Which structure is primarily involved in olfactory processing?

The structure primarily involved in olfactory processing is the piriform cortex. This area of the brain is located in the temporal lobe and is the main cortical region responsible for processing smell. It receives direct input from the olfactory bulb, which is critical for detecting and processing odor information. The piriform cortex plays a significant role in discriminating between different odors and is essential for the perception of scents.

In contrast, the entorhinal cortex primarily serves as a hub for memory and navigation, acting as an interface between the hippocampus and other areas of the brain but is not directly responsible for the initial processing of olfactory information. The occipital lobe is mainly involved in visual processing and does not play a role in olfaction. The prefrontal cortex is associated with higher cognitive functions such as decision-making and social behavior but does not have a primary role in processing olfactory signals. Therefore, the piriform cortex's function and connection to the olfactory pathways make it the correct answer.