Electronic Thesis and Dissertation Repository


Master of Science




Dr. Susanne Schmid


The pedunculopontine tegmentum (PPT) is part of the mesopontine cholinergic system with distinct anterior and posterior subdivisions. With fast sensory input and descending connections to brainstem locomotor centers, we predict posterior PPT (pPPT) mediates prepulse inhibition of acoustic startle reflex, a form of sensorimotor gating that affects attentional processes. Similar to pPPT cholinergic projections to ventral tegmental area, we predict anterior PPT cholinergic input to substantia nigra regulates dopamine release in striatum, which is important for reinforcement learning. We lesioned the PPT bilaterally in male Sprague Dawley rats with ibotenic acid. Posterior cholinergic cell loss was significantly correlated with prepulse inhibition scores, consistent with our predictions for pPPT mediation of PPI. Anterior cholinergic cell loss was not correlated with performance in cued version of Morris water maze task, though lesions were likely insufficient. These results contribute to investigation of anterior vs. posterior PPT contribution to higher cognitive function.