Posts tagged: schizophrenia


Business Logo for Psychological and Neuropsychological IssuesIt is an exciting time to be a neuroscientist.  The last fifty years have revealed more about the brain than the preceding two million years of human history.  The ability to map the electrical activity of brain cells has exponentially increased the understanding of their function.  The October issue of the Scientific American contained an interesting article by two neuroscientists, Terry Sejnowski and Tobi Delbruck.  The authors believe that neuroscientists are close to a breakthrough in understanding the biological underpinnings of thought.  This breakthrough is on the heels of experiments that are revealing how electrical and chemical signals in the brain convey information.

Most people know that the brain contains billions of specialized cells (nearly a trillion), called neurons, that are highly interconnected.  Once an electrical impulse travels down a wire (axon) to the main body of the neuron, it may or may not send a subsequent signal to an adjacent neuron.  Neuroscientists have already discovered how individual neurons function, but not how the neurons interact to yield useful information.  They lacked an understanding of why groups of neurons suddenly discharged electricity, as well as how this excitation ultimately led to thoughts.  By examining the firing of many neurons at the same time, a recent achievement, neuroscientists believe it is the timing of electrical spikes that encodes information and solves complex problems.  The variable rate of when the spikes occur may convey discrete components of information about the physical world.  For example, nerve cells in the retina of the eye appear to coordinate firing with a change in light intensity, which may also occur with a change in spatial orientation or color.  The human brain appears to yield processing time to several neurons switching on at the same time, since a random or accidental grouping of nerves firing is very unusual.

To be more specific, the observation of just one neuron in isolation reveals a pattern of random electrical activity.  Observing the electrical activity in tracts of nerves that connect the eye with middle and hind portions of the brain, researchers note that groups of neurons will fire when the spatial orientation of an object changes.  Neurons in the mid-brain will not fire with input from one, two or even three neurons located in the eye.  Four neurons discharging electricity from the eye to the mid-brain will cause it to relay information to the visual cortex at the back of the brain.  Similarly, exciting single neurons in the retina of the eye produces a random firing pattern.  Once the adjacent neurons in the eye are excited as well, the firing of this single neuron decreases as it becomes synchronized to the firing of the entire group.  As mentioned, it is believed that these synchronized firing patterns respond to a discrete visual components; eventually amassing the data to form an image in our consciousness.  Spaced only a few milliseconds apart, the rhythmic firing of widely dispersed cortical neurons is necessary to yield a visual perception.

It has been observed for some time that when mammals attend to some stimulus, the synchronized firing of multiple neurons increases, and the rate at which these neurons discharge electricity increases as well.  People who suffer with either schizophrenia or autism appear to have a decreased level of this neuronal firing pattern when attending to a stimulus.  The deficit has been traced to specialized cells in the cortex that control the timing of adjacent neural circuits.  Too much excitation or inhibition may cause this attention circuit to be less efficient or imprecise.  Disruption to the pattern of neuronal firing within the most frontal regions of the brain has been a hypothesized etiology of these disorders for decades.  To be sure, many other theories have been advanced as well.

In terms of encoding new memories, the synchronization of neuronal firing is also very important.  If one neuron in the brain causes another to consistently fire within just ten milliseconds, the first neuron in the chain will tend to discharge electricity with greater frequency.  Conversely, if the second neuron in the chain consistently fires less than ten milliseconds before the first neuron, the synchronization between the two declines.  The more groups of neurons become biologically accustomed to firing together, the greater their interconnections, the greater their rate of firing, and greater is the probability that this pattern of synchronous electrical discharges will be encoded into proteins for long-term storage.  As was said in graduate school, neurons that fire together…wire together.

Computers on the Brain

Business Logo for Psychological and Neuropsychological IssuesIt is not uncommon for psychologists to draw parallels between the modern computer and the ancient human brain.  Nearly all the people who read this article will do so with the use of a computer.  The computer allows the rapid categorization and transformation of symbolic information.  The information is symbolic since it does not contain the actual perceptual information of the event, but a representation of the information encoded into standardized symbols.  The symbols must be standardized, or the information could not be shared with others.  The symbols must also have the capacity of accurate storage, or the computer would only be useful on an intermittent and spontaneous basis.

The ancient brain processes sensory information in a symbolic fashion, as well.  It does not store holograms of what we see, smell, hear or touch, but encodes the information in proteins.  Recalling the information encoded in proteins allows categorization and association of the symbols removed from the actual event.  The human brain uses standardized sounds to communicate its symbols, otherwise the information could not be shared with others.  The storage of symbolic information must be fairly accurate, or the human could not learn to operate effectively within a given environment.

Both the brain and computer have an architecture specialized to encode and process information, yet there are differences.  There is no real equivalent of software in the human brain, as the physical architecture of the brain is altered to meet and master novel tasks.  Current computers cannot alter their architecture at this point in their development, but small alterations of software can radically change the type and method of information processed.  Neurotransmitters provide the closest parallel to computer software.  Their respective levels in different areas of the brain may favor and flavor the information processed.  The current understanding of neurotransmitter action does not allow for the sweeping changes possible with computer software.   The human brain exists in a dynamic flowing relationship with the environment, whereas the computer was designed to be an assistant in this relationship.

Currently, mental illness is most often viewed as a biological defect; similar to a diseased heart or lung.  Computer scientists might regard schizophrenia and bipolar disorder as faulty hardware, and depression, anxiety and angst as buggy software.  Similarly, psychosurgery has been used in the past to treat schizophrenia, and current psychiatrists modulate neurotransmitters to control depression.  The former deserves  little comment, and the latter has met with limited success.  Neuroscientists and psychiatrists have beaten the drum of biological mental illness for decades.  They have attempted changing the computer architecture in schizophrenia, and the computer software in depression.  The analogy tends to fail at this point, though, largely due to the negligence of a very important relationship.

The analogy breaks down due to the dynamic relationship between humans and the environment.  A person’s environment, especially their social milieu, may profoundly alter neurotransmitter levels.  Chronic stress is now known to cause actual alterations in the way genes are expressed.  Put another way, the environment alters the hardware and software of the human brain.  The brain evolves over a lifetime, whereas the computer is largely a static entity, such that the computer/brain analogy is always inexact.  To ignore the environment in the treatment of mental illness is similar to ignoring the road while driving a car.  Altering the brain’s software, without altering the environment, is to ignore a major difference between computers and people.  Social relationships may be an architect of human dysfunction, but also a foundation upon which we build our happiness.

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