Vanduffel, Wim Athanoulos Boston
<p>Jun 18, 2010 8:09 PM
 
? Belgian. from Looven  pron.  van Doofull.
intro by Kalanit.
Tirin Moore.  here.  huge turnout ... biggest ever for a FriSem!!
Spectac work but difficult to understand.
 
He studies relationship btwn Attention and Vision.  an area that Tirin Moore also studies.
?  Dorsal Attention System  (a fronto-parietal interaction).
 
first slide:  Lakers vs Celtics with Michael Jordan.   Attention goes to Jordan's head.
What is happening?
 
Electic stim of R Frontal Eye Field  FEF  makes eyes saccade left.
Elect ric of L frontal eye field ... eyes saccade to R.
 
Monkeys  sit in human MRI in the Sphinx position in special apparatus.
 
They do various expts.  They can turn off areas by doing microinjections of gaba-agonist
mscinol or by doing focal microstimulation with electrodes.
They simutlan  record from V4 while stimulating FEF.
 
similar to Moore and Armstrong 2003.
 
FEF causes evoked saccade.
while recording from V4.  (that's what Tirin Moore did; what they do instead is to
do fMRI and see what voxels are affected  while stim FEF.
 
Initl report was in VanDuffel Neuron 2001.
the stim is in microamps:   btwn 20 to 50 or perhaps 100  given as a train of pulses over
250 msec.
This is SUBthreshold  such that NO saccade is evoked.
see report in Ekstrom et al in Science 2008.
See what areas light up on MRI... connex to Super Collic to visual areas and to
? parietal  ? LIP.
while monkey fixates  ? using eye tracking to make sure.
 
Experiemtn...  then also  present visual target...  contrasty grating with lines
sloped at say 45 degr either CW or CCW from vertical.
 
Experiment:  Say u stim the R FEF and determine that the wants saccade down and to
the Left.   
A CONGRUENT  Target wud be one in which the target (the grating) is presented AT
the point where the eyes wud saccade to if they moved  (which they don't cuz the
mokey is fixating a cross at the center.
An INCONGRUENT  position wud be   a position a few degrees away.
Expt Question..   what is the extent of the voxel enhancement.
Expt A:   If the target is at the CONGRUENT position then there is voxel enhancement!!
(recall monkey is just fixating;  the electr stim of the FEF is Subthreshold ...
not enuf to act. induce eye mvmt.
 
If CONGRUENT, u get a BOOST in  CRF  Contrast Response Function
and then only if the contrast of the grating is low or is medium
(but not if its high... perhaps  system is saturated)
 
The response over space over the target looks like a bullseye  (2 concentric circles).
 
Next expt:  Distractors  in the contralateral visual field.
 
I think (not sure) that the effect of distractors is to BOOST the CONGRUENT effect
hugely,  ie. the distractor really narrows the attention to the target.
 
Tirin is our local expert on this stuff.
 
Can detect lower contrasts with congruence.
 
FEF  stim  leads to enhanced responses in higher order areas (high up in the
viz hierarchy) toawrd the favord site and suppression of stimuli in the unfavored
locations (eg contralateral).  This was Anthony Wagners summary.
 
Next Expt:  Causality.
 
Deactivate various brain areas using muscimol  (this is a gaba-agonist).
active prin in Amanita muscaria ...  potent CNS inhibitor.
 
this is confusing??  in one expt he injected muscimol into LIP  vs NaCl.
 
muscimol does turn it off.  but other  areas compensate for loss of LIP.
 
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