1. Introduc)on
Data
Analysis
Size
Tuning
Curves
for
Each
Neuron
Subtype
SOMPV
Experimental
Procedures
Spa)al
Summa)on
Proper)es
of
Excitatory
and
Inhibitory
Neuron
Types
in
Mouse
Visual
Cortex
Paloma
Sanchez-­‐Jauregui1,
Gerald
Pho2,
and
Mriganka
Sur2
1
Biology
Department,
University
of
Puerto
Rico,
Mayagüez,
PR
2
Department
of
Brain
and
CogniFve
Sciences
and
Picower
InsFtute
for
Memory
and
Learning,
MassachuseJs
InsFtute
of
Technology,
Cambridge,
MA
1A.
Two-­‐Photon
Calcium
Imaging
from
mouse
V1
1C.
GCaMP6s
was
selec)vely
targeted
in
specific
neurons
subtypes
using
the
Cre-­‐lox
system
2B.
Difference
of
Gaussians
model
explains
spa)al
summa)on
in
mouse
V1.
Pyr:
GCaMP6s
PV:
TdTomato
+
GCaMP6s
SOM:
Cre-­‐Flexed
GCaMP6s
1D.
Neuron
types
were
tagged
with
gene)c
markers
2A.
Method
used
to
determine
the
size
responses
for
each
cell
Conclusions
Possible
Mechanism
and
Future
Direc)ons
Acknowledgements
0
84
168
252
336
420
504
0
4
10
16
22
28
34
40
45
4.
Distribu)on
of
preferred
size
and
suppression
index
for
Pyr,
PV
and
SOM
neurons
Size
(Deg)
DFF
Time
(s)
AcFvity
DFF
DFF
Size
(Deg)
Normalized
DFF
Suppression
Index
Preferred
Size
(Deg)
Popula)on
Analysis
Size
(Deg)
DFF
Pyr
3.
Overlapping
size
tuning
curves
fiTed
with
the
DoG
model
show
differences
in
size
preference
and
suppression
index
for
the
three
neuron
subtypes
paloma.sanchezjauregui@gmail.com
As
expected,
Pyr
neurons
have
a
low
preferred
size
and
are
highly
suppressed
PV
neurons
have
a
preferred
size
higher
than
Pyr
neurons
but
lower
than
SOM,
and
are
also
highly
suppressed
SOM
neurons
have
higher
preferred
size
but
data
is
more
heterogeneous
than
previously
thought
Future
studies
can
test
this
hypothesis
by
looking
at
the
connecFvity
between
SOM
and
Pyr
neurons.
We
thank
members
from
Mriganka
Sur’s
Laboratory
at
MIT
and
Dr.
Mandana
Sassanfar
,
coordinator
of
the
MIT
Summer
Research
Program
for
Biology/Brain
and
CogniFve
Sciences.
Funding
was
provided
by
the
MARC
Scholars
Program
at
University
of
Puerto
Rico
-­‐
Mayagüez
and
the
Center
for
Brains
Minds
and
Machines
of
the
MassachuseJs
InsFtute
of
Technology.
NSF
Grant
Number:#
CCF-­‐1231216.
A
porFon
of
space
that
elicits
a
specific
neuronal
response
is
called
a
recepFve
field.
Visual
sFmuli
that
are
outside
the
classical
recepFve
field
can
modulate
the
acFvity
induced
by
sFmulaFon
of
the
center.
This
phenomenon
known
as
surround
suppression
is
a
fundamental
operaFon
in
visual
processing.
Adesnik
et
al.(2012,
Nature)
proposed
that
connecFons
between
excitatory
pyramidal
cells
(Pyr)
and
inhibitory
somatostaFn
cells
(SOM)
are
likely
to
be
responsible
for
surround
suppression
in
a
mouse’s
V1.
Specifically,
Pyr
acFvity
is
modulated
by
SOM
inhibitory
acFvity
as
laJer
respond
preferenFally
to
larger
sizes.
However,
the
mechanisms
that
underlie
this
suppression
are
unclear.
In
this
study,
we
record
neural
acFvity
in
Pyr,
SOM
and
parvalbumin
(PV)
inhibitory
neurons
as
they
respond
to
sFmuli
inside
and
outside
of
their
classical
recepFve
field.
It’s
believed
that
SOM
neurons
are
acFvated
due
to
the
summaFon
of
the
excitatory
acFvity
of
Pyr
neurons.
Purpose:
Measure
size
tuning
properFes
of
SOM,
PV,
Pyr
neurons
using
two-­‐
photon
calcium
imaging
in
order
to
determine
their
potenFal
role
in
surround
suppression
Hypothesis:
We
expect
to
find
that
SOM
neurons
will
exhibit
no
suppression
and
they
will
have
a
preference
for
large
sizes.
In
contrast,
Pyr
and
PV
neurons
will
behave
similarly,
showing
a
small
preferred
size
and
a
high
suppression
index.
DFF
3 6 11 22 35 56 90
1B.
Gra)ngs
of
different
sizes
were
presented
to
determine
size
tuning
of
each
neuron
subtype
Sizes:
(Deg)
Number
of
cells
Taken
from
Sceniak
et
al.
(1999)
Nature
Neuroscience,
Images
are
courtesy
of
Gerald
Pho
and
Rajeev
V.
Rikhye
A
B
SOM
inhibitory
neurons
may
inherit
surround
suppression
from
their
inputs.
This
might
explain
a
suppression
index
greater
than
zero
in
these
cells.
The
variaFon
in
preferred
sizes
and
suppression
index
of
SOM
could
be
due
to
varying
degrees
of
input
from
Pyr
cells.
Some
SOM
neuron
may
summate
over
a
shorter
range
therefore
having
a
higher
suppression
index
A,
whereas
others
may
receive
inputs
from
a
broader
range
of
Pyr
cells
B.
Preferred
Size:
Suppression
Index:
57
0.2
18
0.6
**
p < 0.01
***
p <0.0001
NS
p = 0.58
***
p < 0.0001
n = 110 n = 12 n = 46
Time
(s)
Time
(s)
1
0.5
Size
(Deg)