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.
Eating disorders and memory
Glucose is the preferred energy source for the brain, accounting for 25% of the body’s glucose consumption, despite being only 2% of the body’s total weight. Glucose, along with serotonin, have been found to have significant effects within the cingulate cortex, frontal lobe, temporal lobe, and parietal lobe regions of the brain, including in those with anorexia. Individuals with eating disorders such as bulimia and anorexia show lower neural metabolism of glucose, possibly due to neural consequences of the disorder and/or due to heightened anxiety or depression. Studies have indicated the importance of glucose on memory, showing that reduced levels of glucose in the brain impair an individual’s ability to retrieve memories. Most evidence suggests that severe negative impairments are due to long term, prolonged glucose deprivation or restriction, such as those seen in individuals affected by eating disorders, however effects have been studied on a more short-term basis with negative memory impairments seen in individuals who consumed breakfast compared to those who did not.