Agnosia
Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.
Mechanism of anoxic depolarization in the brain
During brain ischemia, glutamate is released in excess from the presynaptic terminal, leading to the uncontrollable opening of the glutamate receptors, including the NMDA and AMPA receptors, which allows for an excessive influx of Ca into the intracellular environment. Purinergic and NMDA receptors activate the pannexin-1 channels, which become hyperactive and allow the release of ATP from the intracellular environment. As the extracellular glutamate and ATP increase, several complexes are activated and converge into apoptotic and necrotic cascade pathways, which cause neuronal damage and death.