Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_123_библиотеки_им_акад_М_И_Перельмана
.pdf
CHAPTER 17 Thinking About Intelligence, Language, and Lateralization 331
Losing language from neural dysfunction
Damage to Wernicke’s area causes a specic language loss called Wernicke’s apha-
sia. An aphasia is a loss of ability to either understand or produce speech, or both,
due to some brain damage. Wernicke’s aphasia is associated with impaired lan-
guage comprehension. People with damage to this area have great diculty
understanding speech. They can produce speech that has a normal-sounding
rhythm, but the speech itself is almost meaningless (also called uent aphasia).
They also have diculty identifying complex nonverbal sounds like jangling keys,
machine noises, and animal vocalizations.
Damage to Broca’s area reduces speech production, depending on the extent of the
damage. Extensive damage to Brodmann areas 44 and 45 may almost totally elim-
inate speech, such as Broca’s famous patient who could only utter one word,
“tan.” Less extensive damage results in people being able to utter only short sen-
tences with simple words. Broca’s patients also have diculty understanding
longer, multisyllabic words, and sentences in passive voice, such as “The apple
was eaten by the boy.”
FIGURE17-2:
Language areas
of the brain.
© John Wiley & Sons, Inc.
https://t.me/med1917
332 PART 3 Understanding Perception and Cognition
Examining visual processing asymmetries
The right hemisphere of the brain has specializations for visual processing, and
these are well documented. The ability to recognize faces, for example, is highly
dependent on the right fusiform face area in the right medial temporal lobe. This
is a high-order visual processing area in the ventral pathway (refer to
Chapter13).
Damage to the right parietal lobe results in hemi-spatial neglect, in which patients
ignore objects in the left visual eld. Men with such damage may not shave the
left sides of their faces, for example, or they may hit the left side of the garage
when driving a car into the garage.
The left hemisphere represents knowledge based on rules, and the right hemi-
sphere represents knowledge based on examples. The left hemisphere represen-
tation of a room would consist of relationships that can be put in words, such as
“The lamp is in the right-rear corner, and the table is in the front middle.” The
right hemisphere representation would be more like a literal image, not some-
thing you could easily verbalize. Expressing this inner image in language requires
sending the right-brain image to the left, language-capable hemisphere.
Considering where consciousness lives
Helen Keller had a brain infection that caused her to lose her vision and hearing
when she was just 19 months old. She gained the ability to communicate with sign
language at around age 7. By her own accounts, Keller was largely unconscious
before she was able to communicate.
Many people suering from epilepsy have had their corpus callosum sectioned to
prevent seizures from spreading from one hemisphere to the other. In these peo-
ple, when stimuli are presented to the right visual eld (left brain hemisphere),
they can verbally identify and discuss the stimuli quite normally. However, they
have little ability to verbally identify or understand objects when stimuli are pre-
sented to the left visual eld (right brain hemisphere).
The reason for these dierences in consciousness is clearly linked to language, but
not to any known specic neural circuit in the left hemisphere that does not exist
on the right. Thirty percent of left-handers and a small percentage of right-
handers have language in the right hemisphere. Severe damage to the left
hemisphere or even its removal in infants can result in normal language located
in the right hemisphere as well.
https://t.me/med1917
CHAPTER 17 Thinking About Intelligence, Language, and Lateralization 333
Consciousness sits on top of a great deal of nonconscious brain processing. Aware-
ness, like animals can have, can exist without consciousness. But unique human
consciousness goes beyond awareness. It’s a symbolic representation system.
Consciousness allows humans to express and manipulate complex thoughts, both
externally (through verbal language) and internally (by thinking). Consciousness
is a process, not a place.
Dening Intelligence
Most people generally think of consciousness (as we discuss in the preceding sec-
tion) as being unique to humans. But intelligence— like awareness— is some-
thing that’s attributed to animals. People say their dogs are intelligent, and robots
are said to be intelligent machines. (Heck, we even have smartphones!) One way
to gure out intelligence is to look at examples of what’s considered intelligent,
which is typically intelligent behavior.
Intelligence is nearly always identied with adaptive behavior. That means perceiv-
ing or inferring information, retaining it, and optimizing what one does in a com-
plex, changing environment. Reexive behavior, however complex, is built into the
genetically determined nervous system. This behavior generally happens without
your thinking about it and isn’t thought of as intelligent— although you could
make a case that evolutionarily adapted behavior, such as refusing to eat some-
thing that tastes good but has produced illness in the past, is intelligent. A similar
comparison could be between machines that are programmed to do things, versus
those that learn to do things.
The following sections provide more details about dierent types of intelligence.
Math, language, and social intelligence
How else can intelligence be dened? Intelligence is the capacity for understand-
ing, logic and reasoning, learning, self-awareness, critical thinking, problem-
solving, and creativity. Many theories of intelligence have been developed over the
last century. Many psychologists agree that there are dierent types of intelli-
gence. The broad range of denitions can pose problems in determining which
aspects of intelligence are being assessed by any given method. The tendency for
an individual’s intelligence score in dierent domains to be correlated across a
variety of tests is represented by Spearman’s g factor (IQ) and its derivatives.
https://t.me/med1917
334 PART 3 Understanding Perception and Cognition
Consider the following about the dierent types of intelligence:
»
Logical/mathematic intelligence: This kind of intelligence refers tothe
ability to reason, think logically, perform mathematical calculations, and
recognize connections.
»
Language intelligence: This kind including vocabulary and the ability to
understand written passages is a left-brain skill. Even though executing
rules-based tasks and mathematical procedures may also be a left-brain skill,
translating real-world situations into mathematical form requires visualization
and other right-brain abilities. Virtually all assessments of intelligence
recognize these kinds of dierences.
»
Social intelligence: Also referred to as interpersonal intelligence, this kind has
received a lot of attention recently. Social intelligence is the adaptive ability to
understand the intentions of others and alter your own behavior to acknowl-
edge and use social situations to your advantage. Social intelligence may have
a neurobiological basis in the orbitofrontal cortex and amygdala system.
Social intelligence can be low in people who otherwise have high verbal and
math intelligence, such as in some kinds of autism. Social, but not IQ test,
intelligence may also be lost with orbitofrontal damage.
»
Other types of intelligence, such as musical and athletic, have been assessed
in schemes such as Gardner’s multi-intelligence list of eight basic components.
People with savant syndrome have exceptionally high aptitude in one domain,
such as mathematics or music but signicant impairments in other areas of social
or intellectual functioning. Most individuals with savant syndrome have a devel-
opmental disability such as autism spectrum disorder or have experienced a brain
injury.
Intelligence components for decisions,
abstract thinking, problem solving
Many people who study intelligence consider what’s called meta-cognition or
meta-intelligence to be its highest form. Meta-cognition is an executive function
that refers to self-reective capabilities, knowing one’s own strengths and weak-
nesses, and being able to predict one’s reactions to situations.
Meta-cognition is composed of meta-components used in problem solving and
decision-making. These meta-components use what are called performance
components to carry out cognition. Performance components are like IQ domains,
basic skills and processes for adaptive modication of behavior, including percep-
tion, long-term memory, language, and spatial abilities.
https://t.me/med1917
CHAPTER 17 Thinking About Intelligence, Language, and Lateralization 335
For example, Gardner’s bodily kinesthetic intelligence domain entails the ability
to control body motions skillfully. Clearly many animals have the ability to do
this— in many cases, far better than humans. However, animals don’t have the
meta-cognitive ability to reect on and reason about body movements or invent
entirely new body moves by reasoning. Only humans do.
Meta-cognition capabilities are associated with the human prefrontal cortex. This
area of the brain develops relatively late, with axons not being fully myelinated
until the late teenage years. Much of what IQ researchers mean by meta-cognition
is embodied in the common idea of wisdom.
Investigating intelligence factors
Two factors that may indicate intelligence are the size of the brain and the speed
at which the brain can process information.
Brain size
The brain takes a lot of energy for the body to maintain. In humans the brain con-
sumes about 20 percent of our total metabolism, but it accounts for only about
2 percent of our body weight. Brains, like other organs, scale up with body weight.
The brains of whales can reach 18 pounds, elephants 11 pounds, and dolphins
3.5 pounds, whereas human brains average just over 3 pounds.
However, some very large animals, such as dinosaurs, lizards, and alligators, have
relatively small brains compared to mammals as a function of body size. Across
species, brains became generally bigger in mammals than nonmammals, and in
primates compared to other mammals, and most recently, in humans compared
to other primates.
Most of the increase in primate and human brain size is in the neocortex. For a
given size, species that appear to behave in an intelligent way tend to have larger
brains than those species that don’t. But, within a species, the correlation is weak
between intelligence and brain size.
Processing speed
The other brain characteristic frequently mentioned as a foundation for intelli-
gence is processing speed or processing eciency. This is particularly true for
processing perceptually complex stimuli. Processing speed is related to how fast a
person can execute a sequence of mental operations to accomplish some task.
https://t.me/med1917
336 PART 3 Understanding Perception and Cognition
Neural processing speed as it relates to IQ dierences appears to be due to a vari-
ety of genetic factors. Individuals who score high on IQ tests tend also to score
higher in speed of neural processing. High processing speed may be a cause of
high IQ, or partly a result of it.
Understanding Consciousness
Consciousness is the 800-pound gorilla in the rooms of neurobiology, psychology,
and philosophy. Many researchers carry on their research without acknowledging
consciousness directly, but it’s always there. Perhaps only one species on earth
has consciousness, and virtually every typical member of that species has it fully.
What can today’s neurobiology say about it?
Consciousness is the state of realizing and understanding your surroundings and
internal existence. Despite centuries of debate and analyses by scientists and phi-
losophers, consciousness remains familiar, mysterious, and controversial.
Without denying the existence of visual, auditory, and other sensory imagery that
is nonverbal, most human consciousness is associated with internal verbalization.
All humans conduct a running internal dialog that explains current reality, recalls
past situations, and plans for future ones. Did language cause consciousness? The
following sections discuss the potential role of language in consciousness.
Learning language instinctually
Prior to the age of about two years, human infants behave much like their closest
relatives, the chimpanzees, though they’re less competent in motor activities
such as moving and climbing. Then the language explosion begins! When humans
are exposed to language, the language ability generally develops in the same
ordered progression. Humans apply labels and sentences to objects in the world,
to their relations, and to actions involving these objects— all without really get-
ting clear instruction. This is what the American linguist Steven Pinker called the
language instinct.
The language instinct is ubiquitous in human brains and evolved rapidly in the
past six million years. Imagine how strong the selection pressure must have been
to master speech. Neuroscientists believe that the brain that evolved such a strong
language instinct must have been compelled to classify and name objects, rela-
tionships, and actions.
https://t.me/med1917
CHAPTER 17 Thinking About Intelligence, Language, and Lateralization 337
Developing internal language and
consciousness
The need to name things was most likely used for person-to-person communica-
tion. What must have been invented next was subvocalization (talking to yourself
in an inner voice without actually speaking). This may have occurred when an
early hominid was about to speak but was interrupted. A brain that has the need
to name objects and see object relations and actions in sentences has an internal
monologue— that internal monologue is consciousness.
Inner-speech consciousness was mankind’s rst digital invention. Speech is digi-
tal because it’s made up of a nite number of sounds (in each language) that are
put together in groups to make words, with a small number of words forming
sentences. Although you can modify the meaning of speech with your tone or
style, the digital nature of speech means that every person can agree on a nite set
of denitions and arrangements that everyone can understand. Internal speech is
a running narrative explanation of reality— past, present, and future.
Theorizing consciousness
One big question is how consciousness arises in the brain. Before the 1990s,
understanding consciousness was more of a philosophical quest than a neurosci-
ence one. In the 1990s Dr. David Chalmers distinguished between the easy and
hard problems of consciousness:
»
The easy problem addresses the functions and behaviors associated with
consciousness and the neural correlates of consciousness: what brain regions,
neurons, and neuronal activities are required. One fact that most neuroscien-
tists agree on it that there’s no one location in the brain where consciousness
takes place nor is a single population of neurons responsible.
»
The hard problem is the problem of explaining why and how humans have
qualia-phenomenal experiences. It’s the problem of why and how humans
have personal, rst-person experiences, often described as experiences that
feel “like something.”
Many theories about the biological and physical basis of consciousness have been
developed with much controversy and debate in the eld. A central debate per-
tains to whether activity in the prefrontal cortex plays an essential and/or central
role in consciousness. Here are some current theories:
»
Global workspace theory (GWT): Developed by Dr. Bernard Baars and
championed by Dr. Stanislas Dehaene, this theory proposes that the brain’s
https://t.me/med1917
338 PART 3 Understanding Perception and Cognition
prefrontal cortex, which controls higher order executive functions, acts as a
central controller that collects and prioritizes information from sensory and
other input.It then broadcasts the information to other parts of the brain that
carry out tasks. This selection process is what is perceived as consciousness.
It relates consciousness to cognitive abilities such as perception, attention,
memory, and evaluation. GWT is a top-down explanation and predicts
all-or-nothing responses.
»
Integrated information theory (IIT): Proposed by Dr. Giulio Tononi, this
theory proposes that consciousness arises from the interconnectedness of
brain networks. The more neurons interact with one another, and the more
complex the resulting network is, the more a being feels conscious— even
without sensory input. IIT proponents suspect this process occurs in the back
of the brain, with the posterior parietal cortex (PPC) proposed as the most
important cortical region. IIT is a bottom-up explanation of consciousness.
As an emergent property of neural complexity, it’s proposed to exist to
dierent degrees that could be measured as a value (phi).
»
Higher order theories (HOT): In this theory, a mental state is conscious by
virtue of being the target of a certain kind of meta representational state. In
HOT, consciousness arises when mental states are represented by higher
order mental states. Higher levels of the brain, especially the prefrontal
cortex, are implicated in HOT.
»
Re-entry theory: Predictive processing proposes that conscious mental
states are associated with top-down signaling. Top-down signaling involves
processes by which higher-level brain regions (such as the prefrontal cortex)
sends information about expectations to lower-level brain regions involved in
bottom-up processing from sensory systems.
https://t.me/med1917
CHAPTER 18 Brain Dysfunction in Developmental and Mental Disorders 339
Chapter18
Brain Dysfunction in
Developmental and
Mental Disorders
T
he complexity of the human neocortex comes with costs: Many things can
go wrong with such a complex system during development and in the adult
brain, leading to problems with mental health. The way clinicians and
researchers talk about mental health is evolving. Previously we used the term
mental illness as a category for brain disorders that aect mental function. Because
mental illness can imply disease and can be stigmatizing, many today prefer to
talk about mental health issues or mental disorders, terms in which we use.
Both developmental and mental disorders can aect cognitive processes, emo-
tions, and behavior, and therefore these disorders are often grouped together. And
clinically, individuals with developmental or mental disorders are usually treated
by psychologists and/or psychiatrists. Developmental and mental disorders (and
mental health issues) are probably the most costly and challenging health prob-
lems in the United States and worldwide.
IN THIS CHAPTER
»
Knowing how the developing nervous
system can be harmed
»
Exploring genetic and developmental
disorders and their treatments
»
Recognizing mental disorders
»
Focusing on depression and risk
factors
»
Unlocking schizophrenia, PTSD, and
epilepsy
https://t.me/med1917
340 PART 3 Understanding Perception and Cognition
What causes developmental and mental disorders? Most aren’t usually caused by
an injury or infection, nor are most associated with a single genetic abnormality.
(Here we dene a genetic abnormality as a mutation in the DNA or structural change
in a chromosome that signicantly change the expression or function of a gene.)
Instead, developmental and mental disorders include many kinds with many con-
tributing factors, including genetic abnormalities or susceptibility variants and
environmental factors, including life experiences. In this chapter we cover the most
common disorders known to involve brain dysfunction. We describe disorders that
arise during development and then discuss mental disorders and their treatment.
Grasping Developmental and Mental
Disorders as Brain Dysfunction
The genetic code used to build the brain (as well as the rest of the body) is often
called a blueprint, but it’s really more like a computer program. Many genes
encode proteins whose function is to regulate expression of other genes. Also,
some genes encode ribonucleic acids (RNAs) that are used to regulate gene expres-
sion, rather than as codes for amino acid sequences in proteins. As the fertilized
zygote divides repeatedly, the daughter cells dierentiate into dierent tissue
types that are determined by what subsets of genes are expressed. During devel-
opment, both intrinsic and environmental factors like chemicals or pathogens can
aect cell dierentiation.
Brain development is the product of both genetics and environmental factors. During
the prenatal period, most of development is hard wired, meaning it’s governed by
intrinsic gene expression programs that don’t require much interaction with the
environment. However, exposure to toxic environmental conditions can lead to
changes in prenatal development with serious outcomes. On the other hand, postna-
tal development involves gene expression that can also be controlled by interaction
with the environment, leading to changes in synaptic function and neuronal activity.
The way development is talked about has also evolved. For clinicians and research-
ers the terms “normal” and “abnormal” generally aren’t considered useful terms
because they can also infer cultural norms. Instead, many prefer terms such as
“typical” or “standard” and “atypical” for use in a description or study. We use
these terms as well. These sections briey overview brain development and inter-
actions between genes and environment.
Building brains
Given that the brain is a product of genetics and environmental factors, a geneti-
cally typical DNA sequence interacts with typical experience to produce a typical
https://t.me/med1917
Соседние файлы в папке Библиотека им академика М.И. Перельмана