Transcript Introduction to Cognitive Neuroscience

Cognitive Architectures
Introduction to Cognitive
Neuroscience
Based on book Cognition, Brain and Consciousness ed. Bernard J. Baars
courses taught by Prof. Randall O'Reilly, University of Colorado, and
Prof. Włodzisław Duch, Uniwersytet Mikołaja Kopernika
and http://wikipedia.org/
http://grey.colorado.edu/CompCogNeuro/index.php/CECN_CU_Boulder_OReilly
http://grey.colorado.edu/CompCogNeuro/index.php/Main_Page
Janusz A. Starzyk
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… from the brain, and from the brain alone, arise our pleasures, joys,
laughter and jokes, as well as our sorrows, pains, grief's 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…
» Attributed to Hippocrates, 5th century BC
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The Brain ...
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The most interesting and the most complex
object in the known universe
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How can we understand the workings of
the brain?
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On what level should we attack this
question? An external description won’t
help much.
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How can we understand the workings of a TV or computer?
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Experiments won’t suffice, we must have an understanding of the
operating principles.
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To verify that we understand how it works, we must make a model.
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How do we know anything?
An important question: how do we know things?
Examples: super diet based on dr. K, Chinese medicine
and other miracle methods. How do we know that
they work? How do we know that they are for real?
Gall noticed that the skull shape decides about ones
abilities. Thousands of cases confirmed his observations.
Craniometry: measuring the bones of the skull
to determine intelligence.
Do I know or I only believe that I know?
Not being certain allows to learn, certainty makes
learning difficult. If we know how easy it is to err
we could avoid a scientific fallacy.
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http://www.harunyahya.com/image/darwinizm_kanli_ideolojisi_fasizm
How to understand the brain?
To understand: reduce to simpler mechanisms?
Which mechanisms? Analogies with computers? RAM, CPU? Logic?
Those are poor analogies.
Psychology: first you must describe behavior, it looks for explanations
most often on a descriptive level, but how to understand them?
Physical reductionism: mechanisms of the brain.
Reconstructionism: using mechanisms to reconstruct the brain’s functions
To create: what must we know in order to create an artificial brain?
We can answer many questions only from an ecological and evolutionary
perspective: why is the world the way it is? Because that’s how it made
itself ... Why does the cortex have a laminar and columnar structure?
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From molecules through neural networks
10-10 m, molecular level: ion channels, synapses, properties of cell
membranes, biophysics, neurochemistry, psychopharmacology;
10-6 m, single neurons: neurochemistry, biophysics, LTP,
neurophysiology, neuron models, specific activity detectors,
emerging.
10-4 m, small networks: synchronization of neuron activity, recurrence,
neurodynamics, multistable systems, pattern generators, memory,
chaotic behaviors, neural encoding; neurophysiology ...
10-3 m, functional neural groups: cortical columns (104-105), group
synchronization, population encoding, microcircuits, Local Field
Potentials, large-scale neurodynamics, sequential memory,
neuroanatomy and neurophysiology.
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… to behavior
10-2 m, mesoscope networks: sensory-motor maps, self-organization,
field theory, associative memory, theory of continuous areas, EEG,
MEG, PET/fMRI imaging methods ...
10-1 m, transcortical fields, functional brain areas: simplified cortical
models, subcortical structures, sensory-motor functions, functional
integration, higher psychic functions, working memory,
consciousness; (neuro)psychology, psychiatry ...
Cognitive effects
Principles of
interactions
Neurobiological
mechanisms
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… to the mind
Now a miracle happens ...
1 m, CNS, the whole brain and organism:
An interior world arises, intentional behaviors, goal-oriented
actions, thought, language, everything that behavioral psychology
examines.
Approximations of neural models:
Finite State Machine, rules of behavior, models based on the
knowledge of cognitive mechanisms in artificial intelligence.
What happened to the psyche, the internal perspective?
Lost in translation: neurons => networks => behavior
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Inside the mind
“What if … we were magically shrunk and
put into someone’s brain while he was
thinking.
We would see all the pumps, pistons,
gears, and levers working away, and we
would be able to describe their working
completely, in mechanical terms, thereby
completely, describing the thought
process of the brain.
But that description would nowhere
contain any mention of thought! It would
contain nothing but descriptions of
pumps, pistons, levers!’
- Gottfried Leibnitz 1690
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Levels of description
Summary (Churchland, Sejnowski 1988)
Sensing outside and inside the body
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Distance – from 10-10 m to one meter
 Small molecules can change brain functions and resulting behavior.
 Around year 1800 people were surprised to find out that nitrous
oxide (N2O) changes their behavior – it produces small amount of
neurotransmitter.
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Time scales - 10 orders of magnitude
 Neurons can fire as fast as 1000 Hz.
 Our brain deals with events on the time
range from years to milliseconds.
 100ms is about the fastest we can react to
an event.
– Slower reaction time would prevent humans from
protecting themselves from dangers and they would
have no chance to survive and reproduce,
– faster reaction time would overwhelm the brain to
combine sensory inputs and determine the direction
and speed of the attacker.
 Some skills take long time to master like
playing guitar or learning how to speak.
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Working Memory
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Observations, based on experimental data, are important in
cognitive science.
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Concepts like working
memory and their size
(7+/-2) are not ‘given’
in nature but are
inferred from
experimental
observations.
Emerge from years of
testing, working
memory proposed
after a 2 decade study
of immediate memory
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Neurocognitive Models
Computational cognitive neuroscience: detailed
models of cognitive functions and neurons.
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Model of self-organization
Topographical representations in numerous areas of the brain:
visual system maps and maps of the auditory cortex.
o
Model (Kohonen 1981):
competition between groups of
neurons and local cooperation.
Neurons react to signals
adjusting their parameters so
that similar impulses awaken
neighboring neurons.
x=data
o=weights of
neurons
x
o
o
o
o x
o
o
x
o
xo
o
N-dimensional
input space
o
o
Weights locate
points in N-D
neural network
w 2-D
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Dynamic model
Strong feedback, neurodynamics.
Hopfield model: associative memory, learning based on Hebb’s law.
Vector of input potentials V(0)=Vini , i.e.
input = output.
Hopfield’s network reaches stationary
states, or the answers of the network to
the posed question Vini (autoassociation).

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Vi  t  1  sgn  I i  t  1   sgn  WijV j   j 
 j

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Advantages of model simulations
Models help to understand phenomena:
 enable new inspirations, perspectives on a problem
 allow to simulate effects of damages and disorders (drugs, poisoning)
 help to understand behavior
 models can be formulated on various levels of complexity
 models of continuous phenomena (e.g. motion or perception)
 models allow detailed control of experimental conditions and exact
analysis of the results
Models require exact specification of underlying assumptions:
 allow for new predictions
 perform deconstructions of psychological concepts (working memory?)
 allow to understand the complexity of a problem
 allow for simplifications enabling analysis of a complex system
 provide a uniform, cohesive plan of action
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Disadvantages of simulations
One must consider limitations of designed models:
 Models are often too simple, they should contain many levels.
 Models can be too complex, theory may give simpler explanation
 why there are no hurricanes on the equator? - due to Coriolis effect
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It’s not always known what to specify in a model.
Even if models work, that doesn’t mean that we understand the
mechanisms.
Many very different models can explain the same phenomenon.
Models need to be carefully designed to fit the observations:
 What’s important in building a model are general rules
 the more phenomena a model explains, the more plausible and universal it is.
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Allowing for interaction and emergence is very important.
Knowledge acquired from models should accumulate.
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Cognitive motivation
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Although the thinking process seems to be sequential information
processing, more detailed models predict parallel processing
 Transition between conscious and subconscious processes
 Parallel processing of sensory-motor signals by millions of neurons
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Specialized areas of memory responsible for various representations
e.g. shape, color, space, time
 Levels of symbolic representation
 More diffuse and fuzzy than binary logic
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Learning mechanisms as a foundation for cognitive science
 When you learn, you change the method of information processing in
your brain
Resonance between ”bottom-up” representation and ”top-down”
understanding
 Prediction and competition of ideas
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Brain Landmarks
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Most terms in
neuroscience are
Latin names.
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Medial (midline) view
of the brain also
called mid-sagittal is
a slice from the nose
to the back of the
head.
Corpus callosum is a fiber bridge flowing between right and
left hemispheres, begins behind the frontal lobe and loops up
and ends in front of the cerebellum.
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Brain Landmarks
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Lateral (side) view of left
hemisphere is shown
here.
Folds in the cortex are
important part of
anatomy.
Longitudinal fissure runs
along the midline
between right and left
hemispheres.
Lateral sulcus runs forward at a slant along the side of the brain
and divides the temporal lobe from the main cortex.
Central sulcus divides the rear half (posterior half) of the brain
from the frontal lobe.
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Brain Landmarks
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Temporal lobe points in the direction of
the eye.
The three major planes of section (cuts)
are:
 Vertical section (sagittal) from the front of
the brain to the back.
– Slice through the midline is called midsagittal.
 Horizontal slice.
 Coronal section (named for its crown
shape).
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Body Landmarks

The three major
planes of section :
 Vertical section
(sagittal) from the
front to the back.
 Horizontal
(transverse) section.
 Frontal (coronal in
the brain) section.
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Other important directions:
 Superior (dorsal) and inferior (ventral)
 Medial and lateral
 Anterior (rostral) and posterior (caudal).
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Mind and Brain
Visual perception: viewing natural imagery
we must understand ways of encoding
objects and scenes.
Spatial awareness: considering the interaction
between streams of visual information will let
us simulate concentration
Memory: modeling hippocampal structures allows us to understand
various aspects of episodic memory, and learning mechanisms show how
semantic memory arises.
Working memory: explaining the capacity to simultaneously hold in the
mind several numbers, while performing calculations requires specific
mechanisms in the neural model.
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Mind and Brain
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Andreas Vesalius (1514-1564), a
Belgian physician, published the
first known detailed anatomy
based on dissections of human
body.
He showed that both men and
women have the same number
of ribs.
Illustrations, like the brain shown
here, were done by Titian.
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Mind and Brain
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Paintings, like the Rembrandt
(The Anatomy Lesson of
Dr.Tulp), show the excitement
generated by dissection of
human body.
René Descartes (1596 -1650) a
mathematician and philosopher
is considered as the originator
of modern mind/body
philosophy.
 He said most famously, cogito ergo sum ("I think, therefore I am").
 Thinking is thus every activity of a person of which he is immediately
conscious.
 Descartes' "error" pointed by António R. Damásio was the separation of
mind and body.
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Mind and Brain
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Charles Darwin (1809 –1882)
wrote a book “Expression of
emotions in man and animals”
pointing towards biological
origins of emotions and not
just cultural as people thought.
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He also stressed the
importance of culture and
environment, that helps to
resolve “nature vs nurture”
debate.
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Mind and Brain
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Santiago Ramon y
Cajal (1852–1934)
founder of brain
science studied
properties of neurons.
He observed neurons under microscope
and showed that they are single cells
that end with synapses
Nerve impulses travel down the axon to synapses
In 1952 Hodgkin and Huxley constructed action potential
model for a spiking neuron
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Neurons
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Cajal’s drawing of a slice of chicken brain
exposed using Gogli staining method
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A Modern version
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Mind and Brain
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Pierre Paul Broca (18241880) discovered the region
in the brain responsible for
speech production
In 1861 he studied a patient
with epilepsy who lost ability
to speak
On the patient’s death Broca performed autopsy and
showed a damage to the posterior part of the third frontal
convolution in the left hemisphere and associated it to
speech production
Much of what we know about brain was first discovered by
studying various deficits
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Mind and Brain
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Wernicke’s area (W), in the left upper part of the
temporal lobe is responsible for receptive language
(understanding).
Carl Wernicke (1848-1905) published his finding shortly
after Broca’s work
The two areas are connected
for speech comprehension
and production.
Damage (in or near) leads to:
 Broca’s area (B): Expressive aphasia,
 Wernicke’s area (W): Receptive aphasia,
 Fibers between B & W: Disconnection aphasia.
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Mind and Brain
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Left hemisphere is responsible for
language production and listening while
right hemisphere is concerned with
emotional aspects of language.
Angelo Mosso (1846-1910), found a
way to measure blood pressure during
demanding mental tasks.
Mosso’s work anticipated current
measures of brain blood flow like fMRI.
 fMRI measures local blood flow changes in
the brain.
 The fMRI shows whenever some brain
regions require more oxygen and glucose.
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Mind and Brain
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Nineteen century scientists were very interested in
consciousness.
William James (1890) declared psychology as a science of
conscious mental life.
Many scientists (Helmholtz, Loeb, Pavlov) disagreed – they
took on a physicalistic view of mental life.
Pavlov experiments with
dogs (1900) on classical
conditioning convinced
psychologists that all
behavior can be derived
from simple reflexes.
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Mind and Brain
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In 1970-ies many
scientists were
dissatisfied with
behaviorism.
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Different methods of
testing conscious and
unconscious brain
events were
developed
Figure compares results of study using visual backward
masking method based on fMRI to compare brain activity for
conscious and unconscious visual words.
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Conclusion
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Debates in cognitive neuroscience:
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Local vs distributed functions in brain
The question of consciousness
Unconscious inferences in vision
Capacity limits in the brain
Short-term and long-term memory – separate or not?
The biological basis of emotions
Nature vs nurture – genes vs environment
http://psychandneuro.duke.edu
Cognitive neuroscience combines psychology, neuroscience and
biology to answer questions about mind and brain.
Modeling cognitive functions of the brain helps to understand
psychological phenomena and predict behavior.
It may simplify complex cognitive processing with full control of
experimental conditions.
It helps to build working models of embodied intelligence
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