Sensory induced long-lasting modification of spontaneous activity in the somatosensory cortex: electrophysiological and modelling studies
Author(s)
Phoka, Elena
Type
Thesis
Abstract
Emerging evidence suggests that spontaneous neocortical activity is not merely noise but can be
modulated and/or engaged by sensory stimulation. We examined whether naturalistic sensory
stimulation can induce specific long-term changes in spontaneous cortical state dynamics in the
mouse somatosensory cortex, using both in vivo electrophysiology and modelling.
Repetitive, high-frequency multi-whisker stimulation using sandpaper resulted in spontaneous
ring rate increase of layer IV and Vb multi-units. The ring rate increase in these layers was
sustained for at least 25 minutes following the stimulus. The ring rate increase was accompanied
by an increase in layer IV sink amplitude. Increase in spontaneous activity was found also in
excitatory single-units in layers IV and Vb. Neither the depth of anaesthesia nor stimulus-induced
desynchronization could account for this effect. Finally, we found that elimination of
lateral inputs, achieved by trimming away all but the principal whisker, abolished the effect.
Single-whisker stimulation resulted in a decrease of activity in layers II/III, IV, Vb and VI, and
was accompanied by a decrease in layer IV sink amplitude.
In parallel, to study whether Spike-Timing-Dependent-Plasticity (STDP) can explain modifications in spontaneous synaptic dynamics, we developed a biologically inspired large-scale model
of rodent barrel layers II, III and IV. Our model consists of approximately 4000 spiking neurons,
1.7 million synapses and 2.2 million dynamical variables. Repetitive sensory stimulation
induced long-lasting changes in synaptic weights. The initial state of the network, described by a
spontaneous attractor, shifted to a post-stimulus stable state following several repetitions of the
same structured stimulation pattern. Furthermore, we found that STDP mediated modifications
enabled our network to distinguish between structured and shuffled stimuli.
Our experimental and modelling results show that sensory experience induces long-term modification of spontaneous activity in the somatosensory cortex. They suggest that lateral projections
and time-dependent plasticity mechanisms play an important role in this process.
modulated and/or engaged by sensory stimulation. We examined whether naturalistic sensory
stimulation can induce specific long-term changes in spontaneous cortical state dynamics in the
mouse somatosensory cortex, using both in vivo electrophysiology and modelling.
Repetitive, high-frequency multi-whisker stimulation using sandpaper resulted in spontaneous
ring rate increase of layer IV and Vb multi-units. The ring rate increase in these layers was
sustained for at least 25 minutes following the stimulus. The ring rate increase was accompanied
by an increase in layer IV sink amplitude. Increase in spontaneous activity was found also in
excitatory single-units in layers IV and Vb. Neither the depth of anaesthesia nor stimulus-induced
desynchronization could account for this effect. Finally, we found that elimination of
lateral inputs, achieved by trimming away all but the principal whisker, abolished the effect.
Single-whisker stimulation resulted in a decrease of activity in layers II/III, IV, Vb and VI, and
was accompanied by a decrease in layer IV sink amplitude.
In parallel, to study whether Spike-Timing-Dependent-Plasticity (STDP) can explain modifications in spontaneous synaptic dynamics, we developed a biologically inspired large-scale model
of rodent barrel layers II, III and IV. Our model consists of approximately 4000 spiking neurons,
1.7 million synapses and 2.2 million dynamical variables. Repetitive sensory stimulation
induced long-lasting changes in synaptic weights. The initial state of the network, described by a
spontaneous attractor, shifted to a post-stimulus stable state following several repetitions of the
same structured stimulation pattern. Furthermore, we found that STDP mediated modifications
enabled our network to distinguish between structured and shuffled stimuli.
Our experimental and modelling results show that sensory experience induces long-term modification of spontaneous activity in the somatosensory cortex. They suggest that lateral projections
and time-dependent plasticity mechanisms play an important role in this process.
Date Issued
2012
Date Awarded
2012-04
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Schultz, Simon
Barahona, Mauricio
Publisher Department
Bioengineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)