Enduring mysteries of brain and mind

The brain and the mind. One is the physical structure housing our capacity for thought. The other is the thing doing the thinking or so we think.

Understanding neuroscience is one of the great challenges facing science. Why do we think? Is it necessary? What exactly is going on? And how does it lead to consciousness? These are some of the questions facing biologists, psychologists, neuroscientists, philosophers, and even chemists.

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We know a great deal about the physical structure of the brain. It is composed of approximately 100 billion neurons and a much greater number of glial cells. Each neuron is connected to a multitude of other neurons through synapses. These synaptic connections, in a few cases, are electrical junctions in which a potential is transmitted across a gap but for the most part they are chemical and regulated by neurotransmitters, such as dopamine or histamine.

At the larger scale, scientists have been able to map out the regions of the brain and locate our visual centre (the occipital lobes), our speech centres (Broca's and Wernicke's areas), and other such regions within the cerebral cortex. They have come to understand the plasticity of the brain - its ability to reprogram itself. They have identified the sub-structures such as the pituitary gland, the superchiasmatic nucleus, and locus coeruleus each with its own specialized functions.

We even know our brain stem and primitive brain control much of the function of our bodies. You don't need to think in order for your heart to beat, your lungs to pump air, or your stomach to digest dinner. These are the autonomic functions of the body and regulated by parts of the brain below the level of consciousness.

One of the most important realizations of the last decade is both how much information is taken in by the brain every moment of our lives and how much of that information is discarded as irrelevant. Our brains are very sophisticated machines which a capacity to sort and analyze millions of sensory inputs into a cohesive picture within our conscious mind. Most of the decisions we make occur below our level of thought.

What happens if this precisely balanced instrument develops a glitch?

The answer depends on the extent and type of glitch.

Alzheimer's disease, for example, is the most common form of dementia we are aware of. It affects 50 million people worldwide and is the seventh leading cause of death in Canada. It gradually robs people of their memories and their lives.

It is not a disease of the modern age although it appears to be a consequence of our longer lifespans as it is predominantly a disease associated with older individuals.

The brains of patients who have died from Alzheimer's disease bear two cellular hallmarks. The first is clumps of beta amyloid proteins, called plaques, which form on the outside of brain cells and appear to interfere with electrical conduction across the surface of neurons. The second are strings of protein, labeled "tau", which are neurofibrillary tangles formed within the cells.

Both types of deposits were recognized over a century ago and have been used as the diagnostic tool for confirming the presence of Alzheimer's disease. It wasn't until 1984 that the beta amyloid protein was isolated by George Glenner. His work with Caine Wong showed it was derived from a much larger protein which crosses the neuronal membrane.

Glenner proposed the beta amyloid protein as the cause of the disease. It was certainly the smoking gun as it is located in the brains of all patients. The hypothesis gathered steam after the discovery of inherited familial mutations which appeared to be linked with Alzheimer's disease running through generations.

However, this argument has come under some scrutiny over the past decade as drugs targeted at the beta amyloid proteins appear to have little or no effect on the progression of the disease. While still controversial, the present thinking is the plaques might be a symptom rather than a cause. Researchers are focusing much more on the tau proteins.

In any case, the presence of the proteins appears to disrupt the function of particular neurons. The retrieval of memories is still a subject about which little is known. How memories are formed, stored, and relived may have something to do with chemical coding in the glial cells surrounding the neurons. By interfering with the communication between cells, Alzheimer's disease might inhibit the ability to retrieve memories.

Except no one really knows for certain what is happening. Scientists know the brains mechanism is thrown out of balance. The exact mechanism is still something of a mystery. But there is no doubt the physical components of the brain affect the mind's ability to recall information.

Both the brain and the mind must work in perfect harmony for consciousness.

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