Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
Chapter 1 Mind and Brain
“… from the brain, and from the brain alone, arise our pleasures, joys, laughter and jokes, as well as our
sorrows, pains, griefs and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from
the beautiful, the bad from the good, the pleasant from the unpleasant… all the time the brain is quiet, a
man can think properly.”
--- Attributed to Hippocrates, 5th century BCE.
(Footnote: quoted by Kandel et al., 1991).
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
Chapter Outline
1.0 Introduction
2.0 An invitation to mind-brain science
3.0 Some starting points
4.0 Some history, and ongoing debates
5.0 The return of consciousness in the sciences
6.0 Summary
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
2.0 An invitation to mind-brain science
•Cognitive Neuroscience: the combined study of mind and brain
•The advent of neuroimaging techniques has revolutionized the study of
human cognition
•These new techniques allow us to explore topics like conscious experience,
unconscious processes, and mental imagery
Neuroimaging techniques allow us to investigate brain
structure and dynamic function in healthy individuals.
Figure 4.1 shows a 3-dimensional structural head and
brain scan (Chapter 4, Figure 1).
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
Distance: seven orders of magnitude from 1 meter to 10-7 meter
a.
b.
c.
d.
e.
A brain image of a subject looking at a rotating black
and white stimulus
A midline view of the cortex, with area V1 marked -the first place where the visual pathway reaches
cortex
The head of a fruit fly: the fruit fly brain has about
1,000,000 neurons
A single neuron: we have tens of billions in our brain
A dopamine molecule: dopamine plays an essential
role in working memory, the experience of pleasure,
and the control of muscles
a
c
Items a-e represent 7 spatial orders of magnitude
b
d
e
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
Time: ten orders of magnitude -- from years to milliseconds
•
When you listen to a high musical note, your auditory nerve is firing as fast
as the sound waves that vibrate your eardrum, up to 1000 times per second
(cycles per second = Hertz =Hz), or one wave per millisecond (ms, 1000th
of a second)
•
Neurons can fire as fast as 1000Hz, although the average neuron n the
cortex fires about 10 times per second
•
The auditory nerve is a bundle of nerve axons, each of which fires slower
than 1000 Hz, but together they can respond at millisecond speed
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
Time: ten orders of magnitude -- from years to milliseconds
•
If the sound track of a movie is delayed by a fraction of second behind the
video, you will notice a disconnect between the sounds and the movements
of an actor’s mouth. The break-up of audio-visual synchrony occurs after
about 100 ms lag, or one-tenth of a second
•
One hundred ms is also about the fastest we can react to an event that we
know will come soon, as in starting a car when a traffic light turns green
•
By comparison, if you count to yourself from one to ten, your counting takes
place on the order of seconds, or tens of seconds. The typical lecture lasts
one hour -- more than 3000 seconds
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
The need to make inferences -- going beyond the raw observation
Science depends on a constant process
of inference, going from raw
observations to explanatory concepts.
Thousands of years ago, when human
beings began to wonder about lights in
the sky like the sun, moon, and stars,
they noticed that some were predictable
and some were not.
The ‘wanderers’ in the night sky were
called planete by the Greeks, we call
them planets in English.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
The need to make inferences -- going beyond the raw observation
It was not until the 17th century that their paths were understood and predicted.
Words like ‘planet’, ‘force’, and ‘gravity’ are inferred concepts. They are far removed
from the first observations of lights in the sky, yet they explain those raw observations:
they are explanatory inferences.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
The need to make inferences -- going beyond the raw observation
Cognitive concepts are based on consistent behavioral observations. Inferred concepts
in cognitive neuroscience include areas of study such as language, learning, memory, or
vision.
Concepts like ‘working memory’ are not given nature, they emerge after many years
of testing, when a large body of evidence seems to be explained by an inferred
concept.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
The need to make inferences -- going beyond the raw observation
Brain measures of working memory are also inferential. Working memory functions in
the brain have been studied using behavioral measures, but also with fMRI, EEG, and
single neuron recordings. Each of these measures has its pros and cons, but none of
them is the ‘ultimate measure’ of working memory.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
The importance of convergent measures
Overall, brain indices of working memory
converge well with behavioral measures.
Cognitive neuroscience is based on the
study of such combined sources of
evidence, but we must be prepared to find
that our current concepts may be
interpreted in a different way with new
findings.
New raw observations lead to refined
inferred concepts and theories about
cognition.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
Major landmarks of the brain, with a medial (midline) view showing the center
portions of the brain between the two cerebral hemispheres, and a lateral (side)
view showing the outer aspects of the cerebral cortex.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 Some starting points
Major planes of sections (slices) of the brain
Top panel shows a vertical section of the brain, called sagittal.
When brain images are collected in this plane, they go from one
side of the brain, across the midline between the two
hemispheres, and to far side of the brain. When the slice is
exactly through the midline between the two hemispheres it is
called mid-sagittal.
Center panel shows a horizontal or axial slice through the brain.
These slices go from the top of the brain to the bottom.
The lower panel shoes a coronal slice (named for its crown
shape) that goes from the front of the brain to the back, from the
forehead to the nape of the neck. Like horizontal slices, coronal
slices include both hemispheres.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
The mind and the brain -- Rene Descartes
Descartes is often considered to be the
originator of the mind/body philosophy. The
basic question seems simple: is the world
basically mental or physical?
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
The mind and the brain -- Rene Descartes
Because Descartes was convinced that the the
soul or psyche was a unified whole, he rejected
the idea that paired structures of the brain could
support the (unitary) soul. But almost all of the
brain looks doubled to the naked eye: two
hemispheres, two eyes, two ears, two
subcortical halves.
Descartes decided that the tiny pineal gland,
which looks like a tiny dot to the naked eye,
must be the point of connection between the
divine soul and the earthly body.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Biology shapes cognition and emotion -- Charles Darwin
Human emotion turns out to have deep
biological roots in the mammalian brain,
regulated by more recent layers of the cortex.
As a result, the evolutionary history of the
human brain, going back some two hundred
million years to early mammals, is relevant to
a host of important questions.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Biology shapes cognition and emotion -- Charles Darwin
More than anyone else, Charles Darwin helped
to establish the biological context of the human
species. Darwin thought about human emotions
as biologically based -- which was not meant to
minimize our vast cultural and individual
influences of course.
Darwin made numerous observations about
emotional expressions in animals and humans
and subsequently wrote a book called The
Expression of Emotions in Man and Animals.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Biology shapes cognition and emotion -- Hermann von Helmholtz
Helmholtz was a great sensory physiologist and
psychologist in the 19th century whose works on
vision and audition are still read. But his biggest
claim to fame is the physical law of conservation
of energy, which he demonstrated using electrical
stimulation of dissected frog’s legs.
The idea that the brain and body are pervaded
with electricity caught the popular fancy, leading
to cult ideas like ‘animal magnetism’.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Biology shapes cognition and emotion-- Hermann von Helmholtz
The insight that electricity was part of nervous
activity led to the discovery of nerve potentials
and the electrical activity of the brain in the early
20th century.
Today, the electromagnetic activity of the brain
gives us a whole set of imaging methods: EEG,
evoked potentials, single-neuron recording, and
MEG. All brain imaging tools make use of
fundamental physics and chemistry.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Ramon y Cajal’s neuron doctrine: the working assumption of brain science
Santiago Ramon y Cajal was a
founder of brain science. An open
and important question of his time
was regarding the nature of the
nervous system -- whether it
consisted of billions of separate
cells or whether it was essentially
one great continuous network.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Ramon y Cajal’s neuron doctrine: the working assumption of brain science
Cajal used Golgi stains to bring out basic facts about nerve cells under the light microscope.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Ramon y Cajal’s neuron doctrine: the working assumption of brain science
Cajal is credited with the neuron doctrine,
one of the founding assumptions of brain
science, stating that “the nervous system
consists of numerous nerve cells (neurons),
anatomically and genetically independent”.
Today’s methods for studying neuronal
microstructure are advanced versions of
the Golgi-Cajal approach.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Pierre-Paul Broca and the localization of speech production
Medical observations are also relevant to the mind
and brain sciences. It was the French physician,
Pierre-Paul Broca, who first discovered a region of
the left hemisphere that was tied to language
production.
Broca had a patient who had lost all ability to speak
except to say the single word ‘tan’. After the patient
died, Broca was able to perform an autopsy, finding
damage to “the posterior part of the third frontal
convolution in the left hemisphere”.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Pierre-Paul Broca and the localization of speech production
He concluded that this part of the frontal lobe
was indispensable for speech production.
This concept was hotly debated among
scientists: were there localized functional areas
in the brain or was the brain equipotential, with
all regions able to support cognition? This
debate continues today.
The ‘speaking’ region of the left hemisphere is
now called Broca’s area, although it precise
function in language production is still being
elucidated.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
Carl Wernicke and the localization of speech comprehension
Some years after Broca’s work on speech output, the German
scientist Carl Wernicke discovered a part of the brain involved in
speech input -- perception and comprehension. Wernicke
discovered this by observing a variety of aphasic patients,
patients who had brain damage that resulted in language deficits.
Wernicke concluded that damage to different areas of the brain
resulted in different types of language disorders.
Although there was evidence provided by Broca and Wernicke
that some aspects of language are processed in specific regions
of the brain, this concept remains hotly debated to this day.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
William James: psychologist, philosopher, physician, and painter
James is best known today as a psychologist and philosopher,
however he also trained to be a physician and painter. James
taught brain anatomy, and his 1890 description of the brain is in
good agreement with our understanding today.
James’ Principles of Psychology is often considered the best
summary of 19th century psychology and brain science in the
English language. Among many other points, James discussed
the brain studies of Dr. Mosso, who observed that the blood
supply to active brain regions increased. That finding is the basis
of modern brain imaging methods based on hemodynamics (the
flow of blood) including PET and MRI.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
William James: psychologist, philosopher, physician, and painter
James showed Broca’s and Wernicke’s areas
based on the medical evidence from brain
damage. These 19th century language regions
of the left hemisphere are similar to modern
neuroimaging findings.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
The conscious and unconscious mind
Nineteenth century scientists were profoundly interested in the question of
consciousness. Ramon y Cajal proposed the idea of a ‘psychic neuron’ in the
cortex, a type of neuron that would support conscious experiences.
The beginning of psychophysics in the early 19th century was very much
inspired by an effort to solve the mind-body puzzle.
At the end of the 19th century, William James proclaimed that “Psychology is
the science of mental life” by which he meant conscious mental life.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Some History, and ongoing debates
The conscious and unconscious mind
About that time, some began to disagree. Scientists
like Helmholtz, Loeb, and Pavlov advocated a more
physicalist view of mental life.After 1900, Pavlov
became famous for his experiments on classical
conditioning in dogs.
This helped to convince many psychologists that ultimately all of behavior could
be explained in terms of simple behavioral units, based on reflexes. Thus,
behaviorism was born and the study of consciousness was criticized as
unscientific.
For much of the 20th century, human consciousness was avoided by scientists.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
5.0 The return of consciousness in the sciences
How conscious and unconscious brain events are studied today
Conscious
Unconscious
Explicit cognition
Implicit cognition
Immediate memory
Long-term memory
Attended information
Unattended information
Effortful tasks
Spontaneous/automatic tasks
Wakefulness and dreaming
Deep sleep, coma, sedation
Declarative memory
Procedural memory
Intentional learning
Incidental learning
Some examples of conscious and unconscious aspects of cognition
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
5.0 The return of consciousness in the sciences
A recent wave of brain studies are investigating conscious and unconscious
phenomena in the brain. For example, a fMRI study compared brain activation for
conscious and unconscious events: unconscious viewing of words activated visual
areas only, while conscious viewing activated expanded regions in the cortex.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
5.0 The return of consciousness in the sciences
Many historical debates are ongoing today:
Local vs widespread functions in the brain
The neuron doctrine
The question of consciousness
Capacity limits in the brain
Short-term and long-term memory -- are they separate?
Nature vs. nurture, gene vs environment
And many more!
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
6.0 Chapter Summary
What are the central questions being explored in the field of cognitive neuroscience?
•The scientific exploration of the relationship between the mind and the brain is a
central issue in the study of human cognition.
•Ancient questions and new ones are being addressed using modern
neuroimaging techniques along with converging evidence from behavioral and
medical studies.
•Cognitive neuroscience combines psychology, neuroscience, and biology.
Questions that could not be addressed earlier are now begin explored.