A circular model for song motor control in Serinus canaria

Song production in songbirds is controlled by a network of nuclei distributed across several brain regions, which drives respiratory and vocal motor systems to generate sound. We built a model for birdsong production, whose variables are the average activities of different neural populations within these nuclei of the song system. We focus on the predictions of respiratory patterns of song, because these can be easily measured and therefore provide a validation for the model. We test the hypothesis that it is possible to construct a model in which (1) the activity of an expiratory related (ER) neural population fits the observed pressure patterns used by canaries during singing, and (2) a higher forebrain neural population, HVC, is sparsely active, simultaneously with significant motor instances of the pressure patterns. We show that in order to achieve these two requirements, the ER neural population needs to receive two inputs: a direct one, and its copy after being processed by other areas of the song system. The model is capable of reproducing the measured respiratory patterns and makes specific predictions on the timing of HVC activity during their production. These results suggest that vocal production is controlled by a circular network rather than by a simple top-down architecture.Fil: Alonso, Rodrigo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Sistemas Dinámicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trevisan, Marcos Alberto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Sistemas Dinámicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Amador, Ana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Sistemas Dinámicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Goller, Franz. University Of Utah. Department Of Biology; Estados UnidosFil: Mindlin, Bernardo Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Sistemas Dinámicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Grammatiklernen und Serielles Reagieren: Zwei Paradigmen - ein Lernmechanismus?

In zwei Experimenten wurde der Frage nachgegangen, ob die impliziten Lerneffekte im Paradigma des Grammatiklernens und dem des seriellen Reagierens entsprechend den Vorstellungen von Frensch und Miner (1994) durch einen strikt assoziativen Lernmechanismus erklärt werden können. Ausgehend von der Theorie finiter Automaten konnten Bedingungen geschaffen werden, durch die die wesentlichen Aspekte beider Paradigmen hinsichtlich der Lern- und Testphase unabhängig voneinander kombinierbar wurden. In Experiment 1 zeigte sich auf der Basis von Zulässigkeitsurteilen, daß Vpn gegenüber der probabilistischen Struktur von Ereignissequenzen sensitiv waren, wenn sie in einer vorausgehenden inzidentellen Lernphase grammatisch strukturierte Sequenzen memoriert hatten (Grammatiklernen), nicht jedoch, wenn sie auf einzeln angezeigte Sequenzelemente unmittelbar zu reagieren hatten (Serielles Reagieren). Um als Alternativerklärung die Transferangemessenheit der Verarbeitung zu prüfen, wurde in Experiment 2 unter sonst gleichen Bedingungen in der Testphase lediglich verlangt, auf einzeln angezeigte Sequenzelemente möglichst schnell zu reagieren. Der Vergleich der Latenzzeiten zwischen den kritischen Übergängen für neue grammatische und agrammatische Sequenzen ergab für beide Lernbedingungen klare Grammatikalitätseffekte. Die Implikationen der Befunde für Annahmen zu Lernmechanismen werden diskutiert

Smooth operator: Avoidance of subharmonic bifurcations through mechanical mechanisms simplifies song motor control in adult zebra finches

Like human infants, songbirds acquire their song by imitation and eventually generate sounds that result from complicated neural networks and intrinsically nonlinear physical processes. Signatures of low-dimensional chaos such as subharmonic bifurcations have been reported in adult and developing zebra finch song. Here, we use methods from nonlinear dynamics to test whether adult male zebra finches (Taenopygia guttata) use the intrinsic nonlinear properties of their vocal organ, the syrinx, to insert subharmonic transitions in their song. In contrast to previous data on the basis of spectrographic evidence, we show that subharmonic transitions do not occur in adult song. Subharmonic transitions also do not arise in artificially induced sound in the intact syrinx, but are commonly generated in the excised syrinx. These findings suggest that subharmonic transitions are not used to increase song complexity, and that the brain controls song in a surprisingly smooth control regimen. Fast, smooth changes in acoustic elements can be produced by direct motor control in a stereotyped fashion, which is a more reliable indicator of male fitness than abrupt acoustic changes that do not require similarly precise control. Consistent with this view is the presence of high fidelity at every level of motor control, from telencephalic premotor areas to superfast syringeal muscles

Criminal recidivism of illegal pornography offenders in the overall population - a national cohort study of 4612 offenders in Switzerland

Convictions for taking, possessing and distributing pornographic photographs of children have increased with the growing use of the Internet. Previous studies of any progression to contact offences have been small scale and only a few of these have included an investigation of subsequent reconvictions for use of illegal and especially of child pornography. The aims of the present study are to compare reconviction rates among illegal pornography offenders with and without previous child contact offences. The former are referred to as “dual offenders”. This study is a national cohort study of all individuals in Switzerland convicted of an illegal pornography offence since 1973 and was followed-up until 1st November 2008. Reconvictions were ascertained using criminal records from the Federal Office of Justice of Switzerland, leading to a total of 4612 offenders, consisting of 4249 illegal pornography offenders and 363 dual offenders. Comparison of 3-year reconviction rates showed that only 0.2% of the illegal pornography offenders were convicted of contact child sex offences, whereas 2.6% of the dual offenders were reconvicted. The illegal pornography offenders were also significantly less likely to be convicted of further pornography offences, or indeed other sexual offences. The very low “progression rate” among illegal pornography offenders to contact child sexual offences, and their low rate of even repeat pornography offences suggests that community sentences remain appropriate. It is important, however, to bear in mind that conviction rates tend to underestimate the true offending rates, and that with greater access to the Internet, characteristics of pornography users may change over time