(jī′rŭs )

(jī′rī″)
pl. gyri [L. gyrus fr. Gr. gyros, ring, circle]
Any of the surface convolutions or rounded ridges that are packed along the cerebral hemispheres of the brain. Each gyrus is separated from its neighbor by a furrow called a sulcus. Details of the shape of gyri vary from individual to individual.
SYN: SEE: convolution; SEE: gyre


CEREBRAL GYRI

angular gyrus

A gyrus of the ventral region of the parietal lobe. It is just ventral to the supramarginal gyrus and caps the posterior (ascending) end of the superior temporal sulcus. The cortex of the angular gyrus plays a role in the association of the visual and tactile perceptions of forms and shapes.
SYN: SEE: gyrus angularis

gyrus angularis

SEE: Angular gyrus.

Broca gyrus

SEE: Broca, Pierre-Paul

callosal gyrus

A large gyrus on the medial surface of the cerebral hemisphere that lies directly above the corpus callosum.

gyrus cerebelli

A layer of the cerebellum.

cingulate gyrus

A long curving gyrus on the medial surface of each cerebral hemisphere. It follows the arch of the corpus callosum, from which it is separated by the callosal sulcus. The cortex of the cingulate gyrus and the cingulum (the underlying axon tract) are parts of the main circuitry of the limbic system.
SYN: SEE: callosal convolution

dentate gyrus

A curved gyrus hidden along the medial surface of the temporal lobe of each cerebral hemisphere. It contains a cortex of three layers, with a single cell layer, that is part of the hippocampal formation, and it is folded inside the hippocampal sulcus, where it lies against the subicular edge of the parahippocampal gyrus. The surface of the dentate gyrus has regularly spaced transverse grooves, which make the gyrus resemble a row of teeth. Dysfunction within the dentate gyrus has been linked to age-related memory loss.
SYN: SEE: fascia dentata
SEE: limbic system for illus

gyrus fornicatus

The ring along the medial surface of each cerebral hemisphere that forms a large segment of the limbic circuitry. This gyrus comprises the subcallosal gyrus, the cingulate gyrus, the retrosplenial area, the parahippocampal gyrus, and the uncus.

fusiform gyrus

SEE: Occipitotemporal gyrus.

Heschl gyrus

SEE: Heschl gyrus

hippocampal gyrus

SEE: Parahippocampal gyrus.

inferior frontal gyrus

The lowest of the three major longitudinal gyri of the lateral surface of the frontal lobe of each cerebral hemisphere. This gyrus is part of the prefrontal cortex. In the dominant hemisphere, the posterior two thirds of the inferior frontal gyrus are the Broca area.
SEE: Broca area under SEE: Broca, Pierre-Paul

inferior occipital gyrus

A short gyrus on the lateral surface of the occipital lobe of each cerebral hemisphere, just below the lateral occipital sulcus.

inferior parietal gyrus

SEE: Inferior parietal lobule.

inferior temporal gyrus

The lowest of the three longitudinal gyri that cover the lateral surface of the temporal lobe.

lingual gyrus

A tongue-shaped gyrus that, at its anterior end (tip), abuts the parahippocampal gyrus on the ventral surface of the occipital lobe. The calcarine fissure (calcarine sulcus) forms the medial (upper) edge of the lingual gyrus, and the collateral sulcus forms the lateral (lower) edge. Part of the primary visual cortex is found along the wall of the lingual gyrus inside the calcarine fissure.

gyrus longus insulae

A lengthy gyrus making up the postinsula.

medial frontal gyrus

The major anterior gyrus of the medial surface of the frontal lobe of each cerebral hemisphere. The medial frontal gyrus is part of the prefrontal cortex. It curves over the cingulate gyrus and is separated from it by the cingulate sulcus.

middle frontal gyrus

The middle of the three major longitudinal gyri of the lateral surface of the frontal lobe of each cerebral hemisphere. It is part of the prefrontal cortex.

middle temporal gyrus

The middle of the three longitudinal gyri that cover the lateral surface of the temporal lobe.

occipital gyrus

The inferior or the superior occipital gyrus.

occipitotemporal gyrus

SEE: The lateral or the medial occipitotemporal gyrus, both of which run longitudinally along the bottom (ventral surface) of the temporal lobe of each cerebral hemisphere.

orbital gyrus

Any of the gyri forming the inferior (concave) surface of the frontal lobe, which lies along the orbital surface of the frontal bone.

paracentral gyrus

SEE: Paracentral lobule.

parahippocampal gyrus

A gyrus along the medial (inner) edge of the temporal lobe of each cerebral hemisphere, bounded by the hippocampal fissure medially and by the collateral sulcus laterally. The medial edge of the parahippocampal gyrus is called the subiculum; the remainder of the gyrus is called the entorhinal cortex. Together, the ventricular side of the subiculum and dentate gyrus form the hippocampus.
SYN: SEE: hippocampal gyrus
SEE: limbic system for illus

paraterminal gyrus

A small area of the cerebral cortex anterior to the lamina terminalis and below the rostrum of the corpus callosum.

postcentral gyrus

A major dorsoventral gyrus in the parietal lobe of each cerebral hemisphere; its anterior border is the central sulcus, and its posterior border is the postcentral sulcus. This gyrus contains the primary somatosensory cortex.
SYN: SEE: ascending parietal convolution

posterior central gyrus

SEE: Postcentral gyrus.

precentral gyrus

A major dorsoventral gyrus in the parietal lobe of each cerebral hemisphere; its anterior border is the precentral sulcus, and its posterior border is the central sulcus. This gyrus contains the primary motor cortex.
SYN: SEE: ascending frontal convolution

gyrus profundus cerebri

One of the very deep gyri of the cerebrum.

gyrus rectus

A longitudinal gyrus on the medial edge of the orbital (ventral) surface of the frontal lobe of each cerebral hemisphere; the lateral edge of the gyrus rectus is the olfactory sulcus.

Retzius gyrus

SEE: Retzius, Anders Adolf

subcallosal gyrus

The short gyrus at the head of the cingulate gyrus, just below the rostrum of the corpus callosum, on the medial surface of each cerebral hemisphere. It is the anterior most segment of the gyrus fornicatus.
SYN: SEE: limbic system for illus

superior frontal gyrus

The superior most gyrus of the three major longitudinal gyri of the lateral surface of the frontal lobe of each cerebral hemisphere; it is part of the prefrontal cortex.

superior occipital gyrus

A stubby, knuckle-shaped gyrus on the lateral surface of the occipital lobe of each cerebral hemisphere, just above the lateral occipital sulcus.

superior parietal gyrus

SEE: Superior parietal lobule.

superior temporal gyrus

The superior of the three longitudinal gyri that cover the lateral surface of the temporal lobe.

supracallosal gyrus

SEE: Indusium griseum.

supracallosus gyrus

The gray matter layer covering the corpus callosum.

supramarginal gyrus

A V-shaped gyrus capping the posterior end of the Sylvian (lateral) fissure in the parietal lobe of each cerebral hemisphere, just dorsal to the angular gyrus. This gyrus plays a role in auditory comprehension.

temporal gyrus

The superior, the middle, or the inferior temporal gyrus.

transverse temporal gyrus

SEE: Heschl gyrus

uncinate gyrus

SEE: Uncus.

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