Piriform cortex: what it is and what functions this part of the brain has

Despite remarkable advances in science, the human brain remains unknown in many respects. There are structures that gradually become known, and one of them is the piriform cortex.

The piriform cortex is part of the olfactory cortex, and in addition to detecting and differentiating odors, it has recently been discovered that it is also responsible for storing long-term memories. We are going to know its anatomy, its functions and the latest findings found.

• Related article: "Parts of the human brain (and functions)"

Pyriform cortex and olfactory system

The piriform cortex is located within a larger region, the so-called olfactory cortex. The olfactory cortex is the area of ​​the cortex in the forebrain and receives direct input from the olfactory bulb. Thus, the piriform cortex is the main region of the olfactory cortex.

The olfactory cortex is the only part of the vertebrate forebrain that receives direct sensory input. Another characteristic of the olfactory system at the brain level is that it is the only one that does not stand out in the

thalamus (as it happens with the other senses). Furthermore, it is ipsilateral (each hemisphere receives information from the nostril on the same side).

On the other hand, the olfactory system is one of the first sensory systems to differentiate and become functional during fetal life.

Characteristics

Humans share the piriform cortex with mammals, amphibians, and reptiles.

The piriform cortex is a part of the brain where the sense of smell is located, which allows to detect and distinguish odors with great precision. However, recently it has also been related to the storage of long term memories.

The neural distribution of this part of the nervous system is apparently random and "chaotic," and until recently it was not known exactly why. However, a team of scientists from Salk University (USA) discovered that this distribution is essential for the brain to distinguish odors correctly and extremely accurately.

neuroanatomy

At the neuroanatomical level, the piriform cortex is part of the rhinencephalon, located in the telencephalon. He telencephalon It is a brain structure located on the diencephalon, it is the anterior part. It is the most voluminous area of ​​the brain and represents the highest level of somatic and vegetative integration.

The piriform cortex is part of Brodmann's area 27. It has been suggested that this bark could be an attractive target for epilepsy treatment, by injury, stimulation or local delivery of drugs.

functions

The most important functions of the piriform cortex are two: it works as an olfactory system and it participates as a kind of "file" where long-term memories can be stored.

1. odor detection

As we have already seen, the piriform cortex is part of the olfactory cortex. But, how does it act when detecting odors?

When scent molecules bind to receptors in the nose, the signal is transmitted to the olfactory bulb and from there to the piriform cortex. The researchers found that every single neuron in the olfactory bulb is connected to nearly every neuron in the piriform cortex.

On the other hand, they found that instead of having a single receptor that detects an odor and lights up a group neurons, each smell has a kind of "fingerprint" that is based more on the strength of the connections.

2. long term memory

Another discovery of the piriform cortex came at the end of 2017, at the hands of two German neuroscientists Christina Strauch and Denise Manahan-Vaughan of the Ruhr University of Bochum (Germany). Their results were published in the journal Cerebral Cortex.

Strauch and Manahan-Vaughan discovered that the piriform cortex, responsible for detecting odors, is also involved in storing memories. Specifically, it deals with retaining memories in long-term memory.

2.1. experimental methodology

These scientists analyzed whether the piriform cortex of rats was capable of expressing plasticity synaptic, a phenomenon that appears when neurons communicate with each other and the storage of memories. Said plasticity did appear in the piriform cortex of rats, demonstrating that long-term memory retention occurs in this area.

To study it, they used electrical impulses in the brain, with the aim of emulating processes that would trigger the encoding of an olfactory sensation that could be memorized. Through a series of protocols, in addition induced long-term effects in the hippocampus (responsible for long-term memory).

2.2. conclusions

The neuroscientists say that their study shows how the piriform cortex can serve as a storage space for long-term memories, although it is also true that to carry it out, it needs "instructions" from the orbitofrontal cortex, a region of the frontal lobe related to cognitive processing of decision making.

Bibliographic references:

• Carlson, N.R. (2005). Behavioral physiology. Madrid: Pearson Education.
• Guyton, A.C. (1994). Anatomy and physiology of the nervous system. basic neuroscience. Madrid: Panamerican Medical Editorial.
• Laufs, H. et al. (2011). Converging PET and fMRI evidence for a common area involved in human focal epilepsies. Neurology, 77(9), 904-910.
• Strauch & Manahan-Vaughan. (2018). In the Piriform Cortex, the Primary Impetus for Information Encoding through Synaptic Plasticity Is Provided by Descending Rather than Ascending Olfactory Inputs. Cereb Cortex, 28(2), 764-776.