Consciousness Beyond Life: The Science of the Near-Death Experience (28 page)

Therapeutic Effects

Applying local and targeted electrical energy to the brain can also have a lasting therapeutic effect, as the functional changes in certain areas of the brain result in different experiences in the mind. A change in the electromagnetic field prompts a change in function. Whereas the effect of transcranial electrical stimulation (TES), like that of TMS, is short-lived, transcranial direct current stimulation (tDCS) causes permanent functional change in some parts of the brain because of its effect on the cerebral cortex.
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This can be used to help seriously depressed patients who do not respond well to antidepressants. The brain state of major depression in such therapy-resistant patients has been demonstrated with the help of fMRI and PET scans, which show that some parts of the brain (such as the subgenual cingulate cortex) are overactive and other parts (such as the prefrontal cortex) are seriously underactive.

Antidepressants can improve these impaired activity patterns in serious depression, but so can various forms of electrical therapy, such as electroconvulsive therapy (ECT), in which a powerful electrical current induces epileptic seizures (convulsions); stimulation of the vagus nerve; and more recently the implanting of deep electrodes in over- or underactive areas of the brain, known as deep brain stimulation (DBS).
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Although the precise mechanism is unknown, it has been found to produce clinical benefits that were confirmed by fMRI. An article in
Nature
recently described how a man who had been in a form of coma for more than six years after sustaining a traumatic brain injury regained consciousness after DBS in the thalamus.
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Targeted magnetic energy, as administered during TMS and magnetic convulsive therapy, sometimes achieves an equally positive effect. But what is even more interesting is that placebo treatment has been found to produce the same neurological improvement in the brain.
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The belief that one is receiving proper treatment thus appears to have the same effect on brain function as medication or electrical and magnetic stimulation therapy. More on how the mind can influence brain function can be found in the section on neuroplasticity below.

Consciousness Research Using TMS

A recent study published in
Science
drew on a combination of TMS and high-density electroencephalography (EEG) to see if changes in the cerebral cortex might play a role in the loss of consciousness during deep, dreamless sleep (non-REM sleep) while the brain remains active.
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People have no memories of this phase of deep sleep, whereas they do remember dreams from the REM phase of sleep. Despite measurable brain activity, people do not usually experience consciousness during non-REM sleep.

The study found that during such deep, dreamless sleep the initial response to TMS was heightened but that the signal was rapidly extinguished a few millimeters from the crown of the skull. The electromagnetic signal did not propagate beyond the stimulation site. In contrast, when the same study was conducted in the daytime during wakefulness, the initial response (15 milliseconds) was followed by a sequence of waves that moved to other cortical areas and to some deeper structures several centimeters away. The study concluded that despite electromagnetic activity in the brain during deep sleep, communication between various cortical areas breaks down. This breakdown in communication between neural networks causes consciousness to fade. But when the connections between the various parts of the cerebral cortex and between the cortex and the thalamus function properly, information exchange is possible thanks to the system’s integrating and differentiating properties. Such information exchange seems to be a condition for the experience of consciousness.
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The latter has also been demonstrated in research using PET scans to explain unconsciousness during general anesthesia, during which brain activity is registered but no (waking) consciousness is experienced. This research, recently published in
Science
and other journals, also shows that a functioning communication system among various neural networks with integration of information is a prerequisite for the experience of (waking) consciousness because during general anesthesia the pathways between thalamus and cortex, in particular, were found to be impaired.
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And this essential condition is lacking during a cardiac arrest, during general anesthesia, and during deep sleep.

That proper communication within the brain is essential for the experience of consciousness has also been demonstrated by a study of people waking up from deep sleep. The process of deep sleep, which, as shown by TMS, includes the loss of communication between certain neural networks, is reversed upon waking. The study in question looked at the order in which brain centers are reactivated after sleep, during the first five and the first twenty minutes after waking. During the first few minutes, activity in the brain stem and thalamus increased, followed a little later by activity in the prefrontal cortex. The authors conclude that the process of regaining awareness of oneself and one’s surroundings after sleep rests on a reorganization process in the brain that involves the recovery of working connections between the aforementioned centers. These centers need to function like a network to enable the experience of consciousness.
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During a cardiac arrest the cerebral cortex, thalamus, hippocampus, and brain stem as well as all connections between them stop functioning, as we have seen, which prevents information from being integrated and differentiated—a prerequisite for communication and thus for the experience of consciousness. The experience of consciousness should be impossible during a cardiac arrest. All measurable electrical activity in the brain has been extinguished and all bodily and brain-stem reflexes are gone. And yet, during this period of total dysfunction, some people experience a heightened and enhanced consciousness, known as an NDE.

The Brain, Information Storage Capacity, and Memory

According to current knowledge, consciousness cannot be reduced to activities and processes in the brain. It is highly unlikely that thoughts and emotions are produced by brain cells. Above, we looked at the influence of electromagnetic fields on consciousness as well as the fact that information exchange between brain stem and cerebral cortex is a prerequisite for the experience of consciousness. The next logical question is how all the memories from a person’s life can be stored and then recalled again together with their associated emotions. How do we explain short-term and long-term memory? How and where in the brain is this virtually unlimited amount of information stored? And how can this information be accessible at all times?

A single cubic centimeter of the cerebral cortex contains no less than a hundred million neurons, and because each neuron has at least a thousand synapses connecting it with surrounding neurons, each cubic centimeter has approximately 100,000,000,000 (10
¹¹
) synapses of dendrites that originate largely in other parts of the cerebral cortex. This means that the brain contains a total of about 10
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synapses. If one synapse contained one bit of information, brain function would require more than 100,000,000,000,000 (10
¹⁴
) bits of information processing, which is far more information than the human DNA, our genetic code, can handle according to current knowledge. For this reason consciousness cannot be stored in our DNA, rendering a cell in our body and brain a highly unlikely producer for consciousness.
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Simon Berkovich, a computer expert, has calculated that despite the brain’s huge numbers of synapses, its capacity for storing a lifetime’s memories, along with associated thoughts and emotions, is completely insufficient. At any waking moment during the day, there are approximately 10
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actions per second in the brain. Add to this the required capacity for long-term memory storage, and the total data storage capacity would have to be 3.10
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bits/cm
³
, which, based on our current understanding of neuronal processes in the brain, is inconceivable. Neurobiologist Herms Romijn, formerly of the Netherlands Institute for Neuroscience, also demonstrated that the storage of all memories in the brain is anatomically and functionally impossible.
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On the basis of these findings, we are forced to conclude that the brain has insufficient capacity for storing all memories with associated thoughts and feelings or retrieving capacity for stored information. Neurosurgeon Karl Pribram was equally certain that memories cannot be stored in brain cells, but only in the coherent patterns of the electromagnetic fields of neural networks. In his view the brain functions like a hologram. This hologram is capable of storing the vast quantity of information of the human memory. According to Pribram’s holographic hypothesis, memories are stored not in the brain itself but in the electromagnetic fields of the brain. Pribram’s hypothesis was inspired by the extraordinary experiments of psychologist Karl Lashley, who proved as early as 1920 that memories are stored not in any single part of the brain but throughout the brain as a whole. His experiments on rats showed that it did not matter which parts or indeed how much of the rats’ brains were removed. The animals were still capable of carrying out the complex tasks that they had learned to do before the brain operations.
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Earlier in this chapter I mentioned that the composition and cohesion of all brain structures, from molecules to neurons, is in constant flux, which raised a question about long-term memory. The debate about information storage and memory is further complicated by an article in
Science
with the provocative title “Is Your Brain Really Necessary?” This article was written in response to English neurologist John Lorber’s description of a healthy young man with a university degree in mathematics and an IQ of 126. A brain scan revealed a severe case of hydrocephalus: 95 percent of his skull was filled with cerebrospinal fluid, and his cerebral cortex measured only about 2 millimeters thick, leaving barely any brain tissue. The weight of his remaining brain was estimated at 100 grams (compared to a normal weight of 1,500 grams), and yet his brain function was unimpaired. It seems scarcely possible to reconcile this exceptional case with our current belief that memories and consciousness are produced and stored in the brain.
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The question is not just how short-term and long-term memory can function properly given the constantly changing synaptic connections in neural networks, but also how memory loss arises. As we get older our brains can atrophy as a result of Alzheimer’s disease or arteriosclerosis. Brain volume decreases when brain cells die and are no longer replaced, giving rise to damaged and less effective neural networks and slowly worsening dementia. Whereas long-term memory can remain intact for some time, short-term memory deteriorates, cognitive functions gradually decline, relatives are no longer recognized, and speech becomes more difficult or altogether impossible. These functions can also be lost after brain damage brought on by a cerebral hemorrhage, serious head trauma with permanent brain damage, long-term alcohol abuse, or encephalitis. The obvious and correct conclusion must be that the brain has a major impact on the way people show their everyday or waking consciousness to the outside world. The instrument, the brain, has been damaged, whereas “real” consciousness remains intact. Consciousness and the brain are interdependent, which is not to say that mental and emotional processes are identical with or reducible to cerebral processes. How else can we explain the fact that people with a severe form of dementia, or patients with chronic schizophrenia, sometimes can experience brief lucid moments (“terminal lucidity”) shortly before they die?
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Neuroplasticity

Throughout life a process of constant adapting is taking place in the cerebral cortex because our mental, intellectual, and physical activities affect both the number and the location of the connections between neurons. This process of ongoing adaptation is called neuroplasticity. Under the influence of mindfulness, emotions, active thought processes as well as movement, the neural networks and electromagnetic activity of the brain undergo constant change. The term
mental gymnastics
or
mental training
speaks volumes. If we remain mentally (and physically) active until late in life, our brains will continue to function better thanks to a more extensive network of synapses. “The power of the mind” can change brain function.
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In his book
The Brain That Changes Itself,
the psychiatrist and psychoanalyst Norman Doidge provides an excellent survey of the many scientific studies offering convincing evidence of neuroplasticity. He also writes at length about the many patients who benefited from the therapeutic use of plasticity of the brain because “our thoughts can change the material structure of our brains at a microscopic level, because the brain is constantly adapting itself. So even talking therapy or imagination can change our brains.”
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At a young age, up to about four, the brain is remarkably plastic. There is evidence that during this period, some hundred thousand synapses are lost and regenerated every second.
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An extreme example of neuroplasticity is the case of a three-year-old girl whose left brain needed to be surgically removed because of serious chronic encephalitis with symptoms of epilepsy (see figure). Doctors at Johns Hopkins Hospital in Baltimore have performed this kind of major operation on at least a hundred young children, many of them suffering from intractable epilepsy precipitated by serious neurodevelopmental disorders. If adults were to undergo this kind of intervention, the consequences would be disastrous: the patients would be unable to speak or understand language, would be paralyzed on the right side, and would lose sight in one eye. But a year after her operation this girl showed almost no more symptoms. The one-sided paralysis was as good as gone, and she could think clearly. She is now developing normally, fluent in two languages, running and jumping about, and doing well in school.
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