Neural mechanisms for the coordination of duet singing in wrens

Plain-tailed wrens (Pheugopedius euophrys) cooperate to produce a duet song in which males and females rapidly alternate singing syllables. We examined how sensory information from each wren is used to coordinate singing between individuals for the production of this cooperative behavior. Previous findings in nonduetting songbird species suggest that premotor circuits should encode each bird's own contribution to the duet. In contrast, we find that both male and female wrens encode the combined cooperative output of the pair of birds. Further, behavior and neurophysiology show that both sexes coordinate the timing of their singing based on feedback from the partner and suggest that females may lead the duet.     

Auditory responses in avian vocal motor neurons: a motor theory for song perception in birds

The hypoglossal motor neurons that innervate the vocal organ (syrinx) of the male zebra finch show a selective, long-latency (50-millisecond) response to sound. This response is eliminated by lesions to forebrain song-control nuclei. Different song syllables elicit a response from different syringeal motor neurons. Conspecific vocalizations may therefore be perceived as members of a set of vocal gestures and thus distinct from other environmental sounds. This hypothesis is an avian parallel to the motor theory of speech perception in humans.     

The cellular basis of a corollary discharge

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.     

A test for responsiveness to song structure and programming in female sparrows

Female song sparrows, primed with implants of estradiol, gave the solicitation display for copulation in response to acoustic stimulation with song. This technique demonstrated that female song sparrows respond more strongly to conspecific song than to alien songs, that they discriminate on the basis of both overall temporal pattern and syllabic structure, that they respond more to several song types than to repetitions of one song, and that they are most responsive to several song types if the songs are organized in bouts of a single type, as they are normally delivered by a male song sparrow. These results demonstrate a substantial correspondence between the structure and programming of the singing behavior of male birds and female responsiveness to song.     

Command neurons in Pleurobranchaea receive synaptic feedback from the motor network they excite

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.     

A specialized forebrain circuit for vocal babbling in the juvenile songbird

Young animals engage in variable exploratory behaviors essential for the development of neural circuitry and adult motor control, yet the neural basis of these behaviors is largely unknown. Juvenile songbirds produce subsong-a succession of primitive vocalizations akin to human babbling. We found that subsong production in zebra finches does not require HVC (high vocal center), a key premotor area for singing in adult birds, but does require LMAN (lateral magnocellular nucleus of the nidopallium), a forebrain nucleus involved in learning but not in adult singing. During babbling, neurons in LMAN exhibited premotor correlations to vocal output on a fast time scale. Thus, juvenile singing is driven by a circuit distinct from that which produces the adult behavior-a separation possibly general to other developing motor systems.     

Neural mechanisms of visual attention: how top-down feedback highlights relevant locations

Attention helps us process potentially important objects by selectively increasing the activity of sensory neurons that represent the relevant locations and features of our environment. This selection process requires top-down feedback about what is important in our environment. We investigated how parietal cortical output influences neural activity in early sensory areas. Neural recordings were made simultaneously from the posterior parietal cortex and an earlier area in the visual pathway, the medial temporal area, of macaques performing a visual matching task. When the monkey selectively attended to a location, the timing of activities in the two regions became synchronized, with the parietal cortex leading the medial temporal area. Parietal neurons may thus selectively increase activity in earlier sensory areas to enable focused spatial attention.     

Rapid changes in throughput from single motor cortex neurons to muscle activity

Motor cortex output is capable of considerable reorganization, which involves modulation of excitability within the cortex. Does such reorganization also involve changes beyond the cortex, at the level of throughput from single motor cortex neurons to muscle activity? We examined such throughput during a paradigm that provided incentive for enhancing functional connectivity from motor cortex neurons to muscles. Short-latency throughput from a recorded neuron to muscle activity not present during some behavioral epochs often appeared during others. Such changes in throughput could not always be attributed to a higher neuron firing rate, to more ongoing muscle activity, or to neuronal synchronization, indicating that reorganization of motor cortex output may involve rapid changes in functional connectivity from single motor cortex neurons to alpha-motoneuron pools.     

Neuroscience. Where the brain monitors the body

Researchers haven't known exactly where in the brain all the signals that allow an animal to keep track of its limbs are located, but now a team may have located some of the neurons that first make these multisensory connections. On page 1782, researchers report evidence that a small region of the parietal cortex of the monkey brain known as area 5 may enable the monkey to integrate many sources of information about its body and thereby update its mental model of what the body is doing. The researchers based this conclusion on their finding that some area 5 neurons fire at their fastest rates when the visual feedback from a monkey's arm matches the sensory feedback, an indication that the neurons are sensitive to both streams of information.     

Motor cortex reflexes associated with learned movement

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.     

Segregation of axial motor and sensory pathways via heterotypic trans-axonal signaling

Execution of motor behaviors relies on circuitries effectively integrating immediate sensory feedback to efferent pathways controlling muscle activity. It remains unclear how, during neuromuscular circuit assembly, sensory and motor projections become incorporated into tightly coordinated, yet functionally separate pathways. We report that, within axial nerves, establishment of discrete afferent and efferent pathways depends on coordinate signaling between coextending sensory and motor projections. These heterotypic axon-axon interactions require motor axonal EphA3/EphA4 receptor tyrosine kinases activated by cognate sensory axonal ephrin-A ligands. Genetic elimination of trans-axonal ephrin-A --> EphA signaling in mice triggers drastic motor-sensory miswiring, culminating in functional efferents within proximal afferent pathways. Effective assembly of a key circuit underlying motor behaviors thus critically depends on trans-axonal signaling interactions resolving motor and sensory projections into discrete pathways.     

Facilitation of spindle-burst sleep by conditioning of electroencephalographic activity while awake

A slow-wave electroencephalographic rhythm recorded from the sensorimotor cortex of the waking cat has been correlated behaviorally with the suppression of movement. Facilitation of this rhythm through conditioning selectively enhances a similar pattern recorded during sleep, the familiar spindle burst. The training also produced longer epochs of undisturbed sleep. The specific neural mechanism manipulated during wakefulness appears to function also in sleep and to be involved with the regulation of phasic motor behavior.     

Genetic control of an insect neuronal network

Motor activity responsible for the calling song of crickets is generated by a small neuronal network whose output is genetically determined. Genes controlling certain output features are located on the X chromosome. The genetic system involved is polygenic and multichromosomal. In some patterns, genetically derived information is adequate to specify the difference of a single impulse in the output of homologous neurons from different genotypes.     

Movement of neural activity on the superior colliculus motor map during gaze shifts

The superior colliculus contains neurons that cause displacements of the visual axis (gaze shifts). These cells are arranged topographically in a motor map on which the vector (amplitude and direction) of the coded movement varies continuously with location. How this spatial representation becomes a temporal code (frequency and duration) in the motoneurons is unknown. During a gaze shift, a zone of neural activity moved continuously on the map from an initial location, defining the vector of the desired gaze shift, to a final "zero" position containing neurons that were active during fixation. Thus, the spatial-temporal transformation may be accomplished by control of gaze throughout the spatial trajectory of activity on the motor map.     

Target-dependent structural changes accompanying long-term synaptic facilitation in Aplysia neurons

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.     

Cerebral cortex: a sensorimotor amalgam in the marsupiala

In the cerebral cortex of the opossum and the wallaby there Is a complete and coincident overlap of the sensory and the motor representations of the body. Within this sensorimotor area It is not possible to draw the line which in other mammals separates a primarily sensory area from a primarily motor area.     

Altered perception of species-specific song by female birds after lesions of a forebrain nucleus

Female birds that do not normally sing possess brain nuclei associated with song production in males. To determine whether one song nucleus, the caudal nucleus of the ventral hyperstriatum (HVc), acts in conspecific song perception, courtship responses of female canaries to canary and white-crowned sparrow songs were compared before and after HVc lesions. Bilateral lesions of a portion of the HVc resulted in copulation solicitations to heterospecific song as well as conspecific song. Control females continued to respond only to conspecific song. This suggests that the HVc is critical for conspecific song perception in females. Because female canaries do not normally sing, neurons in female HVc must develop response selectivity by a mechanism different from that proposed for male birds in the motor theory of song perception.     

Motor control by sensory cortex

Classical studies of mammalian movement control define a prominent role for the primary motor cortex. Investigating the mouse whisker system, we found an additional and equally direct pathway for cortical motor control driven by the primary somatosensory cortex. Whereas activity in primary motor cortex directly evokes exploratory whisker protraction, primary somatosensory cortex directly drives whisker retraction, providing a rapid negative feedback signal for sensorimotor integration. Motor control by sensory cortex suggests the need to reevaluate the functional organization of cortical maps.     

Human motor cortex: sensory input data from single neuron recordings

Recordings were made from single neurons in the hand area of the human motor cortex while peripheral physiologic stimuli were applied. Such cells responded only to active and passive hand movements. Tactile and autditory (click) stimuli were itneffective. The majority of cells were activated only by movements of the contralateral hand, but a significant number (4 of 16) could be excited if a given movement was made by either hand. Of the cells responding to active movement, some showed an increased discharge before onset of the voluntary action. Such cells were excited by the same movement executed passively, a result that indicates sensory feedback from receptors activated by that movement.     

声乐教学中古诗词艺术歌曲特色探究

本文以探究古诗词艺术歌曲特色为视角,从声乐教学角度出发,通过阐述古诗词艺术歌 曲的演唱技巧、声乐教学中古诗词艺术歌曲的意境把握以及声乐教学中古诗词艺术歌曲的美学 价值,进一步明确在声乐教学中应该如何指导学生来演唱此类作品,如何让学生准确的把握古诗 词艺术歌曲的演唱特色。强调在声乐教学中,学习古诗词艺术歌曲不仅要求学生有着一定的声 乐技巧,更要求学生拥有深厚的文化素养,真正切实的唱出古诗词艺术歌曲的魂,有较高的参考 价值和社会意义。