Hardware, Software, and Wetware
Picking Your Brain (And Body)
In This Chapter
Slicing and dicing the brain
Getting up the nerve
Finding out how medications change behavior
Psychology can seem pretty abstract, seemingly having more in common with philosophy than biology. In this book, I introduce you to all kinds of psychological concepts — thoughts, feelings, beliefs, and personalities among them. But have you ever wondered where all of these things exist? If I need to find a thought or feeling, where do I look?
One place that seems logical to look for these psychological concepts is inside the human mind. But where is a person’s mind? The quick response for many people: It’s inside my skull, in my brain! So, I wonder, if you opened someone’s skull and could gaze upon the brain, would you see various kinds of thoughts, feelings, and other psychological stuff tucked away in there? Definitely not. You’d see a wrinkled and convoluted mass of grayish-pinkish-whitish tissue. There are no visible thoughts, feelings, or beliefs. Yet you know they exist because you experience them every day.
The question of where the mind, the home of psychological concepts, exists is an age-old philosophical question. Is the mind in the brain? Is the mind somewhere other than the brain? Are the brain and the mind the same thing? Most scientists today hold the position that the mind and the brain are one and the same. Scientists taking this position, known as monism, believe that the key to understanding the human mind, with all of its psychological concepts, lies in understanding the body, specifically the nervous system.
Psychologist Neil Carlson states, “What we call the ’mind’ is a consequence of the functioning of the human body and its interactions with the environment.” This is a powerful idea — the key to unlocking the mysteries of such psychological concepts as thinking and feeling lies in a thorough understanding of biology.
The idea that all of human psychology can be reduced to biology is known as biological reductionism. This idea seems to insult the esteemed sense of free will, self-awareness, and consciousness. I mean, how can all this complex stuff going on inside my mind be reduced to a hunk of flesh resting between my ears? If you feel this way, maybe you’re not a biological reductionist. But for the sake of this chapter, I’m going to be one. I focus on human biology as the pathway to understanding human psychology.
In this chapter, you’re introduced to the major components of biological psychology, including related body systems, the brain, and the chemical messengers of the brain. The role of genetics in understanding behavior and mental processes is covered as well. The chapter closes with a discussion of medications and newer forms of brain-based treatments for mental disorders.
Believing in Biology
People haven’t always believed that human behavior and mental processes are the consequences of biology. In the times of ancient Greeks and Romans, human behavior was seen as the consequence of supernatural forces, namely the whims and passions of the gods. But somewhere along the line, suspicion grew that maybe the human body had something to do with it. Where would such a radical idea come from?
The history of research in this area is long, but at the core of all the research is a very simple observation: Changes in a person’s biology result in changes in her behavior and mental processes.
Take alcohol consumption, for example. No question that people act differently when under the influence of alcohol. They may flirt, dance like an idiot, get emotional and sentimental, or even become angry and violent. Alcohol has a chemical effect on the brain; it alters the biology of the drinker’s brain. It goes something like this:
Alcohol consumption→chemical effect on brain→thinks he’s Don Juan
What about more serious changes in biology like brain damage? People who suffer from brain damage can exhibit drastic changes in their personality and thinking. They may go from being very organized to very messy. Or a once very laid-back, easygoing person may fly into a rage at the slightest frustration. They may have difficulty with memory or understanding.
I think you probably have an intuitive understanding that what goes on within your body has an effect on your behavior and mental processes. Biological psychologists are a group of psychologists who have extended this intuitive belief and these casual observations, using techniques and methods of modern science to investigate the idea that changes in biology lead to changes in psychology.
Although a lot of this seems logical, you may be thinking that there must be more to you than biology. And I say, that’s just the dualist in you acting up. Try not to struggle with it too much, at least while you read this chapter. Even if you think you’re more than just cells and molecules, you can still benefit from the research of biological psychology.
Did you read about the biopsychosocial model in Chapter 2? (If not, you may want to check it out. Trust me — it’s a good chapter.) That model proposes that human psychology is a function of the three important levels of understanding:
The biological level
The psychological level
The social level
This chapter focuses on the biological level, and the remainder of the book focuses on the other two. But you need to find out how the three levels interact — that is, how biology influences psychology, how psychology influences biology, and so on — to really get a handle on behavior and mental processes.
A useful metaphor for describing how the different levels interact is the modern computer. You may know that a computer has at least two functional components: hardware and software. The hardware consists of the actual physical components of the computer: the processor, hard drive, wires, CD-ROM, and various other components. The software includes the operating system, a word-processing program, and various other tools you use to actually work on a computer.
In this metaphor, the hardware of a computer represents the biological level of understanding. This is the physical body, specifically the nervous system. The software represents the psychological level, and the interface between the user and the software represents the social level. The hardware is useless without software, and vice versa. So, see, even if you’re not a monist, you can still respect the role that biology (hardware) plays in psychology (software).
The word “wetware” in the title of this chapter represents the actual physical substance of the brain. Most people don’t have “hard” ware in their brains (wires, plastic, silicon, and so on); instead, they have “wet” ware (neurons, tissue, and chemicals, for example). To stay consistent in my metaphor, I really focus on the wetware level of psychology in this chapter. Specifically, I introduce the wetware of the human nervous system as well as the endocrine system, genetics, and medications.
Recognizing the Body’s Control Room
The human nervous system consists of two large divisions: the peripheral nervous system (PNS) and the central nervous system (CNS). The CNS includes the brain and spinal cord. The PNS includes the nerves outside the CNS; they are in the rest (the periphery) of the body.
The basic building blocks of the nervous system are nerves, neurons, and neurotransmitters and glial cells. The nerves are, essentially, bundles of neurons, like a box of spaghetti is a bundle of individual strips of pasta. The neurons are individual nerve cells. Usually, they receive signals from other neurons, evaluate those signals, and then transmit new signals to other parts of the nervous system.
Electrical changes allow signals to be transmitted within a neuron: Because these electrical changes involve the movement of chemical ions, the transmission system is called an electrochemical system. Neurotransmitters are chemicals that play a critical role in transmitting signals between neurons. The glial cells are cells within the nervous system that play a variety of support roles for the neurons; they protect neurons from damage, repair them when they are damaged, and remove damaged or dead tissue when it can’t be repaired (“taking out the trash”).
The nervous system is a living part of the body and, therefore, has the same basic needs as any other body part; it needs fuel and immune protection. The components of the nervous system stay alive and healthy by the circulatory system and other regulatory body functions. The specifics of the support systems for each division of the nervous system are described in more detail within each division’s corresponding section in this chapter.
If you’ve studied any physics, chemistry, or biology, you may remember that the building blocks of life begin with atoms (operating under the laws of physics); atoms are grouped in particular ways to make up molecules that then form compounds. Compounds combine to create cells, and cells build tissue, and eventually an entire person is standing there! So if you really want to be a reductionist, you can just study physics and do away with all other branches of science. Or, you can look at human behavior and mental processes from a molecular level. This is the focus of the field of neurobiology.
Typically, however, biological psychology begins at the cellular level of study. Two types of cells appear in the nervous system, supporting cells and neurons. In this section, you discover the main divisions of the human nervous system, the brain, and how the brain is organized.
Tiptoeing into the periphery
Of the two divisions of the body’s nervous system, think of the peripheral nervous system (PNS) as a system of connections that make it possible for the brain and spinal cord to communicate with the rest of the body. Two sets of nerves are involved:
Spinal nerves: These nerves carry neural signals both to and from the spinal cord. Sensory nerves carry information from the body to the central nervous system: For example, they carry signals from sensors in your foot when somebody steps on your foot. Motor nerves carry signals from the central nervous system to the body; they cause the muscles in your limbs to move (raising your hand).
Cranial nerves: These nerves are involved in the muscular (motor) and sensory processes, except that they are connected directly to the brain itself, not to the spinal cord. Cranial nerves support functions occurring in your face and head, including seeing and hearing, blinking and speaking.
In addition to these two sets of nerves, the PNS contains a subsystem known as the autonomic nervous system (ANS). The autonomic nervous system helps regulate two specific types of muscles (smooth and cardiac) and the glands in our body. The ANS is involved in automatic, or involuntary, action. Bodily organs, reflexive muscle contractions, and even the dilation of our pupils are all automatic behaviors governed by the ANS. There are two very important divisions of the ANS:
Sympathetic nervous system (SNS): The sympathetic branch of the ANS is involved in energetic activation of the body when it needs high levels of energy. For example, when you are confronted with a life-threatening situation, your sympathetic nervous system kicks in and gives you the energy to either take on the challenge or flee the situation.
Parasympathetic nervous system: The parasympathetic branch of the ANS deactivates the SNS after it has been engaged. This action is sometimes called the relaxation response because the activity of the SNS is relaxed, or turned off, and then returns to normal functioning.
Moving to the center
The CNS consists of both the brain and the spinal cord. Although the spinal cord is critical, the focus of this section is on the brain, which is considered to be the underlying physical foundation for psychological functioning. It is, literally, the command center for behavior. The brain, with billions of cells and sophisticated networks, is among the most complex biological structures known to scientists.
Throughout the history of studying the brain, many attempts have been made to understand exactly what it is made of and how it works and is organized. So far, the simplest way to think of the brain (the “city”) is in terms of these different levels:
Structural: Basic anatomical divisions of the brain, identified by their major functions (the “neighborhoods”)
Network: The pathways that connect different parts of the brain and allow them to interact (the “roads”)
Neural: Cellular and microcellular functions (the “houses and furniture”)
Essentially, everything people do involves the brain. What happens, though, when some part of the brain gets damaged? The behavior and mental processes associated with the damaged portion of the brain are adversely affected, which affects related functions. Clinical neuropsychologists are particularly interested in the behavioral and mental consequences of brain injuries.
The brain can be damaged in numerous ways:
Closed-head injuries: These injuries occur when someone sustains a blow to the head but the skull is not penetrated. A common form of closed-head injury is a contrecoup injury — the injury occurs to the part of the brain opposite from where the individual was struck. For example, if you’re hit in the back of the head, this could cause the front of your brain to hit the inside of your forehead, and you may sustain damage to your frontal lobe, thus affecting your organizational and planning abilities. Even though the skull is not broken, serious damage can occur if the brain bleeds or swells resulting in pressure and additional damage beyond the site of injury.
Open-head injuries: These injuries occur when the skull is either penetrated or fractured; both closed-head and open-head injuries can lead to serious brain damage.
Other brain disorders: Degenerative diseases such as Alzheimer’s can produce brain damage in the form of atrophied (for example, a reduction in size or loss of cells) brain tissue and cellular death. Strokes (a blood clot or bleed in the brain) and other vascular accidents also can result in brain damage by denying parts of the brain blood and oxygen, causing cellular death.
Running Like a Well-Oiled Machine: Body Systems
Structurally, there are three main divisions of the brain: forebrain, midbrain, and hindbrain. Each of these divisions consists of many substructures that are involved in various behaviors and activity.
The brain is a complex, integrated system. All of its components work together to produce the complexity of human behavior. The concept of localization refers to the idea that there are specific parts of the brain for specific components of behaviors. Various parts work together to produce vision, hearing, speech, and so forth. Neurological techniques such as post-mortem brain examination, CT (co-axial tomography) scans, MRI (magnetic resonance imaging) scans, and PET (positron-emission tomography) scans have been used to identify and explore these systems.
The human forebrain is involved in a wide range of mental processes, including the sensing, perceiving, and processing of information. It is also involved in thinking, problem solving, organizing, and language functions.
The human forebrain consists of four sections:
Cerebral cortex: If you think of the brain as a mushroom, with a top and a stalk, then the cerebral cortex is the top of the mushroom. It’s divided into two halves, called cerebral hemispheres (the left and the right — pretty creative, I know). These halves are connected by a bundle of nerve fibers known as the corpus collosum. Without the corpus collosum, the halves wouldn’t be able to communicate with each other.
Figure 3-1 shows the four major divisions of the cerebral cortex and their corresponding functions:
• Frontal lobe: Planning, organizing, coordinating, and controlling movements (in an area known as the primary motor cortex), reasoning, and overall monitoring of the thinking process
• Parietal lobe: Sensation, spatial and somatosensory (bodily) awareness
• Temporal lobe: Hearing, language, and other verbal activity
• Occipital lobe: Vision
Figure 3-1: The lobes of the cerebral cortex.
Limbic system: Located on the underside of the mushroom top (the cerebral cortex), the limbic system is involved in learning, memory, emotional behavior, and mating or reproduction.
Basal ganglia: This part of the brain is involved in controlling movement.
Thalamus: This “neural switchboard” is a relay station for the different parts of the brain. However, it is more than simply a connection. It analyzes inputs to construct organized outputs.
Hypothalamus: The hypothalamus takes part in the control of the endocrine system and works with the limbic system to control behaviors such as aggression, eating, protection, and mating.
The midbrain is involved in the auditory and visual processes and in motor control.
The midbrain consists of the following divisions and their respective areas of responsibility:
Tectum: Auditory and visual systems
Tegmentum: Sleep, arousal, attention, muscle tone, and reflexes
The hindbrain is involved in the autonomic functions of the body such as heart rate and breathing as well as the coordination of movement.
The hindbrain includes two divisions with assigned duties:
Cerebellum: Motor movement and its coordination
Pons: The bridge connecting the cerebellum to the rest of the brain
Medulla: Vital functions of the body such as the cardiovascular system, breathing, and the movement of skeletal muscles
Finding Out About Cells and Chemicals
At the neural level of the brain is what many brain scientists consider to be the fundamental unit of the brain and the nervous system: the neuron, a specialized cell that provides the foundation for brain functioning: communication among nerve cells. Actually, there is another important type of cell in the brain: the glial cells. Glial cells provide the basic structure to the nervous system and nourish the neurons. But neurons are the star of the brain show according to most scientists.
A neuron is considered the information cell; it’s involved in the processing and storage of information. Neurons contain the following parts:
Soma: The cell body of the neuron containing the nucleus and supportive structures of the cell, including the mitochondria
Dendrite: Projections from the cell body that receive information from other neurons
Axon: The nerve fiber that conducts the electrical impulse
Terminal button: The end of the axon involved in neurotransmitter release and signaling to other neurons
The center of action in the brain happens at the cellular level, when a neuron is activated and fires. Neurons become activated by input from other neurons, which in turn impacts the other neurons in a given network. Simply put, when information from the environment (or inside the brain itself from other neurons) comes into the brain through the sensory organs and activates a particular neuron (or, more often, a set of neurons), an action potential is created.
Action potentials are the movement of electrochemical energy through a neuron toward its terminal button, toward other neurons. Something called the all-or-none law states that neurons are either “on” or “off”; they are either firing an action potential or not. After a neuron is activated, it fires. If it’s not activated: no action, no fire!
Some people consider the firing of a neuron (the action potential) to be an electrical process; others say it’s a chemical process. In essence, however, it’s both. The action potential consists of electrical energy that’s created and activated by the exchange of positive and negative chemical ions between the inside and the outside of the neuron. It’s electrochemical.
When a neuron is not firing, it is considered to be in the state of a resting potential and its electrical charge is more negative on the inside relative to the outside. There are more negatively charged ions inside than outside. But when a neuron receives a signal from another neuron, gates in the cell membrane (its covering) open and positive ions rush into the negatively charged inside of the cell. Chemistry and physics point out that positive charges move toward negative charges; they attract! So as the inside of the cell spikes to the positive, the action potential is created and the neuron “fires”! In many ways, the action potential is an electrical disturbance in the axon that travels along the axon, like the fire moves down a lit fuse of a firecracker.
When the action potential occurs, the cell cannot fire again for a short period of time. During this refractory period, small pumps in the cell membrane work to reset the neuron by moving positive ions back out of the cell, returning the chemical balance of the neuron to its original state to prepare for another round of action.
In this section, you discover more about how a neural signal travels from one neuron to another in a process called synaptic transmission.
Crossing the divide
As an action potential speeds through a neuron toward its terminal button, how does it propagate that signal to other neurons in the network? Before I can answer, you need to know that neurons don’t actually connect to each other in a physical sense. There are gaps between them known as synapse, spaces between axon terminals of one neuron (the neuron sending the signal) and the dendrites of the next neuron (the neuron receiving the signal); this is where inter-neuronal communication happens through chemical messengers called neurotransmitters. Figure 3-2 shows a neuron and a synapse. Although they are only millionths of an inch apart, the sending neuron throws its “message in a bottle” into the sea-napse, where it drifts to the other shore (the receiving dendrite). The message says, “Please hear me; please fire!” Dramatic stuff!
Figure 3-2: Neuron and synapse.
Neurotransmitters are stored in the axon of the sending cell. An action potential stimulates their release into the synapse. They travel (actually drift) to a receiving neuron in which specialized docks known as receptor sites are present. Different shaped neurotransmitters have different docks.
Basically, neurotransmitters have one of two effects; they either excite the receiving neuron (make it more likely to fire) or inhibit the receiving neuron (make it less likely to fire). Some neurotransmitters are excitatory and some are inhibitory. Whether a particular neuron fires (transmits a signal) depends on the balance between excitatory and inhibitory neurotransmitters.
Following the docking process, neurotransmitters are either broken down by enzymes or reabsorbed by the sending neurons in a process called reuptake. These two processes clear neurotransmitters from the synapse after they have done their job (enough, already!). This is critical to prepare the cells for the next neural communication. And neurotransmitter manipulation is a primary mechanism of action for most psychiatric medications (find information on the actions of medications in the Understanding Psychopharmacology section later in this chapter).
Scientists have discovered more than 100 neurotransmitters in the human brain. Many, including the following, play a major role:
Glutamate: The most common excitatory neurotransmitter
GABA: The most common inhibitory transmitter; involved in eating, aggression, and sleep
Acetylcholine: A common neurotransmitter with multiple excitatory and inhibitory functions; involved in movement and memory
Another group of four chemically similar neurotransmitters modify behavior in many ways. These neurotransmitters are particularly important regarding psychological disorders:
Serotonin: An inhibitory transmitter that is involved in balancing excitatory transmitters as well as mood, sleep, eating, and pain
Dopamine: Can be either inhibitory or excitatory and is implicated in attention, pleasure and reward, and movement
Epinephrine: An excitatory transmitter related to stress responses, heart rate, and blood pressure
Norepinephrine: An excitatory transmitter involved in energy regulation, anxiety, and fear
An estimated 86 billion neurons live in the human brain and form trillions of connections among themselves. So you can think of the brain as a massive collection of nodes in a well-connected network. Just exactly how information is kept and processed in the brain remains the focus of incredible amounts of neuroscience research, but here’s what scientists do know.
The brain is a “massively parallel” information-processing system (flip to Chapter 6 for more about information processing). If each neuron was connected to only one other neuron, the neuron system would be considered “massively serial.” Compared to electronic signals, neural signals travel very slowly (like 5—100 mph), so it is efficient to do many things at once — called parallel processing. Think of it like finding a person who is lost in a large national park. The search party probably doesn’t stay together and follow each other on the same path (serial processing); instead, they “branch out” (parallel processing) to cover more ground in the same amount of time. Likewise, the brain, with its billions of neurons and trillions of connections, uses the branching-out method to process, store, and find information among its cells and cell clusters.
Not every neuron is connected to every other neuron, but neurons are connected to multiple others that form clusters or networks involved in particular psychological processes and behaviors. For example, if seeing a red ball activates neurons #3, 4, 192, X, A, and 56, then the network for “seeing a red ball” would be called 3-4-192-X-A-56. Neuroscience researchers are working hard to map the brain and its networks in order to connect cell clusters to respective mental functions and behavior. The International Consortium for Brain Mapping (ICBM) is one such group of scientists that is dedicated to this endeavor.
Activating brain change
Have you ever scratched your nose and noticed that your foot stopped itching? Okay, well, that’s a slight stretch, but there is something called phantom limb syndrome in which people who have lost a limb (an arm or leg for example) continue to report feeling sensations from that limb such as pain, cold, touch, and so on. How can this be? The limb is gone so where are the sensations coming from?
In his book, Half a Brain is Enough: The Story of Nico, Dr. Antonio Battro tells the story of a boy named Nico who has a very significant portion of his brain surgically removed to control seizure activity (a drastic but sometimes necessary surgery for individuals with intractable seizures). However, after having that large portion of his brain removed, Nico remains relatively normal and maintains a fair amount of brain functioning — as if the brain tissue had not been removed. Why does Nico remain relatively unimpaired while working with half a brain?
Both phantom limb and Nico’s brain demonstrate what brain scientists refer to as neuroplasticity — the notion that the brain’s neural networks and connections continually reorganize. At one point in time, scientists believed that the brain’s organization was “fixed,” but this is simply not the case. The brain can change its size and connections throughout a person’s lifetime: this ability is called neuroplasticity.
The ability for the brain to update itself in response to new stimulation and input represents the neurobiological foundation of learning. In phantom limb syndrome it was found that the neural networks devoted to the lost limb (arm, leg, and so on) had been co-opted by neurons and networks proximal to it such as neurons associated with sensation in the in nearby body parts. So, when the face had a sensation, the neurons that were previously associated with the lost limb were being stimulated, and other parts of the brain interpreted the sensations as coming from the limb.
In Nico’s case, the functions performed by the lost brain cells from surgical removal were taken over by neighboring or other cells and networks. Other parts of the brain essentially learned how to do the functions once performed by the lost cells. In both cases, phantom limb and Nico, the brain essentially rewired itself in response to new inputs and learning experiences.
Neuroplasticity is good news for people who lose brain tissue through trauma or disease. But what about growing new brain cells? After all, new skin cells grow after a cut. Does this happen in the brain?
For many years scientists believed that it was not possible to grow new neurons or brain cells. However, research has shown that neurogenesis (regeneration of nerve cells) is possible in specific regions of the brain, particularly the lateral ventricles and the hippocampus. More research is being conducted to see if this process is happening in other parts of the brain as well. If neurogenesis is found to be more widespread or possible in other brain areas or if scientists can find a way to stimulate the process, manipulate it, or otherwise impact it, then there may be a great ray of sunshine for people who now suffer from diseases or trauma such as Alzheimer’s, stroke, traumatic brain injury, or spinal cord injury. However, the science and research is very preliminary in this area and much more work needs to be done before such a thing is possible.
Finding Destiny with DNA
I look a lot like my father’s father. But do I act like him, too? Does your personality come from your parents? Do people inherit intellect and good looks? The field of psychology known as behavioral genetics, the study of the role of genetics and heredity in determining mental processes and behavior, investigates these questions.
The brain influences behavior. The endocrine system influences behavior. But what about your genetic makeup? Scientists have answered this question with a resounding “yes”; genetics do matter! Research implicates genetic contributions to cognition and intelligence, personality, and even psychopathology.
Genetic contributions to psychology have been traditionally performed using twin and adoption studies, in which identical twins (who share a common genetic code) who’ve been adopted separately at birth and raised in different environments are compared for some psychological construct or disorder (such as the presence of ADHD). This testing setup allows for the control of the influence of different environments, so if the identical twins show similar findings on the construct in question, then it is deduced that it must be due primarily to their genetic similarities — DNA. Research continues to evolve, and other techniques, such as large-scale DNA sampling and gene manipulation, push the field of behavioral genetics.
Researchers are looking for genetic markers for particular behaviors, including disorders. A genetic marker is a gene with a known location on the human genome. Genetic markers for such disorders as autism, schizophrenia, and reading disabilities have been found. Just keep in mind that the presence of a genetic marker in a person’s genome does not guarantee that he will have a particular trait or disorder; it simply increases the odds of such.
Although the complexity of behavioral genetics leaves much to be discovered, one thing is clear: genes matter. But where do these inherited traits, behaviors, and mental processes come from? How do gene-behavior relationships come about? Evolution.
Evolutionary psychology is a branch of psychology that says human psychology (behavior and mental processes) is the result of the evolutionary process of natural selection. Natural selection is the process by which specific genes become more or less common in a population of a species through reproduction and mating. In other words, genes that contribute to survival are more likely to be passed on than those that don’t. After all, if your genes help you live long enough to pass them on to your offspring, then those genes perpetuate. If they don’t, and you don’t perpetuate, then your genes don’t survive either.
Evolutionary biologists look at biological phenomena (such as opposable thumbs and walking upright) as adaptations that thrived. Evolutionary psychologists take the same approach with psychological phenomena such as language, memory, attention, visual perception, happiness, and so forth. Finding out how these psychological phenomena helped our ancestors adapt as a way to explain why they exist in us today is a matter of extreme interest. An evolutionary psychologist, for example, may look at attachment theory (see Chapter 10) and propose that the behaviors and mental processes underlying the mother-infant bonding process evolved over time to the state they can be observed today because these behaviors and processes enable the human species to survive.
The use of medications in the treatment of mental disorders (such as schizophrenia and major depressive disorder) gained significant prominence over the last half of the 20th century. (For more about mental disorders see Chapter 13.) Prior to that, medications were used to a lesser extent, along with psychotherapy, psychosocial, and behavioral treatments. But advances in research and drug development led to the creation of more effective drugs, which in turn spurred an increase in their use. Hundreds of drugs have been developed that are used to target the specific symptoms of a particular mental disorder. The primary goals of pharmacotherapy are to produce improvements in behavior and thinking, alleviation of suffering, and enhancement of functioning.
Many brain systems involved in the symptoms of mental illness involve one particular neurotransmitter, and drugs used for the treatment of a particular illness are designed to affect the functioning of that specific neurotransmitter. The sleep difficulties and appetite disturbance often seen in major depressive disorder, for example, are thought to be related to the limbic system. For these symptoms, most drugs for depression target the neurotransmitter serotonin.
In this section, I describe common symptoms of and treatment for depression, schizophrenia, and anxiety, three of the better known mental disorders, pointing out various medications and their biological mechanism of action.
Medications that are used to treat depression are called antidepressants. Most antidepressants affect one or both of two neurotransmitters: norepinephrine and serotonin. Basically, there are two major classes of antidepressant medications (although there are some that don’t fit in either class, such as Wellbutrin, Remeron, or Effexor) differentiated by their mechanism of action:
Tricyclic antidepressants: Block the presynaptic neuron’s re-absorption of mostly norepinephrine (NE). This allows for a functional “increase” in the level of NE in the synapse and prolongs the activation of the postsynaptic neuron when stimulated by NE.
Selective serotonin reuptake inhibitors (SSRIs): Block the re-absorption of serotonin rather than NE and have the similar effect of prolonging activation. Some of the more popular brands of SSRIs are Prozac, Paxil, and Zoloft.
Shushing the voices
The experience of auditory hallucinations or feeling like someone is out to get you can be extremely troubling. These are common symptoms of the mental disorder schizophrenia. One of the most powerful treatments for some of the symptoms of schizophrenia is the use of antipsychotic medications.
Antipsychotic medications have a specific effect on the neurotransmitter dopamine. The dopamine dysregulation hypothesis of schizophrenia holds that the symptoms of psychosis result from disruptions in the action of dopamine in the brain. Antipsychotic medications block the postsynaptic receptor sites of dopamine. This blockage keeps dopamine from being able to activate the postsynaptic neuron and has been found to reduce the presence of psychotic symptoms substantially.
Unfortunately, antipsychotic medications, as do all medications, don’t just affect the neurotransmitters in the brain areas theorized to be implicated in the disorder. Most medications also affect other brain areas and can often lead to very unpleasant side effects. Side effects associated with antipsychotic medication can include weight gain; repetitive, involuntary motor movements (known as tardive dyskinesia); or sexual dysfunction, to name just a few. The experience of these side effects often leads people to stop taking their medication, which can have serious negative consequences. This situation keeps drug researchers searching for even more selective drugs.
Anxiety disorders are the most common mental disorder in the United States. Millions of people suffer from intolerable worry, panic attacks, and disabling phobias. The good news is that medications can help with these symptoms.
Anxiolytic medications are drugs designed to relieve the symptoms of anxiety disorders. Psychiatrists and family physicians prescribe one class of Anxiolytics, benzodiazepines, quite often. Benzodiazepines affect the neurotransmitter GABA, which has a suppressing effect on the central nervous system. In other words, it slows things down in the brain.
Benzodiazepines are very effective in reducing anxiety. Unfortunately, they are also highly addictive. Benzodiazepines have a near-immediate effect and often produce sedation and an overall feeling of calmness. These feelings are highly pleasurable, and patients sometimes don’t want to stop taking these medications even after their anxiety disorder has been successfully medicated. Table 3-1 gives an overview of some frequently prescribed medications.
Table 3-1 Major Medication Groups
Generalized anxiety disorder
Undergoing No-Knife Brain Surgery
Changes in biological functioning can and do result in psychological changes. Medications have a direct biological effect on the brain. Neurosurgeons lesion, excise, and cut brain tissue. But imagine a day when doctors can change your brain directly without a pill or surgery.
Dr. “Bones” McCoy of Star Trek used to use a device that he placed on the head of patients with neurological conditions. Using some form of energy field, the device alleviated all sorts of conditions, including brain injury and bleeding. Well, Dr. McCoy, that day has arrived!
Transcranial Magnetic Stimulation (or TMS) is a technology right out of Star Trek. TMS devices are placed on the head and use electromagnetic pulses to activate specific parts of the brain. This technique is being used to treat migraines, stroke symptoms, hallucinations, and even depression.
For depression, TMS stimulates the brain’s frontal lobe and limbic system, parts impacted by the disorder. The medical world is excited and hopeful about the prospects of TMS as a treatment for a broad range of other disorders.