Clinically speaking, agnosia refers to the inability to recognize and identify sensory inputs from a specific modality, be it visual, tactile, auditory,olfactory, or even cognitive. For example, a interesting but difficult to diagnose agnosia is Anosognosia (difficult because it can be mistaken for denial)
Pet peeve: A prefix of "a" (agnosia) refers to a "total inability to". A prefix of "dy" (dysgnosia) refers to "an impairment in". However, both are used interchangeably, at the expense of the person with the condition. Let's try to be specific and no sloppily label, ne?
Anyway. So you just had a stroke, and now you're having some difficulties adjusting back to regular life. Your memory is fuzzy, trying to remember things is like holding onto a wet noodle, and you have these insistent headaches that refuse to budge. But...this is normal for you. Well, you think so anyway. You are convinced that your forgetting simple dates and these horrible headaches are from being over worked, or tired, or...something.
Anosognosia is characterized by "lack of insight". A profound inability to recognize one's own disorder, or impairment. People may confabulate reasons for which they are symptomatic (e.g., In this case blaming your memory issues on sleep). This agnosia commonly manifests after traumatic brain injury, strokes (and other neurological events), and it's especially common in schizophrenia. Wonder why patient compliance to antipsychotic medication is low? That can be a large reason.
Anyway, another example is visual agonsia. This can be presented in a few ways, but one is with an inability to recognize objects. Like, that thing that's reflective and I see myself on...that thing......I don't know what it is....
Hint: a mirror.
So, in the second episode of Perception, they introduced a man with prosopagnosia, or "face blindness".
This is a super interesting condition, because it can be congenital, though it's usually because of an cerebral accident or trauma. In the cases of developmental prosopagnosia, most individuals don't even know they have it. Fascinating, huh? In cases of neurological accidents, the symptoms tend to be more severe than in developmental, understandably so since the brain has not had years to adapt.
Symptoms can be mild (e.g., difficulty recognizing faces) to severe (e.g., absolute inability to recognize wife, or son's face).
The area that's affected in the brain is the fusiform face area in the fusiform gyrus, which is just posterior to the parahippocampal place area, and anterior to the occipital lobe. As a result, damage to this area may cause difficulties in recognizing faces. While facial recognition in this area is bilateral, damage to the right side of the cortex may cause significantly greater damage than the left due to lateralization.
Very interesting, not everyone has a fusiform face area! The research continues.....
While we're here...the parahippocampal place area encodes information particular to recognizing places,such as your hometown or school.
And the lateral occipital complex specializes in recognizes objects.
Here's some pics from my fMRI poster a year back showing these areas when active:
Fusiform face area
Lateral Occipital Complex
Parahippocampal Place Area
Interestingly, IIRC, this student showed the lowest activation in his FFA, and the highest in his PPA compared to the other six participants. Goes to show how incredibly unique each brain is!
Alright, enough brains. Time for CAKE.
chrisy
Very well written. Me like and me very informed. :)
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