The role of the amygdala in signaling prospective outcome of choice

Can brain activity reveal a covert choice? Making a choice often evokes distinct emotions that accompany decision processes. Amygdala has been implicated in choice behavior that is guided by a prospective negative outcome. However, its specific involvement in emotional versus cognitive processing of choice behavior has been a subject of controversy. In this study, the human amygdala was monitored by functional magnetic resonance imaging (fMRI) while subjects were playing in a naturalistic choice paradigm against the experimenter. In order to win, players had to occasionally choose to bluff their opponent, risk "getting caught," and suffer a loss. A critical period, when choice has been made but outcome was still unknown, activated the amygdala preferentially following the choice that entailed risk of loss. Thus, the response of the amygdala differentiated between subject's covert choice of either playing fair or foul. These results support a role of the amygdala in choice behavior, both in the appraisal of inherent value of choice and the signaling of prospective negative outcomes.     

Modelling the evolution of female choice strategies under inbreeding conditions

Recently, many mate choice studies have discussed the role of genetic compatibility and inbreeding for the evolution of mate choice. With population genetic simulations I compared the potential advantage of three different female choice strategies under inbreeding conditions. Females were assumed to benefit indirectly via a preference for (i) complementary males, (ii) males with few detrimental mutations, and (iii) non-inbred males. Probably related to the reduced inbreeding depression in offspring of choosy females, the choice-allele increased for all three strategies. However, the advantage of the strategies differed widely. Choice of males with fewer mutations provided a comparatively large advantage, choice of complementary males led to a reasonable advantage, and choice of non-inbred males only resulted in a minor advantage of female choice. My results show that complementary mate choice can be almost as beneficial as conventional good-genes choice of mates with lower genetic load. Compared to the two other mate choice strategies, choice of non-inbred males is less likely to contribute to the evolution of costly mate choice. The results of a recent study showing that female sticklebacks prefer males with a larger number of MHC-loci is thus unlikely to be related to an indirect benefit of choosing non-inbred males.     

Measuring the fitness benefits of male mate choice in Drosophila melanogaster

It is increasingly realized that the potential for male mate choice is widespread across many taxa. However, measurements of the relative magnitude of the fitness benefits that such choice can confer are lacking. Here, we directly measured, in a comprehensive set of tests that manipulated key variables, the fitness benefits of male mate choice in Drosophila melanogaster by measuring egg production in females that were chosen or rejected by males. The results provided significant evidence for male mate choice. In absolute terms, the observed degree of choice increased male fitness by an average of only 1.59 eggs. However, using a novel technique we show that this benefit of choice represented 14.5% of the maximum potential fitness benefit of choice. The magnitude of mate choice was not significantly altered by variation in (1) mate compatibility, (2) phenotypic plasticity in male mate choice, or (3) whether choosing males were preferred or nonpreferred by females. Overall, we show that male mate choice represents a subtle but significant opportunity for sexual selection, and we offer a novel and widely applicable method for quantifying mate choice.     

Size-assortative nest choice by the Japanese fluvial sculpin in the presence of male-male competition

Nest choice by the Japanese fluvial sculpin Cottus pollux and its relationship to male reproductive success, was examined in a natural habitat, central Japan. The larger males tended to occupy the deeper nest cavities, suggesting size-assortative nest choice by the species. Stepwise regression analysis showed that cavity area was correlated positively to male reproductive success. Nest choice experiments without a competitive male indicated an absence of size-assortative nest choice, but larger males tended to choose a large nest when another male was present, suggesting that size-assortative nest choice by the species is attributable to male-male competition for large nests, such being related to a resource-defence polygynous mating system.     

Spatial and temporal variations in nesting success and the causes of nest losses of the freshwater three-spined stickleback,Gasterosteus aculeatus

Synopsis Two experients were conducted to determine the effect of male color phenotype present during development on the mate choice of adult female guppies. Females were raised with either a colorful male, non-colorful male, or no male, and then measured for choice of a colorful or non-colorful male in a two-stimulus visual choice test. In the first experiment, adult females were measured for choice between the same male phenotypes used during the developmental exposure. Females raised with colorful males had significantly higher choice scores for colorful males than did females raised with non-colorful males or with no male. In the second experiment, an effect of developmental experience was observed when adult females were tested for choice with a general range of colorful and non-colorful males. However, this effect of experience during development was not detected when females were tested for choice between the same male phenotypes used during the developmental exposure. The predation regime of the source population, either high or low, showed no consistent effect on average female choice or on whether developmental experience changed female mate choice. Overall, these experiments show that experience with male phenotypes can affect the mate choice of adult guppies, but this effect was not observed under all developmental treatments or test conditions. Such an effect could significantly change the dynamics of the evolution of female preference due to sexual selection in the guppy.     

On the resolution of the lek paradox

Directional female mate choice is expected to deplete additive genetic variation in male traits. This should preclude such trait-based choice from resulting in genetic benefits to offspring, and yet genetic benefits are the explanation for the choice. This evolutionary conundrum is known as the lek paradox. Newly proposed resolutions to this paradox aim to unravel mechanisms that contribute to the persistence of genetic variance in traits under directional female mate choice.     

You Can't Not Choose: Embracing the Role of Choice in Ecological Restoration

From the moment of its inception, human choice about how to treat the environment is a key part of ecological restoration. Because many, if not most, restoration projects require continual management once established, human choice remains a vital component of restoration projects for their entire life. But ecological restorationists often downplay the role of choice in restoration, partly because we see the choice to restore as obvious and inherently good and partly because we feel the restoration of more natural conditions for a habitat will lessen the impact of human choice over time. Some critics feel the role of human choice in restoration degrades the value of restoration. However, another response to human choice in restoration is to embrace choice, even with the problems it brings, and use choice as a way to more fully engage humans with the environment. If such choices are approached carefully, with recognition of the potential for poor choices, then restorationists can arrive at restorations that are better for both the environment and us.     

Modeling the dynamics of choice

A simple linear-operator model both describes and predicts the dynamics of choice that may underlie the matching relation. We measured inter-food choice within components of a schedule that presented seven different pairs of concurrent variable-interval schedules for 12 food deliveries each with no signals indicating which pair was in force. This measure of local choice was accurately described and predicted as obtained reinforcer sequences shifted it to favor one alternative or the other. The effect of a changeover delay was reflected in one parameter, the asymptote, whereas the effect of a difference in overall rate of food delivery was reflected in the other parameter, rate of approach to the asymptote. The model takes choice as a primary dependent variable, not derived by comparison between alternatives—an approach that agrees with the molar view of behaviour.     

Apparent size choice of zooplankton by planktivorous sunfish: exceptions to the rule

Synopsis Choice of the apparently largest prey has been implicated as an important component of the size choice behavior of several planktivorous fish species. In this study we describe the effect of several aspects of prey placement, apparent and absolute size, and motion on the choice behavior of bluegill or white crappie. In binary choice experiments, bluegill usually choose Daphnia prey on the basis of apparent size. However, when both prey were close to the fish and the absolutely larger prey was apparently smaller, the fish commonly chose the absolutely larger. The horizontal placement of two prey also altered choice such that the more forward directed prey was chosen even when apparently smaller. White crappie, when offered a choice between a diaptomid copepod or daphnid prey, chose the daphnid most of the time. Bluegill sunfish offered moving versus non-moving heat-killed daphnids commonly chose the one in motion. Apparent size choice is still a good overall describer of bluegill and white crappie prey choice, but it is not the only mechanism involved in prey choice behavior of these fish.     

用稳态视觉诱发电位研究注意的选择机制

众所周知,注意是一种心理活动,是对外界刺激的一种选择,对人的其它认知活动有一定的调节作用。关于注意的选择机制,有两种不同的理论,一种是早期选择机制,另一种是晚期选择机制。稳态视觉诱发电位是视觉通路对外界刺激的一种物理反应,它的产生过程处于认知的早期阶段,如果它能受到注意的调节,这就支持了注意的早期选择机制。在现有的利用闪光稳态诱发电位对注意的研究中,注意的对象是认知任务,而不是闪光。该实验用两种不同频率的闪光分别做诱发源,对在注意与不注意闪光两种情况下(都没有认知任务)的稳态视觉诱发电位进行研究,发现其明显地受注意调节,而且对不同频率光刺激的调节大小不一样。因此,该实验结果支持了注意的早期选择机制。     

Acute differential sensitivity and role of the central nervous system in the feeding behavior of Drosophila melanogaster

Feeding behavior of the fruitfly, Drosophila melanogaster, isexamined quantitatively by determining the amount of fool intakecolorimetrically. The obtained differential sensitivity (Weberfraction l/l = 0.025) by the two-choice test is surprisinglyacute, compared with the previously reported values for insects.Besides, files also choose only the most stimulative prey inthree-choice tests and even a single fly, free from ‘gangingup’ exhibits a clear intake choice. Adaptation in thetest organ was experimentally proved not to play a leading rolein ingestion choice. The present experimental results supportan important role of the central nervous system in choice behavior.Although deprivation significantly enhances the amount of ingestion,it does not affect the choice itself under the present conditions,suggesting that the choice centre exists separately from theingestion center. Discrimination sensitivity depends considerablyon the food distribution and taste intensities paired.     

Directional Influence between the Human Amygdala and Orbitofrontal Cortex at the Time of Decision-Making

There is a growing consensus that the brain makes simple choices, such as choosing between an apple and an orange, by assigning value to the options under consideration, and comparing those values to make a choice. There is also a consensus that value signals computed in orbitofrontal cortex (OFC) and amygdala play a critical role in the choice process. However, the nature of the flow of information between OFC and amygdala at the time of decision is still unknown. In order to study this question, simultaneous local field potentials were recorded from OFC and amygdala in human patients while they performed a simple food choice task. Although the interaction of these circuits has been studied in animals, this study examines the effective connectivity directly in the human brain on a moment-by-moment basis. A spectral conditional Granger causality analysis was performed in order to test if the modulation of activity goes mainly from OFC-to-amygdala, from amygdala-to-OFC, or if it is bi-directional. Influence from amygdala-to-OFC was dominant prior to the revealed choice, with a small but significant OFC influence on the amygdala earlier in the trial. Alpha oscillation amplitudes analyzed with the Hilbert-Huang transform revealed differences in choice valence coincident with temporally specific amygdala influence on the OFC.     

Matching-to-sample by pigeons: the dissociation of comparison choice frequency from the probability of reinforcement

It has been proposed that comparison choice in matching-to-sample should depend on two factors, the relative probability of reinforcement associated with each of the comparison stimuli and the conditional probability of each comparison stimulus being correct given presentation of one of the samples. DiGian and Zentall [DiGian, K.A., Zentall, T.R., 2007. Matching-to-sample in pigeons: in the absence of sample memory, sample frequency is a better predictor of comparison choice than the probability of reinforcement for comparison choice. Learn Behav. 35, 242-261] have shown that sample frequency together with the probability of choosing each of the comparison stimuli in training can influence comparison choice when delays are introduced, when the number of reinforcements associated with each of the comparison stimuli is equated. Furthermore, Zentall and Clement [Zentall, T.R., Clement, T.S., 2002. Memory mechanisms in pigeons: Evidence of base-rate neglect. J. Exp. Psych.: Anim. Behav. Proc. 28, 111-115] have found that sample frequency can affect comparison choice when delays are introduced independently of the number of choices of each of the comparison stimuli in training and the number of reinforcements associated with each of the comparison stimuli is equated. In the present experiment we found that the probability of choosing each of the comparison stimuli in training can affect comparison choice when delays are introduced, independently of sample frequency and when the number of reinforcements associated with each of the comparison stimuli is equated. Together, these experiments suggest that when the sample is not available, there is a partial dissociation between comparison choice and the probability of reinforcement associated with each of the comparison stimuli.     

Dissecting the repeatability of female choice in the grasshopper Chorthippus biguttulus

Repeatable differences in preference between females are a prerequisite for the evolution of female choice. Existing studies have concentrated on the repeatability of female preference for the male trait eliciting the highest female response but have rarely dealt with female choosiness and response rate, which are also important traits for the evolution of female choice and can mimic repeatable variation in preference. We used a method devised to disentangle the effects of preference, choosiness and response rate to examine the repeatability of female choice for acoustic signals in the grasshopperChorthippus biguttulus . We stimulated females with artificial courtship signals that varied in one signal trait and recorded the number of acoustic responses of the females in two sessions separated by several days. Using a normal distribution function within a nonlinear regression between signalling trait and female response rate, we independently calculated values for female preference, choosiness and maximum response rate for the two sessions. All three aspects of female choice showed significant repeatability indicating large differences between females. This method will also be suitable for measuring the heritability of female preference, a crucial question regarding the evolution of female choice. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Effect of 5,6-dihydroxytryptamine and 6-hydroxydopamine on the maze behavior of the snail Helix lucroum

One-trial Y-maze test in snails did not reveal any predominance of the right or left alley choice. The choice of the right alley (but not of the left one) was accompanied by a slowing down of forward motion. After the administration of 10 mg/kg of 6-hydroxydopamine 24 hr before the test, right alley choice without slowing down became more frequent. Administration of 5,6-dihydroxytrypamine (10 mg/kg) caused a reduction of motion rate along all parts of the maze and an increase in frequency of the orienting head movements towards the alley to be chosen.     

Effect of olfactory and visual stimuli on the orientation of the 4th instar larvae of the stem borer Chilo partellus swinhoe (Lepidoptera: Pyralidae).

The orientational responses of 4th instar larvae of Chilo partellus to different sources of stimuli being artificial diet, leaves and stems of maize and sorghum were tested, under free choice and no-choice situations. Larvae were attracted to maize and sorghum in a moderate to high degree dependent on what choice they were given. The orientational preference of the larvae, offered a choice between the visual and the odour sources, depended upon their stimulating capacities which were represented by the percentages of individuals responding to the sources of stimuli. Odour played a greater role than visual stimuli in this close range attraction when the two competed with each other.     

Evaluating the existence and benefit of major histocompatibility complex‐based mate choice in an isolated owl population

How mate preferences evolve in the first place has been a major conundrum for sexual selection. Some hypotheses explaining this assume fitness benefit derived from subsequent generations. Major histocompatibility complex (MHC)‐based mate choice is a representative example of the mate choice that is associated with such trans‐generational mechanisms. To provide evidences for fitness benefit of MHC‐based mate choice, previous studies assessed the association between own MHC genotype and own fitness components. However, the association between MHC‐based mate choice in the parental generation and fitness components in the resultant offspring generation has only rarely been measured in wild populations. Focusing on the isolated population of the monogamous Ryukyu Scops Owl (Otus elegans interpositus) on Minami‐daito Island, Japan, we found evidence of MHC‐based mate choice. However, we found no evidence of MHC‐based mate choice increasing own reproductive success or offspring survival. This is a rare case study that directly examines the existence of the trans‐generational indirect benefit of MHC‐based mate choice for genetic compatibility from trans‐generational data in a wild bird population. By investigating the fitness benefits of mate choice, this study serves to facilitate our understanding of the evolution of MHC‐based mate choice.     

Sexual selection and the evolution of evolvability

Here we show that sexual selection can have an effect on the rate of mutation. We simulated the fate of a genetic modifier of the mutation rate in a sexual population with and without sexual selection (modelled using a female choice mechanism). Female choice for 'good genes' should reduce variability among male subjects, leaving insufficient differences to maintain female preferences. However, female choice can actually increase genetic variability by supporting a higher mutation rate in sexually selected traits. Increasing the mutation rate will be selected against because of the resulting decline in mean fitness. However, it also increases the probability of rare beneficial mutations arising, and mating skew caused by female preferences for male subjects carrying those beneficials with few deleterious mutations ('good genes') can lead to a mutation rate above that expected under natural selection. A choice of two male subjects was sufficient for there to be a twofold increase in the mutation rate as opposed to a decrease found under random mating.     

No evidence of inbreeding avoidance in a polygynous ungulate: the reindeer (Rangifer tarandus)

In polygynous species, mate choice is an integrated part of sexual selection. However, whether mate choice occurs independently of the genetic relatedness among mating pairs has received little attention, although inbreeding may have fitness consequences. We studied whether genetic relatedness influenced females' choice of partner in a highly polygynous ungulate--the reindeer (Rangifer tarandus)--in an experimental herd during two consecutive rutting seasons; the herd consisting of 75 females in 1999 and 74 females in 2000 was exposed to three 4.5-year-old adults and three 1.5-year-old young males, respectively. The females' distribution during peak rut was not influenced by their genetic relatedness with the dominant males of the mating groups. Further, genetic relatedness did not influence the actual choice of mating partner. We conclude that inbreeding avoidance through mating group choice as well as choice of mating partner, two interconnected processes of female mate choice operating at two different scales in space and time, in such a highly female-biased reindeer populations with low level of inbreeding may not occur.     

The role of female dominance hierarchies in the mating behaviour of mosquitofish

While studies of sexual selection focus primarily on female choice and male-male competition, males should also exert mate choice in order to maximize their reproductive success. We examined male mate choice in mosquitofish, Gambusia holbrooki, with respect to female size and female dominance. We found that the number of mating attempts made by a male was predicted by the dominance rank of females in a group, with dominant females attracting more mating attempts than subordinates. The number of mating attempts made by males was independent of the female size. The observed bias in the number of mating attempts towards dominant females may be driven either by straightforward male mate choice, since dominance and female fecundity are often closely related, or via the dominant females mediating male mating behaviour by restricting their access to subordinate females.