lateral competition for cortical space by layer-specific horizontal circuits

8/9/2019 Lateral competition for cortical space by layer-specific horizontal circuits

1/18

Dan OShea

d-Lab Journal Club

17 May 2010

Lateral competition for cortical space bylayer-specific horizontal circuitsHillel Adesnik1 & Massimo Scanziani1


2/18

Overview

- Expression of ChR2 in L2/3 of whisker barrel cortex via in utero electroporation

- Photoinduced gamma activity in vivo and in vitro with light ramp

- Excitation and inhibition matched vertically across layers and horizontally

- Layer-specic ratio of excitation to inhibition leads to:

- feed-forward facilitation of L5 (high E/I from L2/3)

- lateral suppression within L2/3 (low E/I from L2/3)


3/18

Expression of ChR2 in Layer 2/3

Ivry 1996

L2/3

L4

L5

L4

L5

L6

L2/3

200 m

- in utero electroporation (E15-E16) of ChR2 and fluorophore DNA

- 23% 2% expression in L2/3 excitatory cells

NeuNGFP-ChR2


4/18

Overview








5/18

Ramped photostimulation of L2/3 elicits gamma oscillations in vivo

- 2 s light ramp 0.1-2 mW/s to maximum 2 mW

- peak oscillation frequency 42 2 Hz


6/18

Ramped photostimulation of L2/3 elicits gamma oscillations in vitro

- peak oscillation frequency 33 1 Hz

- abolished by NBQX+CPP (glutamate receptor antagonist) or gabazine (GABAA antagonist)


7/18

Gamma oscillation peak frequency increases with light ramp slope in vivo

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8/18

Overview








9/18

L2/3 driven excitation and inhibition are matched vertically


10/18

L2/3 driven excitation and inhibition are matched horizontally

- patch L2/3 or L5 pyramidal, voltage clamp at -70 mV or 0 mV

- photostimulate L2/3 in adjacent barrel columns


11/18

L2/3 driven excitation and inhibition are matched horizontally

- patch L2/3 or L5 pyramidal, voltage clamp at -70 mV or 0 mV

- photostimulate L2/3 in adjacent barrel columns

Barrel column

L2/3

40.00.2

0.4

0.6

0.8

1.0

2 0 2 4

Power(norm.)

Power (2060 Hz)Charge

Barrel column

L2/3

4

0.0

1.0

0.5

0.5

1.0

2 0 2 4

EPSC

IPSCIPSCinv

Charge(norm.)

b

L2/3

L5

2000000

Barrel column

L5

40.0

0.2

0.4

0.6

0.8

1.0

2 0 2 4

Power(norm

.)

Barrel column

L5

4 2 0 2 4

Charge(norm

.)s

Charge Power (2060 Hz)

0.0

1.0

0.5

0.5

1.0

c


12/18

Overview




- Layer-specic ratio of excitation to inhibition from L2/3 leads to:

- feed-forward facilitation of L5 - high E/I

- lateral suppression within L2/3 - low E/I


13/18

Photostimulation increases L5 ring rate, suppresses L2/3 ring rate in vitro

- simultaneously patch L2/3 and L5 pyramidals

- inject current step

- photostimulate same or adjacent barrel with light ramp

- compare L2/3 and L5 cell firing rates with vs. without light

firing rate with / without light


14/18

Photostimulation increases L5 ring rate, suppresses L2/3 ring rate in vivo

- whole cell recording from L2/3, inject current step

- multiunit recording from L5

- compare L2/3 and L5 cell firing rates with vs. without light


15/18

Excitation / inhibition ratio higher in L5 relative to L2/3

- patch L2/3 and L5 pyramidals, voltage clamp at -70 mV or 0 mV

- compare excitatory / inhibitory charge ratio across all simultaneous pairs

- higher E/I ratio in L5 due to increased inhibition

each dot represents onesimultaneously patched L2/3, L5 pair


16/18

Larger excitation / inhibition ratio in L5 neurons with higher ring rates

- cell attached then whole cell recording of L5 pyramidals

- voltage clamp at -70 mV or 0 mV

- compare excitatory / inhibitory charge ratio vs. firing rate during light ramp


17/18

Replay of inhibitory waveforms from other layer reverses ring rate change

- record EPSCs in one layer simultaneously with IPSCs in other layer

- current clamp to inject same layer excitatory waveform plus current step

- dynamic clamp to impose inhibitory conductance waveform from other layer

L2/3 inhibition onto L5

leads to suppressed firing

L5 inhibition onto L2/3

leads to increased firing


18/18

Overview




- Layer-specic ratio of excitation to inhibition from L2/3 leads to:

- feed-forward facilitation of L5 - high E/I

- lateral suppression within L2/3 - low E/I

lateral competition for cortical space by layer-specific horizontal circuits

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