The latest development of Cre-Driver mouse lines for various cortical interneurons should facilitate the probing of their precise roles in olfactory processing (Taniguchi et al., 2011). Lastly, the new findings further raise questions on the exact function of
intracortical connections in olfactory percept formation. Recurrent neural networks may be particularly suited for enhancing perception robustness and olfactory learning (Haberly, 2001). For example, the glomerular spatial activation patterns evoked by a given odorant may vary because of the noises associated with stimulus delivery and intrinsic circuit activity. Intracortical recurrent connections provide the function of pattern completion PI3K Inhibitor Library such that an identical population of cortical neurons
is activated by an odorant despite variable LOT inputs (Barnes HSP inhibitor et al., 2008). However, inappropriate recurrent connections would impair perception precision and stability in an individual animal as well as perception consistency across individuals. An overly strong capability of pattern completion would deny an animal its ability to discriminate different odorants. Excessive plasticity would lead an animal to perceive the same object differently after an unreasonably short period. Similarly, completely random connections would make it difficult to generate consistent perception across individuals, so that fruits may no longer consistently smell “fruity” to human individuals. The connections in the piriform cortex must be carefully carved to achieve a delicate balance among different behavioral needs. The almost wiring stochasticism in the piriform cortex highlights the needs and challenges of searching for logic in the neural circuits underlying animals’ amazing sense of smell. “
“MeCP2 (X-linked methyl-CpG-binding protein
2) is an abundant nuclear protein that binds methylated DNA and historically has been thought to act as a transcriptional repressor critical for normal neural development. Mutations in the gene encoding MeCP2 cause the Autism-spectrum disorder Rett Syndrome (RTT). In this issue of Neuron, Cohen, Greenberg, and colleagues demonstrate that activity-induced phosphorylation of MeCP2 at a single serine residue (S421) controls distinct aspects of synapse development and social behavior ( Cohen et al., 2011). In contrast to prior studies implicating this phosphorylation event in the dynamic regulation of MeCP2 binding at specific promoters, the present study suggests that the primary function of MeCP2 in neurons is not to regulate transcription of specific genes but rather to regulate chromatin remodeling on a global scale. DNA methylation is an epigenetic modification that plays an essential role in mammalian embryogenesis presumably through repressive effects on gene transcription.