Friday, 20 April 2012

‘Dementia brain tour’

Introduction to the brain. The human brain is incredibly complex. It controls everything our body does,from coordinating our movements and our speech, keeping our heart beatingand storing our memories.Despite all this there is still a lot we don’t know about the inner workings of thebrain.Imaging technologies can give us an idea of what is going on inside the brain.The human brain weighs around 1.5 kilos.It is fed by a network of blood vessels that deliver oxygen and nutrients to thecells.The brain can be divided into four main sections, the cerebral hemispheres,the limbic system, the cerebellum and the brain stemThe bulk of the brain is made up of the cerebral hemispheres.This is made up of the grey matter, the processing centre and the whitematter which is like the wiring.The cerebral hemispheres can be split into four different lobes which eachhave different functions.The frontal lobe is responsible for our behaviour.The parietal lobe helps us with tasks like calculation and spelling and itcontrols our complex movements.The temporal lobe is important for language, emotion and memory.And the occipital lobe is responsible for our vision.At the centre of the brain is the limbic system.This area controls a number of functions but importantly it controls learningand memory particularly in the hippocampus.The cerebellum or little brain controls movement, posture and balance,The brain stem is thought to be the oldest part of the brain it controls our vitalliving functions such as breathing, heart beat and blood pressure)Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. Brain cellsThe brain is made up of billions of nerve cells.Nerve cells are specially designed for their function. They are elongated withmany tentacle-like projections called dendrites that make connections with thecells around them.Dendrites form an intricate network between cells and the white matter. Thepoint where two cells meet is called a synapse.Messages are passed along and between cells through tiny electricalimpulses and chemical messages.This is the basis for how the brain works. This is how the brain controls ourmovements, our thoughts, our memories. If something stops the cell fromdoing its job, this can result in dementia.Nerve cells are like any other cell in the body. They need oxygen nutrients tostay alive. They also rely on close contact with their neighbouring cells. If anerve cell is starved on oxygen or nutrients or becomes isolated from itsneighbouring cells it will die.Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. What is dementia?Dementia affects over 750,000 people in the UK. It is not a disease in its ownright and it is not a natural part of ageing. It is an umbrella term that describesa group of symptoms that are caused by many diseases that affect the brainfor example, Alzheimer’s disease.Dementia is caused by loss of nerve cells in the brain. Most dementias areprogressive which mean they gradually get worse. This is because when anerve cell dies it usually cannot be replaced. As more and more nerve cellsdie the brain starts to shrink.This is known as brain atrophy which can often be seen in the brain scan of aperson with dementia.Common symptoms of dementia include memory loss, impaired cognition andlack of physical coordination. However their symptoms do depend on thearea of the brain that is affected.For example if cells in the temporal lobe start to die then that person mightstart to experience difficulties with their language.Or if someone’s occipital lobe is affected this can cause problems with vision.There is currently no cure for dementia and many of the diseases that cause itare terminal.Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. Alzheimer’s diseaseAlzheimer’s disease affects over 400,000 people in the UK. It is the mostcommon cause of dementia and it is also the best understood.Alzheimer’s most commonly develops in the hippocampus which is why it isoften linked to memory loss.The hallmark of Alzheimer’s disease is the development of amyloid plaquesand tau tangles in nerve cells.Amyloid is produced when a much larger protein, the amyloid precursorprotein is broken down. This amyloid then accumulates as plaques on theoutside of nerve cells.Many scientists believe amyloid is toxic and causes cells to die.The second hallmark of Alzheimer’s disease is tangles in a protein called tau.Tau is produced by normal healthy nerve cells however during Alzheimer’sdisease an abnormal version is caused which doesn’t function correctly. Itcauses tangles within the cells and effectively strangles the cells which thendie.Current treatments for Alzheimer’s disease are designed to improvecommunication between cells. However these treatments can only slow theprogression of the symptoms of the disease. Scientists hope in the futuredrugs will target amyloid and tau and hopefully stop the disease altogether.Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. Posterior cortical atrophyPosterior cortical atrophy or PCA is a specific type of Alzheimer’s disease thataffects the back of the brain, the occipital lobe. This is the type of Alzheimer’sthat the author Terry Pratchett has been diagnosed with.The symptoms of PCA are very specific. Since this part of the brain isresponsible for visual processing people with PCA lose the ability to recognisecolours and shapes, to recognise faces, they lose the ability to read.Often the classic symptoms of Alzheimer’s disease such as memory lossdon’t develop till much later on in PCA. This means that PCA is oftenmisdiagnosed or only picked up at the later stages.It is likely that PCA is actually more common that we think as it is oftendismissed as problems with eyesight associated with old age.Alzheimer’s Society funds research into the cause, cure, care and preventionof dementia, including PCA. One of our current research projects is lookinginto whether a brain scanning technology could be developed to helpdiagnose PCA. Vascular dementiaVascular dementia is the second most common type of dementia although itcan also occur it combination with Alzheimer’s disease in a condition calledmixed dementia.Vascular dementia is associated with problems in the blood supply to thebrain. Interruption of the blood supply for example through a blockage or aleak can cause a stroke. A stroke can cause significant damage to the area ofthe brain that is starved of its blood supply.Sometimes a single stroke can be enough to cause the symptoms ofdementia. In other cases a person may experience a series of smaller strokesof many years that gradually causes damage.Vascular dementia can also be caused by small vessel disease which is dueto damage to the tiny blood vessels deep inside the brain.Prevention of vascular dementia is closely linked to maintaining a healthyblood supply. People with higher blood pressure are at a much higher risk ofdementia.The risk can be reduced by stopping smoking, maintaining a healthy weightand regular exercise.Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. Dementia with lewy bodiesDementia with lewy bodies affects about 4% of people with dementia. It isclosely related to Alzheimer’s disease and also to Parkinson’s disease.Lewy bodies are tiny spherical deposits of protein that develop inside nervecells.They prevent the cells from communicating properly by disrupting the tinychemical messages between cells. As yet we have no idea why Lewy bodiesform.Lewy body dementia can affect many different parts of the brain leading tomany different types of symptoms.This type of dementia shares many symptoms with Alzheimer’s diseasehowever people with lewy body dementia often experience hallucinations orproblems with paying attention.They can frequently experience problems with their movement as well in asimilar way to people with Parkinson’s disease.Research is vital in the fight against dementia. Alzheimer’s Society fundsscientists to carry out research into the cause, cure, care and prevention ofdementia. Fronto-temporal dementiaFronto-temporal dementia covers a range of conditions that affect the frontaland temporal lobes.People with damage to their frontal lobes will often experience changes intheir behaviour for example becoming more disinhibited whereas people withdamage to their temporal lobe will often struggle with language.People who experience damage to both of these areas might experience amixture of these symptoms. This is a fairly rare form of dementia and it oftenaffects younger people.Unlike other forms of dementia there maybe a strong family link with frontotemporaldementia. Scientists have identified some genes that are linked tofronto-temporal dementia but our understanding of them is still limited.One of the diseases that causes fronto-temporal dementia is Pick’s disease.Proteins accumulate inside nerve cells causing dementia. As yet we have noidea why certain parts of the brain are far more vulnerable to this disease thanothers.Research is vital in the fight for a cure against dementia. Alzheimer’s Societyfunds scientists to carry out research into the cause, cure, care andprevention of dementia. Rarer causes of dementiaThere are a number of rarer diseases and conditions that cause dementia.People with Down’s syndrome are particularly at risk of developing dementia,and they are more likely to develop Alzheimer’s disease early in life.This is because the gene that has been linked to Alzheimer’s disease is foundon chromosome 21. People with Down’s syndrome have an extra copy of thischromosome and therefore an extra copy of the Alzheimer’s gene. Dementia can also be caused by HIV, Huntingdon’s disease, Prion diseaseslike CJD and also excessive alcohol consumption. The biology of thesedementias is still poorly understood and in most cases treatments are verylimited.Research is vital in the fight for a cure against dementia. Alzheimer’s Societyfunds scientists to carry out research into the cause, cure, care andprevention of dementia.