<unk>  almost always involves an infarct to the left posterior cerebral artery (which perfuses the splenium of the corpus callosum and left visual cortex, among other things). The resulting deficit will be<unk>  – i.e., the patient can write but cannot read (even what they have just written). However, because<unk>  affects visual input, not auditory input, patients with<unk>  can recognize words that are spelled out loud to them. This is because the left visual cortex has been damaged, leaving only the right visual cortex (occipital lobe) able to process visual information, but it is unable to send this information to the language areas (Broca's area, Wernicke's area, etc.) in the left brain because of the damage to the splenium of the corpus callosum. Patients with this deficit mostly do have a stroke to the posterior cerebral artery. But they may be susceptible to<unk>  as a consequence of other traumatic brain injuries (TBIs) as well. Anything that stops proper blood flow to the area necessary for normal reading abilities will cause a form of<unk> . The posterior cerebral artery is a main locale for the cause of this deficit because this artery is not just responsible for itself. It also supplies the anterior temporal branches, the posterior temporal branches, the calcarine branch, and the parieto-occipital branch. What is important about these arteries is their location. All of them supply blood to the back outer parts of the brain. This part of the brain is also referred to as the posterior lateral part of the brain. In cases of<unk> , locations are found in the section of the brain, specifically the temporo-occipital area. This is the area that is activated when people without any sort of<unk>  receive activation when undergoing orthographic processing. This area is known as the visual word form area due to this pattern of activation. The patient can still write because the pathways connecting the left-sided language areas to the motor areas are intact. However, many people with<unk>  are able to identify and name individual letters over time as well as recognize sequences of letters as words. These people typically adapt to their disability and are able to use a style of compensatory reading known as letter-by-letter reading. This style of reading takes longer than the conventional style of reading does. As the number of letters in a word increases, the amount of time it takes for the person with<unk>  increases. For each letter that is added, a patient may take up to an additional three seconds to read the word. Studies have shown that<unk>  may be a result of a disconnection syndrome. Analysis of diffusion images showed that the visual word form area (VWFA) is connected to the occipital lobe via the inferior longitudinal fasciculus (ILF), a projection that runs between the temporal and occipital lobe. functional magnetic resonance imaging (fMRI) and Diffusion Tensor Imaging (DTI) showed that two weeks after surgery in the ILF, the VWFA-Occipital Lobe tract was severely degenerated. The results came from an epileptic patient who showed symptoms of<unk>  after his surgery. Thus, the proposed pathophysiological mechanism is that the ILF lesion interferes with transmission of visual information to the VWFA. There is, however, an alternative view that suggests the "VWFA" is devoted to processing of high acuity foveal input, which is particularly salient for complex visual stimuli like letter strings. Studies have highlighted disrupted processing of non-linguistic visual stimuli after damage to the left pFG, both for familiar and unfamiliar objects<unk>  exhibits some unexpected residual abilities despite the inability to read words. For instance, one patient had preserved calculation capabilities such as deciding which number was greater, and whether a number was odd or even with greater than chance probability. The study showed that the patient was also able to calculate simple arithmetic tasks such as addition, subtraction, and division, but not multiplication, even though the patient could not read the numbers. For example, the patient would be presented with "8 – 6", and he or she would read it as "five minus four", but still come up with the correct answer "two" with greater than chance accuracy.<unk>  patients also seem to retain some residual semantic processing. They are able to perform better than chance when forced to make a lexical decision or make a semantic-categorisation decision. These subjects also performed better with nouns than functors, better with words that had high rather than low imageability, and performed poorly with suffixes. However, this may be due to right hemisphere input or residual left hemisphere input.
Pure alexia
Integrative agnosia
Global aphasia
Asomatognosia
Dysgraphia
Surface dyslexia
Visuospatial dysgnosia
Social-emotional agnosia