12-week lecture series on "the neural basis of consciousness" by Prof Nao Tsuchiya. Given to 3rd year undergraduate level. No prerequisites. Contents: 1) What are the evidence supporting the claim that higher visual areas are the NCC? 2) What are the phenomenological and behavioral characteristics of binocular rivalry? 3) How did the researchers establish the binocular rivalry paradigm with monkeys as participants? 4) What are the implications of the NCC studies using binocular rivalry?

1. Week 7
Neural basis of consciousness:
Higher visual areas and the NCC
Prof Nao Tsuchiya
Twitter: @conscious_tlab
Email: naotsugu.tsuchiya@monash.edu
Facebook: Naotsugu Tsuchiya

2. Recap of Wk 6
The NCC:
● The minimal set of neurons that is sufficient to give rise to
a particular conscious percept.
Empirical NCC search strategies:
● Fix either sensory input, conscious percept, or behavioral
output, while vary the others.

3. Recap of Wk 6
V1 is an unlikely candidate for the NCC.
● Nonconscious orientation-dependent adaptation is likely
mediated by V1. --> V1 not sufficient.
MT is likely to be the neural correlates of motion qualia.
● MAEs are mediated by MT and require visibility of motion
stimulus (MT neurons have to be selectively adapted).
● Lesions, neuronal recordings, microstimulations in MT
strongly imply its sufficiency for motion qualia.

4. In Wk 7,
We will:
● Review the evidence for higher visual areas as the
candidate for the other content-specific NCCs.
● Introduce powerful tools for consciousness research.
E.g., binocular rivalry, CFS, decoding, …

5. Learning Objectives
To be able to answer the following questions:
● What are the evidence supporting the claim that higher
visual areas are the NCC?
QFC Chapter 7 & 8

6. Learning Objectives
● What are the phenomenological and behavioral
characteristics of binocular rivalry?
● How did the researchers establish the binocular rivalry
paradigm with monkeys as participants?
● What are the implications of the NCC studies using
binocular rivalry?
QFC Chapter 16

8. Cortical hierarchy in the
visual system (Week 5)
Is V4 the NCC?
Felleman 1991 Cereb Cor

9. V4 is a part of retinotopic area
Is V4 the NCC?

10. Is V4 responsible for color qualia?
Koch 2004 “Remarkably, this patient—and
others like him—do not notice that they see in
grey in one part of their visual field and in
color in another” Is V4 the NCC?
Gallant et al 2000 Neuron
AR: selective lesion in
right ventral area
(likely V4)s

11. Is V4 responsible for color qualia?
Hue discrimination task. Constant brightness & saturation
(Max hue difference = 180 deg).
Is V4 the NCC?
However, V4 lesioned monkeys show only mild color deficits.
How can we test if V4 is the NCC for color? Gallant et al 2000 Neuron

12. Does V4 react to color afterimages?
Is V4 the NCC?

13. +
Is V4 the NCC?

14. +
Is V4 the NCC?

15. +
Is V4 the NCC?

16. V8 reacts to color afterimages!
Is V4 the NCC?
Hadjikhani 1998 Nat Neu

17. Can stimulating V4/V8 elicit color qualia?
http://movie-usa.glen
coesoftware.com/vid
eo/10.1073/pnas.17
13447114/video-2
Is V4 the NCC?
Schalk 2017 PNAS

18. Summary
V4/V8 is a likely candidate of the neural correlates of color
qualia
● Lesion, afterimages, electrical stimulation
But what is special about neurons in V4/V8 in generating
color?
--> The Hard Problem?
Is V4 the NCC?

20. Can we find the NCC in higher visual areas?
Is IT/FFA the NCC?

21. Inferior temporal cortex for object recognition
Is IT/FFA the NCC?

22. Damage to the ventral cortex
phenomenology of
agnosia
Is IT/FFA the NCC?

23. Fusiform Face Area and Parahippocampal Place Area
Functional localizer
technique.
Isolate areas that respond
to a particular category of
stimuli.
Tong et al 1998 Neuron Is IT/FFA the NCC?

24. Electrical stimulation of FFA. vs V4/V8
Is IT/FFA the NCC?
Schalk 2017 PNAS

25. (Monkey) Face patches in IT
97% of visually
responsive cells
in this patch are
strongly face
selective
Is IT/FFA the NCC?
Tsao 2006 Science

26. RFs for IT neurons are bigger than those for early visual areas
Is IT/FFA the NCC?

27. Receptive field (RF) properties of neurons in IT is complex
Is IT/FFA the NCC?

28. Neurons in IT can respond to a specific face
Is IT/FFA the NCC?

29. Human Medial Temporal Lobe contain neurons with more specificity!
Is IT/FFA the NCC?
Quiroga 2005 Nature
Left posterior
hippocampus

30. Human Medial Temporal Lobe contain neurons with more specificity!
Is IT/FFA the NCC?
Right anterior
hippocampus
Halle Berry
Quiroga 2005 Nature

31. Human Medial Temporal Lobe contain neurons with more specificity!
Is IT/FFA the NCC?
Left anterior
hippocampus
The Sydney
Opera House
and the Baha’i
Temple
Quiroga 2005 Nature

32. These neurons firing correlate with visibility during masking
Is IT/FFA the NCC?
Right entorhinal
cortex
World Trade
Center
Quiroga 2008 PNAS

33. These neurons firing correlate with visibility during masking
Is IT/FFA the NCC?
Quiroga 2008 PNAS

34. Summary
Inferior temporal cortex and ventral temporal cortex are
crucial for object / face recognition.
Lesion -> Object agnosia / Prosopagnosia
fMRI activation -> FFA/PPA
Stimulation -> Face percept
Is IT/FFA the NCC?

35. Summary
Targeted recording within the face patch in monkey reveal
face neurons.
● Localizer + stimulation / phenomenology + recording is a
powerful methods for future NCC research
Is IT/FFA the NCC?

36. Summary
Monkey IT and Human MTL’s neurons are very selective.
● Do they correspond to what we report or what we see?
● Too big RFs? Too transient responses?
● Are single neurons responsible for conscious percept? If
not, then what are responsible?
● Is there a better paradigm for the NCC search?
Is IT/FFA the NCC?

38. Binocular rivalry as a potent tool for the NCC search
BR: a tool for the NCC

39. Set up for binocular rivalry (BR) experiments
Carmel 2010 J Vis Exp
BR: a tool for the NCC

40. BR in everyday life
BR: a tool for the NCC

41. BR in everyday life
BR: a tool for the NCC

42. BR in everyday life
BR: a tool for the NCC
Gallagher & Tsuchiya 2020 iPerception

43. Psychophysical investigation of BR
BR: a tool for the NCC

44. Continuous Flash Suppression (CFS)
Edge-rich changing (10Hz) Mondriaan patterns can reliably suppress the
visual input to the other eye for a long duration.
>> Potent tool for studies of nonconscious processing.
BR: a tool for the NCCTsuchiya & Koch 2005 Nat Neuro

45. Potential neurala models of BR/CFS
Q1. What is the mechanism of “suppression”?
Q2. What is the fate of the suppressed stimulus?
Q3. How does the nature of the stimuli affect
BR/CFS?
Q4. What is the NC of the visible and invisible
stimuli?
Q5. What is the neural mechanisms of perceptual
switches?
BR: a tool for the NCCTong 2006 TICS

46. Summary
BR can be induced in everyday life.
Under constant stimulation of BR, conscious percept flips
between two alternatives in a random manner.
CFS suppresses a stimulus more reliably.
● Precise mechanisms of BR/CFS are still unknown.
What is the neural activity during binocular rivalry?
BR: a tool for the NCC

48. Recording neural activity during BR
NCC in BR
Need to train monkeys to report
binocular rivalry. Can we do this?
Do monkeys perceive BR similar to
humans?
Need to characterize BR in
monkeys.

49. Monkeys and humans experience BR similarly
Leopold 1996 Nature NCC in BR

50. V4 neuron’s activity and monkeys reports in BR!
NCC in BRLeopold 1996 Nature

51. V4 neuron’s activity and monkeys reports in BR!
Neuron 133 started firing
more a few seconds
before the monkey
reported left tilt (red
horizontal bars).
NCC in BRLeopold 1996 Nature

52. Some neurons are anti-correlated with reports!
NCC in BRLeopold 1996 Nature

53. IT neuron firing correlates with BR reports
NCC in BR

54. More NCC found in higher visual areas
NCC in BR
Logothetis 1998 PTRS

55. More NCC found in higher visual areas
NCC in BRBoly 2013 Frontiers

56. Summary
Monkeys can be trained to report their conscious perception
during BR.
Compelling psychophysical evidence supports its validity.
Extensive recordings of neural spiking revealed …
Less NCC in early visual areas
More NCC in higher visual areas + PFC
Mixed NCC in mid visual areas
NCC in BR

57. If IT neurons are the NCC, does it make sense?
● IT neurons have bigger RFs and their responses are
invariant. Does it correspond to our phenomenology?
What is the meaning of anti-correlated firing in mid-level
visual areas?
● Better to consider the NCC as a population of neurons?
What do they tell us about the NCC?
NCC in BR