The occipital lobe is one of the four pairs of main lobes of the human brain. The occipital lobe is so named because it lies beneath the occipital bone of the skull. It is also the smallest of the lobes.
There are actually two occipital lobes, one in each hemisphere of the brain. The central cerebral fissure divides and separates the lobes.
The occipital lobes are located at the back of the top of the brain. They lie behind the lobes temporal y parietal and above the cerebellum, separated from the cerebellum by a membrane called the tentorium cerebelli.
The surface of the occipital lobe is formed by a series of folds, between which are ridges called gyri and depressions called sulci. Because the occipital lobe does not have an ordered structure, scientists use these grooves and gyri to identify the lobe area.
Other than these, there are no structural distinctions in the lobes. Scientists separate the lobes further based on basic function.
The occipital lobe contains different sections or areas, and each has a different set of functions. These include:
- The lateral geniculate bodies
- The lingula
- The primary visual cortex, known as Brodmann’s area 17 or V1Trust source
- The secondary visual cortex, known as Brodmann’s areas 18 and 19 or V2, V3, V4, V5Lonfidence source, which surrounds the primary visual cortex
- The dorsomedial stream
what parts make up the occipital lobe?
Below we will briefly describe the most important areas that make up the occipital lobes, including their main functions
Primary visual cortex
The primary visual cortex, called Brodmann’s area 17 or V1, receives information from the retina. It then interprets and transmits information related to the space, location, motion and color of objects in the visual field.
It does this through two different pathways called streams: the ventral stream and the dorsal stream.
Secondary visual cortex
The secondary visual cortex, called Brodmann’s area 18 and 19 or V2, V3, V4, V5, receives information from the primary visual cortex. Secondary visual cortex deals with much of the same type of visual information.
The ventral stream is one of the pathways used by the primary visual cortex to send information. It carries information to the temporal lobe, which interprets the information and helps the brain make meaning of objects in the visual field.
This helps to recognize objects and give awareness of what the person is seeing.
The dorsal stream is the other pathway that the primary visual cortex uses to send information. It shares information about the location of an object and transmits it to the parietal lobe, which receives other information about the space and shape of objects in the visual field.
Lateral geniculate bodiesThe
lateral geniculate bodies carry some of the raw information from the outer retina to the visual cortex.
The lingula collects general information about the field of vision from the inner half of the retina.
The combination of information from the lateral geniculate bodies and the lingula helps create spatial awareness and gives depth to visual information.
Other important areas
Although modern science has revealed much about how the occipital lobe reveals the visual world, researchers are still learning new information about the occipital lobe and its exact function.
No section of the brain is truly independent, and this includes the occipital lobe. For example, the occipital lobe takes information from the retina of the eye and translates it into the visual world. Thus, it relies heavily on the eyes themselves.
The eyes themselves also have muscles that need to be controlled. The motor cortex of the brain is responsible for these movements, so it also plays a role in vision.
The temporal and occipital lobes also share important interactions. The temporal lobe makes sense of the visual information interpreted by the occipital lobe. It also stores information, to some extent, in the form of memories.
In some cases, it is also possible for other sections of the brain to compensate for any damage affecting the occipital lobe.
what are the main functions of the occipital lobe?
Although we know that the occipital lobe is dedicated to vision, this process is very complex and includes several distinct functions. Among them are:
- Mapping the visual world, which aids both spatial reasoning and visual memory. Most vision involves some form of memory, since scanning the visual field requires remembering what was seen a second ago.
- Determine the color properties of elements in the visual field.
- Assess distance, size and depth.
- Identify visual stimuli, particularly familiar faces and objects.
- Transmit visual information to other brain regions so that these lobes can encode memories, assign meanings, elaborate appropriate motor and linguistic responses, and continuously respond to information from the surrounding world.
- Receive raw visual data from the perceptual sensors of the retina.
Disorders associated with lesions and damage to the occipital lobe
Damage and injury to the occipital lobe, may result in one or more dysfunctions in brain, vision, or daily functioning. It may cause or contribute to any of the following conditions.
Since the occipital lobe deals with vision, a possible consequence of damage to this area is total or partial blindness. However, the loss of sight is not always direct; rather, the person may lose one or more specific functions of his or her vision.
Anton’s syndrome is a rare form of blindness that occurs without the person being aware of it. The person may deny his or her vision loss, even if a health care professional presents evidence that shows he or she has vision loss.
Riddoch syndrome is a rare condition in which the person can only see moving objects. Stationary objects simply do not appear in his or her field of vision. The person also cannot perceive shape or color.
Epilepsy shares a link with the occipital lobe in some cases. If a person is more prone to occipital-type seizures or photosensitivity seizures, flashes of light or images containing various colors can trigger these seizures.
Other forms of dysfunction
The type of dysfunction affecting the body may vary depending on where in the occipital lobe the dysfunction or lesion occurs. Some possible examples are
- Movement difficulties: Even if you can still move, changes in depth perception and vision may result in inadequate movement and difficulty navigating the visual field.
- Difficulties perceiving colors, shape, dimension and size.
- Difficulty recognizing familiar objects or faces.
- Inability to recognize or read written words.
- Inability to detect that an object is moving.
- Difficulty reading or writing; for example, words may appear to move on the page.
- Difficulty locating objects in the environment, even when those objects can be seen.
- Difficulties with fine and gross motor skills and balance