What Does Papez’s Circuit Correspond To?

The appearance of the brain in its middle-lower part, when dissected, resembles limbo. This is why, Paul McLean, the eminent American physiologist and psychiatrist, preferred to baptize this circuit “limbic system”.
What does the Papez circuit correspond to?

James Papez worked on the anatomy of emotions and named this circuit, the Papez circuit, in 1937. The latter consists mainly of the hippocampus, thalamus and cingulum. However, it seems that this idea had already been considered before Papez proposed it.

Indeed, authors like Paul Broca and Paul McLean have added other structures. Among them are the septum, tonsils and hypothalamus, forming the limbic system. Neurologist Paul Ivan Yakovlev proposed an emotional circuit including the orbitofrontal, anterior temporal, insular lobes as well as other nuclei of the thalamus.

It has been observed that Papez’s circuit can be related, besides emotions, to memory and damage caused by its various components. For example, Parkinson’s disease: Alzheimer’s disease, Korsakoff syndrome, semantic dementia and global amnesia.

Image of brain with cogs.

Who was James Papez?

American neuroscientist James Papez (1883 – 1958) was  the pioneer in the study of comparative neuroanatomy. He thus identified a circuit in the brain of mammals that is used for emotional experience. In addition, Papez’s circuit is firmly established in medical vocabulary.

Papez worked in the isolation lab at Cornell University, where he was immersed in the practice of examining slides under a microscope. This allowed him to definitively identify this circuit.

How is the Papez circuit formed?

Papez’s circuit begins from the formation of the hippocampus, called the subiculum. It then passes through the mammillary bodies, then passes through the mammillothalamic bundle, often known as the Vicq bundle of Azir. This vessel then connects to the anterior thalamic nucleus.

From there it reaches the cingulum, crosses the entorhinal cortex and returns to the formation of the hippocampus. It is approximately 350 millimeters in length.

A proposal for the mechanism of emotions

Papez published his observations in 1937 in a landmark paper titled “A Proposal for the Mechanism of Emotions” in the Archives of Neurology and Psychiatry magazine . Here is what he describes:

Before Papez

As we have already mentioned, the concept of an anatomical substrate for emotions did not begin with the work of James Papez. In 1907, the neuropathologist Christfried Jakob (1866 – 1956) alluded to the visceral brain and  conceived the presence of an internal brain that exhibits visceral emotional mechanisms.

This scientist based his hypothesis on experiments on the degenerative brain of monkeys and dogs. As well as autopsied human brain material.

The appearance of the brain in the middle-inferior part, when dissected, resembles limbo. This is why Paul McLean, the eminent American physiologist and psychiatrist, preferred to call this circuit “ the limbic system ”. By the way, other researchers have called it the Papez-McLean circuit.

An illustration of a brain.

The link with memory

Besides the role of Papez’s circuit in the realm of emotions, some authors have found evidence that memory also finds its roots there. They demonstrate a strong synchronization of theta waves in the hippocampus and the anterior ventral thalamus.

Since these waves deal with problems such as memory and learning, several researchers have suggested that Papez’s circuit may be involved in mnemonic functions. Some scientists have even reduced it to the field of spatial and episodic memory.

So it seems that Papez’s circuit is both an emotional system and a system related to memory. Although previously mentioned, it is a discovery that James Papez has finished sketching out and which was instrumental in the neuroanatomy of emotions.

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