00:04One of the most distinctive features of the human brain is that its surface is covered
00:09with a complex pattern of grooves and ridges.
00:12These grooves and ridges are created by the folding of the outer layer of neural tissue,
00:16the cerebral cortex.
00:19The grooves are called sulci, and the ridges are called gyri.
00:23Particularly deep sulci are sometimes referred to as fissures.
00:27The folding of the cerebral cortex dramatically increases the surface area of the cortex,
00:32allowing more neurons to fit within the limited volume of the skull.
00:36While the pattern of sulci and gyri varies between individuals, certain sulci and gyri appear
00:41more consistently and serve as important landmarks of the cerebral cortex.
00:46In this video, I will discuss some of the most prominent sulci and gyri, although I should
00:51note that this will be an overview and won't cover all of the sulci and gyri found throughout
00:55the brain.
00:58Perhaps the most recognizable sulcus is the longitudinal fissure, the deep groove that
01:03runs along the midline of the brain and separates the left and right cerebral hemispheres.
01:09To examine some other major sulci and gyri, we'll start with a side or lateral view of the
01:14brain.
01:16One of the major landmarks of the lateral surface of the brain is the central sulcus, which separates
01:21the frontal lobe from the parietal lobe.
01:24Immediately in front of, or anterior to, the central sulcus is the precentral gyrus, which
01:30contains the primary motor cortex, an area of the brain that is essential for voluntary
01:34movement.
01:36The precentral gyrus extends to the precentral sulcus.
01:41The rest of the lateral surface of the frontal lobe is made up of three gyri, the superior,
01:47middle, and inferior frontal gyri.
01:50The superior frontal gyrus extends onto the medial surface of the brain.
01:55The superior and inferior frontal gyri are separated from the middle frontal gyrus by
02:00the superior and inferior frontal sulci, respectively.
02:04These three gyri make up a large portion of the prefrontal cortex, an area of the brain that's
02:10involved in a variety of important functions but is especially well known for its contributions
02:14to higher cognition, such as planning, decision-making, and self-control.
02:21Just behind, or posterior to, the central sulcus is the postcentral gyrus.
02:28The postcentral gyrus is the location of the primary somatosensory cortex, an area of the
02:33brain that is involved with processing bodily sensations like touch and pain.
02:38The neurons in the primary somatosensory cortex are arranged in a somatotopic map, meaning that
02:44different regions of the cortex receive sensory input from specific parts of the body.
02:50The postcentral gyrus extends to the postcentral sulcus.
02:55A sulcus called the intraparietal sulcus reaches from the postcentral sulcus toward the occipital
03:01lobe.
03:02The intraparietal sulcus creates a division between two parietal regions, the superior and
03:07inferior parietal lobules.
03:10Both of these regions are involved with integrating sensory information to guide perception, attention, and
03:16interaction with the environment.
03:18The inferior parietal lobule also contributes to language processing, and itself is made
03:24up of two gyri, the supramarginal gyrus and the angular gyrus, each of which is involved
03:30with different aspects of language processing.
03:34The lateral sulcus, also known as the sylvian fissure, forms a boundary between the temporal
03:39lobe, the frontal lobe, and part of the parietal lobe.
03:44The lateral surface of the temporal lobe is made up of the superior, middle, and inferior
03:49temporal gyri.
03:51These are separated from one another by the superior and inferior temporal sulci.
03:56The superior temporal gyrus often contains a very small portion of the primary auditory
04:01cortex, although the majority of the primary auditory area is found on separate gyri that
04:08extend into the lateral sulcus and are not visible on the lateral surface of the brain.
04:14The lateral surface of the occipital lobe is made up of a collection of gyri sometimes
04:19simply referred to as the lateral occipital gyri.
04:24If we look at a medial view of the brain, we can see a prominent sulcus called the cingulate
04:28sulcus, which traces a path around the more central structures of the brain and acts as
04:33a demarcation line for what is described in some texts as a fifth lobe of the brain, the
04:38limbic lobe.
04:40The limbic lobe is a region of the brain that is important in emotions, motivated behavior,
04:45and memory, among other things.
04:48It can be considered part of the larger limbic system, which includes structures such as the
04:53hippocampus, amygdala, and others.
04:57The cingulate sulcus extends back to the subparietal sulcus, which often appears to be a continuation
05:02of the cingulate sulcus, but in many brains is a separate sulcus.
05:09Just below the cingulate sulcus is the cingulate gyrus, an important part of the brain thought
05:14to be involved in a variety of emotional, cognitive, and behavioral functions.
05:19A sulcus called the colosal sulcus separates the cingulate gyrus from the corpus callosum,
05:25a structure that connects the left and right cerebral hemispheres, enabling communication
05:29between them to occur.
05:31Just below the anterior, or front, end of the corpus callosum is a gyrus called the subcolosal
05:37gyrus.
05:40The parietal occipital sulcus forms a boundary between the occipital and parietal lobes.
05:45The calcarine sulcus is found in the occipital lobe, and the primary visual cortex, the main
05:51area for the initial processing of visual information, is contained in the walls of the calcarine
05:55sulcus and in the cortex surrounding it.
05:59Just below the calcarine sulcus is a gyrus called the lingual gyrus, an area that is also
06:03involved with visual processing.
06:07Looking at the bottom, or inferior surface of the brain, you can see several other notable
06:12sulci and gyri.
06:14In the frontal lobe, there are a group of gyri that don't have a consistent appearance
06:18and are often simply called the orbital gyri.
06:21Adjacent to the orbital gyri is a gyrus called the gyrus rectus, and between the two is the
06:27olfactory sulcus.
06:28The olfactory bulb and tract, two important structures in the sense of smell, are found
06:33here.
06:35The orbital gyri and gyrus rectus are part of the orbital frontal cortex, a region of the
06:41prefrontal cortex that is involved in functions such as decision-making, reward processing,
06:46and emotional regulation, among other things.
06:50The parahippocampal gyrus lies immediately adjacent to, and partially surrounds, the hippocampus,
06:55and is thought to play a role in memory processes.
06:59And the occipital temporal, or fusiform gyrus, extends from the temporal lobe toward the occipital
07:05lobe.
07:06It is thought to play a role in high-level visual processing, such as in the recognition
07:10of faces, objects, and written words.
07:14A sulcus called the collateral sulcus separates the fusiform gyrus from the parahippocampal
07:19gyrus.
07:21A sulcus called the transverse fissure separates the cerebellum from the rest of the brain.
07:29We have covered most of what are typically considered the major sulci and gyri of the
07:33brain.
07:35If you are interested in learning more about the function of some of the structures mentioned
07:38in this video, check out this video next.
07:54We'll see you next time.
