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Neurogenesis in the adult brain gives rise to functional neurons, which integrate into neuronal circuits and modulate neural plasticity. Sustained neurogenesis throughout life occurs in the subgranular zone (SGZ) of the dentate gyrus in the hippocampus and is hypothesized to be involved in behavioral/cognitive processes such as memory and in diseases. Genomic imprinting is of critical importance to brain development and normal behavior, and exemplifies how epigenetic states regulate genome function and gene dosage. While most genes are expressed from both alleles, imprinted genes are usually expressed from either the maternally or the paternally inherited chromosome. Here, we show that in contrast to its canonical imprinting in nonneurogenic regions, Delta-like homolog 1 (Dlk1) is expressed biallelically in the SGZ, and both parental alleles are required for stem cell behavior and normal adult neurogenesis in the hippocampus. To evaluate the effects of maternally, paternally, and biallelically inherited mutations within the Dlk1 gene in specific behavioral domains, we subjected Dlk1-mutant mice to a battery of tests that dissociate and evaluate the effects of Dlk1 dosage on spatial learning ability and on anxiety traits. Importantly, reduction in Dlk1 levels triggers specific cognitive abnormalities that affect aspects of discriminating differences in environmental stimuli, emphasizing the importance of selective absence of imprinting in this neurogenic niche.

Filial imprinting has become a model for understanding memory, learning and social behaviour in neonate animals. This mechanism allows the youngs of precocial bird species to learn the characteristics of conspicuous visual stimuli and display affiliative response to them. Although longer exposures to an object produce stronger preferences for it afterwards, this relation is not linear. Sometimes, chicks even prefer to approach novel rather than familiar objects. To date, little is known about how filial preferences develop across time. This study aimed to investigate filial preferences for familiar and novel imprinting objects over time. After hatching, chicks were individually placed in an arena where stimuli were displayed on two opposite screens. Using an automated setup, the duration of exposure and the type of stimuli were manipulated while the time spent at the imprinting stimulus was monitored across 6 days. We showed that prolonged exposure (3 days vs 1 day) to a stimulus produced robust filial imprinting preferences. Interestingly, with a shorter exposure (1 day), animals re-evaluated their filial preferences in functions of their spontaneous preferences and past experiences. Our study suggests that predispositions influence learning when the imprinting memories are not fully consolidated, driving animal preferences toward more predisposed stimuli.

Nonsongbirds can produce rhythmical sounds that, at times, have been shown to be meaningful in their communication. This raises the possibility that rhythm is a separate ability that might have evolved earlier than song. We asked whether nearly completely naive domestic chicks perceive rhythm and respond in specific ways to different rhythmic patterns. To do so, specific constituent parameters of rhythmicity were used based on the sound of a natural mother hen's cluck. The sound samples created ranged from a continuous sound to articulated rhythmic patterns of alternating strong and weak events. Chicks' reactivity to the patterns was tested over a series of sound exposure experiments by their propensity to operate a running wheel toward the acoustic source, a paradigm simulating chicks' natural affiliative response to the hen's call. Results showed that motor activity increased markedly when acoustic events were discrete (compared with continuous), and significantly when accent structure was faster (compared with slower rates). Similar to human infants, chicks showed a significant preference for pulsed over continuous patterns. Chicks also ran harder toward calls with fast strong pulsating events, suggesting that different arrangements of events in time can be differently arousing, but independently of whether the events were presented in a regular or nonregular fashion.

La teoria darwiniana dell’evoluzione rappresenta uno dei maggiori successi scientifici di ogni tempo. Eppure una percentuale molto alta di persone nei paesi occidentali fa mostra di credere in varie forme di creazionismo e di rifiutare la teoria dell’evoluzione. Questo difetto di persuasività è per molti versi sorprendente. I dati convergenti della psicologia dello sviluppo, della psicologia evoluzionistica, dell’antropologia e delle neuroscienze suggeriscono una programmazione biologica delle nostre menti per distinguere naturalmente le entità inerti (gli oggetti fisici) e quelle di natura psicologica (gli agenti animati) e per l’attribuzione e, incidentalmente, l’iper-attribuzione, di scopi e intenzioni agli oggetti animati e inanimati. Ciò spiegherebbe l’inclinazione naturale a trovare psicologicamente soddisfacenti le spiegazioni animistiche o quelle basate sul “disegno”, intelligente o divino che dir si voglia, delle nostre origini. La specie umana ci ha abituato alle innovazioni, biologiche prima e culturali poi. Essere consapevoli di come si sono evoluti i nostri vincoli cognitivi potrebbe essere un’occasione per maneggiarli in modo più razionale.

It is well known that a flat ellipse rotating in the frontoparallel plane appears, after brief inspection, as a rigid circular disc tilting back and forth in a 3-D space. We here report that rotation of a grey-shaded ellipse on a white or on a black background produces the compelling illusion of a dark smoke or a dazzling fog (depending on the conditions of the background) moving in front of a completely white or completely black tilting disc. The fog effect disappears when there is a luminance contrast all along the perimeter of the ellipse.,An experiment is reported showing that the effect can be experienced in static conditions only to a limited extent and mostly in the 'dazzling' version, and that relative movement between the contours of the figure and the shaded area is crucial to the occurrence of the effect, while the occurrence of a depth effect is not