12-week lecture series on "the neural basis of consciousness" by Prof Nao Tsuchiya. Given to 3rd year undergraduate level. No prerequisites. Contents: 1) How can we define “attention”? 2) What are the paradigms to manipulate attention? 3) What are the neuronal mechanisms of attention? 4) How can we explain the relationship between attention and consciousness?

1. Week 8
Consciousness & Attention

2. Recap of Wk 1-7
Basics of neuroscience of consciousness
1. Phenomenology
● Introspection of brief viewing of a natural scene
● Color at periphery & eye movements
● Masking, binocular rivalry, aftereffects
● reports from brain lesion patients

3. Recap of Wk 1-7
2. Data
● Anatomy (brain & eyes)
● Neurons
● Behaviors (non-conscious processing)
● Receptive fields, columnar organization
● Hierarchy & pathways in the visual system (V1-V4, MT, IT,
FFA, PPA)

4. Recap of Wk 1-7
3. Theory
● The neural correlates of consciousness (NCC) & its
search strategy, V1 hypothesis
Methods
● Signal Detection Theory
● Various neuronal measures (fMRI, E/MEG, ECoG, single
neuron, microstimulation)

5. Recap of Wk 7
The neural correlates of color qualia in V4/V8
The neural correlates of perception of objects in IT and faces
in FFA
Single neuron recordings in human hippocampus
Binocular rivalry: phenomenology & behaviors
Neural recording in monkeys during binocular rivalry
V1/V2, V4, MT, IT

6. Issues left unanswered in Wk 1-7
Blindsight: subcortical pathway - important for attention?
● Relationship between consciousness and attention
Human single unit, rivalry -> neural correlates of report?
● Relationship between consciousness and report
How is it possible that different regions specialize to give rise
to specific qualia?
● Hard Problem - Integrated Information Theory
>> All issues are at the frontiers of consciousness research!

7. In Wk 8,
We will:
Start examining the relationship between consciousness
and attention.

8. Learning Objectives
To be able to answer the following questions:
● How can we define “attention”?
● What are the paradigms to manipulate attention?
● What are the neuronal mechanisms of attention?
● How can we explain the relationship between attention
and consciousness?
QFC Chapter 9, 10 (Optional: Dehaene 2006 TICS)

10. What do we mean by“attention”?
Intuitive concepts
General arousal, alertness, readiness
Gaze (overt eye movements vs. covert shift of attention)
Selection / focus / concentration
Enhancement / Amplification
Suppression / Inhibition
Defining attention

11. William James (1890)’s definition of attention
Everyone knows what attention is. It is the
taking possession by the mind, in clear and
vivid form, of one out of what seem several
simultaneously possible objects or trains of
thought. It implies attention is bullshit.
Attention is crap.
Defining attention

12. William James (1890)’s definition of attention
Everyone knows what attention is. It is the
taking possession by the mind, in clear and
vivid form, of one out of what seem several
simultaneously possible objects or trains of
thought. It implies withdrawal from some
things in order to deal effectively with others.
Defining attention

13. William James (1890)’s definition of attention
Everyone knows what attention is. It is the
taking possession by the mind [access/focus],
in clear and vivid form, of one out of what
seem several simultaneously possible
objects or trains of thought [selection]. It
implies withdrawal from some
things[inhibition] in order to deal effectively
with others. Defining attention

14. Different names, related concepts
Bottom-up attention
● Automatic, stimulus-driven, task-irrelevant, exogenous,
saliency-based, (pre-attentive)
Top-down attention
● Volitional, goal-driven, task-relevant, endogenous,
(attentive)
Defining attention

15. Other important distinctions of attention
Space (Spatial attention)
Time (Temporal attention)
Feature (Feature-based attention)
Object (Object-based attention)
Defining attention

16. Top-down vs Bottom-up attention
Defining attention

17. Various options on C-A relationship
a) attention determines what becomes conscious and what
not, and hence determines what we can report about.
b) considers nonattentional mechanisms for consciousness.
Defining attention
Lamme 2004 Neural Network

18. Attention = Consciousness (a,b,c): [serial process]
Defining attention
Lamme 2004 Neural Network

19. Conscious state first! [Serial process]
d) many more inputs reach a conscious state, yet to report
about these, we need attention.
a-d) are serial models
Defining attention
Lamme 2004 Neural Network

20. [Parallel process] A is necessary for C
Defining attention
Lamme 2004 Neural Network

21. Consciousness and Attention: Orthogonal
Defining attention
Lamme 2004 Neural Network

22. Summary
“Attention” can be used in various ways.
Scientifically precise definitions are available.
Important to clarify the source / definition of A.
The neuronal mechanisms for A could be different for
different kinds of A.
Relationship with C can be dependent on the kind of A.
Defining attention

23. Summary
Various relationships between C and A have been proposed.
Important distinction (Week 9):
What we consciously experience
vs.
what we can report about
How can we manipulate attention?
Defining attention

25. Psychophysical methods to manipulate attention
To understand the relationship between C and A, it would be
nice to keep unrelated components unchanged.
● Keeping the stimulus the same. Remove eye movement
confounds.
Manipulating attention

26. Psychophysical methods to manipulate attention
Problem: Bottom-up A is, by definition, stimulus-driven.
Still, we can study:
● how A-C relationship changes due to stimuli.
● how eye movements are (consciously/unconsciously)
guided by stimuli.
Manipulating attention

27. Change blindness
https://www.youtube.com/watch?v=bh_9XFzbWV8
Manipulating attention

28. Inattentional blindness
https://www.youtube.com/watch?v=vJG698U2Mvo
Manipulating attention

29. Attentional blink
https://www.youtube.com/watch?v=MH6ZSfhdIuM
Manipulating attention

30. Manipulating attention
Dual tasks
Li 2002 PNAS

31. Manipulating attention
Li 2002 PNAS

32. Manipulating attention
Matthews 2018 Phil Trans

33. Manipulating attention
Matthews 2018 Phil Trans

34. Manipulating attention
Li 2002 PNAS

35. Summary
Many paradigms manipulate various aspects of attention.
To study the relationship between A and C, keeping stimuli,
consciousness, or behaviors is ideal.
Manipulation of bottom-up attention is difficult to interpret.
Promising manipulation of top-down attention includes:
Covert shift of attention through instruction & expectation.
Manipulating attention

36. Summary
Key paradigms in the future are likely to be:
Change/inattentional blindness [and crowding] (spatial)
Attentional blink [and masking] (temporal)
Dual tasks
How much do we know about the neural mechanisms of
attention?
Manipulating attention

38. What is the neural basis of attention?
Key features to consider visual attention:
(Top-down/bottom-up, spatial/temporal/featural/object)
Hierarchical organization of the visual cortex.
Competing neuronal interactions.
Neural basis of attention

39. Need for attentional mechanisms
Architecture of visual
system.
Biasing competition to
resolve ambiguity.
Neural basis of attention

40. V4
V2
Stimulus
Neural basis of attentionTime

41. V4
V2
Stimulus
Neural basis of attentionTime

42. V4
V2
Stimulus
Neural basis of attentionTime

43. V4
V2
Stimulus
Neural basis of attentionTime

44. V4
V2
Stimulus
Neural basis of attentionTime

45. V4
V2
Stimulus
Neural basis of attentionTime

46. Spatial attention [V4 neuron]
Neural basis of attention

47. Feature-based attention [V4 neuron]
Motter 1994 JNS
Reynolds 2004 Ann Rev Neuro
Neural basis of attention

48. Core principles of biased competition
Attentional effects gets stronger …
● [Stimulus] when competition among stimuli becomes
stronger
● [Neuron] when a neuron receives many inputs
○ Higher visual areas with larger RF
● [Psychological] when some biasing process operates
(instruction, expectation, memory …)
As a result, conscious perception can drastically change
without changes in stimuli! Neural basis of attention

49. Frontal & Parietal areas: the source of attention?
Neglect/extinction patients
https://www.youtube.com/watch?v=d4FhZs-m7hA
Neural basis of attention

50. What is the source of attentional bias?
Moore 2003 Nature
Neural basis of attention

51. So, can we explain attention-related blindness?
Inattentional/Change blindness
Competition, feature-based attentional suppression
Attentional blink/masking - temporal competition
All failure of “signal amplification”?
Neural basis of attention

52. Global
Neuronal
Workspace
Theory
Neural basis of attention
Dehaene 2006 TICS

53. Summary
Neuronal basis of attention:
Biasing signals from the frontal and parietal cortex to
resolve competition.
Overlapping RF (the higher visual areas, the bigger
overlap).
Neural basis of attention

54. Summary
Global Neuronal Workspace (GNW) Theory
… can explain various aspects of attention-related reports
of “blindness” through a failure of amplification of signal and
of reaching to global workspace.
GNW explains reports about consciousness.
Can GNW also explain conscious experience per se?
What is the link between the neurons and consciousness?
Neural basis of attention

55. Questions
Is attention necessary when there is no competition?
Can this biased competition model explain the findings of
dual task?
● Under dual tasks, why can we see faces and scenes but
not disks?
Should attention operate on both visible and invisible stimuli?
Neural basis of attention