The aim of this research is to investigate the interplay between excitatory and inhibitory inputs in the cortex of the mouse. Current methods of intracellular recording, such as voltage and current clamp have been used to measure inhibitory and excitatory inputs in isolation. However, Both methods display a similar issue as they provide a weighted average of the inputs over many trials. This poses a problem since neuronal activity dynamically fluctuates as a function of time.
Understanding the mechanism in which neurons integrate their synaptic input is crucial. More specifically, understanding how inputs covary as a function of time and their dynamical role in evoking neuronal activity will allow us to further investigate basic principles of information processing in the healthy and diseased brain.
We developed a new analytical framework for simultaneous measurements of both the excitatory and inhibitory neuronal inputs during a single trial under current clamp recording. The method was demonstrated by simulations, electrophysiological recordings from slices activated by optogenetics and now in-vivo in the barrel cortex of anesthetized mice.
The method is done by AC analysis of the neuron as it is injected with high frequency sinusoidal currents. The changes in membrane potential of the neuron as a result of whisker stimulation are recorded with the injected sinusoidal frequencies using current clamp. The signal is then processed to give the impedance over time at each frequency which then allows us to uncover parameters like the total conductance over time. Then by using the membrane potential equation we are able to extract excitation and inhibition conductance separately giving us real time synaptic information.