The awareness of thirst: proposed neural correlates

The neural and endocrine bases of the generation of thirst are reviewed. Based on this review, a hierarchical system of neural structures that regulate water conservation and acquisition is proposed. The system includes primary sensory-receptive areas; secondary sensory structures (circumventricular organs), which detect levels of hormones, including angiotensin II and vasopressin, which are involved in generating thirst; preoptic and hypothalamic structures; and an area within the ventrolateral quadrant of the periaqueductal gray matter. Hodological and other data are used to determine the hierarchical organization of the system. Based on studies of the effects of lesions to various structures within the hierarchy of the system, it is proposed that the awareness of thirst in rodents is either entirely or predominantly due to neuronal activities in a subsection of the ventrolateral periaqueductal gray matter. It is also hypothesized that the awareness of thirst in primates is due to neuronal activities in both the ventrolateral periaqueductal gray and in a region within the medial prefrontal and anterior cingulate cortex.     

Regional grey matter volume in the posterior cingulate cortex predicts positive risk-taking: A moderation model

Positive risk-taking is a crucial element of individual creativity and social development. However, little is known regarding the relation between individual neural differences and positive risk-taking. In addition, critical thinking (CT) and gender have been proven to be two important individual-specific factors associated with risk-taking behaviour, and different levels of CT and gender may have diverse effects on the relationship between brain structure and positive risk-taking. The present study examined the relationship between positive risk-taking and regional grey matter volume (rGMV) in 292 healthy participants. The results showed that positive risk-taking was significantly positively associated with the rGMV of the posterior cingulate cortex (PCC). In addition, this study investigated individual differences in critical thinking and found that it moderated the relationship between rGMV and positive risk-taking. Individuals with lower CT had a stronger association between rGMV and positive risk-taking. Further analysis showed that for males, a greater rGMV was significantly linked to higher positive risk-taking tendency. These findings suggest that PCC evaluates risk and serves as a behavioural adaptation hub for positive risk-taking. This study thereby contributes to the literature on individual differences in brain structure and risk-taking by elucidating the moderating effects of CT and gender in healthy adults.     

镜像等效或守恒及其打破：从行为到认知神经机制的研究证据

镜像等效或守恒是动物与人类个体对两侧对称自然物体的一种进化自适应加工。但是, 这种知觉特性会妨碍包含镜像字符的文字阅读学习。阅读者有必要学会利用镜像泛化抑制的“去学习”机制, 打破镜像等效或守恒, 以获得识别镜像字符的能力。这一过程中, 左侧梭状回皮层通过与早期视觉皮层、顶叶皮层和口语脑网络的交互作用, 逐渐发展出一个可以识别镜像字符的视觉词形区(visual word form area, VWFA)。今后的研究需要关注两半球及其连合纤维在镜像等效或守恒加工中的作用、镜像泛化与抑制的详尽加工机制及其对镜像书写的影响、正常汉语儿童的汉字镜像泛化加工等问题。     

Interference and conflict monitoring in individuals with amnestic mild cognitive impairment: A structural study of the anterior cingulate cortex

Amnestic mild cognitive impairment (aMCI) is a clinical condition characterized by memory impairment in the absence of any other cognitive impairment and is commonly associated with high conversion to Alzheimer's disease. Recent evidence shows that executive functions and selective attention mechanisms could also be impaired in aMCI. In this study, we investigated performance differences (i.e., reaction times [RTs] and accuracy) between a group of aMCI participants and a group of age‐matched healthy individuals on the attentional network task (ANT) focusing on situations with increased interference. In particular, we assessed the relationship between interference and conflict effects and grey matter volumes (GMVs) of the anterior cingulate cortex (ACC)/pre‐supplementary motor area in the entire sample because of its crucial role in conflict monitoring. When compared with controls, aMCI participants were less accurate on the ANT, showing increased interference and conflict effects, but no differences in RTs. In addition, aMCI participants exhibited lower GMV in the ACC than controls. While better accuracy for interference and conflict effects was associated with an increase of GMV in the ACC for both groups, RTs from the interference effect were negatively correlated with GMV of the ACC only in aMCI participants. In other words, lower GMV values of the ACC were paralleled with significantly impaired performance in terms of interference resolution. In conclusion, our study suggests the presence of a selective impairment in interference and conflict monitoring in aMCI, which in turn is associated with decreased GMVs in the ACC.     

传递性推理的ERP研究

以抽象的内容作为实验材料,测定15名大学生在完成三种不同类型的传递性推理任务和基线任务(记忆判断任务)时的事件相关电位(ERP),探讨传递性推理过程的脑内时程动态变化。研究发现,三种推理任务所诱发的波形基本一致,而推理任务与基线任务之间的ERP波形存在明显的差异。这说明对于传递性推理,被试可能是根据视觉的空间表征对信息进行加工的,结果进一步支持了心理模型理论。     

TMS to the “occipital face area” affects recognition but not categorization of faces

The human cortical system for face perception is comprised of a network of connected regions including the middle fusiform gyrus (“fusiform face area” or FFA), the inferior occipital cortex (“occipital face area” or OFA), and the superior temporal sulcus. The traditional hierarchical feedforward model of visual processing suggests information flows from early visual cortex to the OFA for initial face feature analysis to higher order regions including the FFA for identity recognition. However, patient data suggest an alternative model. Patients with acquired prosopagnosia, an inability to visually recognize faces, have been documented with lesions to the OFA but who nevertheless show face-selective activation in the FFA. Moreover, their ability to categorize faces remains intact. This suggests that the FFA is not solely responsible for face recognition and the network is not strictly hierarchical, but may be organized in a reverse hierarchical fashion. We used transcranial magnetic stimulation (TMS) to temporarily disrupt processing in the OFA in neurologically-intact individuals and found participants’ ability to categorize intact versus scrambled faces was unaffected, however face identity discrimination was significantly impaired. This suggests that face categorization but not recognition can occur without the “earlier” OFA being online and indicates that “lower level” face category processing may be assumed by other intact face network regions such as the FFA. These results are consistent with the patient data and support a non-hierarchical, global-to-local model with re-entrant connections between the OFA and other face processing areas.     

Role of medial prefrontal cortex in representing one’s own subjective emotional responses: A preliminary study

The medial prefrontal cortex (mPFC) has been implicated in attending to one’s own emotional states, but the role of emotional valence in this context is not understood. We examined valence-specific BOLD activity in a previously validated functional magnetic resonance imaging (fMRI) paradigm. Ten healthy subjects viewed emotional pictures and categorized their experience as pleasant, unpleasant or neutral. All three categories activated a common region within mPFC. Subtraction of neutral from pleasant or unpleasant conditions instead revealed ventromedial PFC (vmPFC), suggesting that this region represents emotional valence. During exteroceptive attention, greater mPFC responses were observed in response to emotional relative to neutral stimuli, consistent with studies implicating mPFC in the top-down modulation of emotion-biased attention. These findings may help to integrate the two proposed roles of mPFC in emotional representation and top-down modulation of subcortical structures.     

数字加工与空间关系的研究进展

数学的产生和发展使数字和空间之问产生了紧密的联系,目前的实验已经表明了数字的大小与空间注意存在自动的联系。数字和空间的自动联系是由生物和文化因素共同作用的结果。通过总结数字和空间的脑成像研究,本文认为角回、顶内沟区域可能在数字和空间相互作用中发挥了重要的作用。     

Hippocampus-dependent strategy choice predicts low levels of cell proliferation in the dentate gyrus

Neurogenesis continues to occur throughout life in the mammalian hippocampus. Previous research has suggested that the production of new neurons in the hippocampus during adulthood may be related to hippocampus-dependent learning and memory. However, the exact relationship between adult neurogenesis and learning and memory remains unclear. Here we investigated whether learning strategy selection is related to cell proliferation or to survival of new neurons in the hippocampus of adult male rats. We trained rats on alternating blocks of hippocampus-dependent (hidden platform) and hippocampus-independent (visible platform) versions of the Morris water task with the platform always in the same position. Following training, rats were given a probe session during which the platform was visible and in a novel location. Preferred strategy was determined by observing the initial swim path. Rats were classified as place strategy (hippocampus-dependent) users if they swam to the old platform location. Cue strategy (hippocampus-independent) users were classified as those rats that swam initially to the visible platform. Our results indicate that rats that preferentially used a place strategy had significantly lower cell proliferation than cue strategy users. However, there was no significant difference in cell survival or number of immature neurons between strategy user groups. These results suggest that low levels of cell proliferation in the dentate gyrus may be conducive or coincident with more efficient memory processing in the hippocampus.     

科学发明问题解决的脑机制再探

选取高生态学效度的科学发明问题作为实验材料, 采用“学习−测试”的两阶段实验范式, 利用静息态功能磁共振成像技术, 基于局部一致性(ReHo)和低频振幅(ALFF)的分析方法, 研究科学发明问题解决的神经机制。在控制被试性别、年龄和常规性问题解决能力后, 结果发现左侧前扣带回(Anterior Cingulate Cortex, ACC)的ReHo值和个体科学发明问题解决的正确率显著正相关, ALFF的结果同样印证了这一发现。结果强调了ACC在科学发明问题解决过程中的重要作用。