On hoary grey cells

There is new evidence that the human brain does not generally disintegrate with advancing age. And that even if it does, the maladies are curable

Published: Sunday 15 September 1996

Degeneration of the human brai one common perception shared by almost all of humankind is that as one grows old, the brain gives up; it becomes 'senile', and resultantly, memory and the ability to learn fast are affected. Latest research shows that most of these notions are clearly exaggerated.

In a significant departure from conventional thinking, neurobiologists are proposing that most biological changes in the healthy ageing brain are quite subtle and more importantly, they can possibly be corrected. Until a decade ago, scientists believed that widespread cell death caused the cognitive changes associated with normal ageing. But better methods of distinguishing normal subjects from those suffering from neuro-degenerative diseases, as well as sophisticated technology for examining the brain, have challenged the established dogma. In fact, much of the boost brain research has received in recent years is due to the increasing funds available to study such disorders as Alzhemier's disease. "The study of (brain) ageing is undergoing a major reassessment," says Mark Moses, a neuropsychologist from Boston University School of Medicine, us . "These are exciting times."

New data, some of which is yet to be formally published, shows that cortical neurons are preserved during ageing. These new findings may well have significant implications towards developing drugs to bolster memory. Very few knew the impact of the loss of almost 40 per cent neurons on mental states. It was also thought that the changes were normal consequences of ageing and therefore, irreversible. It was Herbert Haug from the Medical University of Lubeck, Germany, who questioned the premise way back in 1984. He suggested that a common method of preparing brain tissues for microscopic study (which has been the basis for all the conclusions) makes the younger brain tissue shrink more and hence the cell density measurements differ significantly.

Taking shrinkage into account, Haug's group subsequently found no evidence of cortical neuronal loss with advancing age in 120 normal human brains. Haug's critics pointed out that shrinkage alone could not explain all the inconsistencies.

But many subsequent studies from the Boston University School of Medicine have confirmed Haug's contention. There is more support forthcoming from a study that began more than 16 years ago. John Morris, Leonard Berg and their colleagues from the Washington University Medical School, St Louis, us , have been following more than 200 people who were all healthy when recruited. The researchers test the cognitive abilities of the participants annually and interview their close relatives, looking for even subtle signs of mental slippage. When the subjects die, their brains are examined. Results obtained from the first batch of 10 people show that there are no age-related changes in cell numbers -- in persons between 60 and 90 years of age -- in that portion of the cortex critical to memory.

There are, however, contradictory findings as well. Stanley Rapoport from the National Institute of Aging in Princeton, New Jersey, us has used magnetic resonance imaging on the brains of healthy men and observed a 10 per cent drop in brain volume in men over 60 years as compared to 25-year-olds. What is more, shrinkage of grey matter has also been noticed. "There is likely to be a real loss of neurons that occurs with healthy aging," Rapoport maintains.

But irrespective of the fact that there is a perceptible decline in nerve cells with ageing, as long as the cortical neurons remain alive, there may be ways to boost their function and stave off mental decline in old age. With the use of drugs that can, for example, compensate for neurotransmittor deficiency or give an impetus to functional receptors, there are promising prospects of reversing the subtle memory loss that accompanies ageing.

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