CRAIR, Michael, Multiscale Imaging in Developing CNS, Yale, May 31, 2018

<p class="MsoNormal" >CRAIR, Michael, Multiscale Imaging in Developing CNS, Yale, May 31, 2018

This is at noon today in Clark Aud: the weekly SNI seminar at Stfd.

He is a prof. of neurosci at Yale.&nbsp; See Crair Lab and see his

review (with Andrew Huberman (Stfd)) in 2017 in

Annual Reviews in Neurosci:&nbsp; Seabrook, et al.&nbsp;&nbsp; 2017.

he begins...

slide one shows&nbsp; three images:

local circuit imaging:&nbsp; eg with 2Photon Ca imaging of single cells;

and also&nbsp; Cortex wide with one photon&nbsp; calcium imaging and

also fMRI.&nbsp; (goal is to do all three simultaneously)

(my comment:&nbsp; this is a stunning technical tour de force)

he has a huge lab at Yale and he acknowledges his&nbsp; trainees.

introduction&nbsp; (why is spontaneous activity important in the CNS?)

(this work is all in mice.)

use dependence is important&nbsp; (in classical view)

eg ocular dominance columns and plasticity...

he shows classic work on deprived eye (in cats) => impairs

development of ocular dominance columns.

as in LeVay, and Wiesel and Hubel in J Comp Neuro in 1980.

But actually, &nbsp;map <b>development </b>in primates&nbsp; does&nbsp; NOT require

vision... ie setting up the circuits does NOT require visual experience...

rather it relies on&nbsp; molecular factors + spontaneous activity originating in the retina.

this is all in the mouse visual system&nbsp; (b/c of power of genetic manipulations)

work is ALL in mice.

at first, coarse&nbsp; chemical gradient systems are crucial... eg by EphrinB ligand.

mouse...wiring is&nbsp; just like a primate&nbsp; but 95%&nbsp; of projection is to&nbsp;

contralateral as opposed to 50/50 in primates.

and we see segration of wiring in&nbsp; LGN and in superior colliculus.

these form in first week after birth in mice.

coarse targeting is earliest eg at P1&nbsp; but then spontaneous&nbsp; activity shapes it.

(and eye opening only&nbsp; occurs at day P13.)

spontaneous activity in the developing retina.

Carla Shatz showed&nbsp; waves of spontaneous retinal activity.

there are burst and then&nbsp;&nbsp; quiescent periods.

and&nbsp; Marla Feller..... and Markus Meister.

three&nbsp; stages of development from E15 to P14:

stage 1 is&nbsp; GAP-jxn&nbsp; dependent and then

stage 2 is&nbsp; mediated by&nbsp; beta2 nAChR&nbsp; (nicotinic&nbsp; ACh receptors)

stage 3 is&nbsp; med by GluR&nbsp;&nbsp; from P10 to P13.&nbsp; (glutamate)

we wanted to image this activity in vivo... and we did.

see retinal waves in vivo.

if there is a wave of activity in retina

then can get a wave in the target&nbsp; (in the colliculus)

we're measuring&nbsp;&nbsp; waves in the <b>axons&nbsp; </b>of the RGCs as they project to the superior colliculus.

Ackman in Nature 2012...&nbsp;&nbsp; shows video of waves in colliculus.

use&nbsp; GCAMP in retina&nbsp; (in our orig work we used&nbsp; calcium-Green; but now GCAMP)

super collic&nbsp;&nbsp; used imaging of the axonal terminals in SC.

<b>the retinal waves are driving waves in the SC neurons</b>.

Shaul D. Q:&nbsp; how much of variance in SC is accounted for by waves in retina?

mice do NOT have ocular dominance columns but they

do have retinotopy.

<b>retinal waves arise in&nbsp; starburst&nbsp; amacrine cells</b>.

deletion of&nbsp;&nbsp; beta2-nACHRs in the retina disrupts the waves.

here, the animals serve as their own controls

&nbsp; (b/c some areas of the retina

maintain their waves despite our intervention

so, retinal waves and beta2-nAChRs in the retina are needed for

map refinement and eye segregation.

but... he also wants to show that the specific pattern is also important.

(how is the activity INSTRUCTING the circuits)

we next studied&nbsp; strobing light&nbsp; (from an LED)&nbsp; in sync&nbsp; versus out of syn btwn the two eyes;

this is using channel rhodopsin stim of RGCs&nbsp; (rather than native stimulation

by the light from directly of the photoreceptors)

Yes...&nbsp; sync&nbsp;&nbsp; stimulation&nbsp; blurs the segregation...

only get normal segregation if the two eyes are asyncrhonously driven.

ie&nbsp;&nbsp; sync&nbsp; stim profoundly disrupts retinotopy.

both&nbsp; spatial and temporal&nbsp; activity is important.

ie&nbsp; activity is <b>instructrive&nbsp; </b>(not simply permissive)

*

spontaneous activity...

initially willy nilly up to P6-7&nbsp; but then

is is stonrly directional starting at P8 to P11&nbsp; then tamps down

at P13 to 17.

P8 to P11&nbsp; strongly directional&nbsp;&nbsp; from temporal to nasal.

highly directional from P8 to P11&nbsp; (but only in this period)

we wondered about role of retinal waves.

at&nbsp; P8-9&nbsp;&nbsp; strong&nbsp;&nbsp; optic flow of retinal waves...

(is there a pacemaker or is it just an intrinsic circuit)

there is no pacemaker;&nbsp; but waves do always propagate

downward&nbsp; (temporal to nasal);

depends on GABA receptors... ie depends on inhibitory influence.

GABA receptors&nbsp; are what mediate the wave direcitonality&nbsp; and that

derives from retinal inhibition.

so,&nbsp; what's going on...

DS = direction selective circuit&nbsp; is mediated by

starburst amacrine cells&nbsp;&nbsp; SACs.

the waves use these cells

fish and frogs&nbsp; are born with nearly fully functional circuits (and do not have waves)

but must they must have&nbsp; anterior to posterior&nbsp; flow exposure (in fish/ frogs.)

to develop normally&nbsp;&nbsp; (not if flow is reversed)

his hypoth...&nbsp;&nbsp; must have normal optic flow&nbsp; of an animal moving thru space.

conclusion part 2:

retina spontaneous activity is developmentally dynamic and important and remains in the adult!

next... whole brain spontaneous activity

this is in mice.

with GCAMP.

need cellular imaging and wide field at same time.

this is Barson Hamodi et al.

mesoscopic&nbsp; one photon&nbsp; calcium imaging

and simult&nbsp; local circuit&nbsp; two photon.

local&nbsp;&nbsp; circuit&nbsp; images&nbsp;&nbsp; a field of 200 mm by 200 mm

and simult sees entire cortex.

if temporal to nasal... get much greater partic of cells in V1.

(and we can&nbsp; now look at&nbsp;&nbsp; different classes of cells)

not only wide field but also indiv cells.

widefield only&nbsp; shows cortical surface but cannot see

deep nuclei as you can with depth scope.

to see entire brain need&nbsp; fMRI&nbsp; (as in humans)

so,&nbsp; multiscale imaging would be doing all three.

thisis Lake, Ge unpub.

this is fiberscope for simultaneous&nbsp; mesocopic&nbsp; Cal imaging

and simult fMRI&nbsp; !!!!&nbsp; in an 11.7 T magnet.

doing&nbsp; BOLD and calcium imaging&nbsp; simult.

eg&nbsp; paw stimulation... can see it in somatosens&nbsp; activity.

with fMRI can see thalamus simult.

how to align slices of fMRI and&nbsp; calcium imaging&nbsp; (optical)

we use pattern of vasculature.

we look at functional connectivity.... they are stable matrices.

this is Ackman in bioRxiv.

which cells contribute to fMRI signal.

my Q&nbsp;&nbsp; interneuron contrib to fMRI...

will eventually be able&nbsp; image several cell populations during fMRI.

&nbsp;

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