FOSTER Brett Default Mode ECOG Nov 2 2012
<p class="MsoNormal" >FOSTER Brett Default Mode ICOG Nov 2 2012</p>
<p>
FriSem Froday MBC at 3:15PM in Jordan Hall at Stfd.</p>
<p>
did PhD in Australia at Swinbourne</p>
<p>
in Joseph Parvizi's lab... post-doc</p>
<p>
fun fact: high aversion to Foster's Lager beer...
it does NOT enjoy widespread popularity in Australia..</p>
<p>
title is intracranial electrophys and the human default mode netowrk</p>
<p>
he is in SHICEP Lab...(Parvizi)</p>
<p>
<b>PMC = Posterior medial cortex</b>.</p>
<p>
focus is PMC electrophs and DMNetwork...= default mode network</p>
<p>
in Humans...</p>
<p>
ECoG is electrocorticography.. cortical surface...</p>
<p>
coarse grained recording from subdural electrodes...</p>
<p>
clinical context:</p>
<p>
sz = seizure detection: for poss surg resection...</p>
<p>
ECoG (and depth is used for improved localization..)</p>
<p>
refrac sz not amenable to drugs..</p>
<p>
ECoG improved signal quality... cuz not subject to spatiotemp filtering due to scalp skull etc.</p>
<p>
100-500,000 neurons rather than 10X as much with scalp electodes...</p>
<p>
larger magnitude...</p>
<p>
look at RMS voltage in microvolts = 37 for ecog and perhaps 10 for eeg...</p>
<p>
get rid of musc artifact and ecg artifact... gets rid of scalp muscle artifact...</p>
<p>
ecog is not affected by muscles...</p>
<p>
typical 1 cm spacing; some go down to a few mm spacing...</p>
<p>
craniectomy first... over left parietal cortex...</p>
<p>
he shows 8 by 8 grid... = 64 trodes</p>
<p>
in addition to exposed grid...</p>
<p>
you can also run a strip inferior or over and down into interhemispheric space...</p>
<p>
then do elecrtode localizaiton...</p>
<p>
<b>see Foster 2012 in PNAS</b>..</p>
<p>
event related ecog...</p>
<p>
recording from post central gyrus..</p>
<p>
see incr high freq activity for each button press..</p>
<p>
with hand mvmt get focal high freq increase... HF = > 75 Hz...</p>
<p>
indication of incr spiking rate...</p>
<p>
strong correl btwn firing rate and the power spectrum... he overlays them...</p>
<p>
best match is the high freq range... say from 60 to 150 or more...</p>
<p>
firing rate is prob depth electrodes and looking at LFP = local field potential component
Summary... HF broadband has high SNR and is spatially focal</p>
<p>
end of intro
on to
<b>intracranial recordings from PMC posteromedial cortex</b>...</p>
<p>
PMC = mesial parietal</p>
<p>
PMC = combo of posterior cingulat cortex = PCC ba 23
and precuneus = PrC and retrosplenial cortex.= RSC..</p>
<p>
PMC properties ... v high metabolic rate 20-30% higher than over other areas...</p>
<p>
<b>main connecting hub</b>...</p>
<p>
unique physio and anatomic properties...</p>
<p>
highest metab rate in the mesial surface...</p>
<p>
Buckner 2008 in Ann NY Acad Sci</p>
<p>
goal dir attn and auto bio memory and envisioning the future...</p>
<p>
goal directed attn is external non-self-referential vs</p>
<p>
internal self-referential (autobio mem )</p>
<p>
want to try to get to PMC electrophys</p>
<p>
v little ephys data cuz PMC is hidden on medial surface within interhemisph space...</p>
<p>
there has been an evol in thinking abt DMN function...</p>
<p>
is it mind wandering activity during rest... or is it self-referential...</p>
<p>
go down the falx to get recordings...</p>
<p>
PMC homology to macaque... there IS big homology with macaque
areas 31, 7m 23a/b and 29/30...</p>
<p>
PMC task related suppression..</p>
<p>
you do get suppression in a delay to sample memory task in monkey and in human both...</p>
<p>
is there a purpose to task suppression and performance</p>
<p>
unit and ecog suppression show performance correlation...
do reaction times IMPROVE and performance improve when DMN is suppresssed?...</p>
<p>
suppression of DMN is viewed as an active process to limit interference with task performance...</p>
<p>
Q is this related to attn or other?
A... related to whole bunch of task activation...</p>
<p>
is this a shared resource?</p>
<p>
current studyis of 8 subjects 4L 4R 4M and 4F</p>
<p>
task: i ate fruit yesterday self-episodic
then self-semantic i eat fruit often then
self judgment i am an honest person then
rest for 5 seconds then do math eg 59+7 = 66</p>
<p>
look at high freq power for each condition (in single subjects)</p>
<p>
biggest response was self-episdoe i ate fruit yesterday...(T or False: S presses a button to indicate response)</p>
<p>
rest here was just fixation...</p>
<p>
ten self-semantic next highest... math caused suppression of activity...</p>
<p>
rest.... almost nothing
self-judgement... almost nothing</p>
<p>
math => huge suppresion (big negative correlation)</p>
<p>
<b>retrosplenial </b> was area with best response for <b>self-episodic</b>...</p>
<p>
33 electrodes</p>
<p>
his guess... math (or n back or anything) causes suppression it's prob not specific to math...</p>
<p>
he shows x axis = episodic HG z score
vs y axis math suppression...</p>
<p>
r = 0.43 for that and</p>
<p>
math HG suppresion for seconds and correl with reaction times...</p>
<p>
claim is that the suppresion is related to task performance...</p>
<p>
self-episodic might be related to self-localization, navigation (in mice as well as in humans)</p>
<p>
Jon Winawer: fruit yesterday is effortful as well or more than math..
A but from where are you sourcing your answer?...</p>
<p>
asked again what is the conceptual diff?
A egocentric vs not.... parietal cortex/ medial temp lobe is involved with egocentric information</p>
<p>
we've tried to think of tasks that really pull these apart...</p>
<p>
*
temporal hierarchy...
(ie time ... period)</p>
<p>
everything is keyed to button press (the motor response... yes no (ie T or F to the question)</p>
<p>
he shows very sharp boundaries (v sharp fall off in effect)</p>
<p>
consistent with notion of suppressing of DMN to limit cognit interferences...</p>
<p>
future: theta band modulations</p>
<p>
blfoster@stanford.edu ..</p>
<p>
Jon W comments: is it that math is an effective way to suppress self-reflection</p>
<p>
other (he comments) might be navigation in space for the rat...</p>
<p>
</p>
<p>
</p>