KANWISHER Nancy FACES Mar 22 2012

Prof. Nancy K.  gives this talk at 10AM in Clark Aud  at the

CNI 1st year anniversary inaug event.

******

interested in  WHAT selectively lights up voxels in the brain (and where and why)

faces, places, and bodies: very strongly selective  at least 2x as strong as other stim

places and faces: 2 to 1 selectivity ratio (rel. to other stim)

also the  place areas and face areas are in the same location in all people

and bodies.

each stim class has been tested extensively...

but there are at least 2 or more subregions for each of these

bodies  (in green) in her slides

faces  in blue  4 areas.. FFA 

places... 5 regions light up

slides... shows lateral view of brain  and view of ventral surface of brain ;

words/letters light up L fusiform gyrus  in an orthographic alphabet that u know but not in one that u do not know.

other people's thoughts (mirror neurons:  TOMind)... perhaps some specific regions

sl = slide:   so other regions exist that are selective for other categories...

But consider;  there are lots of possible stimuli:... music instruments, faces, bodies, places, cars  - u name it

she does an experiment with other stim but voxels do not light up for other stim categories; 
 but ALL subjects  respond to faces, places and bodies...
all have regions that are selective for those 3...

Amusing slide  showing  Francis Gall;s  attempts and hypotheses to

localize function in the brain...
1758 to 1828

she shows a huge list of functions that Gall thot were selectively and specifically handled by localized brain regions
(very amusing list  ...  BUT...  it includes  faces, places and bodies !!!)...

Here are some generic problems with this line of experimentation:
sl .. problem 1   we only test certain hypotheses...  
But the space of all possible hypotheses is huge: how about regions for  SHOES or vases or cars. 

ie  we're only testing a restricted functional hypothesis space...

so,  there is a huge space of possible stimuli that brain cud  be responsive to..

problem 2  a bias for blobs.... (that is, local regions of contiguous voxels that light up)
it is quite conceivable that the brain could be functionally selective but that the neurons doing the work are spread out
(as in sparse distrib coding)

slide:  so, instead of assuming places, faces etc.  or contig regions,  lets do a
   data-driven  structure discovery experiment  (which she and her group did)

see vul,  lashkari,  hsieh, golland

make no assumpt. abt  the response profile,
no assump  abt  spatial location of voxels  (cud be  really diffuse)

sl  clustering method
scan 11 subjects while they look at 69 stimuli from 9 categories

result is u've got a giant matrix  (10,000 voxels (from each scan) by  69 stimuli ;
in which the value in each cell is the brightness of that voxel)

now look at the most consistent profiles

sl  that the ones where lots of voxels do light up....

our algorithm does not know abt  our a prior categories  (eg it does NOT know abt faces
even tho we did throw in a lot of face pictures to stack the deck.

What does the clustering algo show?  Here it is...

Cluster one: 
1)  is  BODIES  (most responsive)   it discoveries this as cluster #1

2)  categor 2 is FACES.. it discovers this  to be  cluster #2

3)  Places is  categ  #3... (drops out of the data)

so, perhaps this is the dominant  structure of the ventral visual pathway...

hypothesis space is  2**69  and yet it picked out what we have already shown  (ie, faces, places, bodies)

next ones (after these 3)  may just be retinotopic confounds... and other spurious stuff..

this method did NOT assume blobs

spatially pretty tight...

they did spike the mix with more faces, places, and bodies

are there other highly selective stimuli... NOT YET  (per this method)

*****
Next she reports work in which they looked at
 language  eg  in Rebecca Saxe's work.. she found selectivity at TPJ

needed a language expert

Nancy recruited Ev Federenko...

language, of course, has been studied since Broca and before.
look at lesion studies  ( a la Geschwind)

patient literature:  YES...  lots of specificity for language  (eg in Brocas and Wernickes area)

eg  consider case of Tom Lubbock... progressive left temporal tumor  (art critic, died at age 53 of Glioblastoma: L temp lobe)

great quote...  "my language  has become v limited... my experience is as vast as it always has been.

My language to describe things in the world is very small, limited.
My thoughts when I look at the world are vast, limitless and normal, same as they ever were.
My experience of the world is not made less by lack of language but is essentially unchanged.

Stan  Dehaene  

neuro literat shows massive overlap with other brain regions...

sl:  problem with group analysis  (ie  problem that occurs due to combining voxels from several patients)

problem is that group analyses blur data cuz each brain is different  even tho
in indiv subjects they might be  totally non-overlapping  (when u combine across patients,  you get a blurry overlap)

soln:  identify language regions in EACH SUBJECT and then test reponse to NON-language stim.

sl:  do big subtraction (of voxels)

read  "the dog chased the cat all day long"  vs  ank  twou  fasp  cre doove  ner gore en

you get  activation all over...

everybody has  dedicated areas in Left IFG = inferior frontal gyrus (Broca)
but how specific for language...

but do they also process other stimuli...

how abt  math,  how about working mem...

left mid post temporal gyr (Wernicke) and left infer frontal gyrus (Broca) ARE specific for language
(and NOT sensitive to other areas)

why does the brain create these  specialized regions?

John Duncan  2010  multiple  cognitive demand data  (and fluid intelligence);
  she is collab with him and with Ev Federenko...

cognitive control... hard stroop  hard  vMSIT  Hard  Verbal  WM...