1. Spatial Summation Properties of
Excitatory and Inhibitory Neuron
Subtypes in Mouse Visual Cortex
Paloma Sánchez-Jauregui, Gerald Pho, Mriganka
Sur, Ph.D.

2. Processing Visual Information
"Visual Perceptual Processing." Visual Perceptual Processing. N.p., n.d. Web.

3. Brain and Neuron Types
Excitatory Neurons
Pyramidal Cells (Pyr)
Inhibitory Neurons
Somatostatin Neurons (SOM)
Parvalbumin Neurons (PV)
Whiteman, By Lily. "Pond Scum Leads to Critical Brain Research Tool." LiveScience. TechMedia Network, 27. Web
How do neuronal subtypes in visual system
process information in the brain?

4. Spatial Summation in Mouse V1
"Synapses." Synapses. N.p., n.d. Web. http://www.biologymad.com/nervoussystem/summation.jpg
 Receptive Field – Visual system
 Different stimulus sizes
 Primary visual cortex (V1)
 Layer 2/3

5. SURROUND
CENTER
Size
Neural
Activity
Preferred Size: Size of maximum response
Suppression Index: Difference between PF and end response
Receptive Fields and Size Tuning

6. Purpose and Hypothesis
Purpose:
 To determine the potential role of Pyr, SOM and PV neurons in
surround suppression
Methods:
 Measuring size tuning properties of SOM, PV, Pyr neurons using
two-photon calcium and comparing them
Hypothesis:
 SOM neurons will exhibit no suppression and they will have a
preference for large sizes
 Pyr and PV neurons will behave similarly, showing a small
preferred size and a high suppression index.

7. Pyr : GcAMP PV: GcAMP + TdTomato SOM: Cre-Flex + GcAMP
In Vivo Two Photon Calcium Imaging
Image courtesy of Rajeev Rikhye

8. Inside a Mouse’s Brain
Pyr : GcAMP PV: GcAMP + TdTomato SOM: Cre-Flex + GcAMP
Images are courtesy of Rajeev Rikhye and Gerald Pho

9. Two Photon Calcium Imaging

10. Data Analysis
Image courtesy of Rajeev Rikhye and Gerald Pho

11. DFF
Time (s)
ActivityDFF
0 4 10 16 22 28 34 40 45
2 8 14 20 26 32 38
0 84 168 252
Data Analysis

12. Fluorescence(DFF)
Sizes (Deg)
Time (s)
DFF
2 8 14 20 26 32 38
Data Analysis

13. Pyr SOMPV
Size Tuning Curves for each neuron
Size (Deg)
Fluorescence(DFF)

14. Size Tuning Curves for each neuron type
Size (Deg)
1
0.5
Pyr SOMPV
NormDFF

15. Population Analysis
Suppression Index
Preferred Size (Deg)
Numberofcells
p < 0.01 p <0.0001
p = 0.58 p < 0.0001
n = 110 n = 12 n = 46

16. A Circuit for Spatial Summation
Preferred Size Small Medium Large
Suprresion Index Large Large Small
Pyr SOMPVSummary:
* Circuit based on known projections and retinotopic effects
Adesnik et al. 2014, Nature

17. Conclusions and Future Directions
 Pyr are initially excited at all stimulus sizes in its receptive field
center but not in its surround
 Preferred size is at small stimulus sizes but are suppressed
 SOM inhibitory neurons are responsible for surround
suppression of Pyr neurons
 Preferred size is at large stimulus sizes and are not suppressed
 PV neurons have an homogenizing effect but their role in
surround suppression is unknown
 Prefers mid stimulus sizes and are very suppressed
 Future studies should aim in understanding how PV neurons
contribute to spatial summation

18. Sur Lab
MARC Scholars Program
URS5
Gerald Pho
Rajeev Rikhye
Dr. Mriganka Sur
Dr. Mandana
Sassanfar
Acknowledgments

19. A Model for SizeTuning Curves
Sceniak et al. 1999 Nature Neuroscience

20. SOM Pyr
• SOM subtype that is highly connected will be more excited that
one that has less connections
• SOM subtype inherits own inhibition
Variation in SOM SizeTuning Curves

21. Calcium Indicators
o Dye
• Sensitive
o Genetically encoded
• Repeatable
• Selective
GcAMP

22. Two – Photon Microscope

23. H Adesnik et al. Nature , 2012
Pyr PV SOM
Hillel Adesnik