Fear Related Memory

Our memories are closely related to our emotions. Different forms of memory induce different emotions — love, fear, depression, anxiety etc. Our view of the world, therefore, is deeply embedded within our neural networks in the brain. A simplified outline of the mechanism of memory perception begins with the identification of a particular stimulus, stabilization of memory from short term to long term (consolidation) and finally, the storage of long term memory in different regions of the cerebral cortex. The association of memory and the emotion of fear is one of the most widely studied aspects of memory formation in the past decade. Fear can be defined as a conscious state consisting of both associative and non-associative components, caused

Continued exposure to the fear inducing stimulus may even lead to a constant state of hyper vigilance and hyper-arousal. Fear learning therefore gives rise to some of the strongest, most detailed memories, because in the interface between their acquisition and consolidation there is a high degree of emotional arousal that is known to enhance memory consolidation. The recollection of fear memory is also driven by the contextual setting of the individual during the emotional experience. Visual, auditory, gustatory, olfactory and tactile stimuli help an individual better recall a past memory. These sensory associations can be so strong that under experimental conditions, just asking the subject to visualize the environment can lead to the clear recall of the past experience (Smith and Bulkin, 2014). The extent of survival of a species depends on the ability of individuals to anticipate danger by associating environmental stimuli with aversive events. This form of fear learning is studied in the laboratory in a procedure referred to as fear

The amygdala is an almond shaped collection of nuclei found in the temporal lobe of the brain. The basolateral section of the amygdala (consisting of the lateral, basal and accessory basal nuclei) is its major structural portion involved in the mechanism of fear memory consolidation. The lateral nucleus is the primary input nucleus of the amygdala. It receives sensory inputs from the thalamus and the cortex. The central medial nucleus is the primary output nuclei that projects to a number of structures such as the paraventricular nucleus of the hypothalamus (responsible for the release of the stress hormone cortisol), the lateral hypothalamus that stimulates the autonomic nervous system, and the periaqueductal grey matter (which causes fear behavior such as freeze response). Evidence for the involvement of the amygdala in the storage of long term memory is obtained from a number of brain imaging studies. The unconditioned stimulus of the foot shock travels through the spinal cord to two regions that project to the lateral nucleus of the amygdala – the thalamus and the the cortex. The unconditioned input are tring enough to excite the neurons in the lateral amygdala which in turn results in the activation of neurons in the central medial nucleus. This produces a fear