They simultaneously measured activity in both a specific type of inhibitory neuron, called fast-spiking, and a neighboring excitatory neuron. They then stimulated one or the other neuron and measured responses in the second neuron. They found that connections from the fast-spiking neurons were six times stronger when both cells were interconnected than if there was only a one-way inhibitory connection "This demonstrated that neurons primarily inhibited just the cells that excited it, and that tells us there is specificity in these fine-scale circuits." They then went on two show that these neuron pairs with two-way connections belonged to the same fine-scale subnetworks. "This means that inhibitory circuits can also precisely influence the activity of selected sub networks."
Inhibition of behaviour is as important as its generation, and failure to inhibit inappropriate actions—impulsivity—is a central feature of pathologies including attention deficit hyperactivity disorder, drug addiction and obsessive compulsive disorder. Previous work has identified the frontal cortex as a central component in the control of inhibiting impulsive actions. The goal of this project is to understand how this brain area performs this function. Two current specific aims are to reveal the activity of frontal cortical neurons while rats are engaged in impulse control task and to examine the effect of inactivating subregions of frontal cortex on impulse control behavior. Recording from large ensembles of neurons in the medial prefrontal cortex (mPFC) and the secondary motor cortex (M2) of rats during performance of the impulse control task allows us to characterize in detail the neural activity in these areas in relationship to behavior. We find that the activity of subpopulations of mPFC and M2 neurons predict the impulse control performance of rats on a trial-by-trial basis. Preliminary results show that reversible inactivation of the mPFC also impairs the ability of rats to inhibit impulsive action. We are now seeking to understand in more detail the nature of the neural representations underlying impulse control.
The neocortex plays a key role in sensory perception and higher cognitive functions. Unraveling how this seemingly simple sheet of neurons allows so many complex behaviors is one of the great challenges of neuroscience. Our overall goal is to understand the neural computations underlying cortical function. We approach this question by a combination of novel in vivo and in vitro methods to study the structure and function of cortical circuits. Using optical and electrophysiological techniques in brain slices we study the wiring diagram of cortical circuits. We also measure the activity of the same circuits in head-fixed behaving animals using two-photon imaging. This combined approach allows us to understand both the computations implemented by cortical circuits as well as how they emerge from the underlying neuronal network. Using this approach, we are studying how sensory stimuli are combined with internal models of the world to generate percepts in mouse visual cortex.
Channelrhodopsin-2-assisted circuit mapping