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.
Selfish brain theory
In the first DFG funding period from 2004 to 2007 researchers from the Clinical Research Group “Selfish Brain: brain glucose and metabolic syndrome" expanded the scope of validity of the “Selfish Brain" theory in central aspects by carrying out experiments on healthy and diseased test subjects. The researchers in Luebeck found the following key results regarding the axioms of the theory:The special position of the brain during inanition (due to fasting or tumor disease) was already confirmed experimentally over 80 years ago: The body mass reduces, but the mass of the brain hardly reduces, if at all (see 3). Recently this axiom of the selfish brain theory was supported by work at the University of Luebeck involving state-of-the-art magnetic resonance procedures, e.g. during metabolic stress. The ATP content in the brain and musculature of test subjects was examined by a magnetic resonance technique while either an energy deficit or surplus was induced in the blood by insulin or glucose injection. In both situations a sufficiently high ATP-concentration was measured in the brain. The measured high-energy-rich substances changed throughout to the benefit of the brain and to the disadvantage of the body cells. The glucose-supply of the brain had priority despite the physical stress that was being endured (see 11).