1. Attention, prediction and fMRI (cont.) Adaptation-fMRI

2. Class project: due Tues. April 29th
April 29th: Just before start of “reading week”
How long?
The shorter the better! Max. 6 pages
Format?
Front-load the information
1st sentence: What Q are you asking?
2nd sentence: How are you going to ask it?
3rd sentence: Why should the reader care?

3. Class project: due Tues. April 29th
Content?
Show that you have explored to find out what is currently known, what is unknown
Show that you have thought about what an interesting new direction to look would be
Describe in broad terms an expt which would look in that direction
State an explicit hypothesis
Describe explicitly how the data will test that hypothesis
Give elevator pitch?

4. Prediction and prediction errors
rticle/Reward_signals

5. Predictive coding Subtract expectations from bottom-up input
Helmholtz, Mumford, Rao & Ballard, Friston
Jehee & Ballard (2009)

6. Top-down enhancement
Kastner et al. (1999)

7. Attention within a receptive field: Moran & Desimone (1985)
Figure from /week-2.html

8. Trying to pull apart attention and expectation
Kok et al. 2012

9. Trying to pull apart attention and expectation: predictions
Kok et al. 2012

10. Trying to pull apart attention and expectation: results
Kok et al. 2012

11. Top-down feedback of information: Decoding the yellow of a gray banana
Bannert & Bartels, 2013

12. Top-down feedback of information: Decoding the yellow of a gray banana
Bannert & Bartels, 2013

13. Adaptation fMRI A bit like pattern-based analyses:
Beyond “what lit up”
Motivation very similar to that of pattern-based fMRI
Just because two stimuli produce equally intense local avarge activations, that doesn’t mean that the brain can’t tell the two stimuli apart

14. Gaussian spatial smoothing to improve signal-to-noise
Distinction between representations is lost: After smoothing, there’s no difference left
Boynton
Kriegeskorte
Haxby
Raizada
/ra/
/la/
Gaussian spatial smoothing to improve signal-to-noise
Stimulus A
activation
pattern
Stimulus B
Average activation same, but spatial patterns different
Smoothed local average activation ends up the same

15. Key idea: neurons get tired
Neurons have a preferred stimulus
Repeated presentation of a neuron’s preferred stimulus habituates it (makes it tired)
Activation goes down
Presentation of something that the neuron counts as different allows it to recover again

16. Adaptation fMRI as a probe of neural difference-detection (Grill-Spector & Malach)
Two stimuli: can neurons tell the difference?
A voxel containing neurons that respond to all politicians, irrespective of party
A voxel containing some specifically Democratic neurons, and other specifically Republican neurons.
Rajeev Raizada - UW MRI talk, Oct. 2003

17. Responses to individual stimuli do not show whether neurons can tell the difference
Different sets of neurons are active within the voxel, but overall fMRI responses are indistinguishable
Rajeev Raizada - UW MRI talk, Oct. 2003

18. Neural adaptation to repeated stimuli does show the difference: What counts as repetition for neurons in a voxel
Same neurons, adapting:
It’s a politician again
It’s a politician
It’s a Republican
Different, fresh neurons: It’s a Democrat
Rajeev Raizada - UW MRI talk, Oct. 2003

19. Categorical perception: Not all differences make a difference as speech (Alvin Liberman & colleagues)
Stimuli spread evenly along the /ba/-/da/ continuum
Pure /ba/=1, pure /da/=10, perceptual boundary ~ 5
Presented as pairs, constant 3-step distance apart acoustically
1-4 and 7-10 do not cross boundary: perceived as same
3-6, 4-7 do cross boundary, perceived as different
Rajeev Raizada - UW MRI talk, Oct. 2003

20. A brain area is processing the stimuli categorically, and therefore as speech, if activity parallels the subject’s same/diff curve
Acoustic difference within each pair is constant
(1-4, 4-7, 9-6 etc.)
Phonetic difference depends on whether category boundary is crossed
Raizada & Poldrack (2007)
Rajeev Raizada - UW MRI talk, Oct. 2003

21. Release from adaptation
Activation due to release from adaptation =
Extra activation caused by stimulus change =
(Response to the two different stimuli paired together) - (Response to same stimuli presented without the change)
E.g. (1/4 + 4/1) - (1/1 + 4/4)
To look for adaptation paralleling same/diff perception
Make a contrast weighting each adaptation release value by the subject’s behavioural responses on that part of the same/different curve
Rajeev Raizada - UW MRI talk, Oct. 2003

22. Parallel with infant studies
Suppose we measure how long a baby looks at its mother’s face and its father’s face
Suppose it looks for equal amounts of time at each parent
Does that mean that the baby can’t tell Mom and Dad apart?

23. Infant habituation studies: overall design
Johnson, M. H. (2001). Functional brain development in humans. Nature Reviews Neuroscience, 2(7),

24. Infant habituation studies: time-course
Turk-Browne, N. B., Scholl, B. J., & Chun, M. M. (2008). Babies and brains: habituation in infant cognition and functional neuroimaging. Frontiers in Human Neuroscience, 2.

25. Another adaptation-fMRI example: what counts as different?
From Turk-Browne et al., (2008), adapted from Kourtzi & Kanwisher (2001)

26. Another adaptation-fMRI example: tuning, and what counts as different
Malach, R. (2012). Targeting the functional properties of cortical neurons using fMR-adaptation. Neuroimage, 62(2),