Statistics of seismic cluster durations

Using the standard ETAS model of triggered seismicity, we present a rigorous theoretical analysis of the main statistical properties of temporal clusters, defined as the group of events triggered by a given main shock of fixed magnitude m that occurred at the origin of time, at times larger than some present time t. Using the technology of generating probability function (GPF), we derive the explicit expressions for the GPF of the number of future offsprings in a given temporal seismic cluster, defining, in particular, the statistics of the cluster's duration and the cluster's offsprings maximal magnitudes. We find the remarkable result that the magnitude difference between the largest and second largest event in the future temporal cluster is distributed according to the regular Gutenberg-Richer law that controls the unconditional distribution of earthquake magnitudes. For earthquakes obeying the Omori-Utsu law for the distribution of waiting times between triggering and triggered events, we show that the distribution of the durations of temporal clusters of events of magnitudes above some detection threshold \nu has a power law tail that is fatter in the non-critical regime $n<1$ than in the critical case n=1. This paradoxical behavior can be rationalised from the fact that generations of all orders cascade very fast in the critical regime and accelerate the temporal decay of the cluster dynamics.Comment: 45 pages, 15 figure

Localized Brain Activation Related to the Strength of Auditory Learning in a Parrot

Parrots and songbirds learn their vocalizations from a conspecific tutor, much like human infants acquire spoken language. Parrots can learn human words and it has been suggested that they can use them to communicate with humans. The caudomedial pallium in the parrot brain is homologous with that of songbirds, and analogous to the human auditory association cortex, involved in speech processing. Here we investigated neuronal activation, measured as expression of the protein product of the immediate early gene ZENK, in relation to auditory learning in the budgerigar (Melopsittacus undulatus), a parrot. Budgerigar males successfully learned to discriminate two Japanese words spoken by another male conspecific. Re-exposure to the two discriminanda led to increased neuronal activation in the caudomedial pallium, but not in the hippocampus, compared to untrained birds that were exposed to the same words, or were not exposed to words. Neuronal activation in the caudomedial pallium of the experimental birds was correlated significantly and positively with the percentage of correct responses in the discrimination task. These results suggest that in a parrot, the caudomedial pallium is involved in auditory learning. Thus, in parrots, songbirds and humans, analogous brain regions may contain the neural substrate for auditory learning and memory

Gene expression patterns of chicken neuregulin 3 in association with copy number variation and frameshift deletion

[Background]Neuregulin 3 (NRG3) plays a key role in central nervous system development and is a strong candidate for human mental disorders. Thus, genetic variation in NRG3 may have some impact on a variety of phenotypes in non-mammalian vertebrates. Recently, genome-wide screening for short insertions and deletions in chicken (Gallus gallus) genomes has provided useful information about structural variation in functionally important genes. NRG3 is one such gene that has a putative frameshift deletion in exon 2, resulting in premature termination of translation. Our aims were to characterize the structure of chicken NRG3 and to compare expression patterns between NRG3 isoforms. [Results]Depending on the presence or absence of the 2-bp deletion in chicken NRG3, 3 breeds (red junglefowl [RJF], Boris Brown [BB], and Hinai-jidori [HJ]) were genotyped using flanking primers. In the commercial breeds (BB and HJ), approximately 45% of individuals had at least one exon 2 allele with the 2-bp deletion, whereas there was no deletion allele in RJF. The lack of a homozygous mutant indicated the existence of duplicated NRG3 segments in the chicken genome. Indeed, highly conserved elements consisting of exon 1, intron 1, exon 2, and part of intron 2 were found in the reference RJF genome, and quantitative PCR detected copy number variation (CNV) between breeds as well as between individuals. The copy number of conserved elements was significantly higher in chicks harboring the 2-bp deletion in exon 2. We identified 7 novel transcript variants using total mRNA isolated from the amygdala. Novel isoforms were found to lack the exon 2 cassette, which probably harbored the premature termination codon. The relative transcription levels of the newly identified isoforms were almost the same between chick groups with and without the 2-bp deletion, while chicks with the deletion showed significant suppression of the expression of previously reported isoforms. [Conclusions]A putative frameshift deletion and CNV in chicken NRG3 are structural mutations that occurred before the establishment of commercial chicken lines. Our results further suggest that the putative frameshift deletion in exon 2 may potentially affect the expression level of particular isoforms of chicken NRG3

Budgerigars can discriminate Japanese words.

<p><b>A</b> A schematic representation of the inside of the Skinner box. <b>B</b> Protocol of the go/no-go auditory discrimination task. <b>C</b> Sonagrams of the two Japanese words, spoken by a male budgerigar, used in the discrimination task. The top word means ‘hello’, and the bottom word means ‘have a nice day.’ <b>D</b> Mean proportion of correct responses in the go/no-go auditory discriminations. The mean (+ s.e.m.) percentage of correct responses for all of the trained birds over the first 5 sessions of training (100 trials per session) was not significantly above chance, but that over the last 5 sessions before stimulus re-exposure was significantly above chance (<i>n</i> = 7; ***<i>p</i><0.005).</p

Neuronal activation in the brain.

<p><b>A,B</b> Coronal sections of the budgerigar brain at the level of the dNCM and the hippocampus (A, cut at level “a” in D) and at the level of the vNCM and the CMM (B, cut at level “b” in D). Overlays represent the counting frames. Scale bar represents 1 mm. <b>C</b> Photomicrographs of coronal sections of the budgerigar brain showing Zenk immunoreactivity. Representative examples of Zenk-immunoreactive nuclei in the CMM (upper), the dNCM (middle), and the vNCM (lower) of birds that were trained and re-exposed to Japanese words (left), were not trained and exposed to Japanese words (middle), or kept in silence (right). Scale bar represents 50 µm. <b>D,E</b> Schematic diagrams of parasagittal views of the brains of avian vocal learners, parrots (D) and songbirds (E). Yellow regions indicate the caudomedial pallium, the NCM and the CMM. Ascending auditory pathways to Field L are similar in the two taxa (red arrows). Light grey regions indicate the vocal control system in parrots and the song system in songbirds. Lesion studies in adult and young songbirds led to the distinction between a caudal pathway (blue arrows), known as the song motor pathway (SMP), considered to be involved in the production of song, and a rostral pathway (blue dashed arrows), known as the anterior forebrain pathway (AFP), thought to play a role in song acquisition and auditory-vocal feedback processing. Equivalent pathways to the songbird SMP and AFP are proposed in the budgerigar <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038803#pone.0038803-Jarvis4" target="_blank">[45]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038803#pone.0038803-Brauth3" target="_blank">[79]</a>. Scale bar represents 1 mm. AAC, Central nucleus of anterior acropallium; APH, Parahippocampal area; Cb, Cerebellum; CLM, Caudal lateral mesopallium; CM, Caudal mesopallium; CMM, Caudomedial mesopallium; DLM, medial nucleus of dorsolateral thalamus; DMM, Magnocellular nucleus of the dorsomedial thalamus; HD, Densocellular part of the hyperpallium; HI, Intercalated part of the hyperpallium; HP, Hippocampus; HVC, acronym used as a proper name; L1, L2, L3, subdivisions of Field L complex; LaM, Mesopallial lamina; LMAN, Lateral magnocellular nucleus of the anterior nidopallium; LSt, Lateral striatum; MO, Oval nucleus of mesopallium; MStm, Magnocellular part of medial striatum; NAO, Oval nucleus of the anterior nidopallium; NC, Caudal nidopallium; dNCM, Dorsal part of the caudomedial nidopallium; vNCM, Ventral part of the caudomedial nidopallium; NF, Frontal nidopallium; NIVL, Ventral lateral nidopallium; NLC, Central nucleus of the lateral nidopallium; nXIIts, tracheosyringeal portion of the hypoglossal nucleus; RA, Robust nucleus of the acropallium.</p

Neuronal activation related to the strength of auditory learning.

<p><b>A</b> Mean (+ s.e.m.) number of Zenk-immunoreactive cells per square millimetre in the CMM, the NCM and the hippocampus for groups of male budgerigars in the Trained (<i>n</i> = 7), Untrained (<i>n</i> = 5) and Silence (<i>n</i> = 6) groups. Asterisks denote significant differences between the mean of the Trained group and the means of the two other groups (*<i>p</i><0.05, **<i>p</i><0.01). <b>B</b> Number of Zenk-immunoreactive cells per square millimetre in relation to the percentage correct responses in the discrimination task, in the CMM, the dNCM, the vNCM and the hippocampus. The correlation is significant in the CMM and the dNCM, but not in the vNCM or in the hippocampus.</p