CVI glossary of terms
CVI stands for Cortical/Cerebral Visual Impairment. CVI is a brain-based visual impairment caused by damage to the visual pathways or visual processing areas of the brain. Learners struggle with visual attention and visual recognition resulting in a lack of access for understanding the world around them. CVI is fascinating and complex. There are many terms to know and concepts to understand as part of your CVI learning journey.
- Agnosia: The inability to name or describe a familiar object or shape.
- Ataxia: Difficulty guiding your hand toward an object.
- Apraxia: The inability to perform familiar movements.
- Cerebral: Relating to the brain. The cerebral cortex, the outer layer of the brain, contains four lobes on either side.
- Dorsal visual pathway: The route between the occipital and posterior parietal lobes that process surroundings and movement. It’s known as the “where” pathway.
- Frontal lobe: The “control center” of your brain, responsible for voluntary movement.
- Occipital lobe: The back part of the brain, primarily responsible for visual processing.
- Ocular: Relating to the eye.
- Optic: Relating to sight.
- Parietal lobe: Behind the frontal lobe, it integrates sensory information with body movements and language.
- Temporal lobe: The bottom part of the brain, responsible for memory and recognition.
- Form constancy: The skill that allows people to recognize familiar shapes, letters, and objects in various sizes and contexts.
- Fusiform gyrus: Part of the occipital and temporal lobe, it aids in color, facial, and object recognition.
- Higher-order visual processing: Processing that happens cognitively, beyond the retina and primary visual cortex.
- Lateral geniculate nucleus (LGN): Located in the thalamus, which is in the mid-brain—think of this as a central tollbooth where all sensory information goes through before moving on to different parts of the brain. From here, visual information is organized from the retina and sent off to the primary cortex. Just like a highway, there’s one on either side of the thalamus.
- Optic nerve: This cranial nerve sends visual information from your retina to your brain. It consists of more than 1 million nerve fibers. It’s a busy highway!
- Optic chiasm: Think of this like an intersection. It’s where the nerves cross over, allowing your primary cortex to get information from both eyes. Like a busy intersection, this is where visual information is sorted and broken up into component parts for more processing. The left field of vision is processed by the right side (or cerebral hemisphere), and vice versa, moving along an optic tract toward the thalamus.
- Optic radiation: We’re almost at the end of our journey! The optic radiation are axons—or nerve fibers—that convey information to your visual cortex.
- Primary visual cortex (v1): Full of neurons, this is the backside of the occipital lobes, where the first stage of the cortical visual process happens. Think of this as a “sorting area.”
- Prestriate cortex: Here’s where motion and more complex shapes begin to be processed, as well as color, brightness, and depth perception.
- Spatial: Your perception of size, shape, location, direction—basically, the ability to contextualize surroundings.
- Ventral visual pathway: Route between the occipital and temporal lobes that support visual identification. It is known as the “what” pathway.
- Visual attention: Your ability to focus on specific elements by filtering out less pertinent information in a cluttered environment, such as being able to pick out a taxi cab approaching your curb on a crowded city street.
- Visual discrimination: Your ability to recognize details in shapes and color.
- Visual neglect: This happens when kids can’t acknowledge stimuli in the space opposite of their affected part of the brain; for instance, damage to the right occipital lobe could affect the left field of vision. A child might only see half of their dinner plate or one side of a TV screen.
- Visuospatial perception: Your ability to determine where objects are in space: a dog running toward you, a ball flying through the air, a fork coming toward your mouth.
- Visual recognition: Your ability to recognize and identify objects, faces, colors and shapes, both in person and in pictures.
References and resources:
Websites: TeachCVI, CVIScotland, Aapos.org, Apa.org
Banich, M. T., & Compton, R. J. (2018). Cognitive Neuroscience. Cambridge, United Kingdom: Cambridge University Press.
Zihl, J., & Dutton, G. N. (2015). Cerebral Visual Impairment in Children: Visuoperceptive and visuocognitive disorders. Wien: Springer.