Transcript Midterm_Review

The Neural Basis of
Thought and Language
Midterm
Review Session
DISCLAIMER
We haven’t seen the test
We don’t know what’s on the test
What we present today is purely our opinion on
what some of the important topics are
Administrivia
• Midterm in class next Tuesday, March 7th
• Be there on time!
• Format:
– closed books, closed notes
– short answers, no blue books
– up to Feb. 28th lecture
The format for this evening...
• Question
• Work on it
• Discuss
• Repeat...
What’s been covered so far...
• Learning and Memory
• Psycholinguistics
• Connectionist modeling
• Mirror Neurons
• PDP systems
• Color
• Back-propagation
• Image Schemas
• Brain imaging
• Regier System
Hebbian Learning
How do the strengths of the weights change in
Hebbian Learning
if the following neurons fire?
LTP and Hebb’s Rule
• Hebb’s Rule:
neurons that fire together wire together
strengthen
weaken
• Long Term Potentiation (LTP) is the biological
basis of Hebb’s Rule
• Calcium channels is the key mechanism
Long Term Potentiation (LTP)
• These changes make each of the winning synapses more potent
for an intermediate period, lasting from hours to days (LTP).
• In addition, repetition of a pattern of successful firing triggers
additional chemical changes that lead, in time, to an increase in
the number of receptor channels associated with successful
synapses - the requisite structural change for long term memory.
– There are also related processes for weakening synapses and
also for strengthening pairs of synapses that are active at
about the same time.
Questions?
Learning
What type of learning discussed in class solves
the problem of assigning blame?
Back-prop
Questions?
The Brain
What areas of the brain would be active when
picking up an object vs. seeing someone pick
up an object?
How does this play into the embodiment debate?
The Mirror Circuit in Monkeys
• top:
monkey sees
experimenter grasp
an object
• bottom:
monkey sees
experimenter
reaches his hand
behind a screen to
grasp an object
this is what we see in a monkey…
measuring a neuron in the parietal area
Somatotopy
• top:
humans watching foot ,
hand and mouth
actions without an object
• bottom:
humans watching same
actions with an object
• What can we learn from
these two experiments?
Buccino et al., 2001
integrated, multi-modal
representation of
actions, along with the
objects and locations
Concepts
• What Concepts Are: Basic Constraints
– Concepts are the elements of reason, and
– constitute the meanings of words and linguistic
expressions.
Concepts: Traditional Theory
• The Traditional Theory
• Reason and language are what distinguish human
beings from other animals.
• Concepts therefore use only human-specific brain
mechanisms.
• Reason is separate from perception and action, and
does not make direct use of the sensory-motor system.
• Concepts must be “disembodied” in this sense.
The neural theory
Human concepts are embodied. Many concepts
make direct use of the sensory-motor
capacities of our body-brain system.
• Many of these capacities are also present in
non-human primates.
• Let us look at concepts that make use of our
sensory-motor capacities, ex. Grasp.
Questions?
Color
What is the biological basis of basic color terms?
The WCS Color Chips
• Basic color terms:
–
–
–
–
Single word (not blue-green)
Frequently used (not mauve)
Refers primarily to colors (not lime)
Applies to any object (not blonde)
FYI:
English has 11
basic color terms
Results of Kay’s Color Study
Stage I
II
IIIa / IIIb
IV
V
VI
VII
W or R or Y
W
W
W
W
W
W
Bk or G or Bu
R or Y
R or Y
R
R
R
R
Bk or G or Bu
G or Bu
Y
Y
Y
Y
Bk
G or Bu
G
G
G
Bk
Bu
Bu
Bu
Bk
Bk
Bk
Y+Bk (Brown)
Y+Bk (Brown)
W
R
Y
R+W (Pink)
Bk or G or Bu
R + Bu (Purple)
R+Y (Orange)
B+W (Grey)
If you group languages into the number of basic color terms
they have, as the number of color terms increases,
additional terms specify focal colors
Color Opponent Cells
25
50
Mean Spikes / Sec
+R-G
• These cells are found
in the LGN
+Y-B
• Four color channels:
Red, Green, Blue,
Yellow
25
400
700
50
• R/G , B/Y pairs
+G-R
400
25
700
25
• We can use these to
determine the visual
system’s fundamental
hue responses
+B-Y
400
700
400
Wavelength (mμ)
(Monkey brain)
• much like
center/surround cells
700
Questions?
Categories
• Internal structure (classical, radial, family
resemblance, prototype-based, “essentiallycontested,” ad-hoc)
• “External” structure (basic-level,
superordinate, subordinate)
Categories
What are super- and sub-ordinate types to
“red”?
Categories
Superordinate
Furniture
Sofa
leather
sofa
fabric
sofa
Basic-Level Category
Desk
L-shaped
desk
Reception
disk
Subordinate
Basic-Level Category
What constitutes a basic-level category?
• Communication:
• Perception:
– similar overall
perceived shape
– shortest
– single mental image
– contextually neutral
– (gestalt perception)
– first to be learned by children
– fast identification
– first to enter the lexicon
– most commonly used
• Function:
• Knowledge Organization:
– general motor program
Red? yes
– most attributes of category
members stored at this level
Maroon? arguable (expertise)
Categories: Internal Structure
• Classical Category:
– necessary and sufficient conditions
• Radial Category:
– a central member branching out to less-central and non-central
cases
– degrees of membership, with extendable boundary
• Family Resemblance:
– every family member looks like some other family member(s)
– there is no one property common across all members (e.g. polysemy)
• Prototype-Based Category
• Essentially-Contested Category (Gallie, 1956) (e.g. democracy)
• Ad-hoc Category (e.g. things you can fit inside a shopping bag)
Questions?
Image Schemas and Regier
Image Schemas
• Trajector / Landmark (asymmetric)
– The bike is near the house
– ? The house is near the bike
TR
• Boundary / Bounded Region
– a bounded region has a closed boundary
LM
boundary
bounded region
• Topological Relations
– Separation, Contact, Overlap, Inclusion, Surround
• Orientation
– Vertical (up/down), Horizontal (left/right, front/back)
– Absolute (E, S, W, N)