Our primary interest is the cellular mechanisms underlying learning and memory in the mammalian brain. To bridge the gap between learning related behavioral phenomena and their underlying single cell mechanisms, our research combines cellular neurophysiology biochemistry and morphology with behavioral neuroscience. We are using an olfactory conditioning paradigm, in which rats have to memorize odors in order to get rewarded with drinking water. Our data show that odor training results in the following learning-related cellular modifications of intrinsic and synaptic properties in piriform cortex pyramidal neurons: 1. Increased neuronal excitability (Saar et al., 2001; Saar and Barkai, 2003, Zelcer et al., 2003; Brosh et al., 2006) 2. Enhanced synaptic transmission (Saar et al., 2001; 2002). 3. Increased spine density on apical and basal dendrites, and modifications in single spine morphology (Kanfo et al., 2005a,b). 4. Predisposition for long-term potentiation (LTP) is decreased and predisposition for Long-term depression (LTD) is increased as result of a modifications in the subunit composition of the NMDA receptor (Lebel et al., 2001; Quinlan et al., 2004). Our current research is aimed to address four major questions: 1. What are the learning-relevant modifications in inhibitory synaptic transmission, and what are the mechanisms of inducing and maintaining such changes? 2. What is the precise mechanism by which long-lasting enhancement of synaptic transmission is maintained? 3. How is increased neuronal excitability in cortical and hippocampal neurons related to general enhancement in the animals' ability to acquire complex skills? 4. What is the role of metabotropic glutamate receptors in inducing and maintaining learning-relevant neuronal activity?