Research Unit 5159

Short Summary:  During postnatal development, the brain undergoes a series of processes that bring about its mature architecture. These include neuronal migration, apoptosis, synapse formation and maturation. The timeline of cortical maturation is thought to be hierarchical, with primary sensory areas maturing earlier than higher-order areas, such as the prefrontal cortex (PFC). The cortex is a laminar structure with distinct synaptic inputs targeting specific layers. Within each cortical area there is also evidence for layer-specific development. For example, sensory critical periods in the mouse somatosensory barrel cortex (S1BF) follow an “outside-in” pattern, occurring first in thalamo-recipient layer (L)4 followed by superficial L2/3. The maturation of the PFC is thought to be delayed to that of S1BF. However, much less is known about the timeline of this maturation, particularly with respect to the development of synaptic connectivity within specific layers. Determining this may provide insight into when different inputs or cell types undergo synapse maturation. This project aims to determine similarities and differences in the synaptic maturation of a primary sensory barrel cortex (S1BF) and the PFC. To do so we have developed a pipeline for high-throughput synaptic puncta analysis using transgenic mice that express the synaptic protein PSD-95 tagged to GFP. We will compare the maturation of synapses between layers and regions to determine both common rules and region-specific differences of synapse development between cortical areas.