INDICATIONS OF AMYGDALA FUNCTION

This is a very indepth reading but taking a bit apart makes us understand some of the main actions and what leads to our emotional response verus logical response.



Monkeys without amygdalas have difficulty learning to associate a light-signal with an electric shock -- and also have difficulty associating a neutral stimulus with a food reward. It has been suggested that the amygdala functions to associate sensation with reward or punishment. Amphetamine injections to the ventral striatum enhance the effects of a conditioned reinforcing stimulus only if the amygdala is intact.
Neurons in the lateral, basal and central nuclei of primate amygdalas have been found to respond to visual stimuli associated with a food reward. But when the reward was changed to an aversive food (saline) the response of these neurons did not change -- in contrast to neurons in the orbitofrontal cortex and basal forebrain which show a rapid reversal in response to a positive reinforcement becoming a negative one. This implies that the amygdala neuron response corresponds to whether a stimulus has reward/punishment significance (and merits attention), rather than associating the stimulus with a reward or punishment.
Signals from the thalamus, co-ordinated with signals from the visual cortex, evidently allow the amygdala to assist in focusing attention in response to fear [SCIENCE 300:568-569 (2003)]. Fearful images -- notably other humans with fearful facial expressions -- apparently increase attention, arousal and cortical processing through amygdala mediation.


http://www.benbest.com/science/anatmind/anatmd9.html