Cognitive neuroscience of visual object recognition
Agnosia is a rare occurrence and can be the result of a stroke, dementia, head injury, brain infection, or hereditary.
Apperceptive agnosia is a deficit in object perception creating an inability to understand the significance of objects.
Similarly, associative visual agnosia is the inability to understand the significance of objects; however, this time the deficit is in semantic memory. Both of these agnosias can affect the pathway to object recognition, like Marr's Theory of Vision. More specifically unlike apperceptive agnosia, associative agnosic patients are more successful at drawing, copying, and matching tasks; however, these patients demonstrate that they can perceive but not recognize.
Integrative agnosia(a subtype of associative agnosia) is the inability to integrate separate parts to form a whole image. With these types of agnosias there is damage to the ventral (what) stream of the visual processing pathway.
Object orientation agnosia is the inability to extract the orientation of an object despite adequate object recognition. With this type of agnosia there is damage to the dorsal (where) stream of the visual processing pathway.
This can affect object recognition in terms of familiarity and even more so in unfamiliar objects and viewpoints.
A difficulty in recognizing faces can be explained by prosopagnosia. Someone with prosopagnosia cannot identify the face but is still able to perceive age, gender, and emotional expression. The brain region that specifies in facial recognition is the fusiform face area. Prosopagnosia can also be divided into apperceptive and associative subtypes. Recognition of individual chairs, cars, animals can also be impaired; therefore, these object share similar perceptual features with the face that are recognized in the fusiform face area.
Bulimia nervosa
Bulimics are much more likely than non-bulimics to have an affective disorder, such as depression or general anxiety disorder: A 1985 Columbia University study on female bulimics at New York State Psychiatric Institute found 70% had suffered depression some time in their lives (as opposed to 25.8% for adult females in a control sample from the general population), rising to 88% for all affective disorders combined. Another study by the Royal Children's Hospital in Melbourne on a cohort of 2,000 adolescents similarly found that those meeting at least two of the DSM-IV criteria for bulimia nervosa or anorexia nervosa had a sixfold increase in risk of anxiety and a doubled risk for substance dependency.
Some sufferers of anorexia nervosa exhibit episodes of bulimic tendencies through purging (either through self-induced vomiting or laxatives) as a way to quickly remove food in their system. There may be an increased risk for diabetes mellitus type 2. Bulimia also has negative effects on a person's teeth due to the acid passed through the mouth from frequent vomiting causing acid erosion, mainly on the posterior dental surface.