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Mind and Brain
Chapter 1
+Jeff Hawkins, in his book “On Intelligence”, wrote:
“Most big scientific questions involve the very small, the very large, or events that occurred billions of years ago. But everyone has a brain. You are your brain. If you want to understand why you feel the way you do, how you perceive the world, why you make mistakes, how you are able to be creative, why music and art are inspiring, indeed what is is to be human, then you need to understand the brain.”
+Carlson, in “Physiology of Behavior” wrote:
“The last frontier in this world – and perhaps the greatest one – lies within us.”
+Overview
Mind-brain question
Understanding human consciousness Blindsight Split brain Unilateral neglect Phantom limb, Capgras syndrome, Temporal lobe epilepsy
The nature of physiological psychology
The goals of research
Biological Roots of Physiological Psychology
Natural selection and evolution
Ethical issues in research with animals
Careers in neuroscience
+Mind-Body Question
Mind, soul, spirit We are aware of our own existence
What role does the mind play? Does the mind control the NS?
Is it physical and tangible?
Is it a spirit that will always remain hidden?
+Mind-body question
People have followed 2 different approaches:
Dualism Is a belief in the dual nature of reality; the body is
physical but the mind is not
Monism Is the belief that the world consists only of matter
and energy and that the mind is a phenomenon produced by the workings of the nervous system
+Mind-body question
Physiological Psychologists take an empirical, practical and monistic approach to this question
Once we understand how the body, and especially the brain, works the mind-body problem will be solved How we perceive How we think How we remember How we act
+Understanding Human Consciousness: A Physiological Approach Consciousness refers to the fact that humans
are aware of – and can tell others about – our thoughts, perceptions, memories, and feelings.
Is it possible to understand this very complex phenomenon using a scientific approach?
Consciousness can be altered by changes in the brain – therefore we may hypothesize that consciousness is a physiological function
+Understanding Human Consciousness: A Physiological Approach
Blindsight
Split Brains
Unilateral neglect
+Blindsight
The ability of a person who cannot see objects in his or her blind field to accurately reach for them while remaining unconscious of perceiving them
Caused by damage to the “mammalian” visual system of the brain
Visual information can control behavior without producing a conscious sensation
Suggests consciousness is not a general property of the brain Some parts of the brain are more important than others in
consciousness
+Split Brains
Cerebral Hemispheres two symmetrical halves of the brain Receive sensory information from the opposite side of
the body Control movement of opposite side of the body
Corpus Callosum largest commissure of the brain, interconnecting the
areas of neocortex on each side of the brain. Allows each side of the brain to know what the other is
doing
Copyright © 2006 by Allyn and Bacon
+Figure 1.3 The Split-Brain Operation
+
Copyright © 2006 by Allyn and Bacon
Commissurotomy in Human Epileptics Commissurotomy limits convulsive activity
Many never have another major convulsion
Sperry & Gazzaniga Developed procedures to test split-brain patients
The two hemispheres work independently Sensory mechanisms, memories, and motor systems can no
longer exchange information
2 hemispheres have very different abilities Most left hemispheres are capable of speech, while the right
aren’t
+Figure 1.4 Smelling with a Split Brain
Important point: we become conscious of something only if information about it reaches the part of the brain responsible for verbal communication (left hemisphere)
+Unilateral Neglect A syndrome in which people ignore objects located
toward their left and ignore the left sides of objects located anywhere
2 major symptoms: Neglect of the left halves of things in the environment Neglect of the left half of one’s own body
People with unilateral neglect can see things to the left and can tell when someone touches their left side, but they normally ignore it; not normally conscious of them
Most often caused by damage to the right parietal lobe (PL)
Rare cases of unilateral right neglect – damage to left PL Slight, difficult to detect, temporary Why?
+Parietal lobe
Receives information directly from skin, muscles, joints and the internal organs, and the part of the inner ear concerned with balance
Concerned with the body and its position
Also receives auditory and visual information
Its most important function - put together information about the movements and location of the parts of the body with the location of objects in space around us
Hemispatial neglect
+Visual Neglect
Neglect patients may also ignore the contralesional side of their body, shaving or adding make-up only to the non-neglected side.
Neglect may also present as a delusional form, where the patient denies ownership of a limb or an entire side of the body.
+Ramachandran video: Secrets of the Mind
Phantom limb
The sensation that an amputated limb is still attached to the body
Map of the body in the somatosensory cortex Homunculus
+Homunculus
+Phantom limb
Sensations experienced are often painful Mirror box
Provided visual feedback for phantom limb
+Ramachandran video: Secrets of the Mind
Capgras Syndrome (or Capgras delusion) A disorder in which a person holds a
delusion that a friend, spouse, parent or other close family member has been replaced by an identical-looking imposter
Disconnection of visual information from emotion
+Summary
As pointed out by Ramachandran and Carlson, studies of people with brain damage provide some insights, even though we do not know much about the physiology of consciousness
Consciousness seems to involve operations of the verbal mechanisms of the left hemisphere
+The Nature of Physiological Psychology
The field of physiological psychology grew out of psychology First textbook of psychology was written in 1874 by Wilhem
Wundt and was titled Principles of Physiological Psychology
+The Nature of Physiological Psychology
What is the ultimate function of the nervous system?
BEHAVIOR
Physiological psychologists work with biologists, physiologists, and other neuroscientists to explain behavior
+The Goals of Research
The goal of all scientists is to explain the phenomena they study
Two types of scientific explanations: Generalization – a general conclusion based on many
observations of similar phenomena. Reduction – a phenomenon is described in terms of the more
elementary processes that underlie it.
+Biological Roots of Physiological Psychology
Hippocrates (460-370 B.C.) Considered the brain to
be the center of thought and emotions.
Many ancient philosophers assigned this role to the heart
+Biological Roots of Physiological Psychology
René Descartes (17th century) Philosopher and
mathematician (Father of Modern Philosophy)
Reflexes – automatic, stereotyped movement that is produced as a direct result of a stimulus.
Dualism – humans possessed a mind not subject to the laws of the universe
Pineal Body – site of the link between the mind and the body
+Biological Roots of Physiological Psychology
Luigi Galvani (17th century) Electrical stimulation of
the nerve in a frog’s leg produced contraction of the leg muscle.
This happened even when the nerve and muscle were separated from the rest of the body
Brain did not inflate muscles with fluids
+Biological Roots of Physiological Psychology
Johannes Muller (1801-1858) Advocate of using experimental
techniques, rather than observation and classification
Doctrine of Specific Nerve Energies – because all nerve fibers carry the same type of message (i.e., electrical impulse), sensory information must be specified by the particular nerve fibers that are active.
+Biological Roots of Physiological Psychology
Pierre Flourens Experimental
ablation – research method where the function of a particular region of the brain is inferred by observing the behaviors an animal is no longer able to perform after that area is damaged.
+Biological Roots of Physiological Psychology
Paul Broca Extended the concept of
‘experimental ablation’ to humans.
In 1861 he performed an autopsy on the brain of a man who had a stroke that left him unable to speak
Broca’s area – region of the left hemisphere involved in speaking ability.
+Biological Roots of Physiological Psychology
Gustav Fritsch & Eduard Hitzig Used electrical stimulation of the
brain to understand function. Applied weak current to the
exposed surface of a dog’s brain Observed that stimulation to a
specific region, now known as primary motor cortex, caused contractions of muscles on opposite side of the body
+Biological Roots of Physiological Psychology
Hermann von Helmholtz (19th century) Responsible for developing the law of
conservation of energy, the ophthalmoscope, a theory of color vision and blindness
First to attempt to measure the speed of nerve conduction.
Neural conduction (90 feet/s) slower than conduction in wires
+Natural Selection and Evolution
Charles Darwin (1809-1882)
According to Darwin, all of an organism’s characteristics have functional significance
Principles of natural selection and evolution
+Functionalism and the Inheritance
of Traits Functionalism – the principle that the best way to
understand a biological phenomenon is to try to understand its useful functions for the organism.
Darwin formulated his theory of evolution to explain how species acquire adaptive traits – the cornerstone of this theory is the principle of natural selection Natural Selection – process by which inherited traits that
confer a selective advantage become more prevalent in a population.
Mutations – a change in the genetic information contained in the chromosomes of sperms or eggs, which can be passed on to an organism’s offspring.
Selective Advantage – a characteristic of an organism that permits it to produce more than the average number of offspring of its species
+Figure 1.12 Bones of the Forelimb
A) human
B) bat
C) whale
D) dog
Through the process of natural selection these bones have been adapted to suit many different functions.
+Evolution of the Human Species
Evolution – a gradual change in the structure and physiology of plant and animal species, generally producing more complex organisms, as a result of natural selection.
New species evolve when organisms develop novel characteristics that can take advantage of opportunities in the environment.
+Evolution of Large Brains
The evolution of large brains enabled humans to make tools, build fire, develop language, etc. that helped them compete with other species
In terms of absolute size, the human brain is very small compared to other animals such as the elephant and whale.
Proportionally, however, the human brain makes up 2.3% of total body weight
elephant brain - 0.2% shrew brain - 3.3%
+Evolution of Large Brains
Critical issue for intellectual ability is not the size of the brain but the number of neurons available for learning, remembering, and making plans, as opposed to processing sensory and motor information.
The most important factor responsible for the evolution of the human brain is a slowing of brain development Neoteny – a slowing of the process of maturation, allowing
more time for growth; an important factor in the development of large brains.
+Please read on your own!
Ethical Issues in Neuroscience
Careers in Neuroscience
