Research: Neural plasticity and memory

Training and video by Dylan Barnes

Our research on neural plasticity and memory focuses on the role of experience in olfactory system function. We use three paradigms in this work.

Perceptual learning
Sensory processing and perception is influenced by past experience with sensory stimuli. For example, the ability to make fine sensory discriminations can improve with training. We have demonstrated that in olfaction, behavioral discrimination of highly similar molecular compounds improves with experience. This behavioral improvement (perceptual learning) may be associated with rapid changes in receptive field of olfactory cortical neurons. Both the behavioral and receptive field changes are disrupted by cholinergic blockade. Current research is focusing on mechanisms of experience-induced receptive field changes in the olfactory system and their role of olfactory discrimination behavior.

Selected Publications

Wilson, D.A. A comparison of odor receptive field plasticity in the rat olfactory bulb and anterior piriform cortex. Journal of Neurophysiology, 2000, 84:3036-3042.
Wilson, D.A. Scopolamine enhances generalization between odor representations in rat olfactory cortex. Learning and Memory, 2001, 8:279-285.
Fletcher, M. and Wilson, D.A. Experience modifies olfactory acuity: ACh-dependent learning decreases behavioral generalization between similar odorants. Journal of Neuroscience, 2002, 22:RC201(1-5).
Wilson, D.A. and Stevenson, R.J. The fundamental role of memory in olfactory perception. Trends in Neurosciences, 2003, 26:243-247.
Kadohisa, M. and Wilson, D.A. Separate encoding of identity and similarity of complex familiar odors in piriform cortex. Proceedings of the National Academy of Sciences (USA), 2006, 103:15206-15211.

Olfactory memory
We are examing the neural basis of a more simple form of olfactory memory - odor habituation. We are interested in how odor habituation occurs, and also what happens if during early development normal habituation (sensory gating) fails? Sensory gating deficit are associated with a number of disorders, including autism and sachizophrenia. In addition, newborn, altricial mammals of many species learn the odor of their mother and use that learned odor as a cue in identifying and orienting to the mother. In the rat, the odor must be learned (rather than being innate) because the maternal odor is diet -dependent. Given that the mother is the sole source of food, warm and protection, learning this odor cue is critical for the survival of the newborn. Our laboratory, in collaboration with Dr. Regina Sullivan, is exploring the neural basis of this critical form of early learning and memory.
Specific questions addressed by the current research of my students and I are: What are the neural mechanisms of olfactory memory? That is, how is information of past experiences and associations stored in the olfactory system? Are these mechanisms similar in adults and newborns? What is the role of specific neurotransmitter systems in olfactory learning? These questions are addressed primarily using electrophysiological techniques (evoked potential, single-unit, intracellular, chronic and acute preparations), although behavioral neuropharmacological, anatomical and immunohistochemical techniques are also utilized.

Selected Publications

Wilson, D.A. and Sullivan, R.M. Neurobiology of associative learning in the neonate: Early olfactory learning. Behavioral and Neural Biology, 1994, 61:1-18.
Sullivan, R.M. and Wilson, D.A. The locus coeruleus, norepinephrine and memory in newborns. Brain Research Bulletin, 1994, 35:467-472.
Sullivan, R.M., Wilson, D.A., Lemon, C. and Gerhardt, G.A. Bilateral 6-OHDA lesions of the locus coeruleus impair associative olfactory learning in newborn rats. Brain Research , 1994, 643:306-309.
Wilson, D.A. Habituation of odor responses in the rat anterior piriform cortex. Journal of Neurophysiology , 1998, 79: 1425-1440.
Wilson, D.A. Synaptic correlates of odor habituation in the rat anterior piriform cortex. Journal of Neurophysiology, 1998, 80: 998-1001.
Sullivan, R.M., Landers, M., Yeaman, B. and Wilson, D.A. Good memories of bad events in infancy. Nature, 2000, 407: 38-39.
Sullivan, R.M. and Wilson, D.A. Perspective: Molecular biology of early olfactory learning. Learning and Memory, 2003, 10:1-4.
Best, A.R. and Wilson, D.A. Coordinate synaptic mechanisms contributing to olfactory cortical adaptation. Journal of Neuroscience, 2004, 24:652-660.
Best, A.R., Thompson, J.V., Fletcher, M.L. and Wilson, D.A. Cortical metabotropic glutamate receptors contribute to habituation of a simple odor-evoked behavior. Journal of Neuroscience, 2005, 25: 2513-2517.
Thompson, J.V., Best, A.R. and Wilson, D.A. Ontogeny of cortical synaptic depression underlying olfactory sensory gating in the rat. Developmental Brain Research, 2005, 158:107-110.
Yadon, C.A. and Wilson, D.A. The role of metabotropic glutamate receptors and cortical adaptation in habituation of odor-guided behavior. Learning and Memory, 2005, 12:601-605.
Kadohisa, M. and Wilson, D.A. Olfactory cortical adaptation facilitates detection of odors against background. Journal of Neurophysiology, 2006, 95:1888-1896.
Moriceau, S., Wilson, D.A., Levine, S. and Sullivan, R.M. Dual circuitry for odor-shock conditioning during infancy: Corticosterone switches between fear and attraction via amygdala. Journal of Neuroscience, 2006: 26:6737-6748.

Olfactory deprivation
Normal development of many sensory systems is dependent on normal sensory experience early in life. We are exploring the functional consequences of olfactory deprivation in the rat. Specific questions include: How does normal olfactory system function emerge during development? Does deprivation have similar consequences at both initial processing centers (e.g., the olfactory bulb) and higher, cortical centers (e.g., piriform cortex)?

Selected Publications

Guthrie, K.M., Wilson, D.A. and Leon, M. Unilateral olfactory deprivation modifies olfactory bulb function. Journal of Neuroscience, 1990, 10: 3402-3412.
Wilson, D.A. NMDA receptors mediate expression of one form of functional plasticity induced by olfactory deprivation. Brain Research, 1995, 677:238-242.
Wilson, D.A. and Sullivan, R.M. The D2 antagonist spiperone mimics the effects of olfactory deprivation on mitral/tufted cell odor response patterns. Journal of Neuroscience , 1995, 15: 5574-5581.
Wilson, D.A., Best, A.R. and Brunjes, P.C. Trans-neuronal modification of anterior piriform cortical circuitry in the rat. Brain Research, 2000, 853:317-322.
Best, A.R. and Wilson, D.A. A postnatal sensitive period for plasticity of cortical afferents but not cortical association fibers in rat piriform cortex. Brain Research, 2003, 961:81-87.
Leung, C.H.W. and Wilson, D.A. Trans-neuronal regulation of cortical apoptosis in the adult rat olfactory system. Brain Research, 2003, 984:182-188.

Pope, K. and Wilson, D.A. Olfactory system modulation of hippocampal cell death, Neuroscience Letters, 2007, 422:13-17.

Last update 09/07