Olfaction as a model system for the neurobiology of mammalian short-term habituation

Olfaction represents an ideal model system for the study of mammalian habituation given that it is an anatomically relatively simple system with strong reciprocal connections to the limbic system, driving both reflexive and non-reflexive (motivated) behaviors that are easily quantifiable. Data are reviewed here demonstrating short-term habituation of the odor-evoked heart-rate orienting reflex described according to the criteria for habituation outlined by Thompson and Spencer [Thompson, R. F., & Spencer, W. A. (1966). Habituation: A model phenomenon for the study of neuronal substrates of behavior. Psychological Reviews, 73(1), 16–43]. A necessary and sufficient mechanism of short-term habituation is then described, which involves a metabotropic glutamate receptor mediated depression of afferent input to the piriform (primary olfactory) cortex. Finally, evidence for, and a mechanisms of, dishabituation of the orienting reflex and cortical adaptation are described.     

错误加工的神经机制

错误加工在认知控制和行为监控中起着关键的作用。监控自己的认知和行为结果,觉察到应该的反应和实际的反应之间的差别（即错误）,纠正这种错误并防止再犯是错误加工的主要内容。错误反应或由代表反应错误等负性反馈刺激诱发的ERP相对于正确反应或由代表反应正确等正性反馈刺激诱发的ERP,表现出一个相对负走向的波形变化,称为错误相关负波（error-related negativity, ERN）和反馈相关负波（feedback-related negativity, FRN）,两者都定位于前扣回附近。错误加工神经机制的研究主要集中于前扣回与ERN、错误意识与错误加工、ERN与FRN的关系。对于前扣带回和ERN的功能意义的解释主要有错误检测理论、冲突监控理论、强化学习理论和预期违反假说。目前错误加工神经机制的研究在研究内容、研究方法和理论观点等方面还存在些问题,这些可能是未来进一步的研究方向     

Top-down predictions in the cognitive brain

The human brain is not a passive organ simply waiting to be activated by external stimuli. Instead, we propose that the brain continuously employs memory of past experiences to interpret sensory information and predict the immediately relevant future. The basic elements of this proposal include analogical mapping, associative representations and the generation of predictions. This review concentrates on visual recognition as the model system for developing and testing ideas about the role and mechanisms of top-down predictions in the brain. We cover relevant behavioral, computational and neural aspects, explore links to emotion and action preparation, and consider clinical implications for schizophrenia and dyslexia. We then discuss the extension of the general principles of this proposal to other cognitive domains.     

The role of visual experience on the representation and updating of novel haptic scenes

We investigated the role of visual experience on the spatial representation and updating of haptic scenes by comparing recognition performance across sighted, congenitally and late blind participants. We first established that spatial updating occurs in sighted individuals to haptic scenes of novel objects. All participants were required to recognise a previously learned haptic scene of novel objects presented across the same or different orientation as learning whilst they either remained in the same position to moved to a new position relative to the scene. Scene rotation incurred a cost in recognition performance in all groups. However, overall haptic scene recognition performance was worse in the congenitally blind group. Moreover, unlike the late blind or sighted groups, the congenitally blind group were unable to compensate for the cost in scene rotation with observer motion. Our results suggest that vision plays an important role in representing and updating spatial information encoded through touch and have important implications for the role of vision in the development of neuronal areas involved in spatial cognition.     

急性生理应激对大鼠的行为及脑神经颗粒素磷酸化水平的影响

突触特异性蛋白质在应激所致行为效应的中枢机制中的可能角色日益受到关注。神经颗粒素（Neurogranin,NG）是一种新发现的突触特异性蛋白质,主要分布在前额叶、杏仁核和海马区域,参与突触结构和功能可塑性机制,可能涉及到应激所致行为效应中枢机制。但是,关于NG、应激和行为之间的关系国内外尚缺乏系统的研究报道。本研究主要是探讨急性生理应激对大鼠行为和NG的作用,以及NG的变化与应激性行为效应之间的相互关系。以急性强迫性冷水游泳应激,建立生理应激动物模型。将40只雄性SD大鼠随机分为游泳应激组1（SS1,接受游泳应激和行为测试）、游泳应激组2（SS2,接受游泳应激而不接受行为测试）、正常对照组1（C1,接受行为测试）和正常对照组（C2,不给予任何处理）（n=10）。以旷场行为和高架十字迷宫任务来评定大鼠应激后的行为变化,Western blotting方法测定海马和前脑皮层中的NG含量和磷酸化水平。结果表明：应激后SS1组的呆滞行为增加,与C1组比较,差异有显著性, P<0.01; SS1组海马的NG含量和NG磷酸化水平增高,与C1和C2组相比,差异有显著性,均为P<0.05; SS1组皮层的NG含量增高,与C1和C2组相比,差异有显著性,均为P<0.01;SS1组皮层的NG磷酸化水平增高,与C1组相比,差异具有显著性,P<0.01;前脑皮层的NG磷酸化水平与呆滞行为之间的相关达显著水平。提示该应激源能诱发动物明显的恐惧反应,呆滞行为是反映急性生理应激导致行为障碍的敏感的行为学指标,海马和前脑皮层均是对急性生理应激反应敏感的脑区。NG的磷酸化水平可能是反映急性生理应激所致行为障碍的一项新的生物学指标     

Mental time travel,somatic markers and “myopia for the future”

Patients with damage to the ventromedial prefrontal cortex (VMPFC) are often described as having impaired ability for planning and decision making despite retaining intact capacities for explicit reasoning. The somatic marker hypothesis is that the VMPFC associates implicitly represented affective information with explicit representations of actions or outcomes. Consequently, when the VMPFC is damaged explicit reasoning is no longer scaffolded by affective information, leading to characteristic deficits. These deficits are exemplified in performance on the Iowa Gambling Task (IGT) in which subjects with VMPFC perform significantly worse than neurotypicals in a task which requires them learn from rewarding and punishing experience to make decisions. The somatic marker theory adopts a canonical theory of emotion, in which emotions function as part of a valencing system, to explain the role of affective processes. The first part of the paper argues against this canonical account. The second part provides a different account of the role of the role of the VMPFC in decision-making which does not depend on the canonical account of emotion. Together the first and second parts of the paper provide the basis for a different interpretation of results on the Iowa Gambling Task (IGT). In fact the IGT may be probing a deficit in what has been called mental time travel: the ability to access and use information from previous experience and imaginatively rehearse future experiences as part of the process of deliberation.     

Muscarinic cholinergic receptor blockade in the rat prelimbic cortex impairs the social transmission of food preference

Previous findings demonstrate the involvement of the cholinergic NBM in the acquisition of the social transmission of food preference (STFP), a relational associative odor-guided learning task. There is also evidence that muscarinic receptors in the medial prefrontal cortex, an important NBM target area, may modulate olfactory associative memory. The present experiment determined the consequences of blocking muscarinic cholinergic receptors in a component of the medial prefrontal region (the prelimbic cortex) on the STFP task. Adult male Wistar rats were bilaterally infused with scopolamine (20 microg/site) prior to training and showed a severe impairment in the expression of the task measured in two retention sessions, both immediately and 24h after training. Local scopolamine injections in the prelimbic cortex did not affect other behavioral measures such as olfactory perception, social interaction, motivation to eat, neophobia, or exploration. Results suggest that muscarinic transmission in the prelimbic cortex is essential for the STFP, supporting the hypothesis that ACh in a specific prefrontal area is important for this naturalistic form of olfactory relational memory. Current data are discussed in the context of disruption of learning as a result of interferences in PLC functions such as behavioral flexibility, attention, and strategic planning.     

Utilization Behavior: Clinical Manifestations and Neurological Mechanisms

This paper describes a variety of motor release phenomena, including manual grasping and groping, imitation behavior, utilization behavior, and alien hand sign, their clinical manifestations, and proposed neural mechanisms. One of these specific neurobehavioral disorders, initially described by Lhermitte (Brain [1983] 106: 237–255), and termed utilization behavior, is addressed in more detail. Patients with this disorder are described as reaching out and using objects in the environment in an automatic manner. The current paper provides a comprehensive review of studies that have documented utilization behavior in individuals with a variety of pathologies, all having a specific predilection for the frontal lobes and frontal-striatal systems. Goldberg's (Behavioral and Brain Sciences [1985] 8: 567–616) theoretical framework for understanding motor release phenomena, which conceptualizes these behaviors as resulting from an imbalance between proposed medial (voluntary, goal directed, and future directed) and lateral (automatic, stimulus bound, and visually based) motor systems, is also discussed. Utilization behavior may prove to be a common underlying cause of high levels of excessive and intrusive motor behaviors within various clinical populations. A more comprehensive understanding of the neural systems underlying utilization behavior may prove highly useful for the differential diagnosis of conditions involving the mesial frontal cortex and fronto-striatal connections. Recent studies have started to investigate utilization behavior in clinical populations with known or suspected frontal system dysfunction, including adult patients with a variety of psychiatric conditions and children with ADHD.     

海洛因依赖者抑制控制功能的损伤机制及其可逆性

抑制控制障碍是海洛因依赖者认知功能受损的核心问题, 是影响复吸的关键因素。大量研究证实了海洛因依赖者抑制控制功能的受损, 并且发现长期药物滥用者额叶、前扣带回皮层、中脑腹侧被盖区、伏隔核、脑岛等相关脑区活动存在异常。以往研究表明海洛因依赖者抑制控制功能受损是一种持久性的、不可逆的脑损伤, 但最近一些研究却提供了毒品戒断者抑制控制功能生物性恢复的证据。未来的研究应该更加关注多重冲突条件下海洛因依赖者抑制控制功能的研究, 并且在戒毒实践中根据海洛因戒断者自身特点进行区分性治疗。     

社会等级加工的神经基础

社会等级是社会组织的基本原则。社会地位高低的再认与面孔再认及视觉注意均表现出N200的激活, 并不同程度地共享了情感、奖赏回报、数字等级及共情特质等加工的脑区网络, 涉及额区、杏仁核、纹状体、顶内沟和前扣带回皮质等。社会等级加工与5-羟色胺递质多态性等神经递质及内分泌系统具有复杂的交互作用。未来应立足于综合研究和系统分析的视角探讨社会等级加工与神经生物学基础的作用机制并致力于服务人类生活。