Dynamical feature extraction at the sensory periphery guides chemotaxis.

Behavioral strategies employed for chemotaxis have been described across phyla, but the sensorimotor basis of this phenomenon has seldom been studied in naturalistic contexts. Here, we examine how signals experienced during free olfactory behaviors are processed by first-order olfactory sensory neurons (OSNs) of the Drosophila larva. We find that OSNs can act as differentiators that transiently normalize stimulus intensity-a property potentially derived from a combination of integral feedback and feed-forward regulation of olfactory transduction. In olfactory virtual reality experiments, we report that high activity levels of the OSN suppress turning, whereas low activity levels facilitate turning. Using a generalized linear model, we explain how peripheral encoding of olfactory stimuli modulates the probability of switching from a run to a turn. Our work clarifies the link between computations carried out at the sensory periphery and action selection underlying navigation in odor gradients.

Neurofibromatosis type 2: molecular and clinical analyses in Argentine sporadic and familial cases.

Neurofibromatosis 2 is a familial syndrome characterized by the development of schwannomas, meningiomas and ependymomas. Most of them are benign however, their location in the nervous system has harmful effects on important cranial and spinal structures. These tumors are developed as the outcome of NF2 gene (22q12) inactivation. The NF2 protein, merlin or schwannomin belongs to the Ezrin, Radixin, Moesin (ERM) family involved in the cytoskeletal network and has a tumor suppressor function. Inactivating mutations occur as "de novo" (more frequently) or as inherited, and most of them are frameshift or nonsense. Our aim is to study NF2 gene alterations in Argentine patients and relate them to clinical features. 10 families and 29 single patients were analyzed for: 1) at-risk haplotype by STR-segregation analysis and 2) NF2 gene mutations by SSCP/heteroduplex/sequencing. The at-risk haplotype was uncovered in 8 families and mutations were identified in 5 patients. The molecular data are in full agreement with the clinical features supporting previous reports. The obtained results were important for the detection of mutation-carrying relatives and exclusion of other individuals from risk.