Transcript File - Mind Study

April 19, 2016
Language, Thought, and Reality
V
Cognitive Maps:
How the Brain Organizes Knowledge
“Every cellular study of the auditory cortex in cat and monkey
has provided direct evidence for its columnar organization.”
Vernon Mouncastle
Recuerdos de las alhambra 4:50
♫
Outline of the course
I Introduction to Linguistic Relativity
II Behavioral Correlates of Linguistic Relativity
III Spatial Orientation in Different Languages
IV Language and Perception
V How the Brain Organizes Knowledge
and Beliefs
VI Thinking Disorders of Everyday Life
2
Three Worlds
• As we have seen, there are three worlds to consider
– External (the real world)
– Internal (the microcosm, the mental world)
• Categories
• Boundaries
• Enduring objects
– And there is another..
3
Three Worlds
• 1. The real world
• 2. Our internal microcosm
• 3. The projected world
– Has the organization imposed by the internal world
• Categories
• Boundaries
• Enduring objects
– Projected from our minds to the outside world
• Therefore, appears to be “out there”
– We tend to equate it with the real world
• It takes special effort not to do so
4
Mental models
• We operate with mental models
– not directly with the world
• They all differ from one another
– In different language communities
– In different cultures
– Even within communities
• Interpersonal differences
• We each live in our own personal world,
different from all others
• At most one person in the world has it right
• Actually, they are all faulty
5
Categories and reality
– Categories are in the mind, not in the real world
– In the world, everything
•
•
•
is unique
lacks clear boundaries
changes from day to day
–
(even moment to moment)
– Whorf: “kaleidoscopic flux”
Categories
• There are no categories in nature
• All categories are in the mind – in
our internal mental microcosms
• Making/assuming categories seems
to be a universal property of mind
– But different cultures – with
different languages – have
differing systems of categories
7
Exercise: Beards
• Questions
• What are we asking about?
Segmentation
• Some features and combinations of
features are distinguished – mentally
separated from – the “kaleidoscopic flux”
• Often involves the assumption of
boundaries (to aid the distinction)
9
Boundaries
• There are no boundaries in nature
• All boundaries are in the mind – in our internal
mental microcosms
• Making/assuming boundaries seems to be a
universal property of mind
• Boundaries are in the mind, not in the world
• In the real world
– There are no boundaries
– Approximations to boundaries change from
day to day
• even moment to moment
10
Presumed boundaries
• Mountain and Valley
• Land and Sea
• Automobiles
• The Human Body
• The Sun
11
The Illusion of Enduring Objects
A.k.a. The illusion of self-identity through time
•
•
•
•
•
•
Sunshine
A River
Boston
Cape Cod
Joe Biden
Your Body
12
The World we See
• The world we see is projected
from our mental models
• Categorization necessarily entails
ignoring some properties
• As a distorted world it is also to
some extent an illusion
• Inevitably our representations of
reality are filled with illusions
13
The Conceptual System
• Organizes the phenomena of the world
• Inevitably, it simplifies
•
•
•
Boundaries
Categories
Enduring Objects
• Different languages
– Have different categories
– Segment the world differently
• Example: kinds of rocks
14
Quotation from B.L. Whorf
… every language is a vast pattern
system … in which are culturally
ordained the forms and categories by
which the personality not only
communicates, but also analyzes
nature, … channels his reasoning, and
builds the house of his consciousness.
Benjamin Lee Whorf (1945)
15
Every cognitive system is a model
• Cognitive systems necessarily depend upon
simplification:
– boundaries, categories, etc.
•  everyone’s cognitive system is necessarily a
system of illusions
• It would be impossible for all people, despite
their different languages and cultures, to share
the same set of illusions
16
Categories and Boundaries


How do categories and boundaries get built?
By emphasizing some properties while
ignoring other properties
This is not only simplification —
it is distortion of reality
17
Non-linguistic correlates of linguistic differences
• Memory
– English speakers remember differences between
‘orange’ and ‘yellow’ better than Zuni speakers
– Speakers of absolute-reference languages
remember spatial relations differently
• Perceptual discriminability
– English speakers exaggerate the perceptual
differences between ‘blue’ and ‘green’
• Sense of direction
– Speakers of absolute-reference languages have
much better sense of direction than …
– Unreflective gesture while speaking
Recent experiments of Kay et al.
• Experiments at UC Berkeley
– Color perception: do differences in color naming across
languages influence color perception?
• Main finding:
– Lateralized influence of language on perception
– Response time faster for between-category discrimination –
especially for RVF presentation
– A left hemisphere (RVF) phenomenon
green
blue
Types of Conceptual Categories
• Discrete – clear boundaries
– Even integers
– Towns in MA
• Radial – membership comes in degrees
– Birds
– Vehicles
• Family resemblance
– Games
– Furniture
• Ill-defined, vague
– Thought
– Mind
Properties of radial categories
1.
No small set of defining features
–
Example: CUP
–
2.
Fuzzy boundaries
–
3.
What’s the difference between a cup and glass?
Example: VEHICLE
• Car, truck, bus
• Airplane?
• Boat?
• Toy car, model airplane?
• Raft?
• Roller skate?
• Snowboard?
Prototypicality
–
–
Prototypical vehicles: CAR, TRUCK, BUS
Peripheral vehicles: AIRPLANE, TOY CAR, RAFT, ROLLER SKATE, etc
Categories and subcategories
• Subcategories, and sub-subcategories, in hierarchical
chains
–
ANIMAL – MAMMAL – CARNIVORE – CANINE – DOG –TERRIER –
JACK RUSSELL TERRIER – EDDIE
–
Each subcategory has the properties of the category plus
additional properties
Smallest subcategory has the most properties
–
The Cognitive Map Hypothesis
• Hypothesis: Knowledge is organized in the cortex as maps
• Established for somatic and frequency maps
– Local specificity
• Every cortical location has a specific function
– Adjacency
• Adjacent locations for adjacent functions
• Nearby locations for related functions
• Comes in degrees
• Hypothesis: these properties apply to
– Cortical areas in general
– All types of knowledge represented in the cortex
Two hemispheres
Left
Right
Interhemispheric fissure
(a.k.a. longitudinal
fissure)
24
Corpus Callosum Connects Hemispheres
Corpus
Callosum
25
Major Left Hemisphere landmarks
Central Sulcus
Sylvian fissure
26
The Sylvian Fissure opened up (it’s huge)
27
Major landmarks and the four lobes
Central Sulcus
Frontal
Lobe
Parietal
Lobe
Temporal
Lobe
Occipital
Lobe
Sylvian fissure
28
Video of basic cortical anatomy
http://www.youtube.com/watch?v=HVGlfcP3ATI&NR=1&feature=fvwp
From Medical Legal Art (2009)
29
The cerebral cortex is a very large network
• Made up of interconnected neurons
• Very large – billions of neurons
• Dynamic
– Changes take place in connection strengths
• Every neuron is connected (directly or indirectly) to
every other neuron
– Therefore, all of the information in it has the form of a
network
• The information is in the connectivity
30
The brain operates by means of connections
• Neurons do not store information
• Rather they operate by emitting activation
– To other neurons to which they connect
• Via synapses
– Proportionate to activation being received
• From other neurons via synapses
• Therefore, a neuron does what it does by
virtue of its connections to other neurons
– The first big secret to understanding how the
brain operates
31
Gray matter and white matter (coronal section)
Gray
matter
White
matter
32
Some brain quantities
• The cortex accounts for 60-65% of the volume of
the brain
– But has only a minority of the total neurons of the brain
• Surface of the cortex – about 2600 sq cm
– That is, about 400 sq inches
• Weight of cortex –
– Range: 1,130 – 1,610 grams
– Average: 1,370 grams
• Brain mass nears adult size by age six yrs
– Female brain grows faster than male during 1st 4 yrs
• Thickness of cortex – (inf. from Mountcastle 1998)
– Range: 1.4 – 4.0 mm
– Average: 2.87 mm
33
Cortical Neurons
• Cells, but quite different from other cells
– Multiple fibers, branching in tree-like
structures
• Input fibers: Dendrites
• Output fibers: Axons
– Great variation in length of fibers
• Short ones — less than one millimeter
• Long ones — several centimeters
– Only the pyramidal cells have such long ones
34
Cellular Communication:
How to communicate with other cells
• Method One (Nervous System):
– Fibers projecting from cell body
• Branching into multiple fibers
• Input fibers – dendrites
– Allow cell to receive from multiple sources
• Output fiber – axon
– Allows cell to send to multiple destinations
• Method Two:
– Circulation
• Circulatory system
• Endocrine system
• Lymphatic system
35
Primary motor and somatosensory areas
Central Sulcus
Primary
Motor Area
Primary Somatosensory Area
Sylvian fissure
36
Primary Areas
Primary Somatosensory Area
Primary
Motor Area
Primary Auditory
Area
Primary
Visual Area
37
Divisions of Primary Motor and Somatic Areas
Primary
Motor Area
Leg
Primary Somatosensory Area
Trunk
Arm
Hand
Fingers
Mouth
Primary Auditory
Area
Primary
Visual Area
38
Higher level motor areas
Actions perFormed by leg
Leg
Actions
performed
by hand
Actions
performed
by mouth
Primary Somatosensory Area
Trunk
Arm
Hand
Fingers
Mouth
Primary Auditory
Area
Primary
Visual Area
39
The concept DOG
• We know what a dog looks like
– A visual subnetwork, in occipital lobe
• We know what its bark sounds like
– An auditory subnetwork, in temporal lobe
• We know what its fur feels like
– A somatosensory subnetwork, in parietal lobe
• All of the above..
– constitute perceptual information
– are subnetworks with many nodes each
– Are interconnected into a larger network
40
The concept of DOG as a network
A – Auditory
C – Conceptual
M – Memories
P – Phonological
T – Tactile
V - Visual
T
A
P
C
V
M
Each node in this diagram
connects to a subnetwork
of properties
41
Properties of the cortical organization of knowledge
• Local Specificity
– Every node has a specific function
• Appropriate to its location
• Adjacency
– Adjacent nodes have adjacent functions
Properties of category representation in the cortex:
Further details
• Local specifity: Each cell has a specific local function
• Adjacency: Nodes of related function are in adjacent
locations
– More closely related function, more closely adjacent
– Examples:
• Adjacent locations on cat’s paw represented by adjacent cortical
locations
• Similar line orientations represented by adjacent cortical
locations
• Hierarchy: Information is hierarchically organized
Column in a cat’s cortex for a point on the cat’s paw
Properties of cortical representation
• Established for somatic, visual, and auditory maps
– Local specificity
• Every cortical location has a specific function
– Adjacency
• Adjacent locations for adjacent functions
• Nearby locations for related functions
• Comes in degrees
• Hypothesis: these properties apply to
– Higher-level cortical areas
– Therefore, all types of knowledge represented in the cortex
The Cognitive Map Hypothesis
• Hypothesis: Knowledge is organized in the cortex as maps
• Map is a metaphor: local specificity and adjacency
• Support for the hypothesis?
– Established (hence not hypothetical):
• The cognitive map of the body
– Primary motor and somatosensory areas
• The map of pitch frequency
– In primary auditory area
– Hypothesized:
• Higher perceptual levels
• Conceptual information
Extrapolating the findings of perceptual neuroscience
• Extrapolation of experimental findings
– The findings described by Mountcastle can be extrapolated
• To humans
• To higher cortical levels
– to linguistic and conceptual structures
• Justification? Cortical structure, viewed locally, is
– Uniform across mammalian species
– Uniform across different cortical regions
• Cortical structure and function, locally, are essentially the
same in humans as in cats and monkeys and rats
– Moreover, in humans, the regions that support language have the
same anatomic structure as other cortical regions
That‘s it for today!