Download Dendritic organization of sensory input to cortical neurons in vivo

Journal Club
Yu Kai
2010/09/27
1
Introduction
In sensory cortical areas, neurons are turned to
specific stimulus features. In the present paper, the
authers investigate the characteristics of the
synaptic input that cortical neurons receive to
generate their output firing pattern in the visual
cortex of mouse.
2
The mechanism by which neurons generate signals:
Input in
dendritic
synapase
Integration in
neuron soma
Output as spikes
3
Isolation of input from neuron in vivo
They use the approach combining high-speed
two-photon imaging with whole-cell patch
recordings to identify local sub-threshold
calcium signals that correspond to orientationspecific synaptic inputs
4
Isolation of input from neuron in vivo
Whole-cell current-clamp recordings of responses to
drifting gratings of different orientations. Three
trials were superimposed.
5
Isolation of input from neuron in vivo:
Calcium transient in distal dendrites
6
Isolation of input from neuron in vivo:
Calcium recordings from five neighbouring
dendritic regions
7
Isolation of input from neuron in vivo:
Exclusive the dendritic NMDA spike
8
Results:
Visually evoked action potentials, subthreshold
depolarizations
9
Results:Distribution of dendritic hotspots (red
dots) to the prefered orientation stimuli
10
Results: Orientation perfermance different in
the same dentrite
11
Conclusion:
The results reveal basic insights into the
dendritic organization of sensory inputs to neurons
of the visual cortex in vivo.
• Identified discrete dendritic hotspots as synaptic entry sites
for specific sensory features
• Afferent sensory inputs with the same orientation
preference are widely dispersed over thedendritic tree and
do not converge on single dendrites
• Neurons with a highly tuned output signal receive input
signals that are heterogeneous
The results support a neuronal integration model
involving summation of distributed inputs, rather than
models that stress the role of convergent inputs to single
dendrites.
12
Progress Report
13
Verify responsibilities of MGB locus which
very close to the injection position
14
Injetion Lidocaine into the MGB while
continuous recording in A1
Sweep #
F:\yukai data\20100915\20100915_006G_RX5-1_002.src
Lidocaine
Injection
0
600
1200
1800
2400
3000
msec
Raster Plot indicate the lidocaine injection cause inversible change on the firing
pattern of responses to acoustic stimulation.
15
Corresponding recording before
lidocaine injection
16
After
17
Intracellular Recording of cortical neuron in
layer2/3 Before lidocaine into MGB
18
After
19