Which portions of the brain die first

Not all functions of the hemispheres are shared. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. The cerebral hemispheres have distinct fissures, which divide the brain into lobes. Each hemisphere has 4 lobes: frontal, temporal, parietal, and occipital Fig. Each lobe may be divided, once again, into areas that serve very specific functions.

There are very complex relationships between the lobes of the brain and between the right and left hemispheres. In general, the left hemisphere of the brain is responsible for language and speech and is called the "dominant" hemisphere. The right hemisphere plays a large part in interpreting visual information and spatial processing. In about one third of people who are left-handed, speech function may be located on the right side of the brain.

Left-handed people may need special testing to determine if their speech center is on the left or right side prior to any surgery in that area. Aphasia is a disturbance of language affecting speech production, comprehension, reading or writing, due to brain injury — most commonly from stroke or trauma.

The type of aphasia depends on the brain area damaged. If this area is damaged, one may have difficulty moving the tongue or facial muscles to produce the sounds of speech.

The person can still read and understand spoken language but has difficulty in speaking and writing i. Wernicke's area: lies in the left temporal lobe Fig 3. Damage to this area causes Wernicke's aphasia. The individual may speak in long sentences that have no meaning, add unnecessary words, and even create new words.

They can make speech sounds, however they have difficulty understanding speech and are therefore unaware of their mistakes. The surface of the cerebrum is called the cortex. It has a folded appearance with hills and valleys.

The nerve cell bodies color the cortex grey-brown giving it its name — gray matter Fig. Beneath the cortex are long nerve fibers axons that connect brain areas to each other — called white matter. Each fold is called a gyrus, and each groove between folds is called a sulcus. There are names for the folds and grooves that help define specific brain regions.

Pathways called white matter tracts connect areas of the cortex to each other. Messages can travel from one gyrus to another, from one lobe to another, from one side of the brain to the other, and to structures deep in the brain Fig. Hypothalamus: is located in the floor of the third ventricle and is the master control of the autonomic system. It plays a role in controlling behaviors such as hunger, thirst, sleep, and sexual response. It also regulates body temperature, blood pressure, emotions, and secretion of hormones.

Pituitary gland: lies in a small pocket of bone at the skull base called the sella turcica. The pituitary gland is connected to the hypothalamus of the brain by the pituitary stalk. It secretes hormones that control sexual development, promote bone and muscle growth, and respond to stress.

Pineal gland : is located behind the third ventricle. It has some role in sexual development. One of the fundamental problems with the identity theory of mind and thus with both the total brain and the higher brain standards is that the mind is not necessarily identical with the brain.

The mind can be instantiated in more than one way. As an example of a particular mental state, pain seems multiply realizable because it is not produced only by the brain state in humans, but also by brain states in animals, and theoretically in computers.

It is this latter possibility in particular that highlights a fundamental problem with identity views such as the total or higher brain conceptions of death. To see why this is the case, we must first start with a naturalistic conception of mind. The aspects of the mind that we care about—personality, memory, consciousness, and so on—are thus traceable in some way to particular operations of the brain, operations which themselves can be performed in other ways.

The idea would be that uploading our brains onto computers would be theoretically possible because our minds are in some way our brains and our brains operate through physical processes which can be duplicated electronically. Thus, the electronic process related to encoded memories, links between memories, predispositions, and even consciousness and pain—all the things that make us persons—could be replicated through computers and without brains.

That is, the mind is multiply realizable because it can conceivably be instantiated without a brain. The brain, then, is not what matters- what matters are certain functions the brain performs.

In the vast majority of cases, traditional cardiopulmonary standards for death will be sufficient. Such cases will occur when medical technology creates a gap between the body and death. In these cases, the total brain standard serves a more precise definition of death given our currently existing concepts of death and what we value in persons.

Further precision would be obtained if we were to one day move to utilize the higher brain criterion instead. As we have seen, this is because we do not value all parts of the brain, and thus total brain death is not necessary for death of the person, only sufficient. The higher brain standard will more closely mirror what we care about, as it tracks the portions of the brain which produce memories, consciousness, and personality, all of which constitute what we ultimately care about in persons.

The personal identity standards come even closer to matching what we care about, and adherence to those standards would bring us perhaps as close as possible to adequate criteria for death.

However, there are practical problems with the various criteria once we go beyond the total brain standard. There are technological problems with verifying the higher brain criterion, let alone the personal identity criteria. The Commission recognized this in its report and seemed to base its decision to adopt the total brain standard tacitly on problems with the higher brain criterion. Total brain standards also face these measurement problems.

Personal identity would be even more difficult to test for, and would in any case require value judgements regarding what matters in a person so that we would know what to look for in the first place. However, these and other practical problems in determining higher brain death do not prevent us from pragmatically defining death. In simple cases, cardiopulmonary criteria suffice. In harder cases, total brain death would be sufficient, but higher brain death would be necessary. This is because, as has been noted, all cases of total brain death will be cases of higher brain death.

But higher brain death more precisely narrows in on what parts of the brain produce what we value in persons—namely our memories, consciousness, beliefs, desires, and overall psychology. Thus, for our current purposes and given the current state of technology, the increasingly precise trifecta of cardiopulmonary, total brain, and higher brain death suffice for determining. The idea of these transplants, as of yet not successfully implemented, is to transplant a patient's head on to the body of a donor who is brain dead.

While the death criteria trifecta currently suffice, they will not permanently be sufficient for determining death. Given that our concepts and practices relating to death are tied with what we value in persons, as our values change so too will how we relate to death. For instance, in a hypothetical future where experiences become more similar, memories will be similar as well. Alzheimer's is the most common form of mental decline, or dementia, in older adults.

Weiner MD - Psychiatry, Neurology. Author: Healthwise Staff. Medical Review: Anne C. This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. They have identified the right kind of brain activity for a neural explanation of near-death experiences, yet it remains to be verified whether these signatures do actually relate directly to the subjective experience.

Future directions : The obvious next step is to test weather similar patterns of brain activity are observed in humans after clinical death. Then it will be important to show that such activity is strongly coupled to near-death experience.

For example, does the presence or absence of such activity predict whether or not the person would report a near death experience? This second step is obviously fraught with technical and ethical challenges think: The Flatliners , but would provide good evidence to link the neural phenomena to the phenomenal experience. Arch Ital Biol Auyong DB, et al.

May 01, By: Mark Stokes. Aa Aa Aa. Could a final surge in brain activity after death explain near-death experiences? Email your Friend. Submit Cancel. May 31, What does MEG measure?