Piriformis cortex: what is this part of the brain and what are its functions

Although remarkable advances have been made in the field of science, the human brain remains unknown in many ways. There are structures that are gradually making themselves known, and one of them is the piriform cortex.

The piriformis cortex is part of the olfactory cortex, and in addition to detecting and differentiating smells, it was recently discovered that it is also responsible for storing long-term memories. Let’s get to know its anatomy, its functions and the latest findings.

    Pear-shaped bark and olfactory system

    The piriform cortex is located in 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 cerebral level is that it is the only one that is not prominent in the thalamus (as is the case with the other senses). In addition, 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 functional return during fetal life.

    Characteristics

    Humans share the pear-shaped bark with mammals, amphibians, and reptiles.

    The piriformis cortex is a part of the brain where the sense of smell is located, which allows you to detect and distinguish smells very precisely. However, it has also recently been linked to long-term memory storage.

    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) found that this distribution is essential for the brain to be able to distinguish smells correctly and with extreme precision.

    Neuroanatomy

    At the neuroanatomical level, the piriform cortex is part of the rhinencephalon, located in the telencephalon. The telencephalon is a cerebral 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 zone 27. It has been suggested that this crust could be an attractive target for epilepsy treatment, By injury, stimulation or local supply of drugs.

    the functions

    The most important functions of the piriformis cortex are two in number: it functions as an olfactory system and participates as a kind of “archive” in which to store long-term memories.

    1. Odor detection

    As we have seen, the piriform cortex is part of the olfactory cortex. But how does it work to detect odors?

    When aromatic molecules bind to nasal receptors, the signal is transmitted to the olfactory bulb and from there to the piriform cortex. The researchers found that each of the neurons in the olfactory bulb is connected to almost all of the neurons in the piriformis cortex.

    On the other hand, they found that instead of having a single receptor that detects a scent and lights up a cluster of neurons, each scent has a sort of “fingerprint” that relies more on the strength of 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, from the University of the Ruhr in Bochum (Germany). Their results were published in the journal Cerebral Cortex.

    Strauch and Manahan-Vaughan discovered that the pear-shaped bark, responsible for detecting odors, is also involved in Memory storage. Specifically, it deals with the retention of memories in long-term memory.

    2.1. experimental methodology

    These scientists analyzed whether the piriform cortex of rats was able to express synaptic plasticity, a phenomenon that occurs when neurons communicate with each other and memory storage is activated. This plasticity appeared in the piriform cortex of rats, showing that long-term memory retention occurs in this area.

    To study this, they used electrical impulses in the brain, with the aim of emulating processes that triggered the encoding of an olfactory sensation that could be memorized. Through a number of protocols, in addition induces long-term effects in the hippocampus (Responsible for long-term memory).

    2.2. conclusions

    Neuroscientists say their study shows how the piriform cortex can serve as a storage space for long-term memories, although it’s also true that to do this you need the “instructions” from the orbitofrontal cortex, A region of the frontal lobe related to cognitive decision making.

    Bibliographical references:

    • Carlson, NR (2005). Behavioral physiology. Madrid: Pearson Education.
    • Guyton, AC (1994). Anatomy and physiology of the nervous system. Basic neuroscience. Madrid: Editorial Mèdica Panamericana.
    • Laufs, H. et al. (2011). Convergent PET and fMRI tests for a common area involved in human focal epilepsy. Neurology, 77 (9), 904-910.
    • Strauch and Manahan-Vaughan. (2018). In the piriform cortex, the main impetus for encoding information by synaptic plasticity is provided by descending rather than ascending olfactory inputs. Cereb Cortex, 28 (2), 764-776.

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