Of snakes and faces: An evolutionary perspective on the psychology of fear

Snakes and faces are unique stimuli because they are deeply grounded in evolutionarily shaped behavior systems. Snakes are the prototypical stimulus in a predatory defense system promoting escape from predators, which prepares primates for efficient processing, attentional priority, and rapid fear acquisition to snakes and other stimuli related to predation. The social submissiveness system plays a similar role on the social arena by promoting yielding to dominant individuals without jeopardizing the protection of the group. Supporting these theoretical propositions, empirical data from a research program spanning four decades demonstrate enhanced fear conditioning to snakes and threatening faces compared to neutral stimuli, as well as fast nonconscious processing of, and prioritized attention to, snakes and threatening faces. Human brain‐imaging data show that these effects are mediated by an extensive fear‐network centering on the amygdala.     

Acute systemic fibroblast growth factor-2 enhances long-term memory in developing rats

Recent findings have provided much insight into the mechanisms underlying long-term memory formation, and it is now known that long-term memory depends on the activation of a molecular cascade that culminates with structural changes in the brain. However, little is known about the signals that give rise to or regulate these structural changes. In this article we propose that fibroblast growth factor-2 (FGF2), a mitogen for several cell types, may be one of the molecular signals critically involved in the structural changes underlying long-term memory. If FGF2 is part of the signalling cascade involved in long-term memory, then increasing the activation of FGF2 should facilitate memory. In Experiments 1 and 2, we demonstrated that systemic injection of FGF2 (20 ng/g of body weight) facilitated memory for contextual fear in 16, 19, and 22 day old male Sprague Dawley rats. Experiment 3 demonstrated that the observed facilitation of memory was not due to FGF2 increasing rats’ sensitivity to footshock. These results implicate FGF2 as a possible molecular signal in long-term memory, and further, illustrate a novel means of enhancing memory.     

Net Amount of Food Affects Autoshaped Response Rate, Response Latency, and Gape Amplitude in Pigeons

The contribution of net amount of food to conditioned response strength and topography was assessed in four pigeons under autoshaping contingencies. In each session, under one baseline phase and three replication phases, three trial types were presented sequentially: One conditioned stimulus (keylight) signaled one small pellet, another signaled one large pellet, and a third signaled seven small pellets which were weight-matched to one large pellet. Five dependent variables were response rates and latencies based on the occurrence of both keyswitch closures and gapes (beak openings) and gape amplitudes. In result, net amount of food, not pellet diameter or number, affected all dependent variables. Notably, gape amplitudes elicited by the seven-small pellet keylights were larger than the gape amplutides elicited by the one-small pellet keylights even though the gape amplitudes elicited by both unconditioned stimuli (one or seven pellets) were equally small. This mismatch between conditioned and unconditioned responses is incompatible with stimulus substitution accounts but is compatible with an associative strength account. Furthermore, the changes in the dependent variables were most likely determined by Pavlovian and not by inadvertent operant contingencies. The findings demonstrate that an analysis of classical conditioning benefits from the inclusion of topographical measures.     

基于知觉的恐惧泛化的认知神经机制

恐惧泛化是条件性恐惧反应转移到另一个相似但安全的刺激的现象。适当的恐惧泛化对人类有积极意义, 而过度的恐惧泛化则不利于个体有效地适应环境。基于知觉的恐惧泛化研究揭示了恐惧泛化的规律, 因而被广泛应用。本文首先梳理了对知觉恐惧泛化的相关研究, 介绍恐惧泛化的经典理论基础—巴普洛夫条件反射以及恐惧泛化梯度; 其次简要回顾基于多个感觉通道(即视觉、听觉、情景)的知觉恐惧泛化研究现状; 再次, 分别对海马、杏仁核、脑岛和前额叶等脑区在恐惧泛化中的作用进行回顾, 进一步总结出恐惧泛化的神经环路结构模型。最后, 简要区分了基于知觉的恐惧泛化和正在兴起的基于概念的恐惧泛化, 进而指出未来研究需要结合基于概念的恐惧泛化、区分被试对刺激的辨别力、增加恐惧刺激材料的准确性及多样化、结合激素等个体差异和多模态脑成像数据来展开。     

情绪记忆的神经基础

情绪记忆具有强烈、持久的特点,在记忆中具有优势地位。杏仁核是情绪记忆的关键脑区,其外侧核被认为是情绪回路建立的中心部位。恐惧条件反射是情绪记忆,特别是情绪回路研究的有效手段。情绪记忆的编码,储存与提取受到杏仁核与各相关脑区共同影响,其中激素调节在这些过程中发挥重要作用。文中结合最新的研究成果对情绪记忆的神经机制进行讨论     

即刻消退缺损的原因分析及其神经生物学机制

即刻消退缺损(immediate extinction deficit, IED)是指在条件性恐惧习得后, 立即进行的消退训练不能长期抑制恐惧记忆的现象。IED可能与消退起始时的应激水平和事件分割等因素有关。在高应激水平下, 消退记忆的巩固受损导致IED; 而在中等或较低的应激水平条件下, 即刻消退有效但效果可能容易受事件分割的影响。IED的神经生物学机制涉及应激激活蓝斑去甲肾上腺素能系统, 去甲肾上腺素引起杏仁核基底外侧核(basolateral amygdala, BLA)过度兴奋, 然后BLA通过投射突触抑制在恐惧消退中起核心作用的内侧前额叶神经元的活动。未来研究应注意即刻消退缺损引起的长期后果, 并深入探讨如何优化即刻消退在临床上的应用。     

Evidence of the origin of specific spontaneous head turns during intertrial intervals

Direction and the frequency of spontaneous head movements during the ITIs following forward and backward paired trials were compared to an acquisition of a conditioned orienting (alpha) response directed to the side of the tone source. The head movements were analyzed from video recordings using classification of head turns to preferred and to nonpreferred directions. The results showed a significant increase in the alpha responses during the forward paired conditioning to the preferred direction and rapid extinction during the subsequent backward conditioning sessions. Spontaneous head movements during the ITIs increased to the same preferred direction as the conditioned alpha responses. The results of this experiment suggest that the response initially elicited by the CS can later appear as “spontaneous,” instrumental behavior, the form and the nature of which is determined by the characteristics of the conditioned alpha response developing as a result of classical conditioning.     

The Holte Sleeping Technique: An experimental study

The Holte Sleeping Technique is an alternative to medication to facilitate sleep onset in situations of normal stress. The technique is based on a combination of conditioning within the theory of learning, simulation of natural bodily processes, and manipulation of naturally available sleep-releasing stimuli. The author describes the technique and reports on experimental testing of its efficacy. Fifty-six female subjects were selected according to criteria based on questionnaires and sleep logs. The subjects were randomly assigned to a treatment group, a placebo group, and a no-treatment group. A pre-test-post-test design was used. The author questions the generalizability of findings from modern electronic sleep laboratories to the bedrooms of everyday life. In order to optimize the combination of normal stress, objective criteria and generalizability, sleep onset was measured by behavioural criteria based on the "fog-horn procedure" developed by the author. At post-test 67% of the treatment group fell asleep, while only 17% of the placebo group and 25% of the no-treatment group fell asleep. The differences were significant. It is concluded that the Holte Sleeping Technique is highly effective. In a discussion of placebo trials the author argues that traditional medical trials do not take into consideration the differentiating psychological attribution effects occurring by giving the same experimental instruction under different experimental conditions. As a consequence the active treatment is given better conditions than the placebo in traditional clinical trials.     

Subordinate swordtail males escalate faster than dominants: A failure of the social conditioning principle

In previous studies we have shown that subordinate swordtail males (Xiphophorus helleri) direct more bites to their mirror image than dominants and, in confrontations with strange dominant males, approach the opponent more often during the pre-escalation period of fights. Consequently, we predicted that fights between two omega-males should escalate faster than fights between two alpha-males. Indeed, in omega-omega fights preescalation periods were shorter and biting rates were higher than in alpha-alpha fights before the fights escalated from the first retaliation bite onward. Another new observation was that in omega-alpha confrontations the first bite in the pre-escalation period was executed more often by the omega-male and there was also a tendency to bite more compared to the alpha-male in that stage of the encounters. We conclude that sub-ordinate males escalate faster and fight more offensively prior to escalation than do dominant males. The results cannot be explained by the “social conditioning principle.” On the ultimate level moderate costs of losing and high benefits of winning a fight, constraints on continued growth after maturing, short life-expectancy, and habitat saturation are probably factors promoting the offensive tactics of subordinate males. © 1993 Wiley-Liss, Inc.