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Chapter 14

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University of Toronto 1 PSYB65: Human Brain and Behavior Sayanutha Niranjan Chapter 14: Human Brain Damage When a brain suffers significant damage, no amount of effort can restore the brain back to its original healthy state A CNS lesion (meaning “to hurt”) is an area of damaged neural tissue, including the loss of cells or discontinuity of previously present connections Causes of Brain Damage Tumor (aka “ Neoplasms” & “space occupying lesions”)  A mass of new and abnormal tissue that is not beneficial to surrounding structures and the body.  They can cause damage to the CNS by causing pressure and taking up space of the CNS and are space occupying lesions.  These differ depending on the type of cell it grows from, how fast it grows (infiltrate), if it invades neurons, destroys neural tissue(encapsulated), if it has clear borders, and its likelihood of recurrence.  The location and size of a tumor also influence neurological effects, for example a tumor of the pituitary may affect vision, as it would cause pressure on the adjacent optic chiasm. They can also release toxins. There are 2 types:  Benign: these tumors are likely to not reappear after removal and are non cancerous.  Malignant: these tumors are likely to reappear after removal and are cancerous. There are 4 types of brain tumors: those that originate from glial cells, the meninges, nervous tissue or other parts of the body already infected with tumor 1) Tumors Arising from Glial Cells:  Gliomas: tumors that arise from glial cells.  There are 3 types of gliomas: 1. Astrocytoma: tumors that arise from the growth of astrocytes.  These do not grow quickly, and are usually benign and encapsulated (therefore cause damage by pressure or invading neural tissue).  These can be treated easily if they are in a convenient location. 2. Glioblastoma: tumors that grow quickly are highly malignant, non- encapsulated, opposite of astrocytomas. 1 University of Toronto 2 PSYB65: Human Brain and Behavior Sayanutha Niranjan 3. Medulloblastoma: an uncommon type of glioma, highly malignant, and invasive. These tend to form around the cerebellum and brainstem early in life. 2) Tumors Arising from the Meninges:  Meningiomas: tumors that grow out of the meninges, specifically the dura matter. Since these grow outside of the CNS they are usually encapsulated and benign, and cause harm from pressure. 3) Metastatic Tumors : also known as metastases, are secondary tumors formed from migrated tumor tissue. If a tumor forms elsewhere in the body, usually outside the CNS, and if not treated, it can metastasize and enter the blood system and be spread around the body. If one-tumor results it is a simple metastatic tumor, if multiple form it is a multiple metastatic tumor. 4) Neuropsychological Effects of Tumors:  Behavioral symptoms that arise from the formation of a tumor vary widely, just as the size, locations, cell type and growth rate of the tumors varies  E.g tumors of the pituitary gland can have behavioral symptoms of those similar to those of a visual cortex tumor  Tumor can also epileptic seizures and release substances that are toxic to the brain  If the tumor was formed in the ventricles  toxins can be transported easily from the site of origin, producing lesions and behavioral deficits – not confined to the region where the tumor is growing Cerebrovascular Disorders Cerebrovascular Disorder: an illness that occurs when blood supply to the brain is interrupted.  This can occur suddenly, gradually, complete, relative, permanent, or transient.  These create lesions that allow psychologists to study parts and functions of the brain. Cerebrovascular Accident (CVA): a class of cerebrovascular disorders resulting in an interruption to brain blood supply.  This can occur suddenly with a blood clot or artery break or gradually as a result of plaque buildup.  They can also be caused by congenital defects or physical trauma.  Surgery can be used to clip damaged areas, break up thromboses and embolisms, and anticoagulant drugs can prevent blockages. Cerebral Ischemia: a lack of blood supply to the brain as a result of a CVA. 2 University of Toronto 3 PSYB65: Human Brain and Behavior Sayanutha Niranjan  If this occurs long enough, it can cause neuron death, and the damaged area is known as an infarct.  This can be large or small depending on where and the size of the artery affected. Thrombosis: when a blood clot forms within a cerebral blood vessel that stays at the point of origin.  These can also occur in other areas of the body, ex. In the heart would cause a heart attack.  This may be caused by atherosclerosis where cholesterol and plaque build up in the arteries.  This occurs gradually along with its neuropsychological symptoms, and usually in areas of bifurcation where one artery splits into 2. Embolism: when a blood clot forms within a cerebral blood vessel that can break off and travel in the bloodstream.  The blockage occurs when the blood clot moves from a wide to a thin artery.  The obstruction is sudden and complete, however this can be very dangerous if not relieved quickly. Hemorrhage: when there is an interruption in blood supply to the brain due to the breakage of a blood vessel.  A thrombosis or embolism may cause great pressure causing the vessel to break.  Also, if the vessel has a weak spot, called an aneurysm or high blood pressure called hypertension, or the piercing with an object like a bullet can cause a breakage.  This can cause pressure compressing parts of the brain away from the bleed or displacement of neural centers critical for basic functions. Intracerebral Hemorrhage: usually caused by hypertension, occurs within the brain.  This is a result of an interruption in blow flow, toxicity of uncontained blood, and pressure buildup at and away from the site. Subarachnoid Hemorrhage: involves sudden bleeding in the subarachnoid space (b/w pia mater and the arachnoid layers), as a result of hypertension.  The biggest threat is the pressure caused by the buildup of blood.  These tend to not recur.  Symptoms  severe and sudden headache, nausea or even vomiting and perhaps loss of consciousness Arteriovenous Malformation (AVM): weak, malformed arteries and vessels that have extra or missing connections resulting in abnormal blood flow, usually along the middle cerebral artery.  If these bleed, they release small amounts of blood over a long period of time and can occur more than once or not at all.  Therefore, damage is not due to pressure but due to areas being subject to toxic blood. 3 University of Toronto 4 PSYB65: Human Brain and Behavior Sayanutha Niranjan Aneurysm: an area of an artery that has a weak spot that can burst. Depending on the location and speed of leaking it can range from less harmful to fatal. Head Injuries Traumatic Brain Injury: leading cause of closed head injury. Acquired brain injury  Various cognitive impairment based on the severity of the injury  Common impairments – difficulties with executive skills, short-term memory and concentration Closed Head Injuries: an injury in which an individual receives a blow to the head, not penetrating the skull or meninges. 
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