My laboratory features two ongoing lines of research. The primary focus is on plastic changes in the adult primate somatosensory system following peripheral nerve injury. It has been known for nearly two decades that the adult primate somatosensory cortex can undergo a topographic reorganization after transection of one or more of the nerves innervating the hand. We wish to understand the mechanism(s) by which such changes are effected.
To accomplish that, we:
- conduct electrophysiological mapping experiments in the somatosensory cortex, thalamus, and brainstem;
- assess the neurochemical substrates of the plastic changes using specific receptor antagonists, immunocytochemistry, receptor autoradiography, and in vivo microdialysis with high-performance liquid chromatography;
- investigate possible morphological changes in somatosensory neurons by reconstructing Golgi-stained neurons; and
- employ gene and protein assays to reveal the molecular mechanisms of this plasticity. More recently initiated experiments are beginning to investigate the contributions of gonadal and stress hormones to somatosensory plasticity in adult rats.
The second line of research involves assessment of the effects of anticonvulsant compounds, gonadal and stress hormones, or specific neurotransmitter systems, principally using an instrumental appetitive-to-aversive transfer task or a Pavlovian discrimination reversal paradigm, as well as Morris water maze, and spatial working memory tasks. For these experiments, anticonvulsants are delivered to normal adult rats, to adult females throughout pregnancy and nursing with the offspring tested as adults, or transiently to adolescent rats who are then tested as adults. Hormonal manipulations involve gonadectomy in infancy or adulthood, or chronic restraint stress. Specific neurochemical manipulations investigated thus far include cholinergic depletion and NMDA glutamatergic receptor blockade. Associated experiments involve Golgi morphometric studies in targeted brain structures of rats at critical times during the instrumental appetitive-to-aversive transfer task. These experiments relate to the primate somatosensory plasticity studies insofar as critical neurochemical, anatomical, and hormonal mechanisms of injury- and experience-induced plasticity and development are shared.