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1.
Songbirds learn a correspondence between vocal-motor output and auditory feedback during development. For neurons in a motor cortex analog of adult zebra finches, we show that the timing and structure of activity elicited by the playback of song during sleep matches activity during daytime singing. The motor activity leads syllables, and the matching sensory response depends on a sequence of typically up to three of the preceding syllables. Thus, sensorimotor correspondence is reflected in temporally precise activity patterns of single neurons that use long sensory memories to predict syllable sequences. Additionally, "spontaneous" activity of these neurons during sleep matches their sensorimotor activity, a form of song "replay." These data suggest a model whereby sensorimotor correspondences are stored during singing but do not modify behavior, and off-line comparison (e.g., during sleep) of rehearsed motor output and predicted sensory feedback is used to adaptively shape motor output. 相似文献
2.
The neural encoding of serial order was studied in the motor cortex of monkeys performing a context-recall memory scanning task. Up to five visual stimuli were presented successively on a circle (list presentation phase), and then one of them (test stimulus) changed color; the monkeys had to make a single motor response toward the stimulus that immediately followed the test stimulus in the list. Correct performance in this task depends on memorization of the serial order of the stimuli during their presentation. It was found that changes in neural activity during the list presentation phase reflected the serial order of the stimuli; the effect on cell activity of the serial order of stimuli during their presentation was at least as strong as the effect of motor direction on cell activity during the execution of the motor response. This establishes the serial order of stimuli in a motor task as an important determinant of motor cortical activity during stimulus presentation and in the absence of changes in peripheral motor events, in contrast to the commonly held view of the motor cortex as just an "upper motor neuron." 相似文献
3.
The intrinsic electrophysiological properties of mammalian neurons: insights into central nervous system function 总被引：68，自引：0，他引：68
R R Llinás 《Science (New York, N.Y.)》1988,242(4886):1654-1664
This article reviews the electroresponsive properties of single neurons in the mammalian central nervous system (CNS). In some of these cells the ionic conductances responsible for their excitability also endow them with autorhythmic electrical oscillatory properties. Chemical or electrical synaptic contacts between these neurons often result in network oscillations. In such networks, autorhythmic neurons may act as true oscillators (as pacemakers) or as resonators (responding preferentially to certain firing frequencies). Oscillations and resonance in the CNS are proposed to have diverse functional roles, such as (i) determining global functional states (for example, sleep-wakefulness or attention), (ii) timing in motor coordination, and (iii) specifying connectivity during development. Also, oscillation, especially in the thalamo-cortical circuits, may be related to certain neurological and psychiatric disorders. This review proposes that the autorhythmic electrical properties of central neurons and their connectivity form the basis for an intrinsic functional coordinate system that provides internal context to sensory input. 相似文献
4.
Command neurons in Pleurobranchaea receive synaptic feedback from the motor network they excite 总被引：2，自引：0，他引：2
Command neurons that cause rhythmic feeding behavior in the marine mollusc Pleurobranchaea californica have been identified in the cerebropleural ganglion (brain). Intracellular stimulation of single command neurons in isolated nervous systems, semi-intact prepartions, and restrained whole animals causes the same rhythmic motor output pattern as occurs during feeding. During this motor output pattern, action potentials recorded intracellularly from the command neurons occur in cyclic bursts that are phase-locked with the feeding rhythm. This modulation results from repetitive, alternating bursts of excitatory and inhibitory postsynaptic potentials, which are caused at least in part by synaptic feedback to the command neurons from identified classes of neurons in the feeding network. Central feedback to command neurons from the motor network they excite provides a possible general physiological mechanism for the sustained oscillation of neural networks controlling cyclic behavior. 相似文献
5.
A sudden touch on one hand can improve vision near that hand, revealing crossmodal links in spatial attention. It is often assumed that such links involve only multimodal neural structures, but unimodal brain areas may also be affected. We tested the effect of simultaneous visuo-tactile stimulation on the activity of the human visual cortex. Tactile stimulation enhanced activity in the visual cortex, but only when it was on the same side as a visual target. Analysis of effective connectivity between brain areas suggests that touch influences unimodal visual cortex via back-projections from multimodal parietal areas. This provides a neural explanation for crossmodal links in spatial attention. 相似文献
6.
Target-dependent structural changes accompanying long-term synaptic facilitation in Aplysia neurons 总被引：7，自引：0，他引：7
The mechanisms underlying structural changes that accompany learning and memory have been difficult to investigate in the intact nervous system. In order to make these changes more accessible for experimental analysis, dissociated cell culture and low-light-level video microscopy were used to examine Aplysia sensory neurons in the presence or absence of their target cells. Repeated applications of serotonin, a facilitating transmitter important in behavioral dishabituation and sensitization, produced growth of the sensory neurons that paralleled the long-term enhancement of synaptic strength. This growth required the presence of the postsynaptic motor neuron. Thus, both the structural changes and the synaptic facilitation of Aplysia sensorimotor synapses accompanying long-term behavioral sensitization can be produced in vitro by applying a single facilitating transmitter repeatedly. These structural changes depend on an interaction of the presynaptic neuron with an appropriate postsynaptic target. 相似文献
7.
Motor cortex reflexes associated with learned movement 总被引：8，自引：0，他引：8
E V Evarts 《Science (New York, N.Y.)》1973,179(72):501-503
In primates, sensory input can generate reflex motor cortex output in association with learned movement when the sensory input has a strong and direct connection to the motor cortex-for example, when a stimulus calling for repositioning of the hand consists of a perturbation of hand position. This finding supports the proposal that neurons of primate motor cortex may function in a transcortical servo-loop. 相似文献
8.
Electrical activity plays a critical role in shaping the structure and function of synaptic connections in the nervous system. In Xenopus nerve-muscle cultures, a brief burst of action potentials in the presynaptic neuron induced a persistent potentiation of neuromuscular synapses that exhibit immature synaptic functions. Induction of potentiation required an elevation of postsynaptic Ca2+ and expression of potentiation appeared to involve an increased probability of transmitter secretion from the presynaptic nerve terminal. Thus, activity-dependent persistent synaptic enhancement may reflect properties characteristic of immature synaptic connections, and bursting activity in developing spinal neurons may promote functional maturation of the neuromuscular synapse. 相似文献
9.
Synaptic plasticity is the experience-dependent change in connectivity between neurons that is believed to underlie learning and memory. Here, we discuss the cellular and molecular processes that are altered when a neuron responds to external stimuli, and how these alterations lead to an increase or decrease in synaptic connectivity. Modification of synaptic components and changes in gene expression are necessary for many forms of plasticity. We focus on excitatory neurons in the mammalian hippocampus, one of the best-studied model systems of learning-related plasticity. 相似文献
10.
Long-term potentiation in the motor cortex 总被引：4，自引：0，他引：4
Long-term potentiation (LTP) is a model for learning and memory processes. Tetanic stimulation of the sensory cortex produces LTP in motor cortical neurons, whereas tetanization of the ventrolateral nucleus of the thalamus, which also projects to the motor cortex, does not. However, after simultaneous high-frequency stimulation of both the sensory cortex and the ventrolateral nucleus of the thalamus, LTP of thalamic input to motor cortical neurons is induced. This associative LTP occurs only in neurons in the superficial layers of the motor cortex that receive monosynaptic input from both the sensory cortex and the ventrolateral nucleus of the thalamus. Associative LTP in the motor cortex may constitute a basis for the retention of motor skills. 相似文献
11.
Neuronal population coding of movement direction 总被引：41，自引：0，他引：41
Although individual neurons in the arm area of the primate motor cortex are only broadly tuned to a particular direction in three-dimensional space, the animal can very precisely control the movement of its arm. The direction of movement was found to be uniquely predicted by the action of a population of motor cortical neurons. When individual cells were represented as vectors that make weighted contributions along the axis of their preferred direction (according to changes in their activity during the movement under consideration) the resulting vector sum of all cell vectors (population vector) was in a direction congruent with the direction of movement. This population vector can be monitored during various tasks, and similar measures in other neuronal populations could be of heuristic value where there is a neural representation of variables with vectorial attributes. 相似文献
12.
During neural development, coordinate regulation of cell-cycle exit and differentiation is essential for cell-fate specification, cell survival, and proper wiring of neuronal circuits. However, the molecules that direct these events remain poorly defined. In the developing spinal cord, the differentiation of motor neuron progenitors into postmitotic motor neurons is regulated by retinoid signaling. Here, we identify a retinoid-inducible gene, GDE2 (glycerophosphodiester phosphodiesterase 2), encoding a six-transmembrane protein that is necessary and sufficient to drive spinal motor neuron differentiation in vivo. A single amino acid mutation in the extracellular catalytic domain abolishes protein function. This reveals a critical role for glycerophosphodiester metabolism in motor neuron differentiation. 相似文献
13.
How do animals discriminate self-generated from external stimuli during behavior and prevent desensitization of their sensory pathways? A fundamental concept in neuroscience states that neural signals, termed corollary discharges or efference copies, are forwarded from motor to sensory areas. Neurons mediating these signals have proved difficult to identify. We show that a single, multisegmental interneuron is responsible for the pre- and postsynaptic inhibition of auditory neurons in singing crickets (Gryllus bimaculatus). Therefore, this neuron represents a corollary discharge interneuron that provides a neuronal basis for the central control of sensory responses. 相似文献
14.
Blood oxygen level-dependent functional magnetic resonance imaging uses alterations in brain hemodynamics to infer changes in neural activity. Are these hemodynamic changes regulated at a spatial scale capable of resolving functional columns within the cerebral cortex? To address this question, we made simultaneous measurements of tissue oxygenation and single-cell neural activity within the visual cortex. Results showed that increases in neuronal spike rate were accompanied by immediate decreases in tissue oxygenation. We used this decrease in tissue oxygenation to predict the orientation selectivity and ocular dominance of neighboring neurons. Our results establish a coupling between neural activity and oxidative metabolism and suggest that high-resolution functional magnetic resonance imaging may be used to localize neural activity at a columnar level. 相似文献
15.
Foxg1 suppresses early cortical cell fate 总被引：1，自引：0，他引：1
16.
Initiation and performance of the swimming movement in the leech (Hirudo medicinalis) are controlled by neurons organized at at least four functional levels-sensory neurons, gating neurons, oscillator neurons, and motor neurons. A paired neuron, designated as Trl, in the subesophageal ganglion of the leech has now been shown to define a fifth level, interposed between sensory and gating neurons. Cell Trl is activated by pressure and nociceptive mechanosensory neurons, which mediate bodywall stimulus-evoked swimming activity in intact leeches. In the isolated leech nervous system, brief stimulation of cell Trl elicits sustained activation of the gating neurons and triggers the onset of swimmning activity. The synaptic interactions between all five levels of control are direct. Discovery of the Trl cells thus completes the identification of a synaptic pathway by which mechanosensory stimulation leads to the swimming movements of the leech. 相似文献
17.
Although acoustic communication is not pronounced in reptiles, analysis of single auditory neurons in the medulla oblongata shows that the cochlea is a frequency analyser. Auditory neurons of the lizard Coleonyx variegatus respond to acoustic stimuli over a range of less than 0.1 to 17 kilohertz and are maximally responsive between 0.8 and 2.0 kilohertz. The frequencies to which they are most sensitive differ from neuron to neuron, ranging from 0.11 to 4 kilohertz. Some neurons have an inhibitory area which greatly overlaps the response area, so that inhibitory areas do not seem to sharply tune the response area at this level of the auditory tract. The inhibitory area is responsible for producing in some neurons a phasic response and nonmonotonic relation between sound intensity and number of impulses. The response pattern shows a tendency to change from tonic to phasic in more advanced auditory centers. This may serve to code rapid changes in the acoustic stimuli. 相似文献
18.
D1 dopamine receptor activation required for postsynaptic expression of D2 agonist effects 总被引：15，自引：0，他引：15
J R Walters D A Bergstrom J H Carlson T N Chase A R Braun 《Science (New York, N.Y.)》1987,236(4802):719-722
D1 and D2 dopamine receptors exert synergistic effects on the firing rates of basal ganglia neurons and on the expression of stereotyped behavior in rats. Moreover, the ability of D2 agonists to induce changes in basal ganglia single unit activity and spontaneous motor activity is dependent upon the presence of endogenous dopamine to stimulate D1 receptors; in rats treated with alpha-methyl-rho-tyrosine to reduce endogenous dopamine levels, the neurophysiological and behavioral effects of the D2 agonist quinpirole are significantly attenuated, while the effects of nonselective agonists like apomorphine, which stimulate both D1 and D2 receptors, or combinations of a D2 agonist and a D1 agonist are not attenuated. Thus, the previously held view that D2 receptors alone are responsible for evoking the changes in behavior and basal ganglia output induced by nonselective dopamine agonists and endogenous dopamine is not supported by these results, which indicate that these phenomena require concurrent stimulation of both dopamine receptor subtypes. 相似文献
19.
Use-dependent forms of synaptic plasticity have been extensively characterized at chemical synapses, but a relationship between natural activity and strength at electrical synapses remains elusive. The thalamic reticular nucleus (TRN), a brain area rich in gap-junctional (electrical) synapses, regulates cortical attention to the sensory surround and participates in shifts between arousal states; plasticity of electrical synapses may be a key mechanism underlying these processes. We observed long-term depression resulting from coordinated burst firing in pairs of coupled TRN neurons. Changes in gap-junctional communication were asymmetrical, indicating that regulation of connectivity depends on the direction of use. Modification of electrical synapses resulting from activity in coupled neurons is likely to be a widespread and powerful mechanism for dynamic reorganization of electrically coupled neuronal networks. 相似文献
20.
Nishimura Y Onoe H Morichika Y Perfiliev S Tsukada H Isa T 《Science (New York, N.Y.)》2007,318(5853):1150-1155
Transection of the direct cortico-motoneuronal pathway at the mid-cervical segment of the spinal cord in the macaque monkey results in a transient impairment of finger movements. Finger dexterity recovers within a few months. Combined brain imaging and reversible pharmacological inactivation of motor cortical regions suggest that the recovery involves the bilateral primary motor cortex during the early recovery stage and more extensive regions of the contralesional primary motor cortex and bilateral premotor cortex during the late recovery stage. These changes in the activation pattern of frontal motor-related areas represent an adaptive strategy for functional compensation after spinal cord injury. 相似文献