In this technique the device actually measures whether or not a certain memory is being recalled or is being generated on the spot. For example, if you are interrogating a criminal who denies ever being at a crime scene, and you show them a picture of the scene, you can deduce whether he/she has actually seen it or not by measuring if their brain is recalling some sensory data from memory or newly creating and storing it.
A new method of ‘lie detection’ is being perfected using functional near infrared imaging of the prefrontal cortex:
http://www.biomed.drexel.edu/fNIR/Contents/deception/
In this technique the device actually measures whether or not a certain memory is being recalled or is being generated on the spot. For example, if you are interrogating a criminal who denies ever being at a crime scene, and you show them a picture of the scene, you can deduce whether he/she has actually seen it or not by measuring if their brain is recalling some sensory data from memory or newly creating and storing it.