Ray Kurzweil - How to Create a Mind - The Secret of Human Thought Revealed

The cerebellum is an old-brain region that once controlled virtually all hominid movements. It still contains half of the neurons in the brain, although most are relatively small ones, so the region constitutes only about 10 percent of the weight of the brain. The cerebellum likewise represents another instance of massive repetition in the design of the brain. There is relatively little information about its design in the genome, as its structure is a pattern of several neurons that is repeated billions of times. As with the neocortex, there is uniformity across its structure. 9

Most of the function of controlling our muscles has been taken over by the neocortex, using the same pattern recognition algorithms that it uses for perception and cognition. In the case of movement, we can more appropriately refer to the neocortex’s function as pattern implementation. The neocortex does make use of the memory in the cerebellum to record delicate scripts of movements—for example, your signature and certain flourishes in artistic expression such as music and dance. Studies of the role of the cerebellum during the learning of handwriting by children reveal that the Purkinje cells of the cerebellum actually sample the sequence of movements, with each one sensitive to a specific sample. 10 Because most of our movement is now controlled by the neocortex, many people can manage with a relatively modest obvious disability even with significant damage to the cerebellum, except that their movements may become less graceful.

The neocortex can also call upon the cerebellum to use its ability to compute real-time basis functions to anticipate what the results of actions would be that we are considering but have not yet carried out (and may never carry out), as well as the actions or possible actions of others. It is another example of the innate built-in linear predictors in the brain.

Substantial progress has been made in simulating the cerebellum with respect to the ability to respond dynamically to sensory cues using the basis functions I discussed above, in both bottom-up simulations (based on biochemical models) and top-down simulations (based on mathematical models of how each repeating unit in the cerebellum operates). 11

If the neocortex is good at solving problems, then what is the main problem we are trying to solve? The problem that evolution has always tried to solve is survival of the species. That translates into the survival of the individual, and each of us uses his or her own neocortex to interpret that in myriad ways. In order to survive, animals need to procure their next meal while at the same time avoiding becoming someone else’s meal. They also need to reproduce. The earliest brains evolved pleasure and fear systems that rewarded the fulfillment of these fundamental needs along with basic behaviors that facilitated them. As environments and competing species gradually changed, biological evolution made corresponding alterations. With the advent of hierarchical thinking, the satisfaction of critical drives became more complex, as it was now subject to the vast complex of ideas within ideas. But despite its considerable modulation by the neocortex, the old brain is still alive and well and still motivating us with pleasure and fear.

One region that is associated with pleasure is the nucleus accumbens. In famous experiments conducted in the 1950s, rats that were able to directly stimulate this small region (by pushing a lever that activated implanted electrodes) preferred doing so to anything else, including having sex or eating, ultimately exhausting and starving themselves to death. 12 In humans, other regions are also involved in pleasure, such as the ventral pallidum and, of course, the neocortex itself.

Pleasure is also regulated by chemicals such as dopamine and serotonin. It is beyond the scope of this book to discuss these systems in detail, but it is important to recognize that we have inherited these mechanisms from our premammalian cousins. It is the job of our neocortex to enable us to be the master of pleasure and fear and not their slave. To the extent that we are often subject to addictive behaviors, the neocortex is not always successful in this endeavor. Dopamine in particular is a neurotransmitter involved in the experience of pleasure. If anything good happens to us—winning the lottery, gaining the recognition of our peers, getting a hug from a loved one, or even subtle achievements such as getting a friend to laugh at a joke—we experience a release of dopamine. Sometimes we, like the rats who died overstimulating their nucleus accumbens, use a shortcut to achieve these bursts of pleasure, which is not always a good idea.

Gambling, for example, can release dopamine, at least when you win, but this is dependent on its inherent lack of predictability. Gambling may work for the purpose of releasing dopamine for a while, but given that the odds are intentionally stacked against you (otherwise the business model of a casino wouldn’t work), it can become ruinous as a regular strategy. Similar dangers are associated with any addictive behavior. A particular genetic mutation of the dopamine-receptor D2 gene causes especially strong feelings of pleasure from initial experiences with addictive substances and behaviors, but as is well known (but not always well heeded), the ability of these substances to produce pleasure on subsequent use gradually declines. Another genetic mutation results in people’s not receiving normal levels of dopamine release from everyday accomplishments, which can also lead to seeking enhanced early experiences with addictive activities. The minority of the population that has these genetic proclivities to addiction creates an enormous social and medical problem. Even those who manage to avoid severely addictive behaviors struggle with balancing the rewards of dopamine release with the consequences of the behaviors that release them.

Serotonin is a neurotransmitter that plays a major role in the regulation of mood. In higher levels it is associated with feelings of well-being and contentment. Serotonin has other functions, including modulating synaptic strength, appetite, sleep, sexual desire, and digestion. Antidepression drugs such as selective serotonin reuptake inhibitors (which tend to increase serotonin levels available to receptors) tend to have far-reaching effects, not all of them desirable (such as suppressing libido). Unlike actions in the neocortex, where recognition of patterns and activations of axons affect only a small number of neocortical circuits at a time, these substances affect large regions of the brain or even the entire nervous system.

Each hemisphere of the human brain has an amygdala, which consists of an almond-shaped region comprising several small lobes. The amygdala is also part of the old brain and is involved in processing a number of types of emotional responses, the most notable of which is fear. In premammalian animals, certain preprogrammed stimuli representing danger feed directly into the amygdala, which in turn triggers the “fight or flight” mechanism. In humans the amygdala now depends on perceptions of danger to be transmitted by the neocortex. A negative comment by your boss, for example, might trigger such a response by generating the fear of losing your job (or maybe not, if you have confidence in a plan B). Once the amygdala does decide that danger is ahead, an ancient sequence of events occurs. The amygdala signals the pituitary gland to release a hormone called ACTH (adrenocorticotropin). This in turn triggers the stress hormone cortisol from the adrenal glands, which results in more energy being provided to your muscles and nervous system. The adrenal glands also produce adrenaline and noradrenaline, which suppress your digestive, immune, and reproductive systems (figuring that these are not high-priority processes in an emergency). Levels of blood pressure, blood sugar, cholesterol, and fibrinogen (which speeds blood clotting) all rise. Heart rate and respiration go up. Even your pupils dilate so that you have better visual acuity of your enemy or your escape route. This is all very useful if a real danger such as a predator suddenly crosses your path. It is well known that in today’s world, the chronic activation of this fight-or-flight mechanism can lead to permanent health damage in terms of hypertension, high cholesterol levels, and other problems.