1. Brain Function II: Evidence from Neuroanatomy and Perception
Brain, Mind, and Belief: The Quest for Truth
Brain Function II: Evidence from Neuroanatomy and Perception
“Our neural pathways establish reruns of what has gone on before. Like the three-year-old who insists on watching The Little Mermaid over and over again, we cling to our warped illusions with a tenacious grip. Get your bloody hands off my illusion! Even though it makes us miserable, we prefer to place our faith in the disaster we have made.”
                                                                  Pam Grout

2. Where we have been Figuring out how the brain works
Methods in general use
Lesion studies
Functional brain imaging
Guiding principles in current use
Tool-driven inquiry
Misapplied metaphor
The brain is a computer
A better way
Think harder
Use evidence from linguistics

3. Thinking harder Avoid metaphorical thinking
REVIEW
Thinking harder
Avoid metaphorical thinking
The brain is not a computer
Not like a human being with paper & pencil & books
In fact it is not like anything else
It is itself: the brain

4. Where we are The mind is a relational network system
As revealed by evidence from linguistics
We can study relational networks at different levels of precision
Abstract network notation
Narrow network notation
Hypothesis:
Relational networks are implemented in neural structures

5. Levels of precision Abstract relational network notation
Narrow relational network notation
Neural structures
A node of narrow RN notation is implemented physically as a bundle of neurons

6. Where we are headed Consider further evidence Neuroanatomy
Perceptual neuroscience
Examine further findings on perception

7. Functional bundles of neurons: Cortical columns
“[T]he effective unit of operation…is not the single neuron and its axon, but bundles or groups of cells and their axons with similar functional properties and anatomical connections.”
Vernon Mountcastle, Perceptual Neuroscience (1998), p. 192

8. The cortical (mini)column
Compare:
atom and molecule :: neuron and column of neurons
Molecule: a bundle of atoms that function together as a unit
Cortical Column: a
bundle of neurons
that function
together as a unit

9. Gray matter and white matter

10. Coronal section magnified
From top to bottom,
About 3 mm
Has 6 layers

11. Microscopic views
Different stains show different features

12. The node of narrow RN notation vis-à-vis neural structures
The node corresponds not to a single neuron but to a bundle of neurons
The cortical column
A column consists of neurons stacked on top of one another
All neurons within a column act together
When a column is activated, all of its neurons are activated

13. Large-scale cortical anatomy
The cortex in each hemisphere
Appears to be a three-dimensional structure
But it is actually very thin and very broad
The grooves – sulci – are there because the cortex is “crumpled” in order to fit inside the skull

14. Topologically, the cortex of each hemisphere (not including white matter) is..
Like a thick napkin, with
Area of about 1300 square centimeters
200 sq. in.
2600 sq cm for whole cortex
Thickness varying from 3 to 5 mm
Subdivided into six layers
Just looks 3-dimensional because it is “crumpled” in order to fit inside the skull

15. Topological essence of cortical structure
Each column represents a node
The network is thus a large two-dimensional array of nodes
Third dimension for
Internal structure of the nodes (columns)
Cortico-cortical connections (white matter)

16. Neurons, Columns, Cortex
At the small scale..
Each column contains around 80 neurons
At a larger scale..
Each column acts as a node of the cortical network
The cerebral cortex as an array* of columns:
Grey matter — columns of neurons
White matter — inter-column connections
*Array: two dimensional (a lot simpler than 3-dimensional)

17. Composition of a typical minicolumn
Contains about 80 neurons
Range: 70 to 110
Mostly pyramidal neurons
Cell bodies of these neurons are “stacked” vertically
(i.e., in a column – hence the name)
Fibers extending from the cell bodies
Many are vertical (especially those of pyramidal cells)
Some are horizontal
They connect to neighboring columns

18. Evidence for columns Microelectrode penetrations of cortex
Electrode is small enough to detect activation in a single neuron
If perpendicular to cortical surface
Neurons all of same response properties
If not perpendicular
Neurons of different response properties

19. Column in a cat’s cortex for a point on the cat’s paw

20. Columns as functional units: Orientation of lines (visual cortex)
Microelectrode penetrations
K. Obermayer & G.G. Blasdell, 1993

21. Bundles of columns Minicolumn – 30-50 microns diameter
Maxicolumn – a contiguous bundle of minicolumns (typically around 100)
microns diameter
Dimensions vary from one part of cortex to another
In some areas at least, they are roughly hexagonal
(There are also larger bundles)

22. Columns of different sizes
Minicolumn
Larger
column
View: looking downward from top of column. So each circle represents a column

23. Cortical minicolumns: Quantities
Diameter of minicolumn: 30 microns
Neurons per minicolumn: (avg )
Minicolumns/mm2 of cortical surface: 1460
Minicolumns/cm2 of cortical surface: 146,000
Neurons under 1 sq mm of cortical surface: 110,000
Approximate number of minicolumns in Wernicke’s area: 2,920,000 (at 20 sq cm for Wernicke’s area)
(Wernicke’s area is devoted to speech recognition)
Cf. Mountcastle 1998: 96

24. Cortical column operation
The linguistic system operates as a network whose nodes are cortical columns
Columns do not store symbols
Their basic function: receive and send activation
Integration: A column is activated if it receives enough activation from other columns
Can be activated to varying degrees
Can keep activation alive for a period of time
Broadcasting: An activated column transmits activation to other columns
Excitatory – contribution to higher level
Inhibitory – dampens competition at same level

25. Integration and Broadcasting
Now I’ll tell my friends!
Broadcasting
Integration
Wow, I got activated!

26. Operations in neurocognitive networks
Activation moves along lines and through nodes
(along the pathways of the brain)
Integration
Broadcasting
Connection strengths are variable
A connection becomes stronger with repeated successful use
A stronger connection can carry greater activation

27. Basic answer to the what/how question: What goes on in those nodes of the network?
Integration and Broadcasting
Broadcasting
To multiple locations
In parallel
Integration

28. Part of the network for FORK
Each node in this diagram
represents a cortical column C T M
C — conceptual
M — motor
T — tactile
V — visual V

29. Part of the network for FORK
Each node in this diagram
connects to a supporting subnet. For example, C T M
Let’s zoom in on this one V

30. Zooming in on the “V” Node..
A network of
visual features V
FORK
The cardinal node of this subnet
Etc. etc.
(many layers)

31. Some nodes of the cortical net for fork
Ar – Articulation
Au – Auditory
C – Conceptual
M – Motor
P – Phonological
T – Tactile
V – Visual M C Ar P V Au

32. Some nodes of the cortical net for forkPP P V PA

33. Perception: the basic process
A bottom-up process
From primary perceptual area upwards
E.g. primary auditory, for auditory perception
Multiple steps of integration and broadcasting
Takes place in a perceptual area of cortex
E.g. auditory cortex for auditory perception
Works by integrating inputs to the associated sense organ
E.g. auditory input for auditory perception
Multiple steps of integration
From very simple
To more complex

34. Perception: Multiple steps of integration and broadcastingV
DOG
From lower
levels up to
higher levels

35. These are cortical (network) structures that have to be learned
Experiment by David Hubel and Torsten Wiesel
Kittens kept in dark room during critical period for developing vision
Exposed to vertical lines but not horizontal lines
Later, bumped into strings stretched horizontally in their path
Couldn’t see them
Their eyes received the information
But their brains couldn’t integrate it

36. Hints of what goes on in visual perception (multiple steps of integration and broadcasting) I: Shapes recognized by different low level columns

37. Hints of what goes on in visual perception (multiple steps of integration and broadcasting) II. Relatively higher level (but still quite low)

38. Hints of what goes on in visual perception (multiple steps of integration and broadcasting) III. At a somewhat higher level

39. Hints of what goes on in visual perception (multiple steps of integration and broadcasting) IV. Somewhat higher level
Elementary shapes like these..

40. Hints of what goes on in visual perception (multiple steps of integration and broadcasting) IV. Somewhat higher level
..can be integrated into more complex formations

41. We see only the past Perception is a bottom-up process
From primary perceptual area upwards
Step by step through multiple levels
Using network connections that have been established
These connections have been built step by step
From lower levels to higher levels
As a result of previous experience
The whole perceptual structure is built through experience
Therefore, it is based upon the past
Hence, we see nothing as it is now

42. Returning to work after 30 years
Play
video

43. Perception: Refining the starting (simple) view
The simple (starting) view:
A single perceptual modality
Auditory perception in auditory cortex
using auditory information
Step by step from bottom up
Complications/Refinements
It is not confined to a single perceptual modality
Not just bottom-up
Not even confined to posterior cortex

44. The McGurk Effect http://www.youtube.com/watch?v=aFPtc8BVdJk
Acoustic syllable [ba] presented to subjects
with visual presentation of articulatory gestures for [ga]
Subjects typically heard [da] or [ga]
“Evidence has accumulated that visual speech modifies activity in the auditory cortex, even in the primary auditory cortex.”
Mikko Sams (2006)
How does it work?
Visual input
Top-down processing

45. Refining the starting (simple-minded) view: I
It is not confined to a single perceptual modality
Example: The McGurk effect
Auditory perception affected by visual input
i.e., top-down processing from visual to auditory
Conceptual structure affects auditory perception
The influence of context on speech perception
She cooked it in the frying an
I’ll help you if I an

46. An important finding from neuroanatomy: Reciprocal connections
An established fact of neuroanatomy:
A connection from point A to point B in the cortex is generally accompanied by a connection from point B to point A
Separate fibers (axons): (1) A to B, (2) B to A
In short, cortico-cortical connections are generally bidirectional
Hence, Bidirectional Processing A B

47. Bidirectional processing: reciprocal links
excitatory
inhibitory

48. Perception – Refining a simple-minded view: II
Not confined to a single perceptual modality
Example: The McGurk effect
Visual input affects auditory perception
Conceptual structure affects auditory perception
Not just bottom-up
Top-down processing fills in unsensed details
Not even confined to posterior cortex

49. Perception: All these lines represent bi-directional connectionsV
DOG
Etc. etc.
(many layers)

50. A terminological problem
We need to distinguish
Perception narrowly conceived
The basic process of recognition
Single perceptual modality
Bottom-up processing
No motor involvement
Perception broadly conceived
Two different terms needed
Recognition (a.k.a. ‘microperception’)
Bottom-up process in a single perceptual modality
Perception (the broad conception) (a.k.a. ‘macroperception’)

51. “Micro-perception” and “macro-perception”
A.k.a. recognition
The local process of integrating features
Performed in one perceptual modality
Bottom-up
Macroperception
The overall process of perception
Uses multiple modalities
Uses top-down processing

52. Perception – Refining a simple-minded view
Not just bottom-up
Top-down processing fills in unsensed details
Not confined to a single perceptual modality
The McGurk effect
Visual input affects auditory perception
Conceptual structure affects auditory perception
Not even confined to posterior cortex
Can also use motor neurons (frontal cortex)
Experiment: left hand or right hand?
Mirror neurons

53. Left hand or right hand?

54. Left hand or right hand?

55. Left hand or right hand?

56. Left hand or right hand?

57. Left or right hand? How do you do it? Imaging experiment
Subjects were shown pictures of one hand
Asked to identify: left or right
Functional imaging showed increased CBF in hand area of motor cortex
Peter Fox, ca. 2000

58. Motor structures in perception
The left-hand vs. right-hand experiment
‘Mirror neurons’ in motor cortex
Articulation as aid to phonological perception
Articulation in reading
Motor activity in listening to music
Watching an athletic event

59. Mirror Neurons
NY Times: “One mystery remains: What makes them so smart?” (Jan. 10, 2006)
Answer: They are not smart in themselves
Their apparent smartness is a result of their position: at top of a hierarchy
Compare:
The general of an army
The head of a business
Similarly, high-level conceptual nodes
The “cardinal node”

60. Mirror Neurons What makes mirror neurons appear to be special?
Ans.: They receive input from visual perception
The superior longitudinal fasciculus
Connects visual perception to motor areas
How can a motor neuron receive perceptual input?
Motor neurons are supposed to operate top-down
Answer: bidirectional processing
They also receive perceptual information
Bottom-up processing

61. Superior Longitudinal Fasciculus
From O. D. Creutzfeldt, Cortex Cerebri (1995)

62. Are some neurons “smarter” than others?
Alternative: the head of a dedicated net
Dedicated nets have hierarchical structure
It is the hierarchy as a whole that has those ‘smarts’
Similarly, mirror neurons
They get visual input since they are connected to visual areas
Superior longitudinal fasciculus

63. Implications of hierarchical organization
Nodes at a high level in a hierarchy may give the appearance of being very “smart”
This appearance is a consequence of their position — at top of hierarchy
As the top node in a hierarchy, a node has the processing power of the whole hierarchy
Compare:
The general of an army
The head of a business organization

64. Perception of height – Experiment by P. R. Wilson (1968)
Subjects were students in an Australian university
Five separate classes
A man was introduced as a visitor from Cambridge Univ.
Class 1: introduced as a student
Class 2: introduced as a demonstrator
Class 3: introduced as a lecturer
Class 4: introduced as a senior lecturer
Class 5: introduced as a professor
The man then left the room
Students were asked to estimate his height
Height estimates increased avg. ½ inch for each step
“Professor” was estimated to be 2 ½ inches taller than “student”

65. Perception: We see what we expect to see
Top-down effects in thinking and perception
The mechanism: bidirectional connections
Conceptual structure influences perceptual operations
Higher-levels of perceptual structure can likewise influence lower levels
We see what we expect to see
Where do the expectations come from?
Ans: From information already present in our conceptual/perceptual systems
Thus to a large extent we see only the past

66. T h a t ‘ s i t f o r t o d a y !