activation measurements to predict investment choices, showing that nucleus accumbens activation predicts risky stock choices while insula activation predicts conservative bond choices during the anticipatory period.

Conduct shopping experiment with 80 products where subjects decide to buy or decline at given prices. Show nucleus accumbens activation correlates with product preference while another brain region responds to excessive prices and predicts purchase avoidance.