Aristotle and his contemporaries believed that the mind resided in the heart. It was Hippocrates who argued that the brain is responsible for thought, sensation, emotion, and cognition. However, it took almost 2500 years for the next major advance. At the beginning of the 20th century the Spanish anatomist Santiago Ramon y Cajal identified the neuron as the building block of the brain. He identified different types of neurons and advanced the “connectionist” view that it was the connections and communications among the neurons that characterized the activities of the brain.
There are four basic types of neurons. Sensory neurons transmit signals from the brain to the rest of the body. Motor neurons send signals to parts of the body to direct movement, such as muscles. Interneurons provide connections between other neurons, Pyramidal neurons are involved in many areas of cognition.
The connectionist network is amazing. There are about 100 billion neurons in our brains. Each has about 1000 synapses connecting with other neurons. So there are about 100 trillion interconnections in our brain. Our brains are remarkably flexible. This plasticity is due to a special class of neurotransmitter that serve as “neuromodulators.” These neuromodulators “…alter the amount of other neurotransmitters released at the synapse and the degree to which the neurons respond to incoming signals. Some of these changes help to fine tune brain activity in response to immediate events, while others rewire the brain in the long term, which is thought to explain how memories are stored.
Many neuromodulators act on just a few neurons, but some can penetrate through large swathes of brain tissue creating sweeping changes. Nitric oxide, for example, is so small (the 10th smallest molecule in the known universe, in fact) that it can easily spread away from the neuron at its source. It alters receptive neurons by changing the amount of neurotransmitter released by each nerve impulse, kicking off the changes that are necessary for memory formulation in the hippocampus.”
Much of this brain activity takes place outside our conscious awareness. According to Kahneman’s Two Process View of Human Cognition, there are two basic systems for processing information. information in a dynamic environment. System 1 is named Intuition. System 1 is very fast, employs parallel processing, and appears to be automatic and effortless. They are so fast that they are executed, for the most part, outside conscious awareness. Emotions and feelings are also part of System 1. Learning is associative and slow. For something to become a System 1 process requires much repetition and practice. Activities such as walking, driving, and conversation are primarily System 1 processes. They occur rapidly and with little apparent effort. We would not have survived if we could not do these types of processes rapidly. But this speed of processing is purchased at a cost, the possibility of errors, biases, and illusions. Without System 1, we would not have survived as a species. But this fast processing speed has its costs, which sometimes lead to errors.
System 2 is named Reasoning. It is controlled processing that is slow, serial, and effortful. It is also flexible. This is what we commonly think of as conscious thought. One of the roles of System 2 is to monitor System 1 for processing errors, but System 2 is slow and System 1 is fast, so errors to slip through. System 2 can be thought of as thinking. If you know your multiplication tables, if I ask you what is 6 time 7, you’ll respond 42 without really thinking about it. But if I ask you to multiply 67 times 42 you would find it difficult to compute in your head, and would most likely use a calculator or use paper and pencil (which are examples of transactive memory). This multiplication requires System 2 processing without, or most likely with, technological aids.
System 1 requires little or no effort. System 2 requires effort. It is not only faster, but also less demanding to rely on System 1 processes. Consider the following question.
A bat and a ball cost $1.10
The bat costs $1.00 more than the ball.
How much does the ball cost?
The number that quickly comes to mind is 10 cents. But if you take the time and exert the mental effort you will note that the cost would be $1.20 (10 cents for the ball and $1.10 for the bat). If you do the math, which takes a little algebra, you will find that the ball costs 5 cents (the bat costing a $1.00 more than the ball would be $1.05 and $1.05 and $0.05 is $1.10). System 2 must be engaged to get the correct answer. This question has been asked of several thousand college students. More that 50% of the students at Harvard, MIT, and Princeton gave the wrong, System 1, answer. At less selective universities more than 80% of the students gave the wrong answer. Good students tend to be suspicious of a question that is too easy!
So what happens to the brain as we age? The psychologist Dr. Stine-Morrow has an interesting hypothesis about cognitive aging. She argues that choice in how cognitive effort, attention, is allocated may be an essential determinant of cognitive change over the life span. So relying too much on our System 1 processes could increase our risk of suffering dementia. New experiences and new learning call upon our System 2 processes as do any problems that require active thinking. The neurofibrillary tangles and amyloid plaques that define Alzheimer’s Disease have been found in both living and dead individuals who never showed any symptoms of the disease. They evidenced no cognitive impairment. The notion is that they had built a cognitive reserve that protected them from the disease.
So what might this cognitive reserve be? It is reasonable to believe that it consisted of rich interconnections in the brains of these individuals. The brain is remarkably plastic, so even when the plaques and tangles were present, apparently the interconnections were rerouted around them.
So how can someone build up this cognitive reserve? Lifelong learning, continuing to learn throughout one’s lifetime is key. Challenging the mind with tasks that require attention is important. It is also important to revisit those old memory circuits laid down years ago. Trying to remember all acquaintances and events can reactivate those circuits. Sometimes it will be difficult to recall these memories. Nevertheless, your unconscious mind will continue searching after your conscious mind has given up. All of a sudden, seemingly out of nowhere it will just pop into your mind. Trivia games and games such as Jeopardy can be fun and potentially beneficial to a healthy memory. Reminiscing can also be beneficial provided the reminiscing is not always about the same old memories.
The healthymemory blog is devoted to building a cognitive reserve. The Mnemonic Techniques Category provides blog on mnemonic techniques that not only improve memory, but also provide cognitive exercise. Blog posts on meditation and mindfulness can also be found here. The Transactive Memory Category provided information on how technology and your fellow humans can foster memory health. The Human Memory: Theory and Data includes posts on memory and related topics bearing on a healthy memory.