A neurocognitive defect is impairment or reduction of cognitive function in one of these areas, but particularly physical changes in the brain can be seen, such as after, mental illness, neurological illness, brain injury or drug use, neurocognitive functions are closely linked to the function of particular areas such as neural pathways or cortical networks in the brain. Neurocognitive deficits to infer usual psychological control is termed as psychological feature neuro-psychology.