Projections

In neuroscience, the term "projections" refers to the axons that extend from neurons and connect different areas of the nervous system, allowing for communication and transmission of information. These axons essentially 'project' from their origin in one region of the brain (or peripheral nervous system) to their target area in another region.

Neuronal projections can be classified as either efferent or afferent. Efferent projections carry information away from a particular brain region, while afferent projections carry information towards a particular brain region.

The term "projection" can also refer to the pathway itself that these axons create. These projection pathways facilitate various functions depending on the regions they connect. For example, corticospinal projections, which originate in the cerebral cortex and terminate in the spinal cord, are crucial for voluntary motor control.

Moreover, a "projection neuron" is a neuron with long axons that project to different parts of the brain or other areas of the body. For instance, pyramidal cells in the cerebral cortex are examples of projection neurons.

When studying the anatomy and connectivity of the brain, scientists often use "tract tracing" techniques to map these projections and understand how different areas of the nervous system are interconnected. This is known as tractography, an example of which is depicted in the header image^[1].