The long-term objective of our lab is to understand how olfactory information is processed in the mammalian brain. Understanding synaptic mechanisms that lead to representation of sensory stimuli in primary sensory cortices is important in revealing how the brain encodes our perception of the world. This has been under investigation in the auditory, somatosensory, and visual cortices. However, surprisingly little is known about the basic properties of synaptic inputs and circuits that shape odor-evoked neuronal activity in the olfactory cortex. To address this question, this application focuses on the relative responsiveness (""""""""tuning"""""""") of odor-evoked excitatory and inhibitory synaptic currents as well as the olfactory cortical circuitry underlying these relationships. I will use a combination of electrophysiology, pharmacology, and histology techniques. Specifically, I will determine the spiking activity of an olfactory cortical neuron to a panel of odors in cell-attached mode in vivo. Following that, by rupturing the membrane under my cell- attached patch to obtain whole-cell configuration, I will record and characterize excitatory and inhibitory synaptic currents of this neuron to the same panel of odors. I will use pharmacology to determine whether the odor-evoked excitatory activity is contributed by direct sensory afferents or recurrent local intracortical circuitry. In addition, these cells will be filled with biocytin and their morphology reconstructed post hoc, to determine differences in odor-evoked activity for principal cells vs. interneurons, which are the local contributors of odor-evoked excitation and inhibition, respectively. There are three specific aims:
AIM1 : Determine the excitatory and inhibitory synaptic inputs shaping odor-evoked spike output.
AIM2 : Characterize the contribution of direct sensory vs. associational synaptic inputs in shaping odor-evoked activity.
AIMS : Characterize the differences between odor-evoked responses of principal vs. interneurons. PUBLIC HEALTH RELAVENCE: Odors are strong cues in evoking memories of past events, and play an important role in our perception of flavor, contributing significantly to our quality of life. Intriguingly, neonatal mammals (including humans), use olfactory information to form strong maternal attachments. This olfactory """"""""imprinting"""""""" to maternal odors is critical to the initiation of suckling and the animal's survival. It appears that cortical processing of odor information, in contrast to other sensory systems, is both functional and necessary at birth. However, the functional properties of cortical circuits in this powerful and vital sensory system are not well understood. By elucidating the synaptic mechanisms for odor representation, I hope to gain insight into fundamental principals governing cortical processing of olfactory information.
| Poo, Cindy; Isaacson, Jeffry S (2011) A major role for intracortical circuits in the strength and tuning of odor-evoked excitation in olfactory cortex. Neuron 72:41-8 |
| Poo, Cindy; Isaacson, Jeffry S (2009) Odor representations in olfactory cortex: ""sparse"" coding, global inhibition, and oscillations. Neuron 62:850-61 |
