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.