Odor-evoked activity in the mouse lateral entorhinal cortex.

The entorhinal cortex is a brain area with multiple reciprocal connections to the hippocampus, amygdala, perirhinal cortex, olfactory bulb and piriform cortex. As such, it is thought to play a large role in the olfactory memory process. The present study is the first to compare lateral entorhinal and anterior piriform cortex odor-evoked single-unit and local field potential activity in mouse. Recordings were made in urethane-anesthetized mice that were administered a range of three pure odors and three overlapping odor mixtures. Results show that spontaneous as well as odor-evoked unit activity was lower in lateral entorhinal versus piriform cortex. In addition, units in lateral entorhinal cortex were responsive to a more restricted set of odors compared to piriform. Conversely, odor-evoked power change in local field potential activity was greater in the lateral entorhinal cortex in the theta band than in piriform. The highly odor-specific and restricted firing in lateral entorhinal cortex suggests that it may play a role in modulating odor-specific, experience- and state-dependent olfactory coding.