He started off by using a fear conditioning experiment with rats, pairing a tone with a foot shock until the tone triggered the physical responses by the ANS without the shock.LeDoux found, after making several lesions in parts of the rats brains associated with sound processing for example, he found that by examining the activity in the brain during the conditioning, there was also activity in the amygdala. When creating lesions in the amygdala he found that the rats no longer feared the tone because they didn't recognise it. The first signal was quicker and reached the amygdala from the thalamus before the other signal from the cortex. The one from the thalamus was thought to make the rat react to the stimuli quickly, without thinking to much, as if it were a threat. The second was believed to cause the rat to re-analyze the situation to see if there was a threat.