cingulate gyrus

**Anatomy** - Lies on the medial surface of each cerebral hemisphere, arching above the corpus callosum and separated from it by the callosal sulcus. The cingulate sulcus bounds it superiorly. - Part of the limbic lobe. It continues posteriorly via the isthmus to the parahippocampal gyrus. - Blood supply: mainly branches of the anterior cerebral artery (pericallosal and callosomarginal arteries), with posterior portions supplied by the posterior cerebral artery. - The cingulum is the white-matter tract beneath it. It connects the cingulate with the entorhinal cortex and hippocampus.

**Functional subdivisions** - Anterior cingulate cortex (ACC, Brodmann areas 24, 32, 33): - Emotion regulation, motivation, and drive. - Affective (unpleasantness) component of pain. - Attention, conflict and error monitoring, and autonomic regulation. - Empathy and decision making. - Posterior cingulate cortex (BA 23, 31) and retrosplenial cortex (BA 29, 30): - Memory and spatial orientation. - A key hub of the default mode network. - Early hypometabolism on FDG-PET in Alzheimer disease.

**Papez circuit (memory and emotion)** Hippocampus → fornix → mammillary bodies → mammillothalamic tract → anterior nucleus of thalamus → cingulate gyrus → cingulum → entorhinal cortex → hippocampus.

**Clinical correlations** - Bilateral anterior cingulate lesions (for example, ACA stroke): apathy, abulia, and akinetic mutism. - Cingulotomy: historically used for intractable pain, OCD, and severe depression. It reduces the emotional suffering of pain without abolishing sensation. - Subfalcine (cingulate) herniation: the cingulate gyrus is pushed under the falx cerebri. This can compress the ACA and cause contralateral leg weakness and sensory loss. - Psychiatric disease: - ACC dysfunction is implicated in depression, OCD, ADHD, and schizophrenia. - Subgenual ACC (BA 25) is a target for deep brain stimulation in treatment-resistant depression. - Alzheimer disease: early posterior cingulate and precuneus hypometabolism and atrophy. - Chronic pain and the anterior cingulate cortex: hyperactivation is associated with the affective dimension of pain.

**High-yield pearls** - Cingulate gyrus = limbic cortex, Papez circuit, emotion and pain affect. - Think ACA territory for apathy and abulia. - Subfalcine herniation is the most common type of brain herniation. - Do not confuse this with the insula (pain and interoception) or the amygdala (fear).