Dissociated theta phase synchronization in amygdalo-hippocampal circuits during various stages of fear memory

Bergado, J., Kluge, C., Narayanan, R.T., Pape, H.C., & Seidenbecher, T. (2007). Dissociated

Theta phase synchronization in amygdalo-hippocampal circuits during various stages

Of fear memory. European Journal of Neuroscience, 25, 1823-1831. doi: 10.1111/j.

1460-9568.2007.05437.x

Chapter 14 defines memory as the ability to recall or recognize previous experience. Research has shown that the amygdala and hippocampus play a vital role in memory formation and conversion. Both of these brain areas are very plastic and seem to be linked when converting fear memories from short term memory to long term memory for retention. In this study male mice were used and electrodes were place in the left hemisphere and in the lateral amygdala, as well as, the nasal and cerebellar areas. Using Palovian conditioning, a learning procedure whereby a neutral stimulus comes to elicit a response because of its repeated pairing with some event, auditory stimuli and electric shock were used to condition fear. Fear conditioning is a learned association, a conditioned emotional response, between a neutral stimulus and a noxious event such as a shock.

The recorded brain activity suggest that the lateral amygdala and the hippocampus work together in the formation and retrieval of long term fear memory. The hippocampus also works with the prefrontal cortex when coompleting spatial memory tasks after being cued and conditioned to fear. The amygdala and hippocampus do not seem to work together in the formation of fear memory on a short term basis. It is believed that this is because the amygdala deals with the cues and the context and the hippocampus only deals with the context (the shock). The results also showed involvement of the perirhinal and postrhinal cortices, in the temporal lobe, for current and remote fear memory. In conclusion, the amygdala plays a role in complex and simple fear memory and handles new and pre-existing forms of memory. The hippocampus plays a role in long term or permanent fear memory.