Understanding learning and memory from a cellular perspective

Abstract

We learn and create memories but understanding how our brain performs these functions remain a grand challenge. In this talk, I will provide an overview of a currently accepted theory of how memories are formed and discuss our efforts to verify portions of this theory experimentally. We approach this challenge by probing single neurons from rodent brains. We probed how the spatiotemporal patterns of synaptic inputs onto certain dendrites result in the firing of an output or an action potential. I will also talk about our experiments where we probed how electrical signals flow along dendritic bifurcations while these neurons receive synaptic inputs or while they are firing action potentials. The output of a neuron translates to inputs to other neurons via synapses and the strength of these synaptic connections pertain to stored memories in our brain. Our aim is to understand the interaction between synaptic inputs and dendritic electrical activity resulting in memory formation or the strengthening of these synapses. These experiments were performed using a custom-built holographic two-photon laser microscope, which makes use of a hologram that transforms a single laser into multiple foci. Each focus can be used to trigger a synaptic input or record ionic or electrical activity of neurons embedded in brain slices from rodents. Using this microscope, we identified a novel function of a specific set of dendrites that could play a significant role in learning and memory. We were able to observe unique properties that allow these dendrites to be more responsive to synaptic inputs whenever the neuron coincidentally fires an output, which indicates that they have a functional role in the brain's capacity to learn and memorize information. Future experiments are geared to probe these functions in an intact rodent brain in vivo.