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How well are neurotransmitters used in SPA?

How well are neurotransmitters used in SPA?



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How much does the SPAUN and the Semantic Pointer Architecture (SPA) that was used to build it take neurotransmitters into account? In the book How to Build a Brain, various inhibitory and excitatory connections are mentioned as supplying a biological foundation for implementing the Basal Ganglia. Additionally, it's mentioned that the learning rule that the SPA uses, hPES, uses dopamine to modulate learning. However, I'm still a bit confused on the details of all this. How do neurotransmitters fit into Nengo? How much detail does Nengo go into in regards to neurotransmitters? Does it take into account the neurotransmitter distribution and consumption as observed in the brain?

Note: For more information on the relation between Nengo, SPA and SPAUN, please see my previous question.


At this point in time, the difference in neurotransmitter types affect the synaptic time constant (i.e. the filter on the incoming spike train) between neurons in Nengo. See Neural Engineering p.112 and these notes (see the section called "Biologically plausible filter") from a course covering the book.

Neurotransmitters are also leveraged more theoretically. For example, in connection between neurons that involve learning, dopamine is often said to modulate this learning. For example, see Dan Rasmussen's neural hierarchical reinfrocement learning implementation (PHD link pending).

Hypothetically, it would be possible to implement a back-end to Nengo using a more biologically detailed software such as Neuron to take into account neurotransmitter generation, concentration and consumption. Although I can attest anecdotally that this has been attempted with mixed success, there has been no formal release or publication of this approach.


Jobs and Income

As a physiological psychologist, you can work in clinical practice or in research, or teach in your field. Workplaces includes clinics, hospitals, research laboratories and colleges.

At time of writing, the average annual pay for a physiological psychologist is $56,513. Salaries range from $19,500 to $118,500 but most salaries run between $34,500 and $71,500. Years of experience and the location you're working with may be bigger factors in determining your pay than your skill level.


Types of Neurotransmitters

Neurotransmitters that fall into the category of amino acids

✦ Glutamate
✦ Aspartate
✦ Glycine
✦ D-serine
✦ Gamma-aminobutyric acid (GABA)

Monoamines or other biogenic amines considered as neurotransmitters

✦ Serotonin
✦ Norepinephrine
✦ Epinephrine
✦ Histamine
✦ Melatonin

Neurotransmitters that fall into the category of peptides

✦ Beta-endorphin
✦ Opioid peptides
✦ Somatostatin
✦ Calcitonin
✦ Vasopressin
✦ Oxytocin
✦ Glucagon

» Apart from these, there are several other important neurotransmitters, such as acetylcholine, dopamine, adenosine, and nitric oxide. So far, about 50 neuroactive peptides have been discovered.

» Sometimes, neurotransmitters are also classified as excitatory and inhibitory. This classification is based on their actions on the neurons. Excitatory neurotransmitters are those that excite the neurons and stimulate the brain, while inhibitory neurotransmitters are known for having a calming effect on the brain.

» Neurotransmitters like, GABA and serotonin come under the category of inhibitory neurotransmitters, while epinephrine and norepinephrine are the excitatory neurotransmitters. Dopamine on the other hand, can act as an excitatory, as well as an inhibitory neurotransmitter.

» However, the effect of a neurotransmitter on a postsynaptic cell depends on the receptors present in it. For some neurotransmitters, like glutamate, the important receptors have excitatory properties. On the other hand, most of the important receptors produce an inhibitory effect for GABA. But there are some neurotransmitters, for which both types of receptors exist.


What Is The Most Famous Case Study Psychology Has Seen?

Case studies are used to help psychologists and other researchers understand the human mind. There have been many famous case studies in psychology over the years. Some case studieshave shownhow psychological phenomena like memory and personality work. Other studieshave been disproven over time. In considering case studies, which are narratives or stories, it is important to keep in mind what we can and cannot conclude from the information presented. Here are some examples of the most famous case studies psychology has seen.

Phineas Gage

The case of Phineas Gage is one of the most cited cases in psychology. This famous case study showed how different areas of the brain affect personality and cognitive ability. While working as a construction foreman on a railroad, Phineas Gagewas involved in an accident in which a rod was pushed through his cheek and brain. He survived, but as a result of the accident,both his personality and his ability to learn new things were greatly affected.

This is an example of a case study that cannot lead to definitive conclusions. Although the case is frequently cited and referenced, in truth, relatively little information is known about Gage's life before and after the accident. In fact, researchers have discovered that the last two decades of his life were spent in his original job, which is unlikely to have been possible if the extent of his injuries were as severe as originally believed. Still, hiscase study was a starting point for research of how memory and personality work in the brain,and it isa seminal study for that reason.

The Feral Child

Feral children are children who are raised without human interaction, usually as the result of abuse or neglect. One famous case study of a feral child was the child known as Genie. She was raised in a single bedroom with little human interaction. She never gained the cognitive ability of a normal adult, even though she was found at age 13. In fact, later in life, she regressed and stopped speaking altogether. Her case has been studied extensivelyby psychologists who want to understand how enculturation affects cognitive development.

Henry Molaison

This is a case study that has helped psychologists understand memory. It is perhaps the most famous case study in neuroscience. Henry Molaison was in a childhood accident that left him with debilitating seizures. Doctors were able to stop the seizures by removing slivers of his brain&rsquoshippocampus, though at the time they did not fully understanding what they were doing. As a result, scientists learned how important the hippocampus is to forminglong-term memories. After the surgery, Molaison was no longer able to form long-term memories, and his short-term memory was very brief. The case study started further research into memory and the brain.

The case study of Jill Price is in some ways the opposite of that of Henry Molaison. Ms. Price is one of a few documented cases of hyperthymesia, or an overactive memory that allowed her to remember such mundane things as what she had for dinner on an average day in August 20 years previously. Hercase study was used as a jumping-off point to research how the memory works and why some people have exceptional memories. However, through more research, it was discovered that her overall memory was not exceptional rather, sheonly remembereddetails of her own life. She was diagnosed with obsessive-compulsive disorder, withmemories beingpart of her obsession. Thiscase study is still relevant because it hashelpedmodern psychologists understandhow mental illness affects memory.

The John/Joan Case

In the John/Joan case study, a reputable sexologist tested his theory that nurture, not nature, determined gender. The case study has been cited extensively and laid the groundwork for other research into gender identity. Unfortunately, the case study was not legitimate. In this study, Dr. John Money performed surgery on an infant whose penis was damaged during circumcision. The boy was raised as a girl however, henever identified as female and eventually went through more surgery to become male again. Because Dr. Money didn't follow up with the patient appropriatelyand did not reportadverse findings, the case study is still often cited as being successful.

Anna O. was the pseudonym given to a German woman who was one of the first people to undergo psychoanalysis. Her case inspired manyof the theories of Freud and other prominent psychologists of the time. It was determined at the time that Anna's symptoms of depression and illness were eliminated through talk therapy. More recently, it has been suggested that Anna O. had another illness, such as epilepsy, from which she may have recoveredduringthe period of time that the therapy lasted. This case study is still cited as a reason psychologists believe that psychotherapy, or talk therapy, can be helpful to many patients.

Chris Sizemore

One of the most famous case studies in psychology is that of Chris Sizemore. She was one of the first people to be diagnosed with multiple personality disorder, now called dissociative identity disorder. In her case, the &ldquoalter&rdquopersonalities were all merged into one personality over which she had control. She did, however,remember specific eventsin her life as happening to specific personalities. Her case, diagnosis, and treatment informed treatingthis mental disorderin a variety of cases over the years, and it was even turned into a movie, Eve.

Ethical Use Of Case Studies

As shown above, while case studies can provide valuable information and mayinspire further research and study, they are not definitive proof of a theory. It is important to remember that case studies must be used ethically and legitimately. Case studies can be used to supporttheories, but the research must be sound.

When case studies are flawed &mdashfor example, through not having enough information or havingthe wrong information &mdash they can be harmful. Valuable research hours and other resources can be wasted while theories are used for inappropriate treatment. Case studies can thereforecause as much harm as good, and psychologists must be careful about how and when they are used.

Laypeople must be careful as well. Psychologists and doctors often disagree on how case studies should be applied. Most laypeople can&rsquottell whether a case study is built on a faulty premise or misinformation, and it is also possibletogeneralize case studies to situations for which they do not apply. If you think a case study might applyto your case or that of a loved one, the best thing to do is ask a mental health professional.

Other Ethical Concerns

Case studies are descriptions of real people Thoseindividualsarestudied intensively and areoften written about in medical journals and textbooks. While some patients are happy to be studied for science, others are not as happy with their role as test subject. Also, some subjects are not treated with dignity and respect. Sometimes psychologists become ruthless in their pursuit of knowledge, and the humanity of the interaction between researcher and subjectis lost.

It can be helpful when looking at case study psychology to think of the cases as stories of real individuals. When you strip away the science and look at the case as a whole person in a unique situation, you will often get more out of the study than if you look at it as research that proves a theory.

How Case Studies Are Used In Therapy

Case studies are sometimes used in psychotherapy to determine the best course of treatment. If a case study in psychology aligns with your situation, yourtherapist may use the treatment methods outlined in the study. Case studies are also used by psychiatrists and other mental health professionals to understand mental illness and its treatment.

If you need therapy for a challenging life situation or mental disorder, help is available. BetterHelp therapists can help you find the correct treatment. Whatever problem you may face, a therapist can use case studies and other resources to treat you appropriately. Contact BetterHelp today to get started.

How Case Studies Can Inform Therapy

Researchers have reviewed the role of case studies in counseling and psychotherapy. In one study, the authors discussed howreading case studies benefits therapists, providing a conceptual guide for clinical work, i.e., an understanding of the theory behind the practice. They also stressed the importance of teaching psychotherapy trainees to do better case study research, and theyencouraged practitioners to publish more case studies documenting the methods they use in their practice.

The Benefits of Online Therapy

As discussed above, case studies can inform the work of good therapists. But when you&rsquore experiencing mental illness, it can sometimes be hard to leave home for therapy. This is where online therapy comes in. You can access BetterHelp&rsquos platform from the comfort and privacy of your own home. There&rsquos no need to sit in traffic or take time out of your busy workday to drive to your appointment you can speak with your licensed therapist from wherever you have an internet connection. BetterHelp&rsquos licensed therapists have helped people based on case studies. Read below for some reviews of BetterHelp therapists.

Counselor Reviews

&ldquoAmanda provides an excellent balance of warmth, accountability, and security. She keeps you on topic while actively listening and providing guidance as needed. Her credentials and expertise are well applied to our sessions and I am so grateful for her.&rdquo

&ldquoShe's been amazing, helped me process my feelings and work on the things I needed to heal in order to grow stronger and be content with my life. She was available everyday, I managed to connect with her deeply, she was supportive. I never expected to meet someone who'd have such a big positive effect on my life. I want to continue my journey with her and I trust the lessons I've learnt from her will continue to be useful for my present and future.&rdquo


Vagus-Related Treatment of Depression

Basic Pathophysiology of Depression

Major depressive disorder ranks among the leading mental health causes of the global burden of disease (104). With a lifetime prevalence of 1.0% (Czech Republic) to 16.9% (US) (105), the cost of depression poses a significant economic burden to our society (106). The pathophysiology of depression is complex and includes social environmental stress factors genetic and biological processes, such as the overdrive of the HPA axis, inflammation (31), and disturbances in monamine neurotransmission as described above (91). For example, a lack of the amino acid tryptophan, which is a precursor to serotonin, can induce depressive symptoms, such as depressed mood, sadness, and hopelessness (86).

The overdrive of the HPA axis is most consistently seen in subjects with more severe (i.e., melancholic or psychotic) depression, when the cortisol feedback inhibitory mechanisms are impaired, contributing to cytokine oversecretion (107). It has been shown that chronic exposure to elevated inflammatory cytokines can lead to depression (108). This might be explained by the fact that cytokine overexpression leads to a reduction of serotonin levels (109). In line with that, treatment with anti-inflammatory agents has the potential to reduce depressive symptoms (110). In line, IBD are important risk factor for mood and anxiety disorders (111), and these psychiatric conditions increase the risk of exacerbation of IBD (112).

VNS in Depression

A European multicenter study demonstrated a positive effect of VNS on depressive symptoms, in patients with treatment-resistant depression (113). The application of VNS over a period of 3 months resulted in a response rate of 37% and a remission rate of 17%. After 1 year of treatment, the response rate reached 53% and the remission rate reached 33%. A meta analysis that compared the application of VNS to the usual treatment in depressed patients showed a response rate of approximately 50% in the acute phase of the disease and a long-term remission rate of 20% after 2 years of treatment (114). Several other studies also demonstrated an increasing long-term benefit of VNS in recurrent treatment-resistant depression (84, 85, 115). Further, a 5-year prospective observational study which compared the effects of treatment as usual and VNS as adjunctive treatment with treatment as usual only in treatment-resistant depression, showed a better clinical outcome and a higher remission rate in the VNS group (116). This was even the case in patients with comorbid depression and anxiety who are frequent non-responders in trials on antidepressant drugs. It is important to note that all these studies were open-label and did not use a randomized, placebo-controlled study design.

Patients with depression have elevated plasma and cerebrospinal fluid concentrations of proinflammatory cytokines. The benefit of VNS in depression might be due to the inhibitory action on the production of proinflammatory cytokines (117) and marked peripheral increases in anti-inflammatory circulating cytokines (118). Further, improvement after VNS was associated with altered secretion of CRH, thus preventing the overdrive the HPA axis (119). Altered CRH production and secretion might result from a direct stimulatory effect, transmitted from the vagus nerve through the NTS to the paraventricular nucleus of the hypothalamus. Finally, VNS has been shown to inhibit peripheral blood production of TNF-α which is increased in clinical depression (10).

Influence of Nutrition Depressive Symptoms

The gut microbiota is the potential key modulator of the immune (120) and the nervous systems (121). Targeting it could lead to a greater improvement in the emotional symptoms of patients suffering from depression or anxiety. There is growing evidence that nutritional components, such as probiotics (122, 123), gluten (124), as well as drugs, such as anti-oxidative agents (125) and antibiotics (126), have a high impact on vagus nerve activity through the interaction with the gut microbiota and that this effect varies greatly between individuals. Indeed, animal studies have provided evidence that microbiota communication with the brain involves the vagus nerve and this interaction can lead to mediating effects on the brain and subsequently, behavior (127). For example, Lactobacillus-species have received tremendous attention due to their use as probiotics and their health-promoting properties (128). Bravo et al. (129) demonstrated that chronic treatment of mice with Lactobacillus rhamnosus (strain JB-1) caused a reduction in stress-induced corticosterone levels and in anxiety-like and depression-like behavior (129). It has been shown that chronic treatment with L. rhamnosus (JB-1) induced region-dependent alterations in GABA(B1b) mRNA in the brain with increases in cortical regions (cingulate and prelimbic) and concomitant reductions in expression in the hippocampus, amygdala, and LC. In addition, L. rhamnosus (JB-1) reduced GABA(A㬒) mRNA expression in the prefrontal cortex and amygdala, but increased GABA(A㬒) in the hippocampus (129), which counteracts the typical pathogenesis of depressive symptoms: lack of prefrontal control and overactivity of subcortical, anxiogenic brain regions. Importantly, L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behavior. This is not surprising, since alterations in central GABA receptor expression are implicated in the pathogenesis of anxiety and depression (130, 131). The antidepressive and anxiolytic effects of L. rhamnosus were not observed in vagotomized mice, identifying the vagus as a major modulatory constitutive communication pathway between the bacteria exposed to the gut and the brain (129). In line with that, in a model of chronic colitis associated to anxiety-like behavior, the anxiolytic effect obtained with a treatment with Bifidobacterium longum, was absent in mice that were vagotomized before the induction of colitis (132).

In humans, psychobiotics, a class of probiotics with anti-inflammatory effects might be useful to treat patients with psychiatric disorders due to their antidepressive and anxiolytic effects (133). Differences in the composition of the gut microbiota in patients with depression compared with healthy individuals have been demonstrated (134). Importantly, the fecal samples pooled from five patients with depression transferred into germ-free mice, resulted in depressive-like behavior.

Influence of Relaxation Techniques on Depressive Symptoms

It has been shown that self-generated positive emotions via loving-kindness meditation lead to an increase in positive emotions relative to the control group, an effect moderated by baseline vagal tone (135). In turn, increased positive emotions produced increases in vagal tone, which is probably mediated by increased perceptions of social connections. Individuals suffering from depression, anxiety, and chronic pain have benefited from regular mindfulness meditation training, demonstrating a remarkable improvement in symptom severity (9).

Controlled studies have found yoga-based interventions to be effective in treating depression ranging from mild depressive symptoms to major depressive disorder (MDD) (136). Some yoga practices can directly stimulate the vagus nerve, by increasing the vagal tone leading to an improvement of autonomic regulation, cognitive functions, and mood (137) and stress coping (138). The proposed neurophysiological mechanisms for the success of yoga-based therapies in alleviating depressive symptoms suggest that yoga breathing induces increased vagal tone (139). Many studies demonstrate the effects of yogic breathing on brain function and physiologic parameters. Thus, Sudarshan Kriya Yoga (SKY), a breathing-based meditative technique, stimulates the vagus nerve and exerts numerous autonomic effects, including changes in heart rate, improved cognition, and improved bowel function (140). During SKY, a sequence of breathing techniques of different frequencies, intensities, lengths, and with end-inspiratory and end-expiratory holds creates varied stimuli from multiple visceral afferents, sensory receptors, and baroreceptors. These probably influence diverse vagal fibers, which in turn induce physiologic changes in organs, and influence the limbic system (140). A recent study showed that even patients who did not respond to antidepressants showed a significant reduction of depressive and anxiety symptoms compared to the control group after receiving an adjunctive intervention with SKY for 8 weeks (141).

Iyengar yoga has been shown to decreased depressive symptoms in subjects with depression (142). Iyengar yoga is associated with increased HRV, supporting the hypothesis that yoga breathing and postures work in part by increasing parasympathetic tone (143).


Psychopharmacology

Psychopharmacology is the study of how drugs affect behavior. If a drug changes your perception, or the way you feel or think, the drug exerts effects on your brain and nervous system. We call drugs that change the way you think or feel psychoactive or psychotropic drugs, and almost everyone has used a psychoactive drug at some point (yes, caffeine counts). Understanding some of the basics about psychopharmacology can help us better understand a wide range of things that interest psychologists and others. For example, the pharmacological treatment of certain neurodegenerative diseases such as Parkinson’s disease tells us something about the disease itself. The pharmacological treatments used to treat psychiatric conditions such as schizophrenia or depression have undergone amazing development since the 1950s, and the drugs used to treat these disorders tell us something about what is happening in the brain of individuals with these conditions. Finally, understanding something about the actions of drugs of abuse and their routes of administration can help us understand why some psychoactive drugs are so addictive. In this module, we will provide an overview of some of these topics as well as discuss some current controversial areas in the field of psychopharmacology.


The functions of acetylcholine

Most people don’t know anything about acetylcholine except that it helps with memory and concentration. Therefore, it’s one of the most common components of nootropics, those supplements that are used to improve cognitive functions. Even beyond that area, we know that it’s essential since it has a lot of functions.

However, you need to keep in mind that it has multiple fields of action in the body. It’s found both in the central and peripheral nervous systems and also has both excitatory and inhibitory functions.

Therefore, it can facilitate the electrical impulses in a neuron. It can also inhibit the heart rate at any given moment. It’s like the conductor of an orchestra who directs and makes sure that everything’s in harmony, rhythm, and balance.


The Interactionist Approach to Schizophrenia

Interactionist approaches attempt to explain schizophrenia as a combination of nature (biological) and nurture (environmental) factors.

Diathesis-stress model: Meehl (1962) originally proposed that both a vulnerability to schizophrenia and a stress-trigger are necessary in order to develop the condition. Meehl suggested that the vulnerability is genetic (the result of a ‘schizogene’), causing a sensitive personality. Chronic environmental stress, for example having a schizophrenogenic mother, results in the onset of schizophrenia. Those who do not have the ‘schizogene’ would not develop schizophrenia, even if they experienced a chronically stressful upbringing. Both aspect of diathesis-stress must be present to develop the disorder.

The modern understanding of diathesis-stress is slightly different. It is now recognised that the vulnerability could be genetic or __environmental (for example, a traumatic event in early childhood). The stress-trigger could be environmental __or biological (for example, smoking cannabis is linked with schizophrenia).

Treatment: In an interactionist approach, treatments will take more than one form. Antipsychotic medication will often be used alongside CBT, acknowledging the role that biological and psychological factors play in the disorder. Combining treatments is most common in the UK, although it is also sometimes used in the USA. Psychological therapies are very rarely used alone, but sometimes patients may just take drugs without any other therapy.


4.5 Substance Use & Abuse

While we all experience altered states of consciousness in the form of sleep on a regular basis, some people use drugs and other substances that result in altered states of consciousness as well. This section will present information relating to the use of various psychoactive drugs and problems associated with such use. This will be followed by brief descriptions of the effects of some of the more well-known drugs commonly used today. You can find information on WSU’s specific Drug and Alcohol policy at: https://policies.wsu.edu/prf/index/manuals/executive-policy-manual-contents/ep20-alcohol-drug-policy/

SUBSTANCE USE DISORDERS

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders , Fifth Edition (DSM-5) is used by clinicians to diagnose individuals suffering from various psychological disorders. Drug use disorders are addictive disorders, and the criteria for specific substance (drug) use disorders are described in DSM-5. A person who has a substance use disorder often uses more of the substance than they originally intended to and continues to use that substance despite experiencing significant adverse consequences. In individuals diagnosed with a substance use disorder, there is a compulsive pattern of drug use that is often associated with both physical and psychological dependence.

Physical dependence involves changes in normal bodily functions—the user will experience withdrawal from the drug upon cessation of use. In contrast, a person who has psychological dependence has an emotional, rather than physical, need for the drug and may use the drug to relieve psychological distress. Tolerance is linked to physiological dependence, and it occurs when a person requires more and more drug to achieve effects previously experienced at lower doses. Tolerance can cause the user to increase the amount of drug used to a dangerous level—even to the point of overdose and death.

Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued. These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative drugs often produces unpleasant arousal and agitation. In addition to withdrawal, many individuals who are diagnosed with substance use disorders will also develop tolerance to these substances. Psychological dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited utility in determining whether or not someone has a substance use disorder.

DRUG CATEGORIES

The effects of all psychoactive drugs occur through their interactions with our endogenous neurotransmitter systems. Many of these drugs, and their relationships, are shown in the figure below. As you have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.

This figure illustrates various drug categories and overlap among them. (credit: modification of work by Derrick Snider)

Alcohol and Other Depressants

Ethanol, which we commonly refer to as alcohol, is in a class of psychoactive drugs known as depressants (figure below). A depressant is a drug that tends to suppress central nervous system activity. Other depressants include barbiturates and benzodiazepines. These drugs share in common their ability to serve as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system. Because GABA has a quieting effect on the brain, GABA agonists have a quieting effect these types of drugs are often prescribed to treat both anxiety and insomnia.

The GABA-gated chloride (Cl-) channel is embedded in the cell membrane of certain neurons. The channel has multiple receptor sites where alcohol, barbiturates, and benzodiazepines bind to exert their effects. The binding of these molecules opens the chloride channel, allowing negatively-charged chloride ions (Cl-) into the neuron’s cell body. Changing its charge in a negative direction pushes the neuron away from firing thus, activating a GABA neuron has a quieting effect on the brain.

Acute alcohol administration results in a variety of changes to consciousness. At rather low doses, alcohol use is associated with feelings of euphoria. As the dose increases, people report feeling sedated. Generally, alcohol is associated with decreases in reaction time and visual acuity, lowered levels of alertness, and reduction in behavioral control. With excessive alcohol use, a person might experience a complete loss of consciousness and/or difficulty remembering events that occurred during a period of intoxication (McKim & Hancock, 2013). In addition, if a pregnant woman consumes alcohol, her infant may be born with a cluster of birth defects and symptoms collectively called fetal alcohol spectrum disorder (FASD) or fetal alcohol syndrome (FAS).

With repeated use of many central nervous system depressants, such as alcohol, a person becomes physically dependent upon the substance and will exhibit signs of both tolerance and withdrawal. Psychological dependence on these drugs is also possible. Therefore, the abuse potential of central nervous system depressants is relatively high.

Drug withdrawal is usually an aversive experience, and it can be a life-threatening process in individuals who have a long history of very high doses of alcohol and/or barbiturates. This is of such concern that people who are trying to overcome addiction to these substances should only do so under medical supervision.

Stimulants

Stimulants are drugs that tend to increase overall levels of neural activity. Many of these drugs act as agonists of the dopamine neurotransmitter system. Dopamine activity is often associated with reward and craving therefore, drugs that affect dopamine neurotransmission often have abuse liability. Drugs in this category include cocaine, amphetamines (including methamphetamine), cathinones (i.e., bath salts), MDMA (ecstasy), nicotine, and caffeine.

Cocaine can be taken in multiple ways. While many users snort cocaine, intravenous injection and ingestion are also common. The freebase version of cocaine, known as crack, is a potent, smokable version of the drug. Like many other stimulants, cocaine agonizes the dopamine neurotransmitter system by blocking the reuptake of dopamine in the neuronal synapse.

Crack Cocaine

Crack (figure below) is often considered to be more addictive than cocaine itself because it is smokable and reaches the brain very quickly. Crack is often less expensive than other forms of cocaine therefore, it tends to be a more accessible drug for individuals from impoverished segments of society. During the 1980s, many drug laws were rewritten to punish crack users more severely than cocaine users. This led to discriminatory sentencing with low-income, inner-city minority populations receiving the harshest punishments. The wisdom of these laws has recently been called into question, especially given research that suggests crack may not be more addictive than other forms of cocaine, as previously thought (Haasen & Krausz, 2001 Reinerman, 2007).

Crack rocks like these are smoked to achieve a high. Compared with other routes of administration, smoking a drug allows it to enter the brain more rapidly, which can often enhance the user’s experience. (credit: modification of work by U.S. Department of Justice)

Amphetamines have a mechanism of action quite similar to cocaine in that they block the reuptake of dopamine in addition to stimulating its release (figure below). While amphetamines are often abused, they are also commonly prescribed to children diagnosed with attention deficit hyperactivity disorder (ADHD). It may seem counterintuitive that stimulant medications are prescribed to treat a disorder that involves hyperactivity, but the therapeutic effect comes from increases in neurotransmitter activity within certain areas of the brain associated with impulse control.

As one of their mechanisms of action, cocaine and amphetamines block the reuptake of dopamine from the synapse into the presynaptic cell.

In recent years, methamphetamine (meth) use has become increasingly widespread. Methamphetamine is a type of amphetamine that can be made from ingredients that are readily available (e.g., medications containing pseudoephedrine, a compound found in many over-the-counter cold and flu remedies). Despite recent changes in laws designed to make obtaining pseudoephedrine more difficult, methamphetamine continues to be an easily accessible and relatively inexpensive drug option (Shukla, Crump, & Chrisco, 2012).

The cocaine, amphetamine, cathinones, and MDMA users seek a euphoric high, feelings of intense elation and pleasure, especially in those users who take the drug via intravenous injection or smoking. Repeated use of these stimulants can have significant adverse consequences. Users can experience physical symptoms that include nausea, elevated blood pressure, and increased heart rate. In addition, these drugs can cause feelings of anxiety, hallucinations, and paranoia (Fiorentini et al., 2011). Normal brain functioning is altered after repeated use of these drugs. For example, repeated use can lead to overall depletion among the monoamine neurotransmitters (dopamine, norepinephrine, and serotonin). People may engage in compulsive use of these stimulant substances in part to try to reestablish normal levels of these neurotransmitters (Jayanthi & Ramamoorthy, 2005 Rothman, Blough, & Baumann, 2007).

Caffeine is another stimulant drug. While it is probably the most commonly used drug in the world, the potency of this particular drug pales in comparison to the other stimulant drugs described in this section. Generally, people use caffeine to maintain increased levels of alertness and arousal. Caffeine is found in many common medicines (such as weight loss drugs), beverages, foods, and even cosmetics (Herman & Herman, 2013). While caffeine may have some indirect effects on dopamine neurotransmission, its primary mechanism of action involves antagonizing adenosine activity (Porkka-Heiskanen, 2011).

While caffeine is generally considered a relatively safe drug, high blood levels of caffeine can result in insomnia, agitation, muscle twitching, nausea, irregular heartbeat, and even death (Reissig, Strain, & Griffiths, 2009 Wolt, Ganetsky, & Babu, 2012). In 2012, Kromann and Nielson reported on a case study of a 40-year-old woman who suffered significant ill effects from her use of caffeine. The woman used caffeine in the past to boost her mood and to provide energy, but over the course of several years, she increased her caffeine consumption to the point that she was consuming three liters of soda each day. Although she had been taking a prescription antidepressant, her symptoms of depression continued to worsen and she began to suffer physically, displaying significant warning signs of cardiovascular disease and diabetes. Upon admission to an outpatient clinic for treatment of mood disorders, she met all of the diagnostic criteria for substance dependence and was advised to dramatically limit her caffeine intake. Once she was able to limit her use to less than 12 ounces of soda a day, both her mental and physical health gradually improved. Despite the prevalence of caffeine use and the large number of people who confess to suffering from caffeine addiction, this was the first published description of soda dependence appearing in scientific literature.

Nicotine is highly addictive, and the use of tobacco products is associated with increased risks of heart disease, stroke, and a variety of cancers. Nicotine exerts its effects through its interaction with acetylcholine receptors. Acetylcholine functions as a neurotransmitter in motor neurons. In the central nervous system, it plays a role in arousal and reward mechanisms. Nicotine is most commonly used in the form of tobacco products like cigarettes or chewing tobacco therefore, there is a tremendous interest in developing effective smoking cessation techniques. To date, people have used a variety of nicotine replacement therapies in addition to various psychotherapeutic options in an attempt to discontinue their use of tobacco products. In general, smoking cessation programs may be effective in the short term, but it is unclear whether these effects persist (Cropley, Theadom, Pravettoni, & Webb, 2008 Levitt, Shaw, Wong, & Kaczorowski, 2007 Smedslund, Fisher, Boles, & Lichtenstein, 2004).

Opioids

An opioid is one of a category of drugs that includes heroin, morphine, methadone, and codeine. Opioids have analgesic properties that is, they decrease pain. Humans have an endogenous opioid neurotransmitter system—the body makes small quantities of opioid compounds that bind to opioid receptors reducing pain and producing euphoria. Thus, opioid drugs, which mimic this endogenous painkilling mechanism, have an extremely high potential for abuse. Natural opioids, called opiates, are derivatives of opium, which is a naturally occurring compound found in the poppy plant. There are now several synthetic versions of opiate drugs (correctly called opioids) that have very potent painkilling effects, and they are often abused. For example, the National Institutes of Drug Abuse has sponsored research that suggests the misuse and abuse of the prescription pain killers hydrocodone and oxycodone are significant public health concerns (Maxwell, 2006). In 2013, the U.S. Food and Drug Administration recommended tighter controls on their medical use.

Historically, heroin has been a major opioid drug of abuse (figure below). Heroin can be snorted, smoked, or injected intravenously. Like the stimulants described earlier, the use of heroin is associated with an initial feeling of euphoria followed by periods of agitation. Because heroin is often administered via intravenous injection, users often bear needle track marks on their arms and, like all abusers of intravenous drugs, have an increased risk for contraction of both tuberculosis and HIV.

(a) Common paraphernalia for heroin preparation and use are shown here in a needle exchange kit. (b) Heroin is cooked on a spoon over a candle. (credit a: modification of work by Todd Huffman)

Aside from their utility as analgesic drugs, opioid-like compounds are often found in cough suppressants, anti-nausea, and anti-diarrhea medications. Given that withdrawal from a drug often involves an experience opposite to the effect of the drug, it should be no surprise that opioid withdrawal resembles a severe case of the flu. While opioid withdrawal can be extremely unpleasant, it is not life-threatening (Julien, 2005). Still, people experiencing opioid withdrawal may be given methadone to make withdrawal from the drug less difficult. Methadone is a synthetic opioid that is less euphorigenic than heroin and similar drugs. Methadone clinics help people who previously struggled with opioid addiction manage withdrawal symptoms through the use of methadone. Other drugs, including the opioid buprenorphine, have also been used to alleviate symptoms of opiate withdrawal.

Codeine is an opioid with relatively low potency. It is often prescribed for minor pain, and it is available over-the-counter in some other countries. Like all opioids, codeine does have abuse potential. In fact, abuse of prescription opioid medications is becoming a major concern worldwide (Aquina, Marques-Baptista, Bridgeman, & Merlin, 2009 Casati, Sedefov, & Pfeiffer-Gerschel, 2012).

Hallucinogens

A hallucinogen is one of a class of drugs that results in profound alterations in sensory and perceptual experiences (figure below). In some cases, users experience vivid visual hallucinations. It is also common for these types of drugs to cause hallucinations of body sensations (e.g., feeling as if you are a giant) and a skewed perception of the passage of time.

Psychedelic images like this are often associated with hallucinogenic compounds. (credit: modification of work by “new 1lluminati”/Flickr)

As a group, hallucinogens are incredibly varied in terms of the neurotransmitter systems they affect. Mescaline and LSD are serotonin agonists, and PCP (angel dust) and ketamine (an animal anesthetic) act as antagonists of the NMDA glutamate receptor. In general, these drugs are not thought to possess the same sort of abuse potential as other classes of drugs discussed in this section.

Medical Marijuana

While the possession and use of marijuana is illegal in most states, it is now legal in Washington and Colorado to possess limited quantities of marijuana for recreational use (figure below). In contrast, medical marijuana use is now legal in nearly half of the United States and in the District of Columbia. Medical marijuana is marijuana that is prescribed by a doctor for the treatment of a health condition. For example, people who undergo chemotherapy will often be prescribed marijuana to stimulate their appetites and prevent excessive weight loss resulting from the side effects of chemotherapy treatment. Marijuana may also have some promise in the treatment of a variety of medical conditions (Mather, Rauwendaal, Moxham-Hall, & Wodak, 2013 Robson, 2014 Schicho & Storr, 2014).

Medical marijuana shops are becoming more and more common in the United States. (credit: Laurie Avocado)

While medical marijuana laws have been passed on a state-by-state basis, federal laws still classify this as an illicit substance, making conducting research on the potentially beneficial medicinal uses of marijuana problematic. There is quite a bit of controversy within the scientific community as to the extent to which marijuana might have medicinal benefits due to a lack of large-scale, controlled research (Bostwick, 2012). As a result, many scientists have urged the federal government to allow for relaxation of current marijuana laws and classifications in order to facilitate a more widespread study of the drug’s effects (Aggarwal et al., 2009 Bostwick, 2012 Kogan & Mechoulam, 2007).

Until recently, the United States Department of Justice routinely arrested people involved and seized marijuana used in medicinal settings. In the latter part of 2013, however, the United States Department of Justice issued statements indicating that they would not continue to challenge state medical marijuana laws. This shift in policy may be in response to the scientific community’s recommendations and/or reflect changing public opinion regarding marijuana.

SUMMARY

Substance use disorder is defined in DSM-5 as a compulsive pattern of drug use despite negative consequences. Both physical and psychological dependence are important parts of this disorder. Alcohol, barbiturates, and benzodiazepines are central nervous system depressants that affect GABA neurotransmission. Cocaine, amphetamine, cathinones, and MDMA are all central nervous stimulants that agonize dopamine neurotransmission, while nicotine and caffeine affect acetylcholine and adenosine, respectively. Opiate drugs serve as powerful analgesics through their effects on the endogenous opioid neurotransmitter system, and hallucinogenic drugs cause pronounced changes in sensory and perceptual experiences. The hallucinogens are variable with regards to the specific neurotransmitter systems they affect.

Openstax Psychology text by Kathryn Dumper, William Jenkins, Arlene Lacombe, Marilyn Lovett and Marion Perlmutter licensed under CC BY v4.0. https://openstax.org/details/books/psychology

Exercises

Review Questions:

1. ________ occurs when a drug user requires more and more of a given drug in order to experience the same effects of the drug.

b. psychological dependence

2. Cocaine blocks the reuptake of ________.

3. ________ refers to drug craving.

a. psychological dependence

4. LSD affects ________ neurotransmission.

Critical Thinking Questions:

1. The negative health consequences of both alcohol and tobacco products are well-documented. A drug like marijuana, on the other hand, is generally considered to be as safe, if not safer than these legal drugs. Why do you think marijuana use continues to be illegal in many parts of the United States?

2. Why are programs designed to educate people about the dangers of using tobacco products just as important as developing tobacco cessation programs?

Personal Application Question:.

1. Many people experiment with some sort of psychoactive substance at some point in their lives. Why do you think people are motivated to use substances that alter consciousness?

Answers to Exercises

Review Questions:

Critical Thinking Questions:

1. One possibility involves the cultural acceptance and long history of alcohol and tobacco use in our society. No doubt, money comes into play as well. Growing tobacco and producing alcohol on a large scale is a well-regulated and taxed process. Given that marijuana is essentially a weed that requires little care to grow, it would be much more difficult to regulate its production. Recent events suggest that cultural attitudes regarding marijuana are changing, and it is quite likely that its illicit status will be adapted accordingly.

2. Given that currently available programs designed to help people quit using tobacco products are not necessarily effective in the long term, programs designed to prevent people from using these products in the first place may be the best hope for dealing with the enormous public health concerns associated with tobacco use.

codeine: opiate with relatively low potency often prescribed for minor pain

depressant: drug that tends to suppress central nervous system activity

euphoric high: feelings of intense elation and pleasure from drug use

hallucinogen: one of a class of drugs that results in profound alterations in sensory and perceptual experiences, often with vivid hallucinations

methadone: synthetic opioid that is less euphorogenic than heroin and similar drugs used to manage withdrawal symptoms in opiate users

methadone clinic: uses methadone to treat withdrawal symptoms in opiate users

methamphetamine: type of amphetamine that can be made from pseudoephedrine, an over-the-counter drug widely manufactured and abused

opiate/opioid: one of a category of drugs that has strong analgesic properties opiates are produced from the resin of the opium poppy includes heroin, morphine, methadone, and codeine

physical dependence: changes in normal bodily functions that cause a drug user to experience withdrawal symptoms upon cessation of use

psychological dependence: emotional, rather than a physical, need for a drug which may be used to relieve psychological distress

stimulant: drug that tends to increase overall levels of neural activity includes caffeine, nicotine, amphetamines, and cocaine

tolerance: state of requiring increasing quantities of the drug to gain the desired effect

withdrawal: variety of negative symptoms experienced when drug use is discontinued


An Integrative Bio-Psycho-Social Theory of Anorexia Nervosa

The need for novel approaches to understanding and treating anorexia nervosa (AN) is well recognized. The aim of this paper is to describe an integrative bio-psycho-social theory of maintaining factors in AN. We took a triangulation approach to develop a clinically relevant theory with face validity and internal consistency. We developed theoretical ideas from our clinical practice and reviewed theoretical ideas within the eating disorders and wider bio-psycho-social literature. The synthesis of these ideas and concepts into a clinically meaningful framework is described here. We suggest eight key factors central to understanding the maintenance and treatment resistance of anorexia nervosa: genetic or experiential predisposing factors dysfunctional feelings processing and regulation systems excessive vulnerable feelings 'feared self' beliefs starvation as a maladaptive physiological feelings regulation mechanism maladaptive psychological coping modes maladaptive social behaviour and unmet physical and psychological core needs. Each of these factors serves to maintain the disorder. The concept of universal physical and psychological core needs can provide an underpinning integrative framework for working with this distinctly physical and psychological disorder. This framework could be used within any treatment model. We suggest that treatments which help address the profound lack of trust, emotional security and self-acceptance in this patient group will in turn address unmet needs and improve well-being. Copyright © 2016 John Wiley & Sons, Ltd.

Key practitioner message: The concept of unmet physical and psychological needs can be used as an underlying integrative framework for understanding and working with this patient group, alongside any treatment model. A functional understanding of the neuro-biological, physiological and psychological mechanisms involved in anorexia nervosa can help patients reduce self-criticism and shame. Fears about being or becoming fat, greedy, needy, selfish and unacceptable ('Feared Self') drive over-compensatory self-depriving behaviour ('Anorexic Self'). Psychological treatment for anorexia nervosa should emphasize a focus on feelings and fostering experiences of acceptance and trust. Treatment for patients with anorexia nervosa needs to be longer than current clinical practice.

Keywords: Anorexia Nervosa Bio-Psycho-Social Core Needs Emotions Theory Trust.