Lecture 4.1: experimental neuroepistemology

"My most true mind thus makes mine eye untrue"

William Shakespeare, Sonnet CXIII

how to see stars

slide 2

visual motion

figure/ground segmentation on the basis of motion coherence cues only:

visual motion

biological motion is a powerful cue to 3D structure and to "abstract" features of the moving object:

primate electrophysiology


cortical area MT, which specializes in motion processing

primate
electrophysiology

behavioral tasks:

the motion coherence task

moving-dots stimuli at varying degrees of coherence:

the behavioral task is to detect the direction of coherent motion;
the difficulty of this task (and therefore the performance) depends on the degree of coherence.

The motion coherence task: four examples
0 % 5 %
30 % 100 %

slide 8

MT cell responses to motion stimuli

the response of a single cell in area MT columnar organization of area MT by preferred direction of motion

cortical microstimulation

from William T. Newsome's lab (Stanford):

  1. spatial layout of fixation point and eye movement targets

  2. tuning curve illustrating collective responses of neurons in a single MT area column; data obtained from 100%-coherence trials

  3. behavioral data obtained by electrically stimulating the column whose tuning is shown in (B);
    these data are from 0%-coherence trials!

Sonnet CXIII

Since I left you, mine eye is in my mind;
And that which governs me to go about
Doth part his function and is partly blind,
Seems seeing, but effectually is out;
For it no form delivers to the heart
Of bird or flower, or shape, which it doth latch:
Of his quick objects hath the mind no part,
Nor his own vision holds what it doth catch:
For if it see the rudest or gentlest sight,
The most sweet favour or deformed'st creature,
The mountain or the sea, the day or night,
The crow or dove, it shapes them to your feature:
Incapable of more, replete with you,
My most true mind thus makes mine eye untrue.

slide 11

the Astonishing Hypothesis

The Astonishing Hypothesis is that "You," your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. Francis Crick
The Astonishing Hypothesis (1994)

slide 12

the Astonishing Hypothesis

The Astonishing Hypothesis is that "You," your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. Francis Crick
The Astonishing Hypothesis (1994)

"You are nothing but a pack of neurons!"

Implication of the Astonishing Hypothesis:

The perception of a given quality or aspect of the visual stimulus consists of the activity of identifiable neurons in the cerebral cortex.

slide 13

the Astonishing Hypothesis

The Astonishing Hypothesis is that "You," your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. Francis Crick
The Astonishing Hypothesis (1994)

"You are nothing but a pack of neurons!"

functionalism
identity theory of mind
multiple realizability Cutting through the Gordian knot of philosophical doctrines: computational cognitive science