De-novo inter-regional coactivations of pre-configured local ensembles support memory

SummaryNeuronal ensembles in the amygdala, ventral hippocampus, and prefrontal cortex are involved in fear memory; however, how the inter-regional ensemble interactions support memory remains elusive. Using multi-regional large-scale electrophysiology in the afore-mentioned structures of fear-conditioned rats, we demonstrated that local ensembles activated during fear memory acquisition were inter-regionally coactivated during subsequent sleep, which relied on brief bouts of fast network oscillations. During memory retrieval, coactivations reappeared, accompanying fast oscillations. Ensembles contributing to inter-regional coactivation were configured prior to memory acquisition in the amygdala and prefrontal cortex but developed through experience in the hippocampus. Our observation suggests that elements of a given memory are instantly encoded within various brain regions in a pre-configured manner, whereas hippocampal ensembles and the network for inter-regional integration of the distributed information develop in an experience-dependent manner to form a new memory, which is consistent with hippocampal memory index hypothesis.

What maintains signal honesty in animal colour displays used in mate choice?

Many of the colour displays of animals are proposed to have evolved in response to female mate choice for honest signals of quality, but such honest signalling requires mechanisms to prevent cheating. The most widely accepted and cited mechanisms for ensuring signal honesty are based on the costly signalling hypothesis, which posits that costs associated with ornamentation prevent low-quality males from being highly ornamented. Alternatively, by the index hypothesis, honesty can be achieved via cost-free mechanisms if ornament production is causally linked to core physiological pathways. In this essay, we review how a costly signalling framework has shaped empirical research in mate choice for colourful male ornaments and emphasize that alternative interpretations are plausible under an index signalling framework. We discuss the challenges in both empirically testing and distinguishing between the two hypotheses, noting that they need not be mutually exclusive. Finally, we advocate for a comprehensive approach to studies of colour signals that includes the explicit consideration of cost-free mechanisms for honesty. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

The evolution of index signals to avoid the cost of dishonesty

Animals often convey useful information, despite a conflict of interest between the signaller and receiver. There are two major explanations for such ‘honest’ signalling, particularly when the size or intensity of signals reliably indicates the underlying quality of the signaller. Costly signalling theory (including the handicap principle) predicts that dishonest signals are too costly to fake, whereas the index hypothesis predicts that dishonest signals cannot be faked. Recent evidence of a highly conserved causal link between individual quality and signal growth appears to bolster the index hypothesis. However, it is not clear that this also diminishes costly signalling theory, as is often suggested. Here, by incorporating a mechanism of signal growth into costly signalling theory, we show that index signals can actually be favoured owing to the cost of dishonesty. We conclude that costly signalling theory provides the ultimate, adaptive rationale for honest signalling, whereas the index hypothesis describes one proximate (and potentially very general) mechanism for achieving honesty.

Faktor-Faktor yang Mempengaruhi Praktik Perataan Laba pada Emiten dalam Industri Manufaktur dan Indeks LQ45 yang Terdaftar di Bursa Efek Indonesia Periode 2006-2008

The purpose of this research was to test factors that influence income smoothing in manufacture industry which listed in Indonesia Stock Exchange (BEI) and in companies registered in LQ45 index. Factors would be tested were company size, profitability, financial risk, and public ownership structure. Number of sample was 74 companies consist of 65 manufactures and 9 other registered in LQ45 respectively. Sample selection conducted using purposive sampling method. The criteria’s were the companies should been listed from year 2006 until 2008, never reporting net loss, complete data, reporting currency was IDR, did not involve in any merger nor acquit ion, and consistently registered in LQ45 index during observation. To identify the company that conduct income smoothing we using Eckel Index. Hypothesis would be tested using binary logistic regression. The results showed that company size had significant influence toward income smoothing, however profitability, profitability, financial risk, and public ownership structure had not significant influence toward income smoothing.