Degenerative cognitive diseases are some of the most frequent causes of memory loss. According to the World Health Organization, 6 to 10 percent of the North American population 65 years and older have dementia. But strokes, mood disorders and head injury are also common triggers of memory problems.
Degenerative Cognitive Disorders
Researchers believe dementia in the elderly population will become an epidemic. In the population 90 years of age and older, the incidence rate for dementia is 18.2 percent annually and it is on the rise, according to a University of California study, titled The 90+ Study, which appeared in the February 2010 issue of the journal "Annals of Neurology." Dementia, or senility, is a progressive, degenerative disorder. One of its main characteristics is a buildup of plaque in the brain's memory center, also known as the hippocampus. Impairment to this important site for storing memories affects almost all cognitive functions, including learning, speech, emotional regulation and problem solving. Alzheimer's disease counts for two-thirds of all cases of dementia, according to a 2000 report by the World Health Organization.
Strokes
Strokes constitute another common trigger of memory loss. In some people, a stroke affects the ability to store information for the long term. In others, it affects the memory's ability to recognize objects. Harriet Allen, a medical researcher at the University of Birmingham, notes that a patient's stroke that caused lesions to parts of the visual cortex resulted in visual form agnosia, a condition that leaves a person without the ability to recognize objects. According to Allen, objects appear to these patients as "unrecognizable jumbles." Surprisingly, however, while sight could not activate the visual brain regions for object recognition, touch could. This confirms the multimodal nature of the sense of touch, says Allen.
Mood Disorders
Researchers have known for some time that mood disorders are associated with a degeneration of the hippocampus. The brain's memory center literally shrinks, says Ronald Duman, a professor of psychiatry at Yale University. The data were first obtained from studies of the hippocampi of the cadavers of schizophrenics. Later the results were confirmed in brain imaging studies. Studies have also shown that other chronic mood disorders such as major depression and generalized anxiety disorder can result in a breakdown of neurons in the hippocampus, reports Duman. However, common antidepressant treatments can reverse the atrophy by stimulating the growth of new neurons, Duman adds.
Head Injury
Every 23 seconds, an American suffers a traumatic brain injury, says Akiva Cohen, Ph.D., of The Children's Hospital of Philadelphia. It's the leading cause of death among children in the U.S. When it does not cause death, it often results in severe cognitive disabilities. Memory problems are the main trigger of cognitive disabilities. In their research, Cohen and colleagues found that traumatic brain injury leads to reduced levels of the protein potassium-chloride co-transporter 2, or KCC2, in the brain's dentate gyrus. This protein controls overactivity in the brain that can otherwise lead to seizures. But KCC2 also plays a major role in forming new memories, "especially antegrade memory, the ability to learn new things," Cohen says.
References
- "Annals of Neurology"; Dementia Incidence Continues to Increase With Age in the Oldest Old; M.M. Corrada et al.; 2010
- Science Daily: Brain's Object Recognition System Activated by Touch Alone
- Yale University: How Antidepressants Create New Brain Cells
- Science Daily: Exercise May Increase Volume in Certain Brain Areas of Patients With Schizophrenia
- Medical News Today: How Brain Injury Leads To Seizures, Memory Problems
