What can spike train distances tell us about the neural code?

Time scale parametric spike train distances like the Victor and the van Rossum distancesare often applied to study the neural code based on neural stimuli discrimination.Different neural coding hypotheses, such as rate or coincidence coding,can be assessed by combining a time scale parametric spike train distance with aclassifier in order to obtain the optimal discrimination performance. The time scalefor which the responses to different stimuli are distinguished best is assumed to bethe discriminative precision of the neural code. The relevance of temporal codingis evaluated by comparing the optimal discrimination performance with the oneachieved when assuming a rate code.We here characterize the measures quantifying the discrimination performance,the discriminative precision, and the relevance of temporal coding. Furthermore,we evaluate the information these quantities provide about the neural code. Weshow that the discriminative precision is too unspecific to be interpreted in termsof the time scales relevant for encoding. Accordingly, the time scale parametricnature of the distances is mainly an advantage because it allows maximizing thediscrimination performance across a whole set of measures with different sensitivitiesdetermined by the time scale parameter, but not due to the possibility toexamine the temporal properties of the neural code.

Chroma binary similarity and local alignment applied to cover song identification

We present a new technique for audio signal comparison based on tonal subsequence alignment and its application to detect cover versions (i.e., different performances of the same underlying musical piece). Cover song identification is a task whose popularity has increased in the Music Information Retrieval (MIR) community along in the past, as it provides a direct and objective way to evaluate music similarity algorithms.This article first presents a series of experiments carried outwith two state-of-the-art methods for cover song identification.We have studied several components of these (such as chroma resolution and similarity, transposition, beat tracking or Dynamic Time Warping constraints), in order to discover which characteristics would be desirable for a competitive cover song identifier. After analyzing many cross-validated results, the importance of these characteristics is discussed, and the best-performing ones are finally applied to the newly proposed method. Multipleevaluations of this one confirm a large increase in identificationaccuracy when comparing it with alternative state-of-the-artapproaches.

Generalized low-density codes with BCH constituents for full-diversity near-outage performance

A new graph-based construction of generalized low density codes (GLD-Tanner) with binary BCH constituents is described. The proposed family of GLD codes is optimal on block erasure channels and quasi-optimal on block fading channels. Optimality is considered in the outage probability sense. Aclassical GLD code for ergodic channels (e.g., the AWGN channel,the i.i.d. Rayleigh fading channel, and the i.i.d. binary erasure channel) is built by connecting bitnodes and subcode nodes via a unique random edge permutation. In the proposed construction of full-diversity GLD codes (referred to as root GLD), bitnodes are divided into 4 classes, subcodes are divided into 2 classes, and finally both sides of the Tanner graph are linked via 4 random edge permutations. The study focuses on non-ergodic channels with two states and can be easily extended to channels with 3 states or more.

Transcriptional activation of the macrophage migration-inhibitory factor gene by the corticotropin-releasing factor is mediated by the cyclic adenosine 3',5'- monophosphate responsive element-binding protein CREB in pituitary cells.

Macrophage migration-inhibitory factor (MIF) has recently been identified as a pituitary hormone that functions as a counterregulatory modulator of glucocorticoid action within the immune system. In the anterior pituitary gland, MIF is expressed in TSH- and ACTH-producing cells, and its secretion is induced by CRF. To investigate MIF function and regulation within pituitary cells, we initiated the characterization of the MIF 5'-regulatory region of the gene. The -1033 to +63 bp of the murine MIF promoter was cloned 5' to a luciferase reporter gene and transiently transfected into freshly isolated rat anterior pituitary cells. This construct drove high basal transcriptional activity that was further enhanced after stimulation with CRF or with an activator of adenylate cyclase. These transcriptional effects were associated with a concomitant rise in ACTH secretion in the transfected cells and by an increase in MIF gene expression as assessed by Northern blot analysis. A cAMP-responsive element (CRE) was identified within the MIF promoter region which, once mutated, abolished the cAMP responsiveness of the gene. Using this newly identified CRE, DNA-binding activity was detected by gel retardation assay in nuclear extracts prepared from isolated anterior pituitary cells and AtT-20 corticotrope tumor cells. Supershift experiments using antibodies against the CRE-binding protein CREB, together with competition assays and the use of recombinant CREB, allowed the detection of CREB-binding activity with the identified MIF CRE. These data demonstrate that CREB is the mediator of the CRF-induced MIF gene transcription in pituitary cells through an identified CRE in the proximal region of the MIF promoter.

Cyclic AMP induces differentiation in vitro of human melanoma cells.

Treating human melanoma lines with dibutyryl adenosine 3':5'-cyclic monophosphate (dbc AMP) resulted in morphologic changes associated with the altered expression of cell surface antigens. After treatment, cells developed long cellular projections characteristic of mature melanocytes and showed the presence of an increased number of Stage II premelanosomes. In addition, induction of melanin synthesis, detected as brown perinuclear pigmentation, was observed. The AMP further drastically reduced the growth rate of the five melanoma cell lines that were tested. The influence of dbc AMP was completely reversible 3 days after the agent was removed from the culture medium. The antigenic phenotype of the melanoma lines was compared before and after dbc AMP treatment. This was done with four monoclonal antibodies directed against major histocompatibility complex (MHC) Class I and II antigens and 11 monoclonal antibodies defining eight different melanoma-associated antigenic systems. Treatment with dbc AMP reduced the expression of human leukocyte antigen (HLA)-ABC antigens and beta-2-microglobulin in five of five melanoma lines. In the two HLA-DR-positive cell lines dbc AMP reduced the expression of this antigen in one line and enhanced it in the other. No induction of HLA-DR or HLA-DC antigens was observed in the Class II negative cell lines. Furthermore, dbc-AMP modulated the expression of the majority of the melanoma antigenic systems tested. The expression of a 90-kilodalton (KD) antigen, which has been found to be upregulated by interferon-gamma, was markedly decreased in all the five cell lines. A similar decrease in the expression of the high molecular weight proteoglycan-associated antigen (220-240 KD) was observed. The reduced expression of Class I and II MHC antigens as well as the altered expression of the melanoma-associated antigens studied were shown to be reversible after dbc AMP was removed. Our results collectively show that the monoclonal antibody-defined melanoma-associated molecules are linked to differentiation. They could provide useful tools for monitoring the maturation of melanomas in vivo induced by chemical agents or natural components favoring differentiation.