Ventriloquism =LINK=
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Originally, ventriloquism was a religious practice.[1] The name comes from the Latin for 'to speak from the stomach: venter (belly) and loqui (speak).[2] The Greeks called this gastromancy (Greek: εγγαστριμυθία).[citation needed] The noises produced by the stomach were thought to be the voices of the unliving, who took up residence in the stomach of the ventriloquist. The ventriloquist would then interpret the sounds, as they were thought to be able to speak to the dead, as well as foretell the future. One of the earliest recorded group of prophets to use this technique was the Pythia, the priestess at the temple of Apollo in Delphi, who acted as the conduit for the Delphic Oracle.
One of the most successful early gastromancers was Eurykles, a prophet at Athens; gastromancers came to be referred to as Euryklides in his honour.[3] Other parts of the world also have a tradition of ventriloquism for ritual or religious purposes; historically there have been adepts of this practice among the Zulu, Inuit, and Māori peoples.[3]
The shift from ventriloquism as manifestation of spiritual forces toward ventriloquism as entertainment happened in the eighteenth century at travelling funfairs and market towns. An early depiction of a ventriloquist dates to 1754 in England, where Sir John Parnell is depicted in the painting An Election Entertainment by William Hogarth as speaking via his hand.[4] In 1757, the Austrian Baron de Mengen performed with a small doll.[5]
By the late 18th century, ventriloquist performances were an established form of entertainment in England, although most performers \"threw their voice\" to make it appear that it emanated from far away (known as distant ventriloquism), rather than the modern method of using a puppet (near ventriloquism).[a] A well-known ventriloquist of the period, Joseph Askins, who performed at the Sadler's Wells Theatre in London in the 1790s advertised his act as \"curious ad libitum Dialogues between himself and his invisible familiar, Little Tommy\".[6] However, other performers were beginning to incorporate dolls or puppets into their performance, notably the Irishman James Burne who \"carries in his pocket, an ill-shaped doll, with a broad face, which he exhibits ... as giving utterance to his own childish jargon,\" and Thomas Garbutt.
The entertainment came of age during the era of the music hall in the United Kingdom and vaudeville in the United States. George Sutton began to incorporate a puppet act into his routine at Nottingham in the 1830s, followed by Fred Neiman later in the century,[7] but it is Fred Russell who is regarded as the father of modern ventriloquism. In 1886, he was offered a professional engagement at the Palace Theatre in London and took up his stage career permanently. His act, based on the cheeky-boy dummy \"Coster Joe\" that would sit in his lap and 'engage in a dialogue' with him was highly influential for the entertainment format and was adopted by the next generation of performers. A blue plaque has been embedded in a former residence of Russell by the British Heritage Society which reads 'Fred Russell the father of ventriloquism lived here'.[8]
The art of ventriloquism was popularized by Y. K. Padhye and M. M. Roy in South India, who are believed to be the pioneers of this field in India. Y. K. Padhye's son Ramdas Padhye borrowed from him and made the art popular amongst the masses through his performance on television. Ramdas Padhye's name is synonymous with puppet characters like Ardhavatrao[9] (also known as Mr. Crazy),[10] Tatya Vinchu[11] and Bunny the Funny which features in a television advertisement for Lijjat Papad, an Indian snack.[12] Ramdas Padhye's son Satyajit Padhye is also a ventriloquist.
The popularity of ventriloquism fluctuates. In the UK in 2010, there were only 15 full-time professional ventriloquists, down from around 400 in the 1950s and '60s.[13] A number of modern ventriloquists have developed a following as the public taste for live comedy grows. In 2007, Zillah & Totte won the first season of Sweden's Got Talent and became one of Sweden's most popular family/children entertainers. A feature-length documentary about ventriloquism, I'm No Dummy, was released in 2010.[14] Three ventriloquists have won America's Got Talent: Terry Fator in 2007, Paul Zerdin in 2015 and Darci Lynne in 2017.
Presenting simultaneous but spatially discrepant visual and auditory stimuli induces a perceptual translocation of the sound towards the visual input, the ventriloquism effect. General explanation is that vision tends to dominate over audition because of its higher spatial reliability. The underlying neural mechanisms remain unclear. We address this question via a biologically inspired neural network. The model contains two layers of unimodal visual and auditory neurons, with visual neurons having higher spatial resolution than auditory ones. Neurons within each layer communicate via lateral intra-layer synapses; neurons across layers are connected via inter-layer connections. The network accounts for the ventriloquism effect, ascribing it to a positive feedback between the visual and auditory neurons, triggered by residual auditory activity at the position of the visual stimulus. Main results are: i) the less localized stimulus is strongly biased toward the most localized stimulus and not vice versa; ii) amount of the ventriloquism effect changes with visual-auditory spatial disparity; iii) ventriloquism is a robust behavior of the network with respect to parameter value changes. Moreover, the model implements Hebbian rules for potentiation and depression of lateral synapses, to explain ventriloquism aftereffect (that is, the enduring sound shift after exposure to spatially disparate audio-visual stimuli). By adaptively changing the weights of lateral synapses during cross-modal stimulation, the model produces post-adaptive shifts of auditory localization that agree with in-vivo observations. The model demonstrates that two unimodal layers reciprocally interconnected may explain ventriloquism effect and aftereffect, even without the presence of any convergent multimodal area. The proposed study may provide advancement in understanding neural architecture and mechanisms at the basis of visual-auditory integration in the spatial realm.
The ventriloquism effect is intuitively explained by the spatial dominance of vision with respect to the other senses. But how this dominance is accomplished at the neural level is still an open question.
In the last decades, several studies have proposed Bayesian probabilistic models to account for the ventriloquism effect [10], [17], [18] and also aftereffect [19], [20] . Whereas these models successfully describe perceptual responses within the framework of the Bayesian inference, they lack to relate these responses to neural activity and neuron interconnections.
Results presented in Fig. 4 were obtained with the population vector metric. When we tested the other two metrics (the barycenter and the winner-takes-all metric), we found that the barycenter method provides results similar to the vector metric, whereas the winner-take-all metric provides unreliable values of ventriloquism (see Fig. S1 in Supporting Information). This justifies our adoption of the vector metric.
The previous results were attained assuming specific model parameters (see Table 1). However ventriloquism is a robust property of the model, when tested with different parameters values. Fig. 5 shows visual bias of sound location (same simulation as in Fig. 4) obtained by changing the value of one parameter at a time, while maintaining the others at their basal setting.
In order to explain the ventriloquism aftereffect, we assumed that lateral synapses are plastic and can be trained during experimental trials. In particular, we adopted a Hebbian rule with a threshold for the post-synaptic activity: excitatory synapses increase (up to a maximum saturation value) and the inhibitory synapses decrease (down to zero) in case of correlated input-output activity, provided that post-synaptic activity overcomes a given threshold. Furthermore, as often adopted in the neurocomputational literature [31], we implemented a normalization rule: the sum of excitatory and inhibitory synapses entering a given neuron must remain constant. Hence, if some excitatory synapses increase, other excitatory synapses must be depressed to maintain a constant excitatory synaptic input; similarly, if some inhibitory synapses decrease, other inhibitory synapses must be augmented to maintain a constant inhibitory synaptic input.
In this work we propose that a simple neural network, consisting of two spatially organized unimodal layers with different receptive fields and connections in spatial register can explain the ventriloquism effect. Moreover, Hebbian training of the lateral synapses within each layer can account for the ventriloquism aftereffect. The present model makes use of a minimum number of mechanisms to explain the origin of ventriloquism and the subsequent aftereffect phenomenon.
An important point is that the model does not impose strict constrains on RF dimensions for ventriloquism effect to occur. Indeed, results of sensitivity analysis evidence that the ventriloquism effect is quite robust when tested with different dimensions of the RFs: even a moderate difference is sufficient for the more localized stimulus to attract the less localized one. Moreover, experimental manipulations [10] show that the auditory stimulus can capture the visual one if the visual stimulus is spatially degraded. The model can simulate this effect very well, using a spatial input for the visual stimulus wider than for the auditory one (see Fig. 5H and Fig. S2 in Supporting Information). 153554b96e
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