Brett Foster
<p class="MsoNormal" >FOSTER, Brett, Neural Coupling in Human Parietal Cortex, Nov 7, 2014
This is a Stfd FriSem in Psych. MBC Jordan Hall at 3:15PM.
fun fact: Brett (who is 6'5") considered a pro basketball career.</p>
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this is work Brett did when in Josef Parvizi Lab at Stfd using ECoG.
Brett is now in Anthony Wagner's Lab.
his title today: Intrinsic and Task-dependent coupling of neuronal population activity
in human parietal cortex.
talk focuses on neural mechs of Episodic retrieval;</p>
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ECoG: = electrocorticography: from cortical surface; invasive;
but unique spatio-temporal info cuz of proximity to source.</p>
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shows Nate Bennett a pt who was on NPR in Dec 2013...
implanted for rx of refrac epilepsy.</p>
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trodes are right on the pial surface of cortex (post craniotomy)</p>
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<b>standard eeg abt 10 micro volts</b>...</p>
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<b>stnd ECoG signal abt 100 microvolts or larger...
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no smoothing or attenuation... so , more hi frequency component.</p>
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more RMS... more signal to noise.. and also get rid of EMG...
which messes up EEG; but ECoG is unperturbed...</p>
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spatial summation of external eeg is much larger than
ECoG (ecog is far more focal) (clarifies Brian W)</p>
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image of left parietal space post craniotomy...</p>
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large grid: positioned on lat surface...</p>
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64 trodes... 1 cm center on spacing...</p>
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and also into intrahemispheric space...</p>
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ecog is inside scalp, skull and meninges (except pia)</p>
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Hermes 2010 J Neuro Methods...</p>
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can also gain access to medial surface...</p>
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ecog trodes abt 2000 implanted in all (figure from awhile ago)</p>
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and rarely on both medial and lat surface.</p>
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he is interested in MEMORY beyond the MTL...(medial temp lobe)</p>
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and in particular hippocampal = HC correlation with parietal lobe.</p>
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place seed (for correlation) in HC and examine corre with RSC/PCC and AG = angul gyrus...
RSC = retrosplenial cortex; PCC = poster cingulate cortex.</p>
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supported by tract tracing studies...</p>
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Vincent 2006 in J Neurophys.</p>
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want to see what's involved in autobiogr retrieval eg in episodic retrieval...</p>
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are resting state networks (like default mode) giving you a clue to e-phys.</p>
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Default Network: a la marcus raichle et al...</p>
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goal directed attention and WM...(= working memory)</p>
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see review by Randy Buckner in 2008
on auto bio memory and envisioning future, theory of mind and moral decision making..</p>
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looking at changes in high freq activity (ie looking for increase in power in 70 to 180 hz band)...</p>
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looking from abt 70 to 180 hz : the main dep variable... the so-called
HF broadband....</p>
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<b>TASK</b>: (a trial with implanted humans)</p>
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in <b>foster 2012 pnas</b>...
S is shown a sentence that he can look at for up to 15 seconds;
it is a T/F question: eg I ate fruit yesterday. he presses one of two buttons
with his R hand to indicate T or F; then there is a 200 msec interstim interval ISI.</p>
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self episodic question: I ate fruti yesterday vs
past memory: I eat fruit often vs
self judgment: I am an honest person vs
judgment about others: my neighbor is honest; etc.
separ by 200 ms ISI</p>
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8 subjects... with coverage in medial region</p>
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retr activ in MPC...(medial parietal cortex)</p>
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self-episodic showed the biggest mean HG response abt 2.5 intensity
vs self-semantic at 1.2
self judgement at .3
tasks with negative MPC response latency...</p>
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onset around 600 msec...
HG onset latency...</p>
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medial: PrCC precuneus and PCC and RSC... but usu combine the last two...</p>
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lateral will be AG SMG = supramarginal gyrus etc.</p>
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other judgment .. my neighbor is an honest person</p>
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math problem...</p>
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MPC and LPC = lateral parietal response...</p>
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medial: shows PrCC and combo PCC/RSC</p>
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response profile is similar to what is seen in AG = angular gyrus...</p>
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how abt MPC vs LPC subregion correl.</p>
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there is striking corre btwn ang gyus and PCC eg... high correlation btwn the two time series.</p>
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RSC/PCC and AG response timing... we expected coupling...</p>
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relative timing of responses...</p>
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mean resp abt 600 msec...</p>
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HFB = high freq broadband response onset latency ROL</p>
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RSC/PCC light up around 627 to 674 ms</p>
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and angular gyrus... abt 761 msec...</p>
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people are reading the sentences</p>
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did u control for length of sentence?</p>
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but AG seems to be minimally shifted if at all, temporally
he shows zero latency WRT RSC/PCC</p>
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but SPL is later by abt 500 msec.
Since AG and MPC are substantially simultaneous then
perhaps there is shared input that is driving both AG and RSC...</p>
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Br W clarifies: SPL is either being driven or settles later (abt 1/2 second later)</p>
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he shows method of calc. of ROL = response onset latency...</p>
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Resting State Correl</p>
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eg put seed in PCC/RSC...</p>
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eyes closed.... filter HFB and look at amplitude...</p>
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pick a seed and ask for what regions are corr on lat surface...</p>
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see a nice corr to AG = ang gyrus.</p>
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parietal connectivity...</p>
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with seed in PCC... see corr to AG in both task and rest correl.
(so, is rest (ie the so called rest mode or default mode) just a poorly controlled task?)</p>
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during rest, eg people think abt self referential content (a task in and of itself)....</p>
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but during sleep... also we also see similar corr...
(btwn PCC and AG)</p>
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used slow wave and spindles on ecog to judge sleep... (mainly stage 2 and 3 sleep)</p>
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see nice corresp btwn ecog and fMRI...</p>
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resting state ecog vs fMRI... corr abt 0.5</p>
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did not see any anti-correl (big debate in liter. abt that WRT default mode)</p>
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PCC is correl with AG but not with SMG...</p>
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summary: ecog shows robust engagement of par cortex during retrieval.</p>
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espec RSC/PCC medial and AG (lat)</p>
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subregions display areal based coupling ie co-activation</p>
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onset of reponse aroudn 600 to 700 ms</p>
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high similarity of rsECOG vs rsfMRI connectivity...</p>
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high similarity of TASK (the trial) vs rest/sleep (spontant connectivity.)</p>
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<b>medial parietal has no direct connex to primary sensory regions</b>...
(ie this is pure assoc cortex: Brett speculates that its involved in <b>simulation</b>
which is a core activity in thinking abt future, theory of mind, etc)</p>
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blfoster@stanford.edu...</p>
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Q1 dff in func btwn medial and lateral parietal regions... what are they doing?...</p>
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RSC spatial locational info (simulation) ...
Brett recomm. Eddie Chang work to me (ucsf neurosurg, will speak here soon)</p>
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