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Neurosciences, biological psychiatry, neuropsychiatry

Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics, medicine and allied disciplines, philosophy, physics, and psychology. The term neurobiology is usually used interchangeably with the term neuroscience, although the former refers specifically to the biology of the nervous system, whereas the latter refers to the entire science of the nervous system.

The scope of neuroscience has broadened to include different approaches used to study the molecular, cellular, developmental, structural, functional, evolutionary, computational, and medical aspects of the nervous system. The techniques used by neuroscientists have also expanded enormously, from molecular and cellular studies of individual nerve cells to imaging of sensory and motor tasks in the brain. Recent theoretical advances in neuroscience have also been aided by the study of neural networks.

Given the increasing number of scientists who study the nervous system, several prominent neuroscience organizations have been formed to provide a forum to all neuroscientists and educators. For example, the International Brain Research Organization was founded in 1960, the International Society for Neurochemistry in 1963, the European Brain and Behaviour Society in 1968, and the Society for Neuroscience in 1969.

History

The study of the nervous system dates back to ancient Egypt. Evidence of trepanation, the surgical practice of either drilling or scraping a hole into the skull with the purpose of curing headaches or mental disorders or relieving cranial pressure, being performed on patients dates back to Neolithic times and has been found in various cultures throughout the world. Manuscripts dating back to 1700 BC indicated that the Egyptians had some knowledge about symptoms of brain damage.

Early views on the function of the brain regarded it to be a "cranial stuffing" of sorts. In Egypt, from the late Middle Kingdom onwards, the brain was regularly removed in preparation for mummification. It was believed at the time that the heart was the seat of intelligence. According to Herodotus, the first step of mummification was to "take a crooked piece of iron, and with it draw out the brain through the nostrils, thus getting rid of a portion, while the skull is cleared of the rest by rinsing with drugs."

The view that the heart was the source of consciousness was not challenged until the time of Hippocrates. He believed that the brain was not only involved with sensation—since most specialized organs (e.g., eyes, ears, tongue) are located in the head near the brain—but was also the seat of intelligence. Plato also speculated that the brain was the seat of the rational part of the soul. Aristotle, however, believed the heart was the center of intelligence and that the brain regulated the amount of heat from the heart. This view was generally accepted until the Roman physician Galen, a follower of Hippocrates and physician to Roman gladiators, observed that his patients lost their mental faculties when they had sustained damage to their brains.

Abulcasis, Averroes, Avenzoar, and Maimonides, active in the Medieval Muslim world, described a number of medical problems related to the brain. In Renaissance Europe, Vesalius (1514–1564) and René Descartes (1596–1650) also made several contributions to neuroscience.

Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s. The procedure used a silver chromate salt to reveal the intricate structures of individual neurons. His technique was used by Santiago Ramón y Cajal and led to the formation of the neuron doctrine, the hypothesis that the functional unit of the brain is the neuron. Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in 1906 for their extensive observations, descriptions, and categorizations of neurons throughout the brain. The neuron doctrine was supported by experiments following Luigi Galvani's pioneering work in the electrical excitability of muscles and neurons. In the late 19th century, Emil du Bois-Reymond, Johannes Peter Müller, and Hermann von Helmholtz demonstrated that neurons were electrically excitable and that their activity predictably affected the electrical state of adjacent neurons.

In parallel with this research, work with brain-damaged patients by Paul Broca suggested that certain regions of the brain were responsible for certain functions. At the time, Broca's findings were seen as a confirmation of Franz Joseph Gall's theory that language was localized and that certain psychological functions were localized in specific areas of the cerebral cortex. The localization of function hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly inferred the organization of the motor cortex by watching the progression of seizures through the body. Carl Wernicke further developed the theory of the specialization of specific brain structures in language comprehension and production. Modern research still uses the Brodmann cerebral cytoarchitectonic map (referring to study of cell structure) anatomical definitions from this era in continuing to show that distinct areas of the cortex are activated in the execution of specific tasks.

In 1952, Alan Lloyd Hodgkin and Andrew Huxley presented a mathematical model for transmission of electrical signals in neurons of the giant axon of a squid, action potentials, and how they are initiated and propagated, known as the Hodgkin-Huxley model. In 1961-2, Richard FitzHugh and J. Nagumo simplified Hodgkin-Huxley, in what is called the FitzHugh–Nagumo model. In 1962, Bernard Katz modeled neurotransmission across the space between neurons known as synapses. In 1981 Catherine Morris and Harold Lecar combined these models in the Morris-Lecar model. In 1984, J. L. Hindmarsh and R.M. Rose further modeled neurotransmission.

Beginning in 1966, Eric Kandel and collaborators examined biochemical changes in neurons associated with learning and memory storage.

Modern neuroscience

The scientific study of the nervous system has increased significantly during the second half of the twentieth century, principally due to advances in molecular biology, electrophysiology, and computational neuroscience. This has allowed neuroscientists to study the nervous system in all its aspects: how it is structured, how it works, how it develops, how it malfunctions, and how it can be changed. For example, it has become possible to understand, in much detail, the complex processes occurring within a single neuron. Neurons are cells specialized for communication. They are able to contact with neurons and other cell types through specialized junctions called synapses, at which electrical or electrochemical signals can be transmitted from one cell to another. Many neurons extrude long thin filaments of protoplasm called axons, which may extend to distant parts of the body and are capable of rapidly carrying electrical signals, influencing the activity of other neurons, muscles, or glands at their termination points. A nervous system emerges from the assemblage of neurons that are connected to each other.

In vertebrates, the nervous system can be split into two parts, the central nervous system (brain and spinal cord), and the peripheral nervous system. In many species — including all vertebrates — the nervous system is the most complex organ system in the body, with most of the complexity residing in the brain. The human brain alone contains around a hundred billion neurons and a hundred trillion synapses; it consists of thousands of distinguishable substructures, connected to each other in synaptic networks whose intricacies have only begun to be unraveled. The majority of genes belonging to the human genome are expressed specifically in the brain. Thus the challenge of making sense of all this complexity is formidable.

Molecular and cellular neuroscience

The study of the nervous system can be done at multiple levels, ranging from the molecular and cellular levels to the systems and cognitive levels. At the molecular level, the basic questions addressed in molecular neuroscience include the mechanisms by which neurons express and respond to molecular signals and how axons form complex connectivity patterns. At this level, tools from molecular biology and genetics are used to understand how neurons develop and how genetic changes affect biological functions. The morphology, molecular identity, and physiological characteristics of neurons and how they relate to different types of behavior are also of considerable interest.

The fundamental questions addressed in cellular neuroscience include the mechanisms of how neurons process signals physiologically and electrochemically. These questions include how signals are processed by neurites – thin extensions from a neuronal cell body, consisting of dendrites (specialized to receive synaptic inputs from other neurons) and axons (specialized to conduct nerve impulses called action potentials) – and somas (the cell bodies of the neurons containing the nucleus), and how neurotransmitters and electrical signals are used to process information in a neuron. Another major area of neuroscience is directed at investigations of the development of the nervous system. These questions include the patterning and regionalization of the nervous system, neural stem cells, differentiation of neurons and glia, neuronal migration, axonal and dendritic development, trophic interactions, and synapse formation.

Neural circuits and systems

At the systems level, the questions addressed in systems neuroscience include how neural circuits are formed and used anatomically and physiologically to produce functions such as reflexes, sensory integration, motor coordination, circadian rhythms, emotional responses, learning, and memory. In other words, they address how these neural circuits function and the mechanisms through which behaviors are generated. For example, systems level analysis addresses questions concerning specific sensory and motor modalities: how does vision work? How do songbirds learn new songs and bats localize with ultrasound? How does the somatosensory system process tactile information? The related fields of neuroethology and neuropsychology address the question of how neural substrates underlie specific animal and human behaviors. Neuroendocrinology and psychoneuroimmunology examine interactions between the nervous system and the endocrine and immune systems, respectively. Despite many advancements, the way networks of neurons produce complex cognitions and behaviors is still poorly understood.

Cognitive and behavioral neuroscience

At the cognitive level, cognitive neuroscience addresses the questions of how psychological functions are produced by neural circuitry. The emergence of powerful new measurement techniques such as neuroimaging (e.g., fMRI, PET, SPECT), electrophysiology, and human genetic analysis combined with sophisticated experimental techniques from cognitive psychology allows neuroscientists and psychologists to address abstract questions such as how human cognition and emotion are mapped to specific neural substrates.

Neuroscience is also allied with the social and behavioral sciences as well as nascent interdisciplinary fields such as neuroeconomics, decision theory, and social neuroscience to address complex questions about interactions of the brain with its environment.

Ultimately neuroscientists would like to understand every aspect of the nervous system, including how it works, how it develops, how it malfunctions, and how it can be altered or repaired. The specific topics that form the main foci of research change over time, driven by an ever-expanding base of knowledge and the availability of increasingly sophisticated technical methods. Over the long term, improvements in technology have been the primary drivers of progress. Developments in electron microscopy, computers, electronics, functional brain imaging, and most recently genetics and genomics, have all been major drivers of progress.

Translational research and medicine

Neurology, psychiatry, neurosurgery, psychosurgery, anesthesiology, neuropathology, neuroradiology, clinical neurophysiology and addiction medicine are medical specialties that specifically address the diseases of the nervous system. These terms also refer to clinical disciplines involving diagnosis and treatment of these diseases. Neurology works with diseases of the central and peripheral nervous systems, such as amyotrophic lateral sclerosis (ALS) and stroke, and their medical treatment. Psychiatry focuses on affective, behavioral, cognitive, and perceptual disorders. Anesthesiology focuses on perception of pain, and pharmacologic alteration of consciousness. Neuropathology focuses upon the classification and underlying pathogenic mechanisms of central and peripheral nervous system and muscle diseases, with an emphasis on morphologic, microscopic, and chemically observable alterations. Neurosurgery and psychosurgery work primarily with surgical treatment of diseases of the central and peripheral nervous systems. The boundaries between these specialties have been blurring recently as they are all influenced by basic research in neuroscience. Brain imaging also enables objective, biological insights into mental illness, which can lead to faster diagnosis, more accurate prognosis, and help assess patient progress over time.

Integrative neuroscience makes connections across these specialized areas of focus.

Major branches

Modern neuroscience education and research activities can be very roughly categorized into the following major branches, based on the subject and scale of the system in examination as well as distinct experimental or curricular approaches. Individual neuroscientists, however, often work on questions that span several distinct subfields.

Branch Description
Affective neuroscience Affective neuroscience is the study of the neural mechanisms involved in emotion, typically through experimentation on animal models.
Behavioral neuroscience Behavioral neuroscience (also known as biological psychology, biopsychology, or psychobiology) is the application of the principles of biology (viz., neurobiology) to the study of genetic, physiological, and developmental mechanisms of behavior in humans and non-human animals.
Cellular neuroscience Cellular neuroscience is the study of neurons at a cellular level including morphology and physiological properties.
Clinical neuroscience This consists of medical specialties such as neurology and psychiatry, as well as many allied health professions such as speech-language pathology. Neurology is the medical specialty that works with disorders of the nervous system. Psychiatry is the medical specialty that works with the disorders of the mind—which include various affective, behavioral, cognitive, and perceptual disorders. (Also see note below.)
Cognitive neuroscience Cognitive neuroscience is the study of biological substrates underlying cognition with a specific focus on the neural substrates of mental processes.
Computational neuroscience Computational neuroscience is the study of brain function in terms of the information processing properties of the structures that make up the nervous system. Computational neuroscience can also refer to the use of computer simulations and theoretical models to study the function of the nervous system.
Cultural neuroscience Cultural neuroscience is the study of how cultural values, practices and beliefs shape and are shaped by the mind, brain and genes across multiple timescales.
Developmental neuroscience Developmental neuroscience studies the processes that generate, shape, and reshape the nervous system and seeks to describe the cellular basis of neural development to address underlying mechanisms.
Molecular neuroscience Molecular neuroscience is a branch of neuroscience that examines the biology of the nervous system with molecular biology, molecular genetics, protein chemistry, and related methodologies.
Neuroengineering Neuroengineering is a discipline within biomedical engineering that uses engineering techniques to understand, repair, replace, or enhance neural systems.
Neuroimaging Neuroimaging includes the use of various techniques to either directly or indirectly image the structure and function of the brain.
Neuroinformatics Neuroinformatics is a discipline within bioinformatics that conducts the organization of neuroscience data and application of computational models and analytical tools.
Neurolinguistics Neurolinguistics is the study of the neural mechanisms in the human brain that control the comprehension, production, and acquisition of language.
Neurophysiology Neurophysiology is the study of the functioning of the nervous system, generally using physiological techniques that include measurement and stimulation with electrodes or optically with ion- or voltage-sensitive dyes or light-sensitive channels.
Paleoneurology Paleoneurology is a field which combines techniques used in paleontology and archeology to study brain evolution, especially that of the human brain.
Social neuroscience Social neuroscience is an interdisciplinary field devoted to understanding how biological systems implement social processes and behavior, and to using biological concepts and methods to inform and refine theories of social processes and behavior.
Systems neuroscience Systems neuroscience is the study of the function of neural circuits and systems.

Neuroscience organizations

The largest professional neuroscience organization is the Society for Neuroscience (SFN), which is based in the United States but includes many members from other countries. Since its founding in 1969 the SFN has grown steadily: as of 2010 it recorded 40,290 members from 83 different countries. Annual meetings, held each year in a different American city, draw attendance from researchers, postdoctoral fellows, graduate students, and undergraduates, as well as educational institutions, funding agencies, publishers, and hundreds of businesses that supply products used in research.

Other major organizations devoted to neuroscience include the International Brain Research Organization (IBRO), which holds its annual meetings in a country from a different part of the world each year, and the Federation of European Neuroscience Societies (FENS), which holds annual meetings in European cities. FENS comprises a set of 32 national-level organizations, including the British Neuroscience Association, the German Neurowissenschaftliche Gesellschaft, and the French Societé des Neurosciences.

Public education and outreach

In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of awareness and knowledge about the nervous system among the general public and government officials. Such promotions have been done by both individual neuroscientists and large organizations. For example, individual neuroscientists have promoted neuroscience education among young students by organizing the International Brain Bee (IBB), which is an academic competition for high school or secondary school students worldwide. In the United States, large organizations such as the Society for Neuroscience have promoted neuroscience education by developing a primer called Brain Facts, collaborating with public school teachers to develop Neuroscience Core Concepts for K-12 teachers and students, and cosponsoring a campaign with the Dana Foundation called Brain Awareness Week to increase public awareness about the progress and benefits of brain research.

Finally, neuroscientists have also collaborated with other education experts to study and refine educational techniques to optimize learning among students, an emerging field called educational neuroscience. Federal agencies in the United States, such as the National Institute of Health (NIH) and National Science Foundation (NSF), have also funded research that pertains to best practices in teaching and learning of neuroscience concepts.

Biological psychiatry

Biological psychiatry, or biopsychiatry is an approach to psychiatry that aims to understand mental disorder in terms of the biological function of the nervous system. It is interdisciplinary in its approach and draws on sciences such as neuroscience, psychopharmacology, biochemistry, genetics and physiology to investigate the biological bases of behavior and psychopathology. Biopsychiatry is that branch/speciality of medicine which deals with the study of biological function of the nervous system in mental disorders.

While there is some overlap between biological psychiatry and neurology, the latter generally focuses on disorders where gross or visible pathology of the nervous system is apparent, such as epilepsy, cerebral palsy, encephalitis, neuritis, Parkinson's disease and multiple sclerosis. There is some overlap with neuropsychiatry, which typically deals with behavioral disturbances in the context of apparent brain disorder.

Biological psychiatry and other approaches to mental illness are not mutually exclusive, but may simply attempt to deal with the phenomena at different levels of explanation. Because of the focus on the biological function of the nervous system, however, biological psychiatry has been particularly important in developing and prescribing drug-based treatments for mental disorders.

In practice, however, psychiatrists may advocate both medication and psychological therapies when treating mental illness. The therapy is more likely to be conducted by clinical psychologists, psychotherapists, occupational therapists or other mental health workers who are more specialized and trained in non-drug approaches.

The history of the field extends back to the ancient Greek physician Hippocrates, but the term biological psychiatry was first used in peer-reviewed scientific literature in 1953. The term is more commonly used in the US than in some other countries such as the UK. The field, however, is not without its critics and the phrase "biological psychiatry" is sometimes used by those critics as a term of disparagement.

Scope and detailed definition

Biological psychiatry is a branch of psychiatry where the focus is chiefly on researching and understanding the biological basis of major mental disorders such as unipolar and bipolar affective (mood) disorders, schizophrenia and Organic Mental Disorders such as Alzheimers disease. This knowledge has been gained using imaging techniques, psychopharmacology, neuroimmunochemistry and so on. Discovering the detailed interplay between neurotransmitters and the understanding of the neurotransmitter fingerprint of psychiatric drugs such as clozapine has been a helpful result of the research.

On a research level, it includes all possible biological bases of behavior—biochemical, genetic, physiological, neurological and anatomical. On a clinical level, it includes various therapies, such as drugs, diet, avoidance of environmental contaminants, exercise, and alleviation of the adverse effects of life stress, all of which can cause measurable biochemical changes. The biological psychiatrist views all of these as possible etiologies of or remedies for mental health disorders.

However, the biological psychiatrist typically does not discount psychoanalytic approaches (talk therapies). Medical psychiatric training generally includes both psychodynamic and biological approaches. Accordingly, psychiatrists are usually comfortable with a dual approach: "psychotherapeutic methods...are as indispensable as psychopharmacotherapy in a modern psychiatric clinic."

Basis for biological psychiatry

Sigmund Freud developed psychotherapy in the early 1900s, and through the 1950s this technique was prominent in treating mental health disorders.

However in the late 1950s, the first modern antipsychotic and antidepressant drugs were developed: chlorpromazine (also known as Thorazine), the first widely-used antipsychotic, was synthesized in 1950, and iproniazid, one of the first antidepressants, was first synthesized in 1957. In 1959 imipramine, the first tricyclic antidepressant, was developed.

Based significantly on clinical observations of the above drug results, in 1965 the seminal paper "The catecholamine hypothesis of affective disorders" was published. It articulated the "chemical imbalance" hypothesis of mental health disorders, especially depression. It formed much of the conceptual basis for the modern era in biological psychiatry.

The hypothesis has been extensively revised since its advent in 1965. More recent research points to deeper underlying biological mechansisms as the possible basis for several mental health disorders.

Modern brain imaging techniques allow noninvasive examination of neural function in patients with mental health disorders, however this is currently experimental. With some disorders it appears the proper imaging equipment can reliably detect certain neurobiological problems associated with a specific disorder. If further studies corroborate these experimental results, future diagnosis of certain mental health disorders could be expedited using such methods.

Another source of data indicating a significant biological aspect of some mental health disorders is twin studies. Identical twins have the same nuclear DNA, so carefully constructed studies may indicate the relative importance of environmental and genetic factors on the development of a particular mental health disorder.

The results from this research and the associated hypotheses form the basis for biological psychiatry and the treatment approaches in a clinical setting.

Scope of clinical biological psychiatric treatment

Since various biological factors can affect mood and behavior, psychiatrists often evaluate these before initiating further treatment. For example dysfunction of the thyroid gland may mimic a major depressive episode, or hypoglycemia (low blood sugar) may mimic psychosis.

While pharmacological treatments are used to treat many mental disorders, other non-drug biological treatments are used as well, ranging from changes in diet and exercise to transcranial magnetic stimulation and electroconvulsive therapy. Types of non-biological treatments such as cognitive therapy, behavioral therapy, and psychodynamic psychotherapy are often used in conjunction with biological therapies. Biopsychosocial models of mental illness are widely in use, and psychological and social factors play a large role in mental disorders, even those with an organic basis such as schizophrenia.

Diagnostic process

Correct diagnosis is important for mental health disorders, otherwise the condition could worsen, resulting in a negative impact on both the patient and the healthcare system. Another problem with misdiagnosis is that a treatment for one condition might exacerbate other conditions. In other cases apparent mental health disorders could be a side effect of a serious biological problem such as concussion, brain tumor, or hormonal abnormality, which could require medical or surgical intervention.

Disorders and biologic treatment

  • Seasonal affective disorder: Light box, SSRIs
  • Clinical depression: SSRIs (Prozac), SNRIs Effexor, atypical antidepressants: (Wellbutrin, Remeron), tricyclic antidepressants, monoamine oxidase inhibitors, electroconvulsive therapy, transcranial magnetic stimulation
  • Bipolar disorder: lithium carbonate, valproic acid, Lamictal, carbamazepine
  • Schizophrenia: Includes haloperidol, clozapine, olanzapine, risperidone, Quetiapine, Ziprasidone and other antipsychotics
  • Generalized anxiety disorder: SSRIs, benzodiazepines, buspirone
  • Obsessive-compulsive disorder: clomipramine, SSRIs citalopram

History

Early 20th century

Sigmund Freud was originally focused on the biological causes of mental illness. Freud's professor and mentor, Ernst Wilhelm von Brücke, strongly believed that thought and behavior were determined by purely biological factors. Freud initially accepted this and was convinced that certain drugs (particularly cocaine) functioned as antidepressants. He spent many years trying to "reduce" personality to neurology, a cause he later gave up on before developing his now well-known psychoanalytic theories.

Nearly 100 years ago, Harvey Cushing, the father of neurosurgery, noted that pituitary gland problems often cause mental health disorders. He wondered whether the depression and anxiety he observed in patients with pituitary disorders were caused by hormonal abnormalities, the physical tumor itself, or both.

Mid 20th century

An important point in modern history of biological psychiatry was the discovery of modern antipsychotic and antidepressant drugs. Chlorpromazine (also known as Thorazine), an antipsychotic, was first synthesized in 1950, and iproniazid, one of the first antidepressants, was first synthesized in 1957. In 1959 imipramine, the first tricyclic antidepressant, was developed. Research into the action of these drugs led to the first modern biological theory of mental health disorders called the catecholamine theory, later broadened to the monoamine theory, which included serotonin. These were popularly called the "chemical imbalance" theory of mental health disorders.

Late 20th century

Starting with fluoxetine (marketed as Prozac) in 1988, a series of monoamine-based antidepressant medications belonging to the class of selective serotonin reuptake inhibitors were approved. These were no more effective than earlier antidepressants, but generally had fewer side effects. Most operate on the same principle, which is modulation of monoamines (neurotransmitters) in the neuronal synapse. Some drugs modulate a single neurotransmitter (typically serotonin). Others affect multiple neurotransmitters, called dual action or multiple action drugs. They are no more effective clinically than single action versions. That most antidepressants invoke the same biochemical method of action may explain why they are each similarly effective in rough terms. Recent research indicates antidepressants often work but are somewhat less effective than previously thought.

Problems with catecholamine/monoamine hypotheses

The monoamine hypothesis was compelling, especially based on apparently successful clinical results with early antidepressant drugs, but even at the time there were discrepant findings. Only a minority of patients given the serotonin-depleting drug reserpine became depressed; in fact reserpine even acted as an antidepressant in many cases. This was inconsistent with the initial monoamine theory which said depression was caused by neurotransmitter deficiency.

Another problem was the time lag between antidepressant biological action and therapeutic benefit. Studies showed the neurotransmitter changes occurred within hours, yet therapeutic benefit took weeks.

To explain these behaviors, more recent modifications of the monoamine theory describe a synaptic adaptation process which takes place over several weeks. Yet this alone does not appear to explain all of the therapeutic effects.

Latest biological hypotheses of mental health disorders

New research indicates different biological mechanisms may underlie some mental health disorders, only indirectly related to neurotransmitters and the monoamine "chemical imbalance theory."

Recent research indicates a biological "final common pathway" may exist which both electroconvulsive therapy and most current antidepressant drugs have in common. These investigations show recurrent depression may be a neurodegenerative disorder, disrupting the structure and function of brain cells, destroying nerve cell connections, even killing certain brain cells, and precipitating a decline in overall cognitive function.

In this new biological psychiatry viewpoint, neuronal plasticity is a key element. Increasing evidence points to various mental health disorders as a neurophysiological problem which inhibits neuronal plasticity.

This is called the neurogenic hypothesis of depression. It promises to explain pharmacological antidepressant action, including the time lag from taking the drug to therapeutic onset, why downregulation (not just upregulation) of neurotransmitters can help depression, why stress often precipitates mood disorders, and why selective modulation of different neurotransmitters can help depression. It may also explain the neurobiological mechanism of other non-drug effects on mood, including exercise, diet and metabolism. By identifying the neurobiological "final common pathway" into which most antidepressants funnel, it may allow rational design of new medications which target only that pathway. This could yield drugs which have fewer side effects, are more effective and have quicker therapeutic onset.

There is significant evidence that oxiative stress plays a role in schizophrenia. Review.

Criticism

A vocal minority of patients, activists, and psychiatrists dispute biological psychiatry as a scientific concept or as having a proper empirical basis, for example arguing that there are no known biomarkers for recognized psychiatric conditions. This position has been represented in niche academic journals such as The Journal of Mind and Behavior and Ethical Human Psychology and Psychiatry, which publishes material specifically countering "the idea that emotional distress is due to an underlying organic disease." Alternative theories and models instead view mental disorders as non-biomedical and might explain it in terms of, for example, emotional reactions to negative life circumstances or to acute trauma.

Fields such as social psychiatry, clinical psychology, and sociology may offer non-biomedical accounts of mental distress and disorder for certain ailments and are sometimes critical of biopsychiatry. Social critics believe biopsychiatry fails to satisfy the scientific method because they believe there is no testable biological evidence of mental disorders. Thus, these critics view biological psychiatry as a pseudoscience attempting to portray psychiatry as a biological science.

R.D. Laing argued that attributing mental disorders to biophysical factors was often flawed due to the diagnostic procedure. The "complaint" is often made by a family member, not the patient, the "history" provided by someone other than patient, and the "examination" consists of observing strange, incomprehensible behavior. Ancillary tests (EEG, PET) are often done after diagnosis, when treatment has begun, which makes the tests non-blind and incurs possible confirmation bias.

Neuropsychiatry

Neuropsychiatry is the branch of medicine dealing with mental disorders attributable to diseases of the nervous system. It preceded the current disciplines of psychiatry and neurology, in as much as psychiatrists and neurologists had a common training. However, neurology and psychiatry subsequently split apart and are typically practiced separately. Nevertheless, neuropsychiatry has become a growing subspecialty of psychiatry and it is also closely related to the field of behavioral neurology, which is a subspecialty of neurology that addresses clinical problems of cognition and/or behavior caused by brain injury or brain disease. "Behavioral Neurology & Neuropsychiatry" fellowships are jointly accredited through the United Council for Neurologic Subspecialties (UCNS), in a manner similar to how the specialties of psychiatry and neurology in the United States have a joint board for accreditation, the American Board of Psychiatry and Neurology (ABPN). The American Neuropsychiatric Association (ANPA) is the American medical subspecialty society for neuropsychiatrists, offering fellowships and CME credits. ANPA also publishes the peer-reviewed Journal of Neuropsychiatry and Clinical Neurosciences.

The case for the rapprochement of neurology and psychiatry

Given the considerable overlap between these subspecialities, there has been a resurgence of interest and debate relating to neuropsychiatry in academia over the last decade. Most of this work argues for a rapprochement of neurology and psychiatry, forming a specialty above and beyond a subspecialty of psychiatry. For example, Professor Joseph B. Martin, former Dean of Harvard Medical School and a neurologist by training, has summarized the argument for reunion: "the separation of the two categories is arbitrary, often influenced by beliefs rather than proven scientific observations. And the fact that the brain and mind are one makes the separation artificial anyway." These points and some of the other major arguments are detailed below.

Mind/brain monism

Neurologists have focused objectively on organic nervous system pathology, especially of the brain, whereas psychiatrists have laid claim to illnesses of the mind. This antipodal distinction between brain and mind as two different entities has characterized many of the differences between the two specialties. However, it is argued that this division is simply not veridical; a plethora of evidence from the last century of research has shown that our mental life has its roots in the brain.[2] Brain and mind are argued not to be discrete entities but just different ways of looking at the same system (Marr, 1982). It has been argued that embracing this mind/brain monism is important for several reasons. First, rejecting dualism logically implies that all mentation is biological and so immediately there is a common research framework in which understanding—and thus treatment—of mental suffering can be advanced. Second, it removes the widespread confusion about the legitimacy of mental illness: all disorders should have a footprint in the brain-mind system.

In sum, one reason for the division between psychiatry and neurology was the difference between mind or first-person experience and brain. That this difference is artificial is taken as good support for a merge between these specialties.

Causal pluralism

Another broad reason for the divide is that neurology traditionally looks at the causes of disorders from an "inside-the-skin" perspective (neuropathology, genetics) whereas psychiatry looks at "outside-the-skin" causation (personal, interpersonal, cultural). This dichotomy is argued not to be instructive and authors have argued that it is better conceptualized as two ends of a causal continuum. The benefits of this position are: firstly, understanding of etiology will be enriched, in particular between brain and environment. One example is eating disorders, which have been found to have some neuropathology (Uher and Treasure, 2005) but also show increased incidence in rural Fijian school girls after exposure to television (Becker, 2004). Another example is schizophrenia, the risk for which may be considerably reduced in a healthy family environment (Tienari et al., 2004).

Secondly, it is argued that this augmented understanding of etiology will lead to better remediation and rehabilitation strategies through an understanding of the different levels in the causal process where one can intervene. Indeed, it may be that non-organic interventions, like cognitive behavioral therapy (CBT), better attenuate disorders alone or in conjunction with drugs. Linden's (2006) demonstration of how psychotherapy has neurobiological commonalities with pharmacotherapy is a pertinent example of this and is encouraging from a patient perspective as the potentiality for pernicious side effects is decreased while self-efficacy is increased.

In sum, the argument is that an understanding of the mental disorders must not only have a specific knowledge of brain constituents and genetics (inside-the-skin) but also the context (outside-the-skin) in which these parts operate (Koch and Laurent, 1999). Only by joining neurology and psychiatry, it is argued, can this nexus be used to reduce human suffering.

Hitherto psychiatric disorders have organic basis

To further sketch psychiatry's history shows a departure from structural neuropathology, relying more upon ideology (Sabshin, 1990). A good example of this is Tourette syndrome, which Ferenczi (1921), although never having seen a patient with Tourette syndrome, suggested was the symbolic expression of masturbation caused by sexual repression. However, starting with the efficacy of neuroleptic drugs in attenuating symptoms (Shapiro, Shapiro and Wayne, 1973) the syndrome has gained pathophysiological support (e.g. Singer, 1997) and is hypothesized to have a genetic basis too, based on its high inheritability (Robertson, 2000). This trend can be seen for many hitherto traditionally psychiatric disorders (see table) and is argued to support reuniting neurology and psychiatry because both are dealing with disorders of the same system.

Linking traditionally psychiatric symptoms to brain structures and genetic abnormalities. (This table is in no way exhaustive but aims to show some of the neurological bases to hitherto psychiatric symptoms)
Psychiatric symptoms E.g. Psychoanalytic explanation E.g. Neural correlates Source
Depression Narcissistic Limbic-cortical dysregulation Mayberg (1997)
Obsessive Compulsive Disorder Poor maternal parenting frontal-subcortical circuitry, right caudate activity Saxena et al. (1998), Gamazo-Garran, Soutullo and Ortuno (2002)
Schizophrenia Narcissistic/escapism NMDA receptor activation in the human prefrontal cortex Ross et al. (2006)
Visual hallucination projection retinogeniculocalcarine tract, ascending brainstem modulatory structures Mocellin, Walterfang, Velakoulis, 2006
Auditory hallucination projection frontotemporal functional connectivity Shergill et al., 2000
Eating disorder   Atypical serotonin system, right frontal and temporal lobe damage Kaye et al. (2005), Uher and Treasure (2005)
Bipolar disorder Narcissistic Prefrontal cortex and hippocampus, anterior cingulate, amygdala Barrett et al. (2003), Vawter, Freed, & Kleinman (2000)

Improved patient care

Further, it is argued that this nexus will allow a more refined nosology of mental illness to emerge thus helping to improve remediation and rehabilitation strategies beyond current ones that lump together ranges of symptoms. However, it cuts both ways: traditionally neurological disorders, like Parkinson's disease, are being recognized for their high incidence of traditionally psychiatric symptoms, like psychosis and depression (Lerner and Whitehouse, 2002). These symptoms, which are largely ignored in neurology, can be addressed by neuropsychiatry and lead to improved patient care. In sum, it is argued that patients from both traditional psychiatry and neurology departments will see their care improved following a reuniting of the specialties.

Better management model

Schiffer et al. (2004) argue that there are good management and financial reasons for rapprochement.

The case for maintaining the separation of neurology and psychiatry

No psychiatric disorder has been completely "mapped"

The fact that no complete syndrome has been mapped in the brain or genome is used to suggest that psychiatric disorders are not bona fide and should thus be kept separate (e.g. Baughman and Hovey, 2006). On this issue, it is worth remembering that research into the neural correlates of psychiatric disorders is in its infancy: the answers may still be to come. One reason why they may not have been found so far is that complex mental disorders may result from minute and intricate brain-wide damage and complicated gene-environment interactions, which are only beginning to be understood. Disorders may not exist as tidy, localized neurodysfunction or genetic abnormalities but multi-factorial brain-wide disorders with complex interactions between environment and genetics (e.g. Green, 2001). Such distributed dysfunction may not be resolvable in the living brain with current technology. E.g. disparate behavioral disorders have been linked to identical neurodysfunction with imaging but show significant organic differences following neurohistological analysis (Rempel–Clower et al., 1996). Where physiopathology is extremely small and distributed or neural tissue is actually healthy it may be the disturbed information-processing that should be studied. E.g. Bell, Halligan and Ellis' (2006) work on cognitive deficits in delusions.

Pragmatic issues

The extent to which neuropsychiatry is practically possible has been questioned. As Sachdev (2005) has noted, psychiatrists and neurologists operate very different patient management strategies, which are skills honed by years of experience:

  • Neurologist: Clinical examination skills; empiricism; objectivity; surgery
  • Psychiatrist: Rich description of mental phenomena, well developed interviewing skills; understanding multiple causation; appreciation of individual differences; interpersonal context; psychological and behavioral therapies

Sachdev suggests to join them may be to dilute them both. Further, the ability to maintain a competent knowledge and skill base for both neurology and psychiatry with the advent of the inexorable increase in scientific knowledge may not be possible.

Summary of the arguments for neuropsychiatry

Diseases of the body have a physical manifestation that can often be caused by internal factors, external factors, or a combination of the two. Mental disorders should be no different and when together neurology and psychiatry's aim was to show that this was the case. Psychiatry departed the union preferring ideology over empiricism, including very environmentally-based etiology as well as espousing that the mind was something fundamentally different from the brain. Neurologists, however, finding no physiopathology for certain disorders left them to the psychiatrists, while themselves pursuing the diseases with clear physiopathology.

However, the cleavage between mind and brain and the causal dichotomies are argued not to be veridical. Psychiatric disorders are increasingly showing organic manifestation and demonstrate causation from something as distant as culture. Thus the reasons for the initial division are argued not to be useful or real ones. The two specialties are both dealing with disorders of the same system. Biological psychiatry and behavioral neurology show how the boundaries are being blurred. It is argued that there can be no objection to a reunion on philosophical or scientific grounds. However, there may be reasons to question whether neuropsychiatry would be practically possible. The differences in patient management, knowledge base and skill competency between neurology and psychiatry mean that being proficient in both may be impossible.

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