August 25, 2010

Fear, the Survival Emotion

Fear is a pure and fundamental emotion and is preprogrammed in the amygdala. No one has to learn to be afraid but everyone has to update his or her database and learn what new things are frightening. There is an archetypal list of feared objects: snakes, insects, heights, night, and small, dark, damp spaces that may hide creepy, crawly and slimy things. Humans are afraid of capture and imprisonment and fear small, closed spaces that may lack oxygen.

All animals are in danger everyday and yet must carry on with their lives and careers as if they are going to survive. Animals need calm, functional states and emergency programs that focus their attention and mobilize their resources to deal with danger.

Fear and anger are emergency programs. The basic idea is that as soon as a danger signal is detected, all attention is focused on the signal source and consciousness floods with an unpleasant feeling. The feeling is there to make sure you do not try to override the emergency program. The fear program is broadcast into the body via the sympathetic nervous system and the hormone adrenalin, secreted by the adrenal gland. Energy is mobilized through the release of glucose. The heart races and pumps more blood. Respiration accelerates to increase the oxygen content of the blood and all muscle tissue is put on alert.

Fear is preparation for fight or flight. The term “panic” describes fear that is associated with confused or vacillating behavior. Panic is a confused mixture of flight and flight. A movie audience panics when the theatre catches fire. They push and shove, punch and kick as they attempt to flee the building. When crowds panic, people die of suffocation and those who fall down, are trampled under foot.

Misslin describes the neural mechanisms of fear as a hierarchical network with the amygdala as the point of convergence of threatening stimuli. The central nucleus of the amygdala projects to the midbrain periaqueductal gray (PAG), the hypothalamus and the brainstem that coordinate flight, freezing, avoidance reactions, submissive postures, reduced pain sensitivity and autonomic arousal.

Fear is a strong aversive emotion and animals and humans quickly learn to avoid situations that made them afraid. One of the goals of an affluent society is to reduce danger so that average citizen can feel confident that they are going to survive the day. Fear is the opposite of security and a fearful person does not feel confident that he or she is going to be safe. Fear, as a conditioning state, is also generalized to associated signals.

Humans are conditioned to associate fear with a wide range of stimuli that by themselves do not suggest danger. Conditioned fear may last a lifetime if the fear-triggering event was intense or repeated. Phobias are recurrent fears linked to avoidance behaviors that may result from conditioning or arise spontaneously because the fear program is overly active.

Anxiety is a common but fuzzy term that should refer to low intensity fear and to conditioned fear that tends to be recurrent, context dependent and not linked to an obvious threat such as a hungry lion confronting you on the sidewalk. Anxiety also refers vaguely to many kinds of discomforts and dysphoria that all humans experience. An elaborate ethos of urban anxiety has developed in literature and in the curious and sometimes bizarre world of medical-psychiatric descriptions of the human experience. Physicians diagnose anxiety after brief conversations with patients and drug companies promote chemicals for the treatment of “anxiety disorders” as if experiencing life’s discomforts is a medical problem with a medical solution -- eating pills obtained from the pharmacy.

Terror is big fear just as rage is big anger. Terror is the emotion of impending injury or death. Beyond fear and anger terror seizes us as real danger impacts on our body. Terror may expressed by loud noises and wild gesticulating, but we also recognize the possibility of being immobilized - "frozen in terror" when the danger is imminent. Young animals in danger cry out to gain the protection of parents and all animals cry out as they are attacked to warn others.

A 10-yar old girl walking though the bushes in her swimsuit as she left the beach was attacked by wasps and shrieked as she ran wildly on the spot waving her arms in the air and all around her body. Her screams, shrieks and wild gestures brought her mother and other adults quickly to her rescue, but even as they surrounded her, she shrieked all the more loudly. A dog who has been injured will run away in a crouched posture, also shrieking with high-pitched barking and crying – unmistakably terrified.

From Neuroscience Notes by Stephen Gislason available for download from Persona Digital Online

August 18, 2010

Cognition New Definition

There are a large number of problems in human cognition that limit our ability individually and in groups to evaluate information and make the right decisions. Some of the problems begin with the careless use of language; examples are wrong names for things and events, lack of precise definitions, use of inappropriate metaphors, self-aggrandizing claims, illogical arguments, and deliberate lying. In Neuroscience Notes I have attempted to create a descriptive language that really works. Here is how a description of cognition begins:


“Here is Edward Bear coming downstairs now, bump, bump on the back of his head, behind Christopher Robin. It is, as far as he knows, the only way of coming downstairs, but sometimes he feels there really is another way, if he only could stop and think of it.” A.A. Milne, Christopher Robin

The term cognition is a general category, not well understood. Cognition refers to processes that allow humans to know what is going on out there and how to respond. You can begin to understand cognition by examining how humans find food, eat and move in a coherent spacetime frame. The brain contains feature matrices that create meaningful connections between the body inside and the environment outside.

Humans have an innate sense of spacetime. Maps of spacetime can be found in the cerebral cortex. Sensory information flows into these spacetime maps and motor output flows out. Our speech grows from movements in spacetime and communications with sounds. We often use metaphors of movement in descriptions of everything that happens. Humans act on the world through praxis or skilled movements.

The term, thought, is often used as a synonym for cognition but this is incorrect. A giant leap in understanding cognition is realizing that talking is thinking. We talk to each other and talk to ourselves. Thinking is selftalk, listening to others, speaking with others, reading and writing. Speakers and listeners form thinking groups and in the best case arrive at a common understanding of what is going on out there.

Selftalk is the only conscious mode of thinking and is so implicit in consciousness that “thinkers” fail to identify selftalk as their primary mode of thinking. Thinking is, therefore, storytelling, a form of argument. If you want thinking to mean something else such as processing information, solving problems, making decisions or creating new ideas, then “thinking” is not a voluntary process that occurs in consciousness. Cognition involves many abilities that existed before language developed.

Cognition is rooted in a deep and innate understanding of how the world works. Cognitive structures in the brain are built from raw materials such as sensation, movement and emotion. Deep cognitive processes are about recognizing the relationships among events, making decisions, sequencing in spacetime, and problem solving. Nonverbal “thinking” is revealed in tool making, tool use, mimetic behavior, actions and simulations. Gestures, drawings, models and constructions are independent of language and proceed spontaneously in the brain.

The best way to problem solve is to examine the problem closely, talk about, write about it, draw pictures and diagrams, make models and then wait. Each human has a built in query system and a problem-solver that operates in its own way, on its own schedule and delivers solutions to consciousness when it is ready. Sometimes selftalk is part of the problem-solving process but often talking is not required. The solution to a problem or a creative new idea arises from an unknowable process, as a gift. I wait hours before I understand new information or can solve a problem. Big problems may take weeks or months to solve. New insights and paradigm shifts may occur after many years of struggling with wrong notions. This book consists of a long series of spontaneously arising ideas that I record. Sometimes, a new idea makes old ideas obsolete and I have to change an entire text to accommodate the new understanding. The process of writing requires selftalk rehearsal and constant revision that is more or less spontaneous and evolutionary.

Meaningful conversation is a common method of “thinking”, but repeating clich├ęs, repetitive stories and case-making conversations are not recommended. I heard Marvin Minsky, then the guru of artificial intelligence at MIT, claim at a digital arts conference many years ago, that he hated to repeat himself. Subsequently, I heard him repeat this idea at least twice. My guess is that Minsky made this claim numerous times over several decades. Life is a repetitive affair and most humans copy and repeat what they and others say and do with little or no modification over a lifetime. Minsky’s aversion was to humans who repeat themselves mindlessly and tediously, people who annoy and obstruct smarter, more progressive humans who are interested in continuous learning and evolving understanding.

From Neuroscience Notes by Stephen Gislason. Download eBook from Persona Digital Online.

August 15, 2010

Anger, the Dominant Emotion

Emotions are Social Behaviors

Emotions are visible and obvious behaviors that communicate states of arousal and activation. Emotions are body language and can be read with little or no learning and from a distance. Humans can read emotional body language across cultures and can read animal emotions with little difficulty. Feelings are subjective, inner bodymind state that may not be apparent to an outside observer.

Feelings are the inner states that are produced along with emotions but may be separate from emotions. A feeling is the for-me-ness of an experience. Feelings are often not distinct and are difficult to describe. Emotions sometimes express, or are associated with feelings but feelings have a life of their own and may be independent of or incongruent with emotions.

Behavior in human groups is regulated by displays of status, intentions, body states, needs and distress. Emotions are obvious displays that add dynamics to human interactions. The face is the bulletin board of emotions, complemented by sounds, head movements, arm and hand gestures. The goal of polite society is to maintain a neutral state with little or no display of emotions.


Anger is the dominant emotion and displays of anger disrupt social gatherings. Polite humans learn proper conduct that minimizes conflict. Elaborate polite greeting and parting behaviors are required. The interaction of humans in public spaces is controlled by a variety of rules, devices and enforcement that minimize the opportunity for anger to emerge. When one person becomes angry in gatherings, others act to minimize the tendency for anger to lead to fighting. The primary dynamic of dominance and submission is always at work when humans interact. Emotions are the outer language of dominance and submission. Feelings represent the evaluation of dominant and submissive behaviors as monitor images in consciousness.

Anger is expressed by noisy displays and attacks. All human interactions are influenced by the threat of anger and much brain power is devoted to anger management. Anger is an old animal program that emerges from the reptilian brain - the lizard rises up hisses and attacks. The human rises, threatens with gestures and then, optionally, attacks. Anger energizes aggressive behavior and is both protective and destructive at the same time.

Anger, viewed as a program, has several stages expressed at different levels of intensity. Often anger intensity escalates from threatening behavior to all-out attack. The victor in a dispute intimidates his opponent who either submits with conspicuous supplication behavior or is attacked. Anger progresses to fighting. Combatants are injured or killed in a fight. Fights leave body scars, accounts to be settled and long-lasting memories that facilitate future fighting. Anger is a pure and fundamental emotion that is preprogrammed in the amygdala.

Human children get angry as infants when they are hungry or uncomfortable and do not achieve immediate satisfaction. The term “frustration” refers to an angry outburst that arises when seeking behaviors are blocked short of achieving the desired goal. Infants and young children demand instant gratification of their needs and are easily frustrated. An essential part of social maturation is learning to tolerate delays in gratification of basic drives. Children get angry often during the day and sometimes display alarmingly violent thoughts and behaviors. Anger is a daily feature of sibling interaction and is common in unsupervised children's play.

Anger is a daily experience in the lives of most adult humans. In the USA, psychologists report that the average person gets angry 10-14 times a day. Anger is endemic both at home and at work. At work, common anger triggers are unfair performance appraisals, favoritism, and sexual harassment. One anger management advisor teaches that “No one has a right to get angry; it is delusional to think that anger can be effective.” Cornell et al found that anger is a predictor of aggression among incarcerated adolescents. Self-reported anger scales were administered to 65 incarcerated male adolescents and higher scores were predictive of subsequent physical and verbal aggression.

To become a useful and acceptable member of society each person must learn to avoid making others angry and must lean to inhibit their own anger. The term “violence’ is often used to describe displays of anger. Other terms are invented to describe angry displays in specific places and circumstances such as “road rage” or “airplane rage”.

I was standing in a post office line when a three-year-old boy, nicely dressed in a suit, lifted a shinny silver foil package from a shelf at his eye level. His mother took the package from him and replaced it. In seconds, he was transformed into an angry demon. The whole anger program emerged almost instantly with screaming, running on the spot, shaking his head and torso. His mother looked embarrassed and confused but had the presence of mind to give back the package. The boy became calm immediately and within two minutes, replaced the package himself with obvious satisfaction.

The three-year-old boy exemplified one of the most troubling aspects of human behavior. Anger turns on and off quickly. The triggers for anger are many and, often, the emotion is disproportionate to the triggering event. The angry little boy could be described as displaying “post-office rage.” The post office syndrome is amplified in stories that appear on the news every day. An angry human can become quickly and inappropriately destructive and injures or kills other humans.

We often call children’s anger a “temper tantrum” and experienced parents learn to tolerate tantrums as a common response when the child is frustrated and tired. The three-year-old boy in the Post Office cannot say to his mother: ‘Please mother, let me examine the foil package because that is what three-year-old children are supposed to do. I have to complete this transaction with the world in order to feel that I am doing a good job and have the right of self-determination. When you take the package from me, my whole being is threatened and I have to oppose you with all the might I can muster. “

Anger is not derived from any other emotion as too many psychologists have claimed. Anger is not a fluid that is stored in the brain as Freudian psychodynamics suggests. Freud’s idea has become one of the most popular and persuasive wrong views of anger, that anger is an energy that accumulates, stored somewhere in the brain and has to be released from time to time. Some imaginative folks even believe that disease is caused by stored anger. However, there is no evidence of any kind that anger accumulates anywhere in the body or brain. Anger is a program in the amygdala and when it is turned on, it is really on; when it is turned off, it is really off.

Busman et al at Iowa State University concluded that expressing anger “to release your anger” increases rather than decreases aggressive behavior. Self-help books, support groups and self-styled therapists have promoted punching pillows and other forms of anger expression with the promise that this practice will reduce conflict. Angry therapists have sometimes justified challenging and abusing their clients, claiming that releasing anger was therapeutic. They are wrong. Anger researchers found that articles and books that recommended anger catharsis did persuade their student subjects to favor punching pillows and punching bags as a form of catharsis, but actually produced angrier students. Expressing anger is not cathartic, does not relieve “psychic pressure” and does not make you a better person. Expressing anger repeatedly facilitates anger. The more you practice being angry the better you become at being angry. If you want to become an antisocial, angry person, practice being angry.

Social mammals have developed anger protocols that permit angry outbursts but limit the damage done. Predators, sharing a kill, will growl, snap and jostle each other for a bigger share of the catch, but a pre-established pecking order will usually prevail and minimize the harmful consequences of the competition for food. If every competition led to a serious fight, there would be few survivors. Some members of a group must submit to minimize conflict; anger-submission is a behavioral dyad with survival value. Without submission, anger escalates into aggressive conflict leading to injury or death.

Modern diplomacy is an alternative to armed conflict and continues to use the anger-submission dyad. The art of diplomacy is to speak softly and carry a big stick. The stick is often an implicit threat that motivates a reluctant negotiator to compromise. Diplomacy fails when anger escalates and submission fails. When diplomacy fails, humans fight. Fights tend to have their own rules and suspend rules that tend to promote rational and humane behavior. If diplomacy fails at the level of competitive and hostile nations, fighting is transformed into war by the application of rational and sustained, but not humane group activity.

Rage is the tornado of emotions, a full-volume, high energy anger that overrides all constraint and control. Rage is physical, brief, violent and destructive. Raging humans destroy property, injure and kill others. Rage is produced by maximal activation of flight and fight systems, rapid heart rate, rapid breathing, high blood pressure, flushing and hypertonicity of all skeletal muscles. Maximal muscle strength is achieved in rage and amazing displays of destructive energy are characteristic of rage attacks.

From Neuroscience Notes by Stephen Gislason MD. You can download an eBook from Persona Digital Online.

August 13, 2010

Introducing the Brain: from Neuroscience Notes

Sense, decide, act and remember

The right way to proceed with the description of science is to begin with a foundation of true statements that are supported by evidence. The challenges are many. In Neuroscience Notes, I begin with statements that have general validity and introduce terms and concepts from neuroscience that every reader must learn. The statement "Nervous systems allow organisms to sense, decide, act and remember" is undeniably true. If you begin to understand these four domains of brain function, sense, decide, act and remember, then you accelerate beyond common language where confusion prevails.


Neuroscience is the broad inquiry into the structure and function of animal nervous systems. Neuroscience begins with the consideration of how the simplest animals on the planet interact with their environments. A deep sense that develops in humans who study and understand life is that every creature that lives on planet earth shares common properties. Nervous systems allow organisms to sense, decide, act and remember. These properties begin as simple devices and evolve into sensing strategies that are increasingly complicated, more accurate and more effective. A complex device such as the human eye is easier to understand if you already understand a simple device such as light detecting pigment spot in a snail. Thus, it makes sense for a neuroscientist to study all animals and to assume that principles learned about older, simpler animals can be applied to newer, more complex animals such as humans.

The brain is the organ of the mind. Anatomists have described the brain in terms of our evolutionary path. We have old-age, middle-age and new-age parts, each with different properties. A neuroscientist, Paul McLean, suggested that the human brain could be viewed as three systems of different ages - an old reptilian brain, a middle (early mammalian) brain, topped off with a new, advanced brain, the neocortex. The neocortex allows us to learn, adapt and create new modes of behavior.

New babies are not born with the new brain programs. Old programs are built into us and need not be learned. Old programs include some of the most negative qualities – predatory and territorial aggression, anger and fighting, for example. Some of our most positive qualities are also innate such as the tendencies to mate, bond and form social units with altruistic features. The old brain remains in control of our bodies and our minds.

The infant cerebral cortex is folded in an adult pattern but has one third the total surface area. Hiila et al compared cerebral cortices of 12 healthy infants born at term with 12 healthy young adults and demonstrated regions of lateral temporal, parietal, and frontal cortex expand nearly twice as much from infancy as other regions in the insular and medial occipital cortex. They suggested:" This differential postnatal expansion may reflect regional differences in the maturity of dendritic and synaptic architecture at birth and/or in the complexity of dendritic and synaptic architecture in adults. This expression may also be associated with differential sensitivity of cortical circuits to childhood experience and insults. By comparing human and macaque monkey cerebral cortex, we infer that the pattern of human evolutionary expansion is remarkably similar to the pattern of human postnatal expansion. We hypothesize that it is beneficial for regions of recent evolutionary expansion to remain less mature at birth, perhaps to increase the influence of postnatal experience on the development of these regions or to focus prenatal resources on regions most important for early survival. "

Whatever we value about civilized human existence - culture, knowledge, social justice, respect for human rights, and dignity must be learned anew and stored in each person's neocortex. Information always comes with noise, that extra, confusing, unnecessary stuff which burdens our brain not with the task of remembering but of forgetting. There is so much we do not want to remember that it is a wonder that a modern citizen manages to cope with information overload. Information noise interacts with molecular noise, useless or bad chemicals that flow through the brain from food, water and air.

Neuroscience views minds as manifestations of the living processes found in brains. Brain science does not "explain" mind, or consciousness, but does give us strategies for understanding the properties of mind. Neuroscientists have made rapid progress in the past few decades and some of them are asking the same sorts of questions that only philosophers used to ask. The difference is that neuroscientists are sometimes able to ask more specific questions that may lead to more insight into the basic principles of the human experience. Neuroscientists are motivated and equipped to find real and practical answers to philosophical questions, leaving philosophers behind in an anachronistic philological niche, repeating discussions of what philosophers said hundreds to thousands of years ago. This is not to argue that all neuroscientists are philosophers or that all neuroscientists understand the human mind, since many are focused on highly specialized tasks that reveal little or nothing about how the whole system works.

In the year 2000, the Nobel committee awarded the Prize for Physiology or Medicine to three neuroscientists, Arvid Carlsson, Paul Greengard, and Eric R. Kandel. Their research revealed basic processes at work in animal brains. Carlsson identified dopamine as at brain neurotransmitter. Greengard revealed the molecular cascade triggered inside neurons by the dopamine signal. Kandel realized that the molecular basis of learning should be studied in simple animal systems as the basis for understanding learning in human brains. He spent many years studying the nervous system of Aplaysia, the Moon Snail. His 1976 text “The Cellular Basis of Behavior” can be considered a classic in the study of nervous systems.

Kandel stated: “All animals are faced with the universal problems of reproduction, adaptation and survival. An important assumption of biology is that phylogenetically diverse organisms share similar sets of solutions to these problems. Since in the end we are concerned with identifying biological principles applicable to human behavior, the invertebrate is a convenient but necessary substitute for people. Although a solution found in invertebrates may not be the only mechanisms for a given problem, the solution is likely to be a common mechanism that might be found as well in vertebrates, including man.”

Neuroscience would say that consciousness is produced by brains and can be destroyed by brain lesions and brain death. Consciousness is a property of the old, middle, and new brains working together, but if old brain structures are damaged, consciousness is obliterated. If the neocortex is damaged, consciousness remains, but specific memory content, sensations, and skills may drop-out.

Cognitive philosophers increasingly provide commentary on what neuroscientists are doing and saying. Tim Smith stated that:” A large number of articles and books have monitored the growth of Cognitive Neuroscience… motivated by a feeling that "things are about to be understood." As advances in imaging has added new potential to the neurosciences, so too neural networks and computational models have added new power to the cognitive approaches. Neural networks are tools that enable researchers to "probe how high-level functions such as perceiving, attending, learning, planning, and remembering emerge from the massively parallel neural architecture of the brain."

Michael Gazzaniga stated that "Psychology departments across the country have realized that they've got to get into brain science- in humans and not just rats…. universities should be looking for people who can liaison with clinicians working with brain-damaged patients, with people doing brain imaging, with the computer jocks". Cohen remarked that research efforts have not been integrated. Integration requires uniquely trained individuals, people who can understand a number of disciplines. Since smart, humans with diverse knowledge and skills are not produced by university education, Schneider observed that finding staff with the right blend of cognitive psychology, neurophysiology, computational modeling, and brain imaging.... is a tall order. Gazzaniga suggested that the work of figuring out the brain will take another 200 years and I believe he is underestimating the task. If you want to know exactly how the brain works, the investigation is likely to go on for thousands of years. Humans tend to be impatient. They overestimate their accomplishments and underestimate the extreme complexity of natural phenomena.

In their introduction to advances in neurotechniques. Gray and Chouard stated:" It is an exciting time to be a neuroscientist. The experimental landscape has changed markedly over the past few years with advances in molecular genetics, optogenetics and functional imaging. Neuroscience research was once dominated by anatomical techniques. But, with the advent of electrophysiology, and subsequently molecular biology, anatomical labelling techniques were eclipsed. Now, improved anatomical methods are experiencing a renaissance, thanks to the ability to deliver molecules in a cell-type-specific manner, with advances in imaging methods, together with electrophysiological technique, makes it feasible to study the relationships between specific neural circuits and particular behaviours in rodents. Neuroscientists are also poised to benefit from systems-based approaches to data collection and analysis but lag behind other researchers, such as tumour biologists, in implementing these strategies. Using the results from such approaches to direct hypothesis-driven work and improve the design of these experiments could focus efforts on candidate genes in the genetic network associated with disease. "

From Neuroscience Notes by Stephen Gislason MD. Available for download at Persona Digital Online.

August 12, 2010

For Me Ness from Neuroscience Notes

I believe that every educated person should understand something about neuroscience. The problem is that articles and books about the brain have become as popular as they are misinformed. Each writer appears to attach to one or two ideas out of context and then improvises on their own pet theories and speculations. For many years, my goal has been to develop a coherent story of animal and human brain function that is accessible to intelligent readers. For any science to make sense, you have to build on a solid foundation of basic principles and well established facts. Since the brain is the organ of the mind, the study of neuroscience is really a study of everything; everything we experience and know is in the mind.

I will dedicate this blog for the next several weeks to topics taken from my book Neuroscience Notes. I would, of course, prefer that everyone would read, study and discuss the entire book.


There is a tension in us that will never completely go away. Feelings are polarized from negative (dysphoria) to positive (euphoria). Feelings are mixed with cognitions to arrive at the formeness or the salience of experiences. Negative feelings are associated with aversive behaviors that encourage us to avoid illness, injury and death. Positive feelings are associated with seeking behaviors that encourage us to find good food, clean water, safe places to rest and nice to people to share all of the above.

Composite feelings such as tenderness and concern lead us to consider the feelings of others and encourage us to share advantages that bring happiness. Feelings are conscious experiences that are real and important but have the elusive quality of all inside experiences – only I experience my feelings. You can guess my feelings by watching my behavior or hearing my description of what it feels like inside. Feelings vary from a low rumble in the mix to the turbulent inner state associated with all-consuming emotions such as rage.

Feelings tend to be short-lived; minutes rather than hours or days. Humans often cannot localize the source or the effects of their feelings and tend to blame others whenever they are not feeling well. Humans tend to become emotional when they are not doing well. Feelings are evanescent and can change abruptly. Criticism, an angry remark or an insult can switch a happy person to an angry person in seconds. An overly sensitive person may walk away from an argument in deep despair and may want to die. Drastic “thinking” is common. Pessimistic, sometimes nihilistic, thoughts are attached to the ancient feeling of dread; the occasion is usually some threat to your status in a social group.

Humans are usually tuned into behaviors that suggest other people have feelings. The sense of other people’s feelings is described as “empathy” A sensitive person will often pick up subtle signals that that are not conscious or explicit.

Some people talk about “vibes” psychics see “auras” and ordinary folk have “hunches and intuition” or just have feeling responses to others. You might meet a new person and walk away saying “I don’t know what it was… but I didn’t feel comfortable talking to that man.”

Insensitive people are not aware of others people’s feelings, are socially inappropriate and can be dangerous. Humans who routinely hurt others tend to have little or no empathy and injure or kill others with no hesitation or remorse. Even sensitive people who are capable of empathy have a range of sensitivity and can be remarkably kind and responsive to some and insensitive to others.

You can download the eBook version of Neuroscience Notes from Persona Digital Online. The author is Stephen Gislason MD. Published 2010.

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