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.
Opioid overdose
Permanent brain damage may occur due to cerebral hypoxia or opioid-induced neurotoxicity. Opioids inhibit the medulla's chemoreceptors through the mu and delta receptors. Opioids bind to receptors that are part of the endogenous opioid system as well as other central nervous neurotransmitter systems, binding to excitatory neurotransmitters like dopamine or glutamate, or inhibitory neurotransmitters like GABA. The main excitatory chemoreceptor, glutamate, and main inhibitory chemoreceptor, GABA, are the main neurotransmitters that control respiration. Because of its fatal consequences, opioid induced respiratory depression is one of the major limiting factors of its analgesic effects. Opioids vary in the rate of metabolism amongst individuals. The rate of metabolism of opiates vary due to genetic factors while tolerance of the opiates can determine risk.