limbic system

Meaning: The limbic system is a group of interconnected structures beneath the cerebral cortex that link emotion, motivation, and memory. Textbooks differ slightly on which structures count, but the core is the amygdala, hippocampus, and hypothalamus, often with the thalamus, septal nuclei, and cingulate cortex. The amygdala evaluates threat and produces fear and aggression responses. The hippocampus is needed to form new explicit (declarative) memories. The hypothalamus regulates drives such as feeding and sexual behavior and, through the pituitary, hormonal stress responses.

On the MCAT: Passages describe a lesion, stimulation, or imaging study and ask which function changes. Amygdala damage tends to reduce fear and aggression. Hippocampal damage causes anterograde amnesia: new explicit memories fail to form, while old memories and procedural skills are largely spared. Hypothalamic changes alter feeding, thirst, or temperature regulation. Expect fMRI items showing amygdala activation to threatening faces.

Common confusion: Students call the hippocampus the site where all memories are stored. It is needed for forming (consolidating) new explicit memories, but long-term storage is spread across the cortex. Likewise, the amygdala is not the only region involved in emotion; the prefrontal cortex also shapes emotional responses.