Stimulus intensity determines experience-dependent modifications in neocortical neuron firing rates

Area of Science:

• Neuroscience
• Sensory processing
• Cortical plasticity

Background:

• Neocortical sensory neurons receive broadly tuned subthreshold inputs, but their spiking output is more restricted.
• Subthreshold inputs modulate spiking output based on stimulus intensity and allow for experience-dependent plasticity.

Purpose of the Study:

• Investigate how stimulus intensity affects the firing output of individual neurons in layer 2/3 of the mouse barrel cortex.
• Examine the impact of single-whisker experience (SWE) on neuronal firing output across different stimulus intensities.

Main Methods:

• Recorded firing output of individual neurons in mouse barrel cortex layer 2/3.
• Stimulated principal whiskers over a 30-fold range of intensities.
• Compared responses in naive animals with those after 7 days of SWE.

Main Results:

• Decreasing stimulus intensity reduced firing rates and the size of the responding neuronal ensemble in naive animals.
• After SWE, low-intensity whisker stimulation showed a >10-fold increase in mean firing output compared to controls.
• Under control conditions, ~15% of neurons fired at low intensity; after SWE, >70% showed firing.
• Experience-dependent changes in spike output were highly dependent on stimulus intensity.

Conclusions:

• Stimulus intensity is a critical factor in observing experience-dependent plasticity in neocortical neurons.
• Single-whisker experience profoundly enhances the sensitivity of barrel cortex neurons to low-intensity stimuli.
• The functional organization of sensory cortex is dynamically shaped by experience, particularly at lower stimulus intensities.