Visual receptive fields sensitive to absolute and relative motion during tracking

Some neurons in the visual cortex of awake monkeys visually tracking a moving target showed receptive fields that were excited only by stimulus motion relative to a background, while other neurons responded to any kind of stimulus motion. This result was found with two methods, one in which tracking eye movements were identical in both relative-motion and absolute-motion conditions, and another in which stimulus motions on the retina were identical in both conditions. This response pattern can differentiate translation of the retinal image during eye movement from motion of objects in the world.     

Sustained dendritic gradients of Ca2+ induced by excitatory amino acids in CA1 hippocampal neurons

Spatially resolved measurements of intracellular free calcium and of the changes produced by excitatory amino acids were made in neurons isolated from adult mammalian brain. Extremely long-lasting (minutes) Ca2+ gradients were induced in the apical dendrites of hippocampal CA1 neurons after brief (1 to 3 seconds), local application of either glutamate or N-methyl-D-aspartate (NMDA). These gradients reflect the continuous flux of Ca2+ into the dendrite. The sustained gradients, but not the immediate transient response to the agonists, were prevented by prior treatment with the protein kinase C inhibitor sphingosine. Expression of the long-lasting Ca2+ gradients generally required a priming or conditioning stimulus with the excitatory agonist. The findings demonstrate a coupling between NMDA receptor activation and long-lasting intracellular Ca2+ elevation that could contribute to certain use-dependent modifications of synaptic responses in hippocampal CA1 neurons.     

Conversion of working memory to motor sequence in the monkey premotor cortex

To plan a serial order behavior, we hold serial sensory information in our minds and convert it to a movement program. We trained monkeys to memorize a sequence of positional cues and to reproduce it by making saccades in either the original or reverse order. The order was determined in the middle of a trial on the basis of an instruction stimulus. Triggered by the instruction stimulus, single neurons in the dorsal premotor cortex became transiently active only when the order needed to be determined. These transient neurons, together with nearby sustained neurons that hold information on cue or movement sequences, appear to mediate the generation of a motor program from the maintained information.     

Neuronal mechanisms of habituation and dishabituation of the gill-withdrawal reflex in Aplysia

The cellular mechanisms of habituation and dishabituation of the gill-withdrawal reflex in Aplysia were studied with an isolated abdominal ganglion connected to a piece of skin from the tactile receptive field of the reflex. By obtaining simultaneous intracellular recordings from both the sensory neurons and one of the main identified motor neurons, we have been able to reduce the reflex to its monosynaptic components. The monosynaptic excitatory postsynaptic potentials showed a profound low-frequency depression when repeatedly elicited and showed heterosynaptic facilitation after application of a strong stimulus to another pathway. Thus, both habituation and dishabituation can be explained in part and perhaps entirely by changes in the efficacy of specific excitatory synapses.     

电压门控钠离子通道scn1Laa参与斑马鱼脑神经发育和运动行为调节的研究

电压门控钠离子通道对于脊椎动物脑神经起始、传播动作电位具有重要作用。为了解斑马鱼电压门控钠离子通道基因scn1Laa在脑神经中的作用,通过CRISPR/Cas9基因编辑技术,首次构建了可稳定遗传的生长没有受明显影响的scn1Laa缺陷型（scn1Laa-/-）斑马鱼家系。相比野生型,5 dpf（days post-fertilization,受精后5天）scn1Laa缺陷型斑马鱼兴奋抑制性神经元（氨基丁酸类神经元）表达相对增加,兴奋类神经元（谷氨酸能类神经元）和成熟神经元显著减少,脑部细胞增殖也显著减少。受精后5天和90 天的 scn1Laa缺陷型斑马鱼的运动较同时期野生型斑马鱼更为活跃,受精后90天的 scn1Laa缺陷型斑马鱼的运动具有明显的爆发性。以上结果表明,scn1laa缺失导致兴奋类神经元（谷氨酸能类神经元）以及神经细胞增殖减少,影响脑周围神经放电,导致运动神经调节障碍,出现运动行为异常活跃。即电压门控钠离子通道基因scn1Laa参与斑马鱼脑神经发育和生长,间接参与运动行为调节。同时本文也为进一步探究电压门控钠离子通道在脑神经中的作用奠定基础。     

The contribution of single synapses to sensory representation in vivo

The extent to which synaptic activity can signal a sensory stimulus limits the information available to a neuron. We determined the contribution of individual synapses to sensory representation by recording excitatory postsynaptic currents (EPSCs) in cerebellar granule cells during a time-varying, quantifiable vestibular stimulus. Vestibular-sensitive synapses faithfully reported direction and velocity, rather than position or acceleration of whole-body motion, via bidirectional modulation of EPSC frequency. The lack of short-term synaptic dynamics ensured a highly linear relationship between velocity and charge transfer, and as few as 100 synapses provided resolution approaching psychophysical limits. This indicates that highly accurate stimulus representation can be achieved by small networks and even within single neurons.     

A neural mechanism for working and recognition memory in inferior temporal cortex

Inferior temporal (IT) cortex is critical for visual memory, but it is not known how IT neurons retain memories while new information is streaming into the visual system. Single neurons were therefore recorded from IT cortex of two rhesus monkeys performing tasks that required them to hold items in memory while concurrently viewing other items. The neuronal response to an incoming visual stimulus was attenuated if it matched a stimulus actively held in working memory, even when several other stimuli intervened. The neuronal response to novel stimuli declined as the stimuli became familiar to the animal. IT neurons appear to function as adaptive mnemonic "filters" that preferentially pass information about new, unexpected, or not recently seen stimuli.     

Synaptic transmission in the crayfish: increased release of transmitter substance by bacterial endotoxin

Bacterial endotoxin increases the frequency of miniature excitatory postsynaptic potentials, decreases facilitation, and increases the evoked excitatory postsynaptic potential without changing membrane resistance. These data indicate that endotoxin acts on the presynaptic nerve terminal by increasing the amount of transmitter substance released in response to an applied stimulus.     

Associative induction of posttetanic and long-term potentiation in CA1 neurons of rat hippocampus

Electrical stimulation of fibers in the stratum radiatum causes an excitatory postsynaptic potential in CA1 neurons of the hippocampus. Other excitatory inputs to or direct depolarization of these CA1 neurons during stimulation of the stratum radiatum caused a subsequent increase in the excitatory postsynaptic potential. This enhancement was characterized as a brief potentiation (2 to 3 minutes, similar to posttetanic potentiation) and a long-term potentiation (presumed to be involved in learning and memory). These potentiations are probably induced by an interaction of the postsynaptic cell or other presynaptic terminals with the test presynaptic terminals.     

Neuronal correlates of subjective visual perception

Neuronal activity in the superior temporal sulcus of monkeys, a cortical region that plays an important role in analyzing visual motion, was related to the subjective perception of movement during a visual task. Single neurons were recorded while monkeys (Macaca mulatta) discriminated the direction of motion of stimuli that could be seen moving in either of two directions during binocular rivalry. The activity of many neurons was dictated by the retinal stimulus. Other neurons, however, reflected the monkeys' reported perception of motion direction, indicating that these neurons in the superior temporal sulcus may mediate the perceptual experience of a moving object.     

V1 neurons signal acquisition of an internal representation of stimulus location

A fundamental aspect of visuomotor behavior is deciding where to look or move next. Under certain conditions, the brain constructs an internal representation of stimulus location on the basis of previous knowledge and uses it to move the eyes or to make other movements. Neuronal responses in primary visual cortex were modulated when such an internal representation was acquired: Responses to a stimulus were affected progressively by sequential presentation of the stimulus at one location but not when the location was varied randomly. Responses of individual neurons were spatially tuned for gaze direction and tracked the Bayesian probability of stimulus appearance. We propose that the representation arises in a distributed cortical network and is associated with systematic changes in response selectivity and dynamics at the earliest stages of cortical visual processing.     

Photoelectric technique for measuring eye movements

By the system described, the movement of a stimulus and the correlated tracking movements of the eye are recorded simultaneously. The technique for measuring the eye movements consists of detecting and amplifying by photomultiplication the total amount of light passing through a small slit upon which is imaged a small portion of the light-dark field represented by the iris and sclera of the eye. This total amount of light varies directly with the angular position of the eye.     

Neurons containing NADPH-diaphorase are selectively resistant to quinolinate toxicity

Exposure of cultures of cortical cells from mouse to either of the endogenous excitatory neurotoxins quinolinate or glutamate resulted in widespread neuronal destruction; but only in the cultures exposed to quinolinate, an N-methyl-D-aspartate agonist, was there a striking preservation of the subpopulation of neurons containing the enzyme nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d). Further investigation revealed that neurons containing NADPH-d were also resistant to the toxicity of N-methyl-D-aspartate itself but were selectively vulnerable to the toxicity of either kainate or quisqualate. Thus, neurons containing NADPH-d may have an unusual distribution of receptors for excitatory amino acids, with a relative lack of N-methyl-D-aspartate receptors and a relative preponderance of kainate or quisqualate receptors. Since selective sparing of neurons containing NADPH-d is a hallmark of Huntington's disease, the results support the hypothesis that the disease may be caused by excess exposure to quinolinate or some other endogenous N-methyl-D-aspartate agonist.     

Eye and head movements in peripheral vision: nature of compensatory eye movements

Simultaneous recordings of both eye and head movements in response to a peripheral signal indicated that the backward compensatory eye movement was initiated during the constant velocity of the head rotation. This compensatory movement began before the eyes had actually reached the peripheral signal.     

Zinc selectively blocks the action of N-methyl-D-aspartate on cortical neurons

Large amounts of zinc are present in synaptic vesicles of mammalian central excitatory boutons and may be released during synaptic activity, but the functional significance of the metal for excitatory neurotransmission is currently unknown. Zinc (10 to 1000 micromolar) was found to have little intrinsic membrane effect on cortical neurons, but invariably produced a zinc concentration-dependent, rapid-onset, reversible, and selective attenuation of the membrane responses to N-methyl-D-aspartate, homocysteate, or quinolinate. In contrast, zinc generally potentiated the membrane responses to quisqualate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and often did not affect the response to kainate. Zinc also attenuated N-methyl-D-aspartate receptor-mediated neurotoxicity but not quisqualate or kainate neurotoxicity. The ability of zinc to specifically modulate postsynaptic neuronal responses to excitatory amino acid transmitters, reducing N-methyl-to-aspartate receptor-mediated excitation while often increasing quisqualate receptor-mediated excitation, is proposed to underlie its normal function at central excitatory synapses and furthermore could be relevant to neuronal cell loss in certain disease states.     

Substance P: a putative sensory transmitter in mammalian autonomic ganglia

Repetitive presynaptic stimulation elicited slow membrane depolarization in neurons of inferior mesenteric ganglia from guinea pigs. This response was not blocked by cholinergic antagonists but was specifically and reversibly inhibited by a substance P analog, (D-Pro2, D-Phe7, D-Trp9)-substance P, which also depressed the depolarization induced by exogenously applied substance P. The atropine-sensitive slow excitatory and slow inhibitory postsynaptic potentials evoked in neurons of rabbit superior cervical ganglia were not affected by the substance P analog. These and previous results provide strong support for the hypothesis that substance P or a closely related peptide is the transmitter mediating the slow depolarization. The latter may represent a sensory input from the gastrointestinal tract to neurons of the prevertebral ganglia.     

Eye movement-retina delayed feedback

Time delays between ocular movement and retinal input have been studied by yoking a visual target to eye movement by experimental programming methods and a laboratory real-time computer system. The subject's task was to manipulate this eye movement-yoked target cursor to perform either compensatory or pursuit eye tracking. The computer thereafter was programmed to store input eye-movement signals and read them out after a delay interval to control the yoked visual target cursor controlled by the eye movements. Delay time constants of 0.1 second significantly affected tracking. Eye movement-retinal feedback delays appeared to have an even more marked effect on positive pursuit eye tracking.     

Electrophysiologic responses in hamster superior colliculus evoked by regenerating retinal axons

Autologous peripheral nerve grafts were used to permit and direct the regrowth of retinal ganglion cell axons from the eye to the ipsilateral superior colliculus of adult hamsters in which the optic nerves had been transected within the orbit. Extracellular recordings in the superior colliculus 15 to 18 weeks after graft insertion revealed excitatory and inhibitory postsynaptic responses to visual stimulation. The finding of light-induced responses in neurons in the superficial layers of the superior colliculus close to the graft indicates that axons regenerating from axotomized retinal ganglion cells can establish electrophysiologically functional synapses with neurons in the superior colliculus of these adult mammals.     

Effect of deafferentation on a conditioned avoidance response

To determine whether peripheral afferent pathways could be bypassed in the performance of purposive movement, a group of monkeys was trained to avoid shock by flexing a forelimb in response to an auditory stimulus. The dorsal roots of the responding limb were then sectioned. Postoperatively it was found that the affected limb could be reconditioned.     

Responses of vomeronasal neurons to natural stimuli

The vomeronasal organ (VNO) of mammals plays an essential role in the detection of pheromones. We obtained simultaneous recordings of action potentials from large subsets of VNO neurons. These cells responded to components of urine by increasing their firing rate. This chemosensory activation required phospholipase C function. Unlike most other sensory neurons, VNO neurons did not adapt under prolonged stimulus exposure. The full time course of the VNO spiking response is captured by a simple quantitative model of ligand binding. Many individual VNO neurons were strongly selective for either male or female mouse urine, with the effective concentrations differing as much as a thousandfold. These results establish a framework for understanding sensory coding in the vomeronasal system.