Neuronal correlates of the integrative activity in the monkey striatum

The unit activity was studied in monkeys during various behavioural activities. The striatum unit responses revealed no functional specifics. Separate units reflected the character of activity in their firing rate as well as in different interrelationships between excitatory and inhibitory responses. The putamen units were shown to discriminate experimental alternatives mainly when the money arrived at a decision, and successful solving of the problem was shown to depend on the level of the discrimination. Specific corticofugal signals from different and dispersed cortical areas seem to converge while interacting at the striatum.     

Neuronal correlates of metacognition in primate frontal cortex

Humans are metacognitive: they monitor and control their cognition. Our hypothesis was that neuronal correlates of metacognition reside in the same brain areas responsible for cognition, including frontal cortex. Recent work demonstrated that nonhuman primates are capable of metacognition, so we recorded from single neurons in the frontal eye field, dorsolateral prefrontal cortex, and supplementary eye field of monkeys (Macaca mulatta) that performed a metacognitive visual-oculomotor task. The animals made a decision and reported it with a saccade, but received no immediate reward or feedback. Instead, they had to monitor their decision and bet whether it was correct. Activity was correlated with decisions and bets in all three brain areas, but putative metacognitive activity that linked decisions to appropriate bets occurred exclusively in the SEF. Our results offer a survey of neuronal correlates of metacognition and implicate the SEF in linking cognitive functions over short periods of time.     

Neuronal correlates of kinematics-to-dynamics transformation in the supplementary motor area

It is widely acknowledged that movements are planned at the level of the kinematics. However, the central nervous system must ultimately transform kinematic plans into dynamics-related commands. How, when, and where the kinematics-to-dynamics (KD) transformation is processed represent fundamental and unanswered questions. We recorded from the supplementary motor area (SMA) of two monkeys as they executed visually instructed reaching movements. We specifically analyzed a delay period following the instruction but prior to the go signal (motor planning). During the delay, a group of neurons in the SMA progressively came to reflect the dynamics rather than the desired kinematics of the upcoming movement. This finding suggests that some neurons in the SMA participate in the KD transformation.     

Neuronal correlates of the set-size effect in monkey lateral intraparietal area

It has long been known that the brain is limited in the amount of sensory information that it can process at any given time. A well-known form of capacity limitation in vision is the set-size effect, whereby the time needed to find a target increases in the presence of distractors. The set-size effect implies that inputs from multiple objects interfere with each other, but the loci and mechanisms of this interference are unknown. Here we show that the set-size effect has a neural correlate in competitive visuo-visual interactions in the lateral intraparietal area, an area related to spatial attention and eye movements. Monkeys performed a covert visual search task in which they discriminated the orientation of a visual target surrounded by distractors. Neurons encoded target location, but responses associated with both target and distractors declined as a function of distractor number (set size). Firing rates associated with the target in the receptive field correlated with reaction time both within and across set sizes. The findings suggest that competitive visuo-visual interactions in areas related to spatial attention contribute to capacity limitations in visual searches.     

Neuronal correlates of corticalization in mammals: a theory

The cerebral cortex of mammals has been found to be uniformly organized, and to be composed of elementary processing units or modules having an essentially constant number of neurons. In the present paper the hypothesis is put forward that the relative proportion of local circuit neurons (LCNs) within a module reflects the evolutionary level of corticalization of a mammal. The modules, in turn, are interconnected so as to form basic neuronal networks or columns with a species-specific width varying from 90 to 310 microns. A mathematical formalism is presented from which the hypothetical ratio between LCNs and projection neurons, as well as the size of the cortical column and the number of modular units that it contains, can be calculated.     

Neuronal correlates of the motor function of the cerebral motor cortex

Modern ideas about the motor cortex neuronal mechanisms ensuring the initiation and correction of the instrumental manipulational movements in mammals have been analysed. A close correlation has been established to exist between the neuronal activity and various characteristics of movement including those that are not induced by muscle force. The role of somatic afferentation in the formation and realization of the movement programme is analysed as well as in motor output modulation by means of fast feedback.     

Neuronal correlates of an alimentary instrumental conditioned reflex in rats

Elaboration of an instrumental reaction of getting the food from a narrow tube with a defnite forepaw (handedness) brings about a distinct re-distribution of cellular activity in the motor cortex and in the caudate nucleus, contralateral to the instrumental paw. The changes were observed at a 250 msec. interval before and 512 msec. interval after the beginning of the movement. Two types of cellular discharge changes were recorded: phasic and tonic. The phasic reactions (both inhibitory and activating) were grouped around the beginning of movement, with an average duration of about 100 msec. The tonic reactions lasted a few hundred milliseconds.     

Neuronal correlates of a perceptual decision in ventral premotor cortex

The ventral premotor cortex (VPC) is involved in the transformation of sensory information into action, although the exact neuronal operation is not known. We addressed this problem by recording from single neurons in VPC while trained monkeys report a decision based on the comparison of two mechanical vibrations applied sequentially to the fingertips. Here we report that the activity of VPC neurons reflects current and remembered sensory inputs, their comparison, and motor commands expressing the result; that is, the entire processing cascade linking the evaluation of sensory stimuli with a motor report. These findings provide a fairly complete panorama of the neural dynamics that underlies the transformation of sensory information into an action and emphasize the role of VPC in perceptual decisions.     

Food conditioned reflexes in dogs during activation and blockade of the cholinoreactive system of the amygdala

By means of chemical stimulation of subcortical structures it has been found that the cholinoreactive system of the basolateral part of amygdala is involved in realization of secretory component of alimentary conditioned reactions and takes no direct part in accomplishment of the instrumental component. Activation of the cholinoreactive system of the amygdalar basolateral part has an inhibitory effect and the blockade has an activating effect on the realization of the secretory component of alimentary conditioned reactions. A change in characteristics is observed of the differentiation inhibition and of the correlation of conditioned salivation in response to various stimuli presented in a stereotype order.     

Neuronal activation in the hypothalamus and brainstem during feeding in rats

We trained rats to a regime of scheduled feeding, in which food was available for only 2 hr each day. After 10 days, rats were euthanized at defined times relative to food availability, and their brains were analyzed to map Fos expression in neuronal populations to test the hypothesis that some populations are activated by hunger whereas others are activated by satiety signals. Fos expression accompanied feeding in several hypothalamic and brainstem nuclei. Food ingestion was critical for Fos expression in noradrenergic and non-noradrenergic cells in the nucleus tractus solitarii and area postrema and in the supraoptic nucleus, as well as in melanocortin-containing cells of the arcuate nucleus. However, anticipation of food alone activated other neurons in the arcuate nucleus and in the lateral and ventromedial hypothalamus, including orexin neurons. Thus orexigenic populations are strongly and rapidly activated at the onset of food presentation, followed rapidly by activity in anorexigenic populations when food is ingested.     

Neuronal plasticity in the adult invertebrate nervous system

This essay provides a brief overview of neuronal plasticity in adult invertebrate nervous systems. Our discussion focuses on the factors which influence sprouting by adult neurons, i.e., (1) the nature of the neuron itself, (2) axon integrity, (3) the presence of targets, (4) diffusible factors, and (5) ageing. Evidence that the neurites of some adult neurons exhibit a dynamic equilibrium of expansion and retraction is presented, a topic which prompted us to speculate on the significance of such plasticity in altered behavioral states. We conclude with some suggestions as to specific questions that need to be addressed by future studies in this challenging area.     

Neuronal activation and plasticity in Schistosoma mansoni infected mice

Schistosomiasis leads to structural and functional changes which may result from unbalanced release of some inflammatory mediators. The aim of the study was to investigate the effect of intestinal parasitic infection on nitric oxide release and to evaluate the neural plasticity that leads to motility disturbance. Experiments were performed in Swiss mice 8- and 12-weeks following infection with Schistosoma mansoni compared to untreated controls. Jejunal motility was assessed using a Trendelenburg preparation to study aboral directed peristaltic pressure waves. Histological examination was used to determine the pathological characteristics of inflammation.Parasitic infection produces diffuse inflammatory infiltrate in both 8- and 12-weeks infected animals. Inflammation had significant effect on peristaltic pressure waves amplitude and intervals at 8-weeks compared to control; whereas, in 12-weeks post infection there was a significant decrease in peristaltic pressure waves amplitude and interval compared to 8- weeks and control.Nitric oxide synthase inhibitor (L-NAME 100 μM) induced a significant increase in amplitude and decrease in intervals in control, 8- and 12- weeks infected animals. In conclusion, parasitic infection leads to disturbance in the release of the inflammatory mediators. This study indicated the role of nitric oxide in developing granulomatous inflammation and participating in motility disturbance.     

Neuronal replacement in microcircuits of the adult olfactory system

The local-circuit inhibitory interneurons containing gamma-aminobutyric acid (GABA) are continuously replaced in the adult olfactory bulb. Here, we describe how the production of new GABAergic interneurons is adapted to experience-induced plasticity. In particular, we discuss how such an adaptation is sensitive to the level of sensory inputs and how, in turn, neurogenesis may adjust the neural network functioning to optimize processing of sensory information. Finally, this review brings together recently described properties of interneurons as well as emerging principles of their functions that indicate a much more complex role for these cells than just that of gatekeepers providing inhibition.     

Neuronal correlates of changes in the defensive behavior of Helix lucorum L. during ontogeny

In experiments on the isolated nervous system, responses of the same command neurones of avoidance behaviour to electrical stimulation of the intestinal nerve were compared in adult snails (Helix pomatia) and in snails 1-20 days old. Dynamics of spike reactions of the command neurones to rhythmic nerve stimulation differed in adult and newborn snails. In the neurones of young snails, no sensitization, common in the adult animals, was observed. Study of excitatory input in the command neurones during rhythmic nerve stimulation suggests independence of habituation of synaptic input amplitude and spike response sensitization, because dynamics of habituation coincided in the young and adult snails while spike response underwent sensitization only in adult animals.     

中枢神经系统内神经元信号处理(英文)

一种新颖的轴突断端(axon bleb)膜片钳记录方法大力促进了中枢神经系统轴突功能的研究。我们的工作应用这一方法揭示了大脑皮层锥体神经元的数码信号(具全或无特性的动作电位)的爆发和传播机制。在轴突始段(axon initial segment,AIS)远端高密度聚集的低阈值Na+通道亚型Nav1.6决定动作电位的爆发;而在AIS近端高密度聚集的高阈值Na+通道亚型Nav1.2促进动作电位向胞体和树突的反向传播。应用胞体和轴突的同时记录,我们发现胞体阈下膜电位的变化可以在轴突上传播较长的距离并可到达那些离胞体较近的突触前终末。进一步的研究证明了胞体膜电位的变化调控动作电位触发的突触传递,该膜电位依赖的突触传递是一种模拟式的信号传递。轴突上一类特殊K+通道(Kv1)的活动调制动作电位的波形,特别是其波宽,从而调控各种突触前膜电位水平下突触强度的变化。突触前终末的背景Ca2+浓度也可能参与模拟信号的传递。这些发现深化了我们对中枢神经系统内神经信号处理基本原理的认识,进而帮助我们理解脑如何工作。