INTRODUCTION

1 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN The Psychotherapist’s Essential Guide to the Brain provides an overview of the essential parts and functions of the brain that every modern-day therapist should be familiar with. Written in accessible language and consolidating a large body of neuroscientific knowledge, this handy “beginner’s guide” forms a practical and accessible introduc- tion to brain science for psychotherapists. The current chapter lays the groundwork for a big-picture view of how the brain functions, providing essential reference points from which the reader may go on to develop an under- standing of what is happening in the brains of clients, as well as in his or her own. The contemporary psychotherapist has access to a more sophisticated model of mental health than ever before, yet key elements of that model entail an understanding of the neural functions that underpin behaviour, relation- ships, personality, and a sense of self and the surrounding world. This guide aims to bridge the gap between the of- ten esoteric realm of neuroscience research and the pragmatic realities of psychotherapy with clients. The therapist with a practical grasp of the concepts, regions and functions of the nervous system will be rewarded with improved outcomes that reflect a more holistic and integrated understanding of clients. Since Freud, the brain has been variously conceived in terms of an electrical system, a chemical system, and, more recently, a highly interconnected electrochemical network. In terms of convention, we are only now emerg- ing from an outdated medical model that conceptualized the brain primarily as a chemical system that could be “fixed” by means of drug intervention, and coming to the realization that the brain is a malleable communication network where the patterns of connections within and between brain regions are as important as the chemicals that serve the impulses travelling these routes. Understanding this communication network, which happens to be the most complex system we know, can enhance our practice of psychotherapy as we tune in to the intricacies of its various attributes. As a stand-out example, understanding the basic concept of a fast-reacting limbic system versus a slower prefrontal cortex can shed light on why cognitive therapies are often largely ineffective until more basic emotional issues have been addressed via a “bottom up” approach. Or, understanding that emotional memories can be “unhinged” from the hippocampal time/space marker for an event can furnish not only greater empathy for the PTSD sufferer but also ideas on how to reintegrate the traumatic memories from the past so that they stop intruding on the now. We can create better interventions when we know that memory is everything when it comes to brain function, and that memories can change, our neural networks can be altered, and even genetic expressions that support those neural networks can change. And so, with a debt to modern neuroscience, we embark on this modest overview of the brain, trusting it will serve you well in your conceptualizations of clients and arouse your curiosity for further learning.

A connectogram of a healthy control subject. Connectograms are graphical representations of connectomics, the field of study dedicated to mapping and interpreting all of the white-matter fibre connections in the human brain. These circular graphs based on diffusion MRI data utilize graph theory to demonstrate the white-matter connections and cortical characteristics for single structures, single subjects, or populations. In this image: From outside to inside, the rings represent the cortical region, grey matter volume, surface area, cortical thickness, curvature, degree of connectivity, node strength, betweenness central- ity, eccentricity, nodal efficiency, and eigenvector centrality. Between degree of connectivity and node strength, a blank ring has been added as a place- holder. Thisconnectogram includes five additional nodal measures not included in the standard con- nectogram. Image: Wikipedia.

INTRODUCTION 2 THE DIVIDED BRAIN Iain McGilchrist, in his noteworthy book The Master and His Emissary: The Divided Brain and the Making of the Western World (2009), describes the asymmetry of the brain and the very different natures of the left and right hemispheres. This horizontal understanding of the mental system, as opposed to the vertical triune perspec- tive, gives us insight into the distinctly different yet complementary functions of the two hemispheres. In short, the right hemisphere handles broad attention (what we attend to comes first to us through the right hemisphere); is good at making connections so that we can appreciate the wholeness of dynamic structures and relationships that change over time; is attuned to emotion; and is empathic, intuitive, and moral. In con- trast, the left hemisphere has narrow atten- tion; is good at deconstructing things into parts; and has an appreciation for static, decontextualized, inanimate structures and abstractions. McGilchrist (2009) summarizes the “two worlds” of the hemispheres in this way:

The brain has to attend to the world in two completely different ways, and in so doing to bring two dif- ferent worlds into being. In the one [that of the right hemisphere], we experience—the live, complex, em- bodied world of individual, always unique beings, forever in flux, a net of interdependencies, forming and re- forming wholes, a world with which we are deeply connected. In the other [that of the left hemisphere] we “experience” our experience in a special way: a “re-presented” version of it, containing now static, separa- ble, bounded, but essentially fragmented entities, grouped into classes, on which predictions can be based. This kind of attention isolates, fixes and makes each thing explicit by bringing it under the spotlight of attention. In doing so it renders things inert, mechanical, lifeless. But it also enables us for the first time to know, and consequently to learn and to make things. This gives us power. (p. 31)

Allan Schore explains that the early-maturing right hemisphere is the locus of attachment formation and es- sentially the gateway to affect regulation later in life—so much so, indeed, that developing an expanded capacity for right-hemisphere processing (an emphasis on right-brained affective skills rather than a left–cognitive bias) is central to clinical expertise (Schore, 2012). In a similar vein, Badenoch (2008) warns therapists to be grounded in right-brain engagement with clients or run the risk of being disengaged from the regulating and integrating influence of right brain-to-right brain connection with clients. She further encourages therapists to widen their window of tolerance, be conscious of implicit vulnerabilities, and develop mindfulness to be present with both the client and self. There is a place for left-brain focus when thinking about specific interventions, but McGilchristas admonishes, the left should remain servant to the right hemisphere as master. 3 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN Left Hemisphere Right Hemisphere

• Less white matter—prioritizing local informa- • More white matter—facilitating faster transfer tion transfer within regions, reflected in an in- of information across regions, reflected in an in- creased ability to localize attention and enhanc- creased ability to hold global attention. ing its self-referring nature. • More sensitive to testosterone. • More reliant on dopamine. • More reliant on noradrenaline. • Superior in the expression of anger. • More intimately connected with the limbic sys- • Highly focused attention to detail; local, nar- tem—identifies emotions faster and more accu- rowly focused attention—sees “parts”. rately than the left and is more involved in emo- • Attends narrowly to the right field of view, the tional expression (except anger). right side of the body, the right side of objects • Open to broad awareness; on the lookout in a (demonstrated in what is known as “hemi-ne- broad and flexible way with vigilance and global glect” following a right-hemisphere stroke). sustained attention—sees the “whole”. • More engaged with the known, the learned, the • Processes information in a non-focal manner. expected; prefers what it knows—“grasps” what • Attends to the peripheral field of vision and the is in focus and has been prioritized. entire left–right visual field. • Efficient when routine is predictable. • Alert and attentive to the new and the nov- • Finds solutions perceived to fit best with current el—awareness begins in the right hemisphere, knowledge or schemas grounding and integrating the experience, before • Processes information in an increasingly focal being further processed in the left on a more de- way that suppresses information not immedi- tailed level. ately relevant. • More engaged in the learning of new informa- • Suppresses the right-hemisphere ability to make tion—explores. distant associations among words or objects • Outperforms the left when prediction is difficult; (and the broader scope of attention in general). more capable of shifting the frame of reference • Takes a local, short-term view. (important for problem solving). • Identifies things by labels rather than context; • Can associate words or objects that are not close- does not deduce from context like the right ly related; can understand unfamiliar (non-cli- hemisphere—in conversation takes things more chéd) metaphor. literally and has difficulty understanding -im • Better able to integrate perceptual processes from plied meaning. Things aredecontextualized and different senses. interpreted by an internal logic. • Longer working memory. • Proficient at abstraction—storing and manipu- • Recognizes broad or complex patterns. lating information in abstracted types, classes, categories, and representations that are imper- • More involved in insight and deductive reason- sonal, fixed, and equivalent. Recognizes objects ing. in a category in a generic, non-specific way, but • Sees things in context and in terms of relation- not the uniqueness of individuals. ships; attentive to context in conversation—vital • Codes non-living things and has an affinity for for a sense of humour. the mechanical. • Can recognize the individual and uniqueness • Better at identifying simple shapes that are eas- within a category, such as recognizing individual ily categorized. faces in the category of faces. • Interested in the utility of things—machines, • Interested in the personal, the living, rather than tools, man-made things. the impersonal and non-living. • Sees one’s own body as an assemblage of parts • Plays a primary role in empathy, the theory of from which it maintains a level of detachment. “mind”, identification with others, social interac- tion, and emotional understanding. • More sophisticated in language and symbol ma- nipulation, with greater vocabulary and more • Connected with the self as an embodied whole. subtle and complex syntax than the right hemi- • Specializes in non-verbal communication, the sphere. implicit, subtle unconscious perceptions, emo- tional shifts, subtle clues and meanings. • Gives an appreciation of depth in time and space.

INTRODUCTION 4 THREE LAYERS

well-known model of the human brain is that described by neuroscientist Paul MacLean as the triune brain (MacLean, 1990). This evolutionary view of the brain describes three main regions in an evolutionary hierarchy: the primitive “reptilian” complex (the brain- Astem), the “palaeomammalian” complex (the limbic system), and the “neomammalian” complex (the cortex). The reptilian complex is fully developed at birth, while the palaeomammalian com- plex is partly developed and continues to develop during early childhood, and the neomamma- lian complex is mostly underdeveloped at birth and is the last part of the triune brain to develop (The Neuropsychotherapy Institute, 2014c). The implications of the model are that the survival instincts of the palaeomammalian complex (the limbic system) are significantly developed during the early years of life, distinct from the later-developing cognitive processes of the neomammalian complex (Rossouw, 2011). More sophisticated contemporary models of the brain and behaviour do not fully support MacLean’s evolutionary model (the brain is much more integrated and seam- less than MacLean’s model might suggest); however, the “bottom-up” perspective of development remains instructive for a corresponding bottom-up therapeutic approach (Rossouw, 2011). This bottom-up approach, as distinct from a top-down, cognitive approach, looks to establish safety through down-regulation of sympathetic over-arousal and activation of a state of parasympathetic security, resulting in increased cortical blood flow to the left frontal cortex for effective activation of cognitive abilities, and limiting “looping” activity within the limbic system (Rossouw, 2011, p. 4) to allow for effective new learning.

The Primitive Brain (Reptilian Complex) This system of the brain is responsible for the most basic survival functions, such as heart rate, breathing, body temperature, and orientation in space. Needless to say, functions like heart rate and breathing are of consider- able importance, and the control mechanisms in this part of the brain are accordingly consistent. It is important to recognize that the functions of the primitive brain will take precedence over other brain activity. For example, if you try to hold your breath (a prefrontal cortex-initiated activity), you will find that as carbon dioxide builds up in your bloodstream, this primitive part of your brain is going to want to take over and make you breathe again. Through training you may be able to increase your re- sistance to the basic urge to breathe, but inevitably you will eventually give in and take a breath. Such threats to survival are first addressed by the primi- tive brain—as illustrated in “peripheral shutdown”, where blood vessels on the periphery of the body are constricted in anticipation of physical trauma—and are prioritized over less vital functions.

5 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN The Limbic System (Paleomammalian Complex) Sometimes referred to as the “emotional brain”, the limbic system is the reactive part of us that initiates the “fight or flight” response to danger. Key areas of interest to psychotherapy are the hippocampus, the amygdala, and the hypothalamus. These form a very fast subconscious evaluation and response system designed to keep us safe. The amygdala is like an early-warning system, with the motto “safety first”—put that safety plan into effect before consulting the executive brain (the new cortex). Picture yourself jumping out of the way of a snake-like object before closer examination reveals it to be just a garden hose in the grass. This is a very important first response, because if it were left to theprefrontal cortex to initiate, for example, a leap out of the way of a bus you had inadvertently stepped in front of, then it might be too late: that evaluation system is too slow. The amygdala makes very fast, albeit not always accu- rate, evaluations and has a fast track from the thalamus (incoming information) through to the hypothalamus that can initiate a stress response to forestall impending doom. The hippocampus plays an equally important role by encoding events in time and space and consolidating them from short- term to long-term memory. Of particular interest to therapists is the case where the limbic system gets the cues wrong: where there is no danger in actuality, but the body is thrown into stress response anyway. From chronic low-grade stress to full- blown panic attacks, a maladaptive limbic system could be the key to what is troubling your client.

The New Cortex (Neomammalian Complex) The new cortex is our “smart” brain, the executive part of our system that is responsible for all higher-order con- scious activity such as language, abstract thought, imagination, and cre- ativity, to name just a few. It also houses much of our memory—not just our biographical memory, but all of the automatic memo- ries essential to talking, writing, walking, playing the piano, and countless other familiar activities (keep in mind, howev- er, that the division of the brain into three large parts is a highly simplified conception: functionally the connectivity between all these regions greatly blurs the boundaries). Of special interest to therapists is the prefrontal cortex—the part of the brain right behind our forehead— which may be slower in responding to incoming informa- tion than the limbic system, but is much more sophisticat- ed in its processing. Such “slow” thinking is the hallmark of our human intelligence. Complex and new thinking on tech- nical, emotional, social, and logical planes takes place here. It is where we can be rational and logical, creative and inventive. But, significantly, theprefrontal cortex can be “hijacked” by the limbic system in the event of a perceived threat (whether imagined or real). Our prefrontal can “go offline” as blood flow is directed to the deeper limbic sys- tem, the first responder in a priority one mission to keep us safe.

INTRODUCTION 6 AMAZINGLY NETWORKED

7 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN he human brain has about 100,000 miles of white matter (bundles of myelinated ax- ons) shooting electrochemical signals Tdown 100 billion neurons through 100 trillion synaptic connections1—we are spectacularly connected! The pattern of neural connectivity in our brains has long captured the attention of neuroanatomists. It can be described at several levels of scale: the individual synaptic connections that link individual neurons, networks connecting neuronal populations, and en- tire brain regions linked by white-matter highways. Mapping the large-scale connectivity within and be- tween brain regions is what has captured the imagina- tion of the National Institutes of Health in the US, which has funded the Human Connectome Project (HCP), a $40 million effort to map the human brain. Each of us has a unique neural map, rather like the uniqueness of our fingerprints, that has been shaped by our genet- ics, environment, and life experiences. It is this map, or “connectome”, that researchers would like to recreate in a virtual space to model the highways and byways of neural connectivity. The connectome is extremely complex and not yet well understood. It is the hope of the HCP that by map- ping many individuals, they will establish a baseline of normal connectivity and reveal how connectivity differs across individuals displaying psychopathology. In a recent study published in Nature Neuroscience (Smith et al., 2015), investigators found a significant relationship between the brain’s default-mode network and personal traits such as IQ, language skills, and life satisfaction. The researchers examined 461 subjects, looking at the correlations between their resting-state functional connectivity and behavioural and demo- graphic measures. They found that the subjects who re- turned high scores for cognition, memory, education, White matter fibre architecture from the Connectome and income level—as opposed to more “negative” meas- Scanner dataset. The fibres are colour-coded by direc- ures such as substance use and aggression—showed tion: red = left–right, green = anterior–posterior, blue = higher connectivity in components of their default net- ascending–descending (RGB = XYZ). work. Such connections included the medial frontal and parietal cortex, the temporo-parietal junction, the Courtesy of the Laboratory of Neuro Imaging and the anterior insula, and the frontal operculum. This cor- Athinoula A. Martinos Center for Biomedical Imaging, relation between attributes of positive life functional- Consortium of the Human Connectome Project. www. ity and underlying brain connectivity was interesting humanconnectomeproject.org indeed—but did higher connectivity between compo- nents of the default network give rise to more “positive” understood, it may become feasible to use this informa- life outcomes, or were there other developmental, rela- tion to assist a transition in the brain toward the positive tional, and environmental factors at play? The research- axis. ers admit that it was impossible to tell from their study. Interestingly, one of the factors that most impacted However, as causal relationships are progressively better the brain toward the negative axis was marijuana use

INTRODUCTION 8 A connectogram showing the average connections and cortical measures of 110 normal, right-handed males, aged 25–36. Image by John Darrell Van Horn—PLoS One: http://journals.plos.org/plosone/article?id=10.1371/journal. pone.0037454

Van Horn, J. D., Irimia, A., Torgerson, C. M., Chambers, M. C., Kikinis, R., & Toga, A. W. (2012). Mapping connectivity damage in the case of Phineas Gage. PLoS ONE, 7(5):e37454. doi:10.1371/journal.pone.0037454

9 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN within the few weeks prior to the study. Such findings left and right hemispheres. The abnormal microstruc- should raise a red flag and highlight the importance of ture of sensory white matter tracts in children with SPD more research to determine how marijuana affects the likely alters the timing of sensory transmission, so that brain. the processing of sensory stimuli and the integration of In addition to mapping the adult brain, the HCP has information across multiple senses becomes difficult or a developmental arm based at King’s College London, impossible. Imperial College London, and Oxford University. It is The imaging results showed a stronger correlation the Developing Human Connectome Project (dHCP), with the direct measurements of tactile and auditory whose aim is to break new ground with the creation of processing taken during the neurological testing than four-dimensional connectomes of early life. The pro- with the parent report survey, which the researchers put ject is looking to map brain connectivity from 20 to 44 down to the likelihood that the direct measurements weeks that will link clinical, behavioural, and genetic in- were more objective. formation to the connectome image. Another impressive tool employed by researchers Massive change occurs in the developing brain of mapping the connectome is the connectogram, a two- a child, and the challenge to map and understand it is dimensional graph used to study the arrangement of substantial. One of the studies the dHCP is currently white-matter fibre in the brain. Based on diffusionMRI engaged in involves 8-year-old children, half of whom data, this circular graph highlights the strength of con- were born prematurely and half full-term, to see if there nections between different regions of the brain. The are any brain network differences between them. Pre- connectogram can display 83 cortical regions within mature babies are at greater risk of neuro-developmen- each hemisphere, and unlike other representations of tal problems, but little is known about how they develop the connectome that require software to display the such impairments. A huge amount of brain develop- three dimensions, these representations can show con- ment in infants occurs just prior to full term, and for nected regions in a flat, two-dimensional graph. that development to take place outside the mother, in The left half of theconnectogram depicts the left the case of pre-terms, may be significant for these chil- hemisphere, and the right half depicts the right hemi- dren. For instance, the fibres forming connections to sphere. The circular graph is further broken down into and from the thalamus, the central exchange centre of sections representing the frontal lobe, insular cortex, the brain, grow extensively during the time period in limbic lobe, temporal lobe, parietal lobe, occipital lobe, which dHCP teams monitor premature babies. A map subcortical structures, and cerebellum. The brain stem of this area during these critical developmental stages is also represented, between the two hemispheres at the could yield valuable insights. bottom of the graph. Each cortical area within the lobes One of the principal investigators, David Edwards, is labelled and features a unique colour that can be used says that there are structures being developed in the last to designate the same cortical region in other figures, so trimester that may underlie conditions like schizophre- that the reader can find the corresponding cortical area nia, autism, and depression, and it is his hope that the on a geometrically accurate surface and see exactly how project can identify subtle differences in connectivity disparate the connected regions may be. Inside the cor- that may predispose some children to mental illness. tical surface ring are concentric circles representing dif- A recent study at the University of California, San ferent attributes of the corresponding cortical regions. Francisco (Chang et al., 2016) demonstrated measur- In order from outermost to innermost, these metric able differences in the connective wiring of children rings represent the grey matter volume, surface area, with sensory processing disorder (SPD) compared to cortical thickness, curvature, and degree of connectiv- typically developing children. The study is the largest ity. The lines in the diagram on the facing page show the ever conducted with child SPD sufferers and the first to connections between regions. The opacity and colour of compare white-matter tracts in the brains of typically the lines represent the strength of the connection. developing children against those with SPD. Our brains are wonderfully and complexly connect- The imaging done with these children detected ab- ed, and the cutting-edge research currently revealing the normalities in the SPD subjects in the white-matter connectome is leading us to highly objective assessment tracts that serve as connections for the auditory, visual, using quantifiable biomarkers. This will not only yield a and somatosensory (tactile) systems involved in sen- more refined and sophisticated definition of pathology, sory processing, including in the connections between but may lead to much more personalized treatments in the days to come.

INTRODUCTION 10 11 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN NEURONS ur genes provide an organizational map for the have more recently been acknowledged to form a com- development of our brains. While some desig- munication network themselves, working in tandem nation of the place and function of neurons is with neurons (Keleman, 2013; Verkhratsky & Butt, Ofixed by coding genes, other functional aspects are sub- 2007). The function of a neuron is determined by where ject to the influence of experience, in the form of non- it is in the brain, how it is connected with neighbouring coding genes that make up the so-called “nurture” part cells, and its individual functional character. Take the of our genetic expression (The Neuropsychotherapy In- analogy of a human individual: our function in society stitute, 2014a). Our genetic blueprint, along with epige- is determined by where we are, who we are connected to, netic (experience dependent) expression of genes and and how we interact with others and our environment memory formation, creates a complex neural commu- (Cozolino, 2014). The anatomist JánosSzentágothai es- nication system throughout the nervous system, which timated that our individual neurons are able to contact is itself a complexity of synaptic/dendritic connections any other neuron via no more than six interneuronal modulated by neurochemicals. connections (Drachman, 2005). This six“ degrees of The nervous system has two main divisions of cells: separation” has become a popular social idea—that peo- nerve cells (neurons), and glial cells (glia). Glial cells ple are connected six or fewer steps from each other in have traditionally been recognized as a kind of support a “friend of a friend” relationship—popularized by the network for neurons, providing many essential func- play and film Six Degrees of Separation by John Guare tions to facilitate the neural network. However, they in the early 1990s and followed by numerous books, films, and TV shows based on the same idea. While there are different types of nerve cells per- forming a variety of functions, it is helpful to consider a generic model that represents the fundamentals of all neurons. The figure to the left illustrates the main components of the neuron (see Chapter 2 of Kandel, Schwartz, Jessell, Siegelbaum, & Hudspeth, 2012, for a comprehensive description of neuron physiology). Neurons communicate by means of two primary processes that have been comprehensively studied: an electrical signal within the neuron, and chemical sig- nals between neurons. Using various chemicals known as neurotransmitters, neurons transmit signals across a very small gap between cells in an area known as the synaptic cleft. Most neurons can send and receive sig- nals by different types of neurotransmitters, and different neurotransmitters work at different speeds (The Neuropsychotherapy Institute, 2014a).

INTRODUCTION 12 The figure below is a radically simplified representa- −67 mV), in a process called depolarization, and “fire”. tion of a synapse. The upper part represents the presyn- Conversely, an increase in the membrane potential (e.g., aptic terminal of one cell’s axon, and the lower part the from −70 mV to −72 mV), known as hyperpolarization, postsynaptic dendrite of another cell. Communication decreases the likelihood of the neuron firing. Depolari- flows from the presynaptic terminal to the dendrites of zations are termed excitatory postsynaptic potentials a neighbouring cell. Dendrites are like the branches of (EPSPs) because they increase the likelihood of firing, a tree that spread out to reach other cells, and are the and hyperpolarizations are termed inhibitory postsyn- main areas for receiving incoming signals (Kandel et al., aptic potentials (IPSPs) because they have the opposite 2012). effect. Neurons have a resting potential somewhere be- Synaptic vesicles are packets of neurotransmitters tween −60 and −70 mV, whereas glia cells measure be- that migrate to special release sites called active zones. tween −80 and −90 mV (Lewis et al., 2011). These packets come to the surface of the presynaptic Ionotropic receptors, such as AMPA, accept transmit- terminal and release their contents, by a process known ters that directly alter the receiving cell’s potential, and as exocytosis, into the synaptic cleft. The released mol- are thus fast-acting, whereas NMDA receptors require ecules diffuse across the gap, and some are received by prior activation of the postsynaptic neuron through an- receptors on the opposite-facing dendrite. The receptor other channel before its ion channel can be opened (see sites on the dendrite bind to specific neurotransmitters, Grawe, 2007, pp. 36–37). Some neurotransmitters will producing either an inhibiting or excitatory effect on the cause the receiving dendrite to become more positively receiving cell. This occurs via an opening ofion channels charged, and others will cause the dendrite to become in the membrane of the cell that essentially produces a more negatively charged. The receiving dendrite “sums” membrane potential in the dendrite (a positive or nega- the incoming chemical signals to arrive at a resultant tive charge within the cell). There can be many different synaptic potential which is then communicated to the types of ions in neurons, but the most common are so- main body of the cell. All of these signals are summed dium ions (Na+) and potassium ions (K+), and it is the at the beginning of the axon, at the axon initial seg- balance of Na+ and K+ inside and outside the cell that ment (Bender & Trussell, 2012). If the resulting charge determines the overall “charge” or potential of the cell. rises above a resting potential, an electrical signal flows This balance is regulated by sodium–potassium pumps down the axon to the presynaptic terminals, causing that continually exchange Na+ inside the cell for K+ the membrane of each terminal to open up channels outside the cell. The more positively charged a neuron allowing calcium into the cell. In turn, this causes the becomes, the more likely it will pass a certain synaptic vesicles to release their threshold of potential (e.g., from −70 mV to chemicals into the synaptic cleft.

13 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN This (albeit simplified) description of the process illus- to “recognize” small, specific elements. These fragments trates the binary nature of neurotransmitters in either are then assembled by more complex neural networks initiating an action potential or not. involving higher-order cells that recognize the assem- The figure on the previous page also shows some bly of the parts. At the top of the hierarchy are cells and of the neurotransmitters being reabsorbed into the networks in the cortex that recognize the “whole pic- presynaptic terminal. Such uptake, via plasma mem- ture”. Once this broader perception is realized, further brane transporters, serves two purposes: recapturing cognitive/affective processes can occur as a result of this the chemicals for reuse, and terminating the synaptic input. The flow of information is not serial but a com- action of the cell (Kandel et al., 2012). Drugs used to plexity of parallel processing that utilizes feedback from inhibit the re-uptake of neurotransmitters will, in ef- various brain regions. There is no neuron that can rec- fect, keep the neurotransmitter in the vicinity of the ognize the complexities of an object like a chair. Only postsynaptic dendrite, so that when receptors are avail- through the summation of complex networks, and with able for that particular chemical, they will bind with it. experience, can we recognize a chair for what it is. Nor Thus, antidepressants are designed to inhibit serotonin is there a single area of the brain that handles a specific re-uptake, keeping it in the synaptic cleft and prolong- mental function in isolation. Just as neurons do not per- ing postsynaptic activation (The Neuropsychotherapy ceive on their own, neural profiles activate and integrate Institute, 2014b). Another process whereby neurotrans- with other regions across the nervous system (Siegel, mitters are removed from the synaptic cleft is degra- 2012). dation, in which enzymes chemically break down the The brain is further organized into functional sys- neurotransmitter and the resulting molecules are taken tems that to some extent can be identified by elements up by the presynaptic terminal. Within the presynap- of the physical architecture of the central nervous sys- tic terminal, the neurotransmitter is then reassembled tem. From a single sensory input neuron, the scale of and repackaged for release once again. Finally, glial cells operations increases to complex hierarchies of neural also remove neurotransmitters from the synaptic space networks that form maps representing input features in to prevent further interaction with the postsynaptic cell. specific areas of the cortex. These complex signals are in turn processed within broad functional systems of Activation Patterns organization according to the physical architecture of the brain. Such functional architecture is currently be- A single neuron does not produce much information ing mapped by the Human Connectome Project (http:// on its own through firing or not firing. Firing entails www.humanconnectomeproject.org). a certain rate, intensity, and resulting neurotransmitter output at the synapse. A single neuron simply responds to specific inputs from other neurons, or directly from the environment in the case of sensory cells. To make sense of the flow of information coming from our sen- sory organs, the neural system is organized into a hi- erarchy of increasingly complex networks. One hun- dred billion individual neurons, boasting and average of 7,000–10,000 synaptic connections each, together contribute to neural network profiles that represent an aspect of brain function (such as perceiving a particular sound), and these profiles integrate with many others to form various functions of our nervous system, some of which are concentrated in different areas of the brain (Siegel, 2012). The hierarchy of neural networks is organized from sensory input to the perception of complex objects/ understandings to even more complex cognitive and affective processes. For example, the “raw” visual data streamed from the sensory input of the retina is recog- Above: Voltage-gated channels found along the axon and nized by neurons in a fragmented fashion whereby indi- synapse of neurons propagate electrical signals down the vidual parts of the scene are processed by neurons tuned neuron

INTRODUCTION 14 GLIA THE OVERLOOKED CELLS The brain contains two major classes of cells: neurons and glia. While both are neural cells, conventionally, the fundamental difference between the two classes has been understood to be that neurons are electrically excitable, whereas glia are non-excitable. Various types of glial cells make up about 90% of all cells in the human brain. In the central nervous system, they are referred to as macroglial or neuroglial cells, and can be categorized into three types: astrocytes, oligodendrocytes, and ependymal cells (Verkhratsky & Butt, 2007). Glial cells have traditionally been regarded as passive supporting cells. The nameglia is from Greek, literally meaning “glue”. Rudolf Ludwig Karl Virchow (1821–1902), who coined the term for neuroscience, thought of glia as a sort of “nerve putty”—a connective tissue void of any cellular elements (Verkhratsky & Butt, 2007). However, today we have a very different understanding of the function of glia in the nervous system. Glia play a vital role in the growth and development of neurons as well as their maintenance and death. Atroglial cells provide the stem el- ements to birth neurons; they compartmentalize neurons, synapses, and capillaries into functional units and help modulate chemical signals between neurons. Oligodendroglia even myelinate the axons of neurons in the central nervous system (as Schwann cells do in the peripheral nervous system), creating faster communication pathways. In 1984, researchers discovered that astrocytes and oligodendrocytes possessed GABA receptors. GABA (Gam- ma-aminobutyric acid) is an inhibitory neurotransmitter that plays a counterpart role to the glutamates, if glu- tamate is the accelerator of the brain, GABA is the brake. A few years later, others found that astroglial cells can communicate over long distances by propagating calcium waves. Since then it has been demonstrated that glial cells can express practically every type of neurotransmitter and can detect the activity of neighbouring neurons. In fact, far from being mere passive, non-excitable glue for neurons, glia form a whole other communication circuit in tandem with the neuronal circuit, the two systems communicating with each other via chemical and electrical signalling. The communication network of glia is what Stanley Keleman (2013) has called the “slow brain”—a support sys- tem for a wide order of connections and cortical growth. This slower system is vitally connected to the voluntary muscular signalling from the body which has a bidirectional effect on the brain and body posture and responses. Much is still being discovered about these cells that make up the greater part of our brain, but what is not in doubt is that there is much more to glia than we ever imagined.

Astrocytes (meaning “star-like cells”) are the most abundant cells in the central nervous system. This simplistic diagram shows an astrocyte forming the scaffolding for a num- ber of neuron axons and a blood vessel. The blue myelin around the axons originates from oligodendrocytes (not shown here).

15 THE PSYCHOTHERAPIST’S ESSENTIAL GUIDE TO THE BRAIN Location Terminology Anterior relating to the front or to the nose end Dorsal relating to the back or toward the surface of the back or top of the head Lateral relating to the sides or away from the midline Ventral relating to the underside or toward the surface of the chest or bottom of the head Parietal relating to the wall of the body or of a body cavity or hollow structure Medial relating to the middle or the midline Basal relating to the bottom layer or base

Planes Horizontal Horizontal sections are the images of the brain you would see as if from directly above or from directly below (the dorsal or ventral perspective) Sagittal The sagittal sections are the side-on views, like the image above Frontal The frontal sections are views from the anterior or posterior perspective Cross The cross sections are views from a rostral/caudal perspective

INTRODUCTION 16