<P> The medial nucleus is involved in the sense of smell and pheromone - processing . It receives input from the olfactory bulb and olfactory cortex . The lateral amygdalae, which send impulses to the rest of the basolateral complexes and to the centromedial nuclei, receive input from the sensory systems . The centromedial nuclei are the main outputs for the basolateral complexes, and are involved in emotional arousal in rats and cats . </P> <P> In complex vertebrates, including humans, the amygdalae perform primary roles in the formation and storage of memories associated with emotional events . Research indicates that, during fear conditioning, sensory stimuli reach the basolateral complexes of the amygdalae, particularly the lateral nuclei, where they form associations with memories of the stimuli . The association between stimuli and the aversive events they predict may be mediated by long - term potentiation, a sustained enhancement of signaling between affected neurons . There have been studies that show that damage to the amygdala can interfere with memory that is strengthened by emotion . One study examined a patient with bilateral degeneration of the amygdala . He was told a violent story accompanied by matching pictures and was observed based on how much he could recall from the story . The patient had less recollection of the story than patients with functional amygdala, showing that the amygdala has a strong connection with emotional learning . </P> <P> Emotional memories are thought to be stored in synapses throughout the brain . Fear memories, for example, are considered to be stored in the neuronal connections from the lateral nuclei to the central nucleus of the amygdalae and the bed nuclei of the stria terminalis (part of the extended amygdala). Of course, these connections are not the sole site of fear memories given that the nuclei of the amygdala receive and send information to other brain regions that are important for memory such as the hippocampus . Some sensory neurons project their axon terminals to the central nucleus . The central nuclei are involved in the genesis of many fear responses such as defensive behavior (freezing or escape responses), autonomic nervous system responses (changes in blood pressure and heart rate / tachycardia), neuroendocrine responses (stress - hormone release), etc . Damage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses . </P> <P> The amygdalae are also involved in appetitive (positive) conditioning . It seems that distinct neurons respond to positive and negative stimuli, but there is no clustering of these distinct neurons into clear anatomical nuclei . However, lesions of the central nucleus in the amygdala have been shown to reduce appetitive learning in rats . Lesions of the basolateral regions do not exhibit the same effect . Research like this indicates that different nuclei within the amygdala have different functions in appetitive conditioning . Nevertheless, researchers found an example of appetitive emotional learning showing an important role for the basolateral amygdala: The naïve female mice are innately attracted to non-volatile pheromones contained in male - soiled bedding, but not by the male - derived volatiles, become attractive if associated with non-volatile attractive pheromones, which act as unconditioned stimulus in a case of Pavlovian associative learning . In the vomeronasal, olfactory and emotional systems, Fos protein show that non-volatile pheromones stimulate the vomeronasal system, whereas air - borne volatiles activate only the olfactory system . Thus, the acquired preference for male - derived volatiles reveals an olfactory - vomeronasal associative learning . Moreover, the reward system is differentially activated by the primary pheromones and secondarily attractive odorants . Exploring the primary attractive pheromone activates the basolateral amygdala and the shell of nucleus accumbens but neither the ventral tegmental area nor the orbitofrontal cortex . In contrast, exploring the secondarily attractive male - derived odorants involves activation of a circuit that includes the basolateral amygdala, prefrontal cortex and ventral tegmental area . Therefore, the basolateral amygdala stands out as the key center for vomeronasal - olfactory associative learning . </P>

What part of the brain plays an important role in emotional conditioning