The piriform cortex, the main smell (olfactory) cortex, is at the front of the inner underside of each temporal lobe. In humans it is described as the cortical amygdala, the uncus and the front of the parahippocampal gyrus, in front of and beside the amygdala. [1]
The 3D brain needs JavaScript. The text below still says where the piriform cortex is and what it does.
Opens cut by a front (coronal) slice through the parahippocampal gyrus, which holds the piriform cortex. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Lit: the whole parahippocampal gyrus, on both sides. The area is part of this gyrus; its exact border is not drawn. In humans it has been described as the cortical amygdala, the uncus and the front of the parahippocampal gyrus. The model has no piriform or uncus shape and draws the parahippocampal gyrus as one shape, so the whole gyrus is lit; the amygdala is not. [1][2]
Takes part in: smell — see every part of each lit together.
Where it is
It is part of the rhinencephalon, the “smell brain”, in the cerebrum. [1]
In humans it has been described as consisting of the cortical amygdala, the uncus and the front (anterior) part of the parahippocampal gyrus. [1]
It lies between the insula and the temporal lobe, in front of and to the side of the amygdala. [1]
The uncus houses the olfactory cortex, which includes the piriform cortex, the amygdala, the olfactory tubercle and the parahippocampal gyrus. [3]
What it does
Its function is olfaction, the perception of smell; in humans this has been shown in particular for its rear (posterior) part. [1]
It has two main divisions: the anterior piriform cortex seems better at telling the chemical structure of an odour molecule, the posterior piriform cortex at sorting smells into categories and judging how alike they are. [4]
Many of its neurons respond to many different odours, unlike the orbitofrontal cortex, where half the neurons answer only one; how it processes smell is still largely unknown. [4]
In rodents and some primates it holds cells carrying markers of plasticity (doublecortin and PSA-NCAM), which the noradrenaline system modulates. [1]
Piriform regions are found in amphibians, reptiles and mammals; in humans and Old World monkeys the much larger neocortex wraps around it, and it takes up a smaller share of the brain than in insect-eating mammals. [1]
Connections
The mitral cells of the olfactory bulb leave in the lateral olfactory tract, which ends in five main regions: the anterior olfactory nucleus, the olfactory tubercle, the amygdala, the piriform cortex and the entorhinal cortex. [4][5]
The anterior olfactory nucleus carries signals both ways between the olfactory bulb and the piriform cortex. [3]
It projects to the medial dorsal nucleus of the thalamus, which projects on to the orbitofrontal cortex; it also sends fibres to hypothalamic nuclei, the hippocampus and the amygdala. [4]
Other names
Piriform cortex, also spelled pyriform cortex; in other animals sometimes called the olfactory cortex, olfactory lobe or paleopallium. [1]
Size
The model has no shape for the piriform cortex itself, so it is not measured here. The whole left parahippocampal gyrus that holds it measures about 49 mm front to back, 22 mm top to bottom and 21 mm side to side on this model (the box it fits in, not its volume). [2]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.