Investigating the Neural Basis of Audiovisual Speech Perception with Intracranial Recordings in Humans

Speech is inherently multisensory, containing auditory information from the voice and visual information from the mouth movements of the talker. Hearing the voice is usually sufficient to understand speech, however in noisy environments or when audition is impaired due to aging or disabilities, seeing mouth movements greatly improves speech perception. Although behavioral studies have well established this perceptual benefit, it is still not clear how the brain processes visual information from mouth movements to improve speech perception. To clarify this issue, I studied the neural activity recorded from the brain surfaces of human subjects using intracranial electrodes, a technique known as electrocorticography (ECoG). First, I studied responses to noisy speech in the auditory cortex, specifically in the superior temporal gyrus (STG). Previous studies identified the anterior parts of the STG as unisensory, responding only to auditory stimulus. On the other hand, posterior parts of the STG are known to be multisensory, responding to both auditory and visual stimuli, which makes it a key region for audiovisual speech perception. I examined how these different parts of the STG respond to clear versus noisy speech. I found that noisy speech decreased the amplitude and increased the across-trial variability of the response in the anterior STG. However, possibly due to its multisensory composition, posterior STG was not as sensitive to auditory noise as the anterior STG and responded similarly to clear and noisy speech. I also found that these two response patterns in the STG were separated by a sharp boundary demarcated by the posterior-most portion of the Heschl’s gyrus. Second, I studied responses to silent speech in the visual cortex. Previous studies demonstrated that visual cortex shows response enhancement when the auditory component of speech is noisy or absent, however it was not clear which regions of the visual cortex specifically show this response enhancement and whether this response enhancement is a result of top-down modulation from a higher region. To test this, I first mapped the receptive fields of different regions in the visual cortex and then measured their responses to visual (silent) and audiovisual speech stimuli. I found that visual regions that have central receptive fields show greater response enhancement to visual speech, possibly because these regions receive more visual information from mouth movements. I found similar response enhancement to visual speech in frontal cortex, specifically in the inferior frontal gyrus, premotor and dorsolateral prefrontal cortices, which have been implicated in speech reading in previous studies. I showed that these frontal regions display strong functional connectivity with visual regions that have central receptive fields during speech perception

On Cournot-Nash equilibria with exogenous uncertainty

A large body of literature has accumulated which examines how the optimal solution of an agent maximizing the expectation of a real-valued function, depending on a random parameterp and the agent's behaviorx, reacts to perturbations in the first and second moments ofp. Here, by an approximation valid for small uncertainty, we allow many agents and consider their behavior in a Cournot-Nash equilibrium. We also allowp to depend on the behaviors of the participating agents. We apply the analysis to two models, one of a Cournot oligopoly, the other of a cooperative of individuals where there is uncertainty in the return to communal work

The Kalai-Smorodinsky Bargaining Solution Manipulated by Pre-Donations is Concessionary

This study examines the manipulability of simple n-person bargaining problems by pre-donations where the Kalai-Smorodinsky solution is operant. We extend previous results on the manipulation of two-person bargaining problems to the n-person case and show that in a world where a prebargaining stage is instituted in which the bargainers may unilaterally alter the bargaining problem, bargainers with greater ideal payoffs transform the bargaining set into one on which the Kalai- Smorodinsky solution distributes payoffs in accordance with the Concessionary division rule of disputed property.Bargaining Solutions, Pre-donation, Kalai-Smorodinsky

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Taha Toros Arşivi, Dosya No: 142-Zekeriya-Yıldız-Sabiha Serte

Yorgun Savaşçı ve bilimsel tarih

Taha Toros Arşivi, Dosya No: 133-Kemal Tahir ve Yorgun SavaşçıUnutma İstanbul projesi İstanbul Kalkınma Ajansı'nın 2016 yılı "Yenilikçi ve Yaratıcı İstanbul Mali Destek Programı" kapsamında desteklenmiştir. Proje No: TR10/16/YNY/010

Tan olaylarından 55 yıl sonra demokrasinin neresindeyiz?:55 yıldır hiçbir şey değişmedi

Taha Toros Arşivi, Dosya No: 142-Zekeriya-Yıldız-Sabiha Serte

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Taha Toros Arşivi, Dosya No: 142-Zekeriya-Yıldız-Sabiha Serte

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Taha Toros Arşivi, Dosya No: 239-Pertev Boratav. Not: Gazetenin "Görüş" köşesinde yayımlanmıştır