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The Papez circuit (1937) is a classic limbic system pathway that links the hippocampus, hypothalamus, thalamus, and cingulate cortex, playing a key role in emotion and memory consolidation.
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“Hippos For Many Ancient Civilizations”: Hippocampus → Fornix → Mammillary bodies → Anterior thalamus → Cingulate gyrus → back to Hippocampus.
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The Papez circuit is a network within the limbic system of the brain that is responsible for emotional expression. The main image depicts the primary structures of the circuit within the context of the rest of the brain, color-coded for clarity. In the inset to the right, the structures have been isolated and the direction of the pathway highlighted using arrows. The arrows are color-coded to distinguish between the pathway as it is traditionally understood (light purple), while highlighting new neural connections that been discovered recently (lime).
****Structures and connections of the Papez Circuit – Carolyn Chen Biomedical Visualization. https://carochenmedart.com/papez/
| Hippocampus | Origin of the circuit, involved in learning and memory. |
|---|---|
| Fornix | • Major efferent tract of hippocampus. |
| • Projects to mammillary bodies. | |
| Mammillary bodies (hypothalamus) | • Relay station; integrate memory signals. |
| • Project via mammillothalamic tract. | |
| Anterior nucleus of thalamus | • Receives input from mammillary bodies. |
| • Projects to cingulate gyrus. | |
| Cingulate gyrus (limbic cortex) | • Processes emotional experience, adds affective component to memory. |
| • Sends fibers via cingulum back to hippocampal formation. | |
| Parahippocampal gyrus → Hippocampus | Completes the loop. |
| Wernicke–Korsakoff syndrome (thiamine deficiency) | Damage to mammillary bodies and thalamus → anterograde amnesia, confabulation. |
|---|---|
| Alzheimer’s disease | Early involvement of hippocampus and cingulate cortex → memory deficits. |
| Epilepsy (temporal lobe) | Hippocampal sclerosis disrupts circuit → seizures + memory impairment. |
Axial T2-weighted (A) magnetic resonance imaging shows left anterior thalamic hyperintense (arrow) chronic infarction. Inferior axial T2-weighted images (B, C) show left mammillothalamic tract hyperintensity (red arrow) and atrophic left mammillary body (white arrow). Anteriorly, column of the left fornix is atrophic (dashed arrow). Note normal right-sided structures (black arrowhead). Coronal T2-weighted images (D–E) show abnormal signals in the left mammillothalamic tract (red arrow), and atrophic left fornix crus (white arrow). Diffusion tractography coronal (F), left (G), and right parasagittal (H) images demonstrate a decrease in the left Papez' circuit (dashed rectangle) and mammillothalamic tracts (yellow rectangle).
Aker L, Vattoth S, Paksoy Y. Injury to the circuit of Papez: An overlooked cause of recurrent seizures. Clinical Case Reports. 2023;11(8). doi:10.1002/ccr3.7743