Delay of gratification is associated with white matter connectivity in the dorsal prefrontal cortex: a diffusion tensor imaging study in chimpanzees (Pan troglodytes)

Individual variability in delay of gratification (DG) is associated with a number of important outcomes in both non-human and human primates. Using diffusion tensor imaging (DTI), this study describes the relationship between probabilistic estimates of white matter tracts projecting from the caudate to the prefrontal cortex (PFC) and DG abilities in a sample of 49 captive chimpanzees (Pan troglodytes). After accounting for time between collection of DTI scans and DG measurement, age and sex, higher white matter connectivity between the caudate and right dorsal PFC was found to be significantly associated with the acquisition (i.e. training phase) but not the maintenance of DG abilities. No other associations were found to be significant. The integrity of white matter connectivity between regions of the striatum and the PFC appear to be associated with inhibitory control in chimpanzees, with perturbations on this circuit potentially leading to a variety of maladaptive outcomes. Additionally, results have potential translational implications for understanding the pathophysiology of a number of psychiatric and clinical outcomes in humans.     

猕猴F2及F4区皮层神经元在空间有序运动中的放电活动

用胞外单位放电记录的方法,研究了猕猴在执行记忆引导的空间有序运动（ＭＳＳ）时,大脑皮层弓形沟距背侧Ｆ２及腹侧Ｆ４区的放电活动。对于以绿色为暗示信号的ＭＳＳ－Ｇ任务,在暗示期,Ｆ２（７８．２％）比Ｆ４区（４１．５％）有更多的细胞发生放电变化（χ＾２＝１５．２,Ｐ＜０．００５）;在图形期,Ｆ４（６７．９％）比Ｆ２区（４５．４％）有更多的细胞发生放电变化（χ＾２＝５．５,Ｐ＜０．０５）;在触摸反应期,Ｆ     

Set-Related Activity in the Premotor Cortex of Rhesus Monkeys: Effect of Triggering Cues and Relatively Long Delay Intervals

“Set-related activity” has been defined as a significant alteration in neuronal discharge rate during an “instructed delay period,” a period when a previously instructed movement is being withheld. It has been argued that set-related activity in the primate premotor cortex, or at least a significant proportion of it, reflects motor preparation. In most previous investigations, however, in which visual stimuli have triggered the movement and simultaneously indicated its target, set-related activity might reflect either the anticipation of or attention to the trigger stimulus. The present report shows that set-related activity is robust and can be directionally selective when trigger stimuli do not indicate the target and when a trigger stimulus is absent. Another feature of previous studies has been the relatively brief intervals between the instruction and trigger stimuli (typically 3 sec or less). In the present study, we were able to observe the activity of a small number of cells during longer delay periods. Set-related activity persists, although it becomes less consistent, for as much as 7.5 sec after an instruction stimulus. These results support the hypothesis that set-related activity reflects the preparation for specific limb movements.     

Diffusion tensor imaging of dolphin brains reveals direct auditory pathway to temporal lobe

The brains of odontocetes (toothed whales) look grossly different from their terrestrial relatives. Because of their adaptation to the aquatic environment and their reliance on echolocation, the odontocetes'' auditory system is both unique and crucial to their survival. Yet, scant data exist about the functional organization of the cetacean auditory system. A predominant hypothesis is that the primary auditory cortex lies in the suprasylvian gyrus along the vertex of the hemispheres, with this position induced by expansion of ‘associative′ regions in lateral and caudal directions. However, the precise location of the auditory cortex and its connections are still unknown. Here, we used a novel diffusion tensor imaging (DTI) sequence in archival post-mortem brains of a common dolphin (Delphinus delphis) and a pantropical dolphin (Stenella attenuata) to map their sensory and motor systems. Using thalamic parcellation based on traditionally defined regions for the primary visual (V1) and auditory cortex (A1), we found distinct regions of the thalamus connected to V1 and A1. But in addition to suprasylvian-A1, we report here, for the first time, the auditory cortex also exists in the temporal lobe, in a region near cetacean-A2 and possibly analogous to the primary auditory cortex in related terrestrial mammals (Artiodactyla). Using probabilistic tract tracing, we found a direct pathway from the inferior colliculus to the medial geniculate nucleus to the temporal lobe near the sylvian fissure. Our results demonstrate the feasibility of post-mortem DTI in archival specimens to answer basic questions in comparative neurobiology in a way that has not previously been possible and shows a link between the cetacean auditory system and those of terrestrial mammals. Given that fresh cetacean specimens are relatively rare, the ability to measure connectivity in archival specimens opens up a plethora of possibilities for investigating neuroanatomy in cetaceans and other species.     

Areal Distributions of Cortical Neurons Projecting to Different Levels of the Caudal Brain Stem and Spinal Cord in Rats

Distributions of corticospinal and corticobulbar neurons were revealed by tetramethylbenzidine (TMB) processing after injections of wheatgerm agglutinin conjugated to horseradish peroxidase (WGA:HRP) into the cervical or lumbar enlargements of the spinal cord, or medullary or pontine levels of the brain stem. Sections reacted for cytochrome oxidase (CO) allowed patterns of labeled neurons to be related to the details of the body surface map in the first somatosensory cortical area (SI). The results indicate that a number of cortical areas project to these subcortical levels: (1) Projection neurons in granular SI formed a clear somatotopic pattern. The hindpaw region projected to the lumbar enlargement, the forepaw region to the cervical enlargement, the whisker pad field to the lower medulla, and the more rostral face region to more rostral brain stem levels. (2) Each zone of labeled neurons in SI extended into adjacent dysgranular somatosensory cortex, forming a second somatotopic pattern of projection neurons. (3) A somatotopic pattern of projection neurons in primary motor cortex (MI) paralleled SI in mediolateral sequence corresponding to the hindlimb, forelimb, and face. (4) A weak somatotopic pattern of projection neurons was suggested in medial agranular cortex (Ag_m), indicating a premotor field with a rostromedial-to-caudolateral representation of hindlimb, forelimb, and face. (5) A somatotopic pattern of projection neurons representing the foot to face in a mediolateral sequence was observed in medial parietal cortex (PM) located between SI and area 17. (6) In the second somatosensory cortical area (SII), neurons projecting to the brain stem were immediately adjacent caudolaterally to the barrel field of SI, whereas neurons projecting to the upper spinal cord were more lateral. No projection neurons in this region were labeled by the injections in the lower spinal cord. (7) Other foci of projection neurons for the face and forelimb were located rostral to SII, providing evidence for a parietal ventral area (PV) in perirhinal cortex (PR) lateral to SI, and in cortex between SII and PM. None of these regions, which may be higher-order somatosensory areas, contained labeled neurons after injections in the lower spinal cord. Thus, more cortical fields directly influence brain stem and spinal cord levels related to sensory and motor functions of the face and forepaw than the hindlimb.

The termination patterns of corticospinal and corticobulbar projections were studied in other rats with injections of WGA:HRP in SI. Injections in lateral SI representing the face produced dense terminal label in the contralateral trigeminal complex. Injections in cortex devoted to the forelimb and forepaw labeled the contralateral cuneate nucleus and parts of the dorsal horn of the spinal cord. The cortical injections also demonstrated interconnections of parts of SI with some of the other regions of cortex with projections to the spinal cord, and provided further evidence for the existence of PV in rats.     

Neuronal Activity Preceding Directional and Nondirectional Cues in the Premotor Cortex of Rhesus Monkeys

Pre-cue activity, the neuronal modulation that precedes a predictable stimulus, was studied in the premotor cortex of three rhesus monkeys. In one condition, a directional cue dictated the timing and target of a forelimb movement. In another condition, a non-directional cue provided identical timing information but did not indicate the target. Of 501 task-related neurons recorded in premotor cortex, 168 showed pre-cue activity. The onset time of pre-cue activity varied markedly from trial to trial and cell to cell, ranging from trial initiation to 4.8 sec later. No pre-cue activity reflected the direction of limb movement; thus, the data argue against the hypothesis that pre-cue activity reflects preparation for specific limb movements. A small number of cells showed greater pre-cue activity before directional than before nondirectional cues, and this difference may reflect anticipation of the cue's directional information. However, the vast majority (84%) of neurons lacked such differences. We therefore hypothesize that most pre-cue activity reflects or contributes to a facet of behavior common to the two conditions: anticipation of the time and/or nature of events.     

脑网络：从脑结构到脑功能

人脑是自然界中最复杂的系统之一,不同的功能区域相互作用、互相协调,共同构成一个网络来发挥其功能。人脑是一个复杂的网络,具有高效的“小世界”拓扑属性。本文从脑结构到脑功能方面介绍了从不同模态影像学数据构造脑网络的主要进展,并探讨不同的脑疾病患者脑网络拓扑结构是否发生了异常,以及这些异常特征能否用来进行疾病分类,最后对本领域未来的研究做了简单的展望。     

条件性运动学习的神经基础

人和动物形成多样的、快速可变的刺激－反应联合关系的过程被称为条件性运动学习。条件性运动学习使得人和动物具有很强的适应优势。损毁或行为电生理研究表明：运动前区背外侧部、基底神经节以及前额叶皮层腹侧部在条件性运动学习中起至关重要的作用;海马在条件性运动学习中也起着一定的作用;而杏仁核等一些结构在条件性运动学习中不起作用。     

通过运动纤维束形态变化预测高风险脑胶质瘤术后运动功能

目的 运动功能区胶质瘤会破坏皮质脊髓束（CST）,导致运动功能障碍。如何评估CST的破坏程度目前还缺少统一的方法,尤其是对病灶至CST最小距离（LTD）小于10 mm的高手术风险患者。本文拟进一步阐明此类患者CST形态改变的分类方法和意义。方法 本研究回顾性分析了2014～2024年间109例高风险功能区胶质瘤患者。所有患者均在术前开展弥散张量成像（DTI）并接受术中电刺激指导的神经外科手术治疗。所有患者CST与病灶的LTD均小于10 mm。根据术前的DTI评估CST受累导致的形态学变化。将患者分为3组：CST与健侧形态对称（对称组） 17例（15.6%）,CST形态较健侧明显改变（形变组） 48例（44.0%）,CST与肿瘤重叠（重叠组） 44例（40.4%）。根据术前的评估受累导致的形态学变化进行分类,并对每种分类对应的患者的术后运动功能进行分析。结果 术后病理显示CST重叠组中高级别胶质瘤（HGG）的比例明显高于另外两组（P=0.001）。Logistics回归分析显示CST重叠是HGG的预测因素（P<0.001）。CST形变组和重叠组肿瘤的全切除率较CST对称组更低（P=0.008）。术后偏瘫者共41例,其中CST对称组偏瘫4例（23.5%）,CST形变组偏瘫者11例（22.9%）,CST重叠组偏瘫者26例（59.1%）。CST与肿瘤重叠可预测术后偏瘫（P=0.016）。对患/健侧和CST形态学分组进行双因素ANOVA分析,发现CST分组和健-患侧的主效应显著（P=0.017和P=0.010）,交互作用不显著（P=0.31）。CST重叠组各向异性分数（FA）值和患侧的FA值更低。患侧FA值的下降可预测术后偏瘫（灵敏性为69.2%,特异性为71.9%）。结论 本文建立了一套根据术前CST的形态改变预测高危型的运动功能区胶质瘤患者术后偏瘫的方法。CST的重叠会导致通过CST FA值的下降。此方法可用于患者的精准管理,有助于精确开展术前手术规划。     

Prediction of motor outcome using remaining corticospinal tract in patients with pontine infarct: Diffusion tensor imaging study

The aim of this study was to investigate the relationship between the remaining corticospinal tract (CST) as determined by diffusion tensor imaging (DTI) and 6-month motor outcome in patients with pontine infarct. Ratios of fractional anisotropy (FA), fiber number (FN), and CST area were calculated, and the FN ratio and CST area ratio showed significant correlation with all 6-month motor outcome. Thus, the remaining CST in the pons measured using DTI at early stage of stroke could predict motor outcome in patients with pontine infarct.     

儿童失神癫痫的默认模式网络的结构连接研究

大脑结构连接是其功能连接的物质基础．已有研究表明,失神癫痫患者默认模式网络(default mode network,DMN)中的功能连接发生了改变．为了探索这些改变相应的结构基础,对11名儿童失神癫痫患者和12名正常对照,使用基于弥散张量成像(diffusion tensor imaging,DTI)的纤维束追踪技术,构建了每个被试DMN脑区间的纤维束连接．结果表明,在所有被试的DMN网络中一致发现后扣带/楔前叶到内侧前额叶、后扣带/楔前叶到左右双侧的内侧颞叶都存在纤维束连接．通过两组间统计比较这些纤维束连接的平均长度、连接强度、平均部分各向异性(fractional anisotropic,FA)值和平均弥散度(mean diffusivity,MD)值等参数,发现患者组的后扣带/楔前叶到内侧前额叶纤维束连接上的平均FA值及连接强度都显著降低,而平均MD值显著增加,并且其FA值与癫痫病程呈显著的负相关关系,这些改变可能影响了患者DMN网络的功能连接．本研究结果为DMN功能连接异常提供了相关的结构上的依据,提示后扣带/楔前叶到内侧前额叶的连接异常可能在儿童失神癫痫中起着非常重要的作用．     

On the Status of Lysolecithin in Rat Cerebral Cortex During Ischemia

Abstract: Lysolecithin (lysoglycerophosphocholine, LPC) was isolated from rat cerebral cortex and quantitatively analyzed at various times after postdecapitative ischemic treatment. In addition, different procedures for extraction and analysis of the LPC in brain were evaluated. Results indicated that LPC can be quantitatively extracted into the organic phase using the conventional extraction procedure with chloroform-methanol (2:1, vol/ vol). However, care should be taken to avoid using strong acids, which can hydrolyze the alkenylether side chain of the plasmalogens, resulting in the release of 2-acyl-phospholipids. Quantitative GLC analysis using myris-toyl-LPC as internal standard revealed a level of 1.8 nmol LPC/mg protein in brain with acyl groups comprised mainly of 16:0, 18:0, and 18:1. The acyl group profile reflects that the LPC are derived mainly from phospho-lipase A₂ action. An increase of 46% in the LPC level was observed at 1 min after ischemic treatment, but this was followed by a steady decline. Ischemia induced an increase in the LPC species that are enriched in 18:0 and 18:1 fatty acids. The transient appearance of LPC during ischemia further suggests that this phospholipid is undergoing active turnover, possibly hydrolysis by the lysophospholipase. This mechanism of action may account, at least in part, for the increase in both saturated and unsaturated fatty acids during the early phase of the ischemic treatment.     

Diffusion Imaging in the Rat Cervical Spinal Cord

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.