How can you jump at a shape in the grass before you know it is a stick? · Grey Matter

Sensory signals reach the amygdala by two routes from the thalamus: a short one that goes straight there, and a longer one through the cortex, which identifies the object properly.

How can you jump at a shape in the grass before you know it is a stick?

Sensory signals reach the amygdala by two routes from the thalamus: a short one that goes straight there, and a longer one through the cortex, which identifies the object properly. In rats LeDoux showed that the direct route alone, from the auditory thalamus, is enough to learn and express fear of a sound, and it is faster because it skips the cortical stages. The short route carries a coarse picture (something long, something moving), enough to start a startle and a racing heart; a moment later the cortical route reports that it is a stick, and the prefrontal cortex calms the alarm. Tractography has since traced a matching pathway in humans.