Dopamine regulation of human speech and bird song: a critical review

To understand the neural basis of human speech control, extensive research has been done using a variety of methodologies in a range of experimental models. Nevertheless, several critical questions about learned vocal motor control still remain open. One of them is the mechanism(s) by which neurotransmitters, such as dopamine, modulate speech and song production. In this review, we bring together the two fields of investigations of dopamine action on voice control in humans and songbirds, who share similar behavioral and neural mechanisms for speech and song production. While human studies investigating the role of dopamine in speech control are limited to reports in neurological patients, research on dopaminergic modulation of bird song control has recently expanded our views on how this system might be organized. We discuss the parallels between bird song and human speech from the perspective of dopaminergic control as well as outline important differences between these species.     

Deficits in prospective memory following damage to the medial subdivision of the mediodorsal thalamic nucleus

Identifying the neurocognitive mechanisms that lead individuals remembering to execute an intention at the right moment (prospective memory, PM) and how such mechanisms are influenced by the features of that intention is a fundamental theoretical challenge. In particular, the functional contribution of subcortical regions to PM is still unknown. This study was aimed at investigating the role of the medial subdivision of the mediodorsal thalamic nucleus (mMDT) in PM, with particular focus on the processes that are mediated by the projections from/to this structure. We analysed the performance of a patient (OG) with a right-sided lesion involving the mMDT in a series of PM tasks that varied for focality (i.e., overlapping of processes for the PM and ongoing tasks) and emotional valence of the stimuli, comparing the patient's performance with that of a control group. We found that the mMDT damage led to deficits in PM that were modulated by focality and emotional valence. OG indeed showed: a greater cost in the ongoing performance when a non-focal PM task was added; a slowing down in retrieving the intentions, in particular when these were associated with focal PM cues; an abnormal performance in the task with positive PM cues. Our findings provide evidence of a contribution of mMDT to PM and suggest a modulation of prefrontal-dependent strategic monitoring and a possible interaction with the limbic structures in the integration of emotion and PM processes. They also give support to the still controversial idea that connections with the perirhinal cortex mediate familiarity-based recognition.     

前瞻记忆的神经机制：来自临床研究的证据

前瞻记忆是指对预定事件或行为的记忆。本文总结了前瞻记忆脑机制相关的文献,介绍了前额皮层、丘脑,内侧颞叶等脑区域在前瞻记忆中的作用,并通过分析注意缺陷多动障碍儿童、老年痴呆症患者、酒精依赖症和内侧颞叶癫痫患者前瞻记忆的表现,从临床角度深入探讨了前瞻记忆神经机制的问题。证据表明,前额皮层参与前瞻记忆的编码、提取和监控过程,与意向保持也有密切的关系;丘脑与意向的执行有关,并且与前额叶互动在前瞻记忆监控中起着重要的作用;内侧颞叶与编码来源的提取和意向的激活都有密切的关系。研究认为前额皮层在前瞻记忆加工过程中起着核心的作用,同时与丘脑、内侧颞叶等区域相互作用,共同成为前瞻记忆编码、保持、提取、执行的神经基础。     

Lesions in the Central Nucleus of the Amygdala: Discriminative Avoidance Learning, Discriminative Approach Learning, and Cingulothalamic Training-Induced Neuronal Activity

The amygdala is critically involved in discriminative avoidance learning. Large lesions of the amygdala block discriminative avoidance learning and abolish cingulothalamic training-induced neuronal activity. These results indicated that amygdalar processing is critical for cingulothalamic plasticity. The larger lesions did not allow differentiation of the specific functioning of various amygdalar nuclei. Anatomical analysis showed that damage in the central (CE) nucleus of the amygdala was correlated with the severity of the behavioral deficit. The present study was carried out to determine whether smaller lesions, centered in the CE nucleus, would impair discriminative avoidance learning and block cingulothalamic plasticity. In addition, the possible role of the CE nucleus in appetitively motivated discriminative approach learning was examined for the first time. New Zealand White rabbits with CE nuclear lesions were first trained in the discriminative approach task. After attaining asymptotic performance, discriminative avoidance training sessions were alternated with continuing approach training sessions, one session each day. The rabbits with lesions were severely impaired in avoidance learning but showed no impairment of approach learning. Surprisingly, the attenuating effects of the lesions on cingulothalamic training-induced neuronal activity were more prevalent during approach learning than during avoidance learning. These results indicated that avoidance learning can be impaired by lesions centered in the CE nucleus that leave cingulothalamic plasticity largely intact and that the CE nucleus is involved in extra-cingulothalamic learning processes.     

触觉刺激对触觉注意启动作用的研究

目的：探讨触觉刺激对触觉注意的影响,以揭示选择性注意的机制。方法：利用在体电生理记录技术,记录了288个丘脑腹侧基底核（ventrobasal nuleus of thalamus,VB）神经元放电活动,并着重考察了不同强度触觉刺激对丘脑神经元细胞自发放电活动的影响。结果发现：触觉刺激对大部分的触觉神经元的自发放电活动均有抑制性影响。提示触觉刺激降低背景噪声可能是触发选择性触觉注意的神经机制。     

基底神经节损伤对知觉性启动效应影响的进一步研究

基底神经节的认知和记忆功能是近年认知神经科学研究的热点。该研究采用两项语义性启动效应（自由联想、偏好）和一项知觉性启动效应（字辨认）任务,发现基底神经节损伤、分别伴两侧海马或右侧丘脑损伤的两例患者的语义性启动效应正常,知觉性启动效应障碍。由于先前研究已经证实海马或丘脑结构与启动效应无关,因此该两例患者表现的知觉性启动效应障碍可归因于基底神经节损伤,进一步证实了王常生等人认为基底神经节可能具有或参与知觉性启动效应调节作用,与语义性启动效应无关的观点。