Browsing by Subject "Temporal ventriloquism"
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Item Open Access Audiovisual interactions in time and spatial grouping principles of vision(2016-10) Öğülmüş, CansuMultisensory integration is often studied with intermodal con ict where either visual input dominates and alters the percept of simultaneous auditory input or the other way around. For instance, when put in con ict, visual stimuli can drive the perception of where a sound originates (spatial ventriloquism) [1, 2] whereas auditory stimuli can drive the perception of when visual events occur (temporal ventriloquism) [3, 4, 5] .These interactions make adaptive sense given the auditory system´s superior temporal resolution and the visual system´s superior spatial resolution [6]. Moreover, it was found that temporal ventriloquism can change the perceived speed of visual motion [7]. By taking advantage of this in uence of auditory timing on perceived speed, we investigated how audiovisual interactions in time (i.e., temporal ventriloquism) are modulated by the spatial grouping principles of vision. In our experiments, we manipulated spatial proximity, common fate and uniform connectedness between moving ashes. Observers compared the speed of motion between different auditory timing conditions. Our results revealed that auditory in uences on perceived speed were significantly modulated by only uniform connectedness. More specifically, we found that auditory effects on vision was significantly less when a horizontal gray connecting bar grouped multiple sequential moving ashes. When horizontally placed moving ashes were grouped with a vertical connecting bar, the degree of auditory in uences in time was significantly stronger compared to not grouped (control) and horizontal connecting bar conditions. The effect of auditory clicks on single apparent motion grouped with horizontal connecting bar was smaller relative to the not-grouped condition. In addition, our analysis on EEG activities revealed consistent trends in agreement with the behavioral results. Audiovisual interaction patterns were observed both earlier (around P1) and later (around N1 and P2). Less auditory capture over the horizontal connecting bar condition relative to the vertical connecting bar condition was observed around 50-100 ms (P1) on the frontal and temporal channels and around 200-300 ms (N1) on the frontal, central, temporal and occipital-parietal channels. The larger effect of sound over the single apparent motion without connecting bar condition was observed around 50-100 ms and 200-300 ms on the central channels and 200-300 ms on the occipital-parietal channels. The difference between the individual effects of inner and outer sound conditions was found to be less for the horizontal connecting bar condition relative to the vertical connecting bar condition over the frontal, temporal, central and occipital-parietal channels while less individual effects of the inner and outer sound conditions on the single apparent motion with horizontal connecting bar condition relative to the without connecting bar condition was only observed over the central channels and late time intervals of the occipital-parietal and temporal channels. Overall the individual effects of both sound conditions were consistently similar on the horizontal connecting bar condition (compared to the vertical connecting bar condition) for all ROIs and on the single apparent motion with horizontal connecting bar condition (compared to the no-connecting bar condition) over the central channels. In general, our findings here suggest that temporal ventriloquism effects exist in different spatial grouping conditions of vision, but they can be also modulated by certain intra-modal grouping principles such as uniform connectedness.Item Open Access Auditory modulation of spiking activity and local field potentials in area MT does not appear to underlie an audiovisual temporal illusion(American Physiological Society, 2018) Kafalıgönül, Hulusi; Albright, T. D.; Stoner, G. R.The timing of brief stationary sounds has been shown to alter the perceived speed of visual apparent motion (AM), presumably by altering the perceived timing of the individual frames of the AM stimuli and/or the duration of the interstimulus intervals (ISIs) between those frames. To investigate the neural correlates of this “temporal ventriloquism” illusion, we recorded spiking and local field potential (LFP) activity from the middle temporal area (area MT) in awake, fixating macaques. We found that the spiking activity of most MT neurons (but not the LFP) was tuned for the ISI/speed (these parameters covaried) of our AM stimuli but that auditory timing had no effect on that tuning. We next asked whether the predicted changes in perceived timing were reflected in the timing of neuronal responses to the individual frames of the AM stimuli. Although spiking dynamics were significantly, if weakly, affected by auditory timing in a minority of neurons, the timing of spike responses did not systematically mirror the predicted perception of stimuli. Conversely, the duration of LFP responses in β-and γ-frequency bands was qualitatively consistent with human perceptual reports. We discovered, however, that LFP responses to auditory stimuli presented alone were robust and that responses to audiovisual stimuli were predicted by the linear sum of responses to auditory and visual stimuli presented individually. In conclusion, we find evidence of auditory input into area MT but not of the nonlinear audiovisual interactions we had hypothesized to underlie the illusion. NEW & NOTEWORTHY We utilized a set of audiovisual stimuli that elicit an illusion demonstrating “temporal ventriloquism” in visual motion and that have spatiotemporal intervals for which neurons within the middle temporal area are selective. We found evidence of auditory input into the middle temporal area but not of the nonlinear audiovisual interactions underlying this illusion. Our findings suggest that either the illusion was absent in our nonhuman primate subjects or the neuronal correlates of this illusion lie within other areas.Item Open Access Auditory modulation of visual apparent motion with short spatial and temporal intervals(Association for Research in Vision and Ophthalmology, 2010) Kafalıgönül, Hulusi; Stoner, G.Recently, E. Freeman and J. Driver (2008) reported a cross-modal temporal interaction in which brief sounds drive the perceived direction of visual apparent-motion, an effect they attributed to “temporal capture” of the visual stimuli by the sounds (S. Morein-Zamir, S. Soto-Faraco, & A. Kingstone, 2003). Freeman and Driver used “long-range” visual motion stimuli, which travel over long spatial and temporal intervals and engage high-order cortical areas (K. G. Claeys, D. T. Lindsey, E. De Schutter, & G. A. Orban, 2003; Y. Zhuo et al., 2003). We asked whether Freeman and Driver’s temporal effects extended to the short-range apparent-motion stimuli that engage cortical area MT, a lower-order area with well-established spatiotemporal selectivity for visual motion (e.g. A. Mikami, 1991, 1992; A. Mikami, W. T. Newsome, & R. H. Wurtz, 1986a, 1986b; W. T. Newsome, A. Mikami, & R. H. Wurtz, 1986). Consistent with a temporal-capture account, we found that static sounds bias the perception of both the direction (Experiment 1) and the speed (Experiment 2) of short-range motion. Our results suggest that auditory timing may interact with visual spatiotemporal processing as early as cortical area MT. Examination of the neuronal responses of this well-studied area to the stimuli used in this study would provide a test and might provide insight into the neuronal representation of time.Item Open Access Temporal ventriloquism along the path of apparent motion: speed perception under different spatial grouping principles(Springer Verlag, 2018) Öğülmüş, Cansu; Karacaoğlu, Merve; Kafalıgönül, HulusiThe coordination of intramodal perceptual grouping and crossmodal interactions plays a critical role in constructing coherent multisensory percepts. However, the basic principles underlying such coordinating mechanisms still remain unclear. By taking advantage of an illusion called temporal ventriloquism and its influences on perceived speed, we investigated how audiovisual interactions in time are modulated by the spatial grouping principles of vision. In our experiments, we manipulated the spatial grouping principles of proximity, uniform connectedness, and similarity/common fate in apparent motion displays. Observers compared the speed of apparent motions across different sound timing conditions. Our results revealed that the effects of sound timing (i.e., temporal ventriloquism effects) on perceived speed also existed in visual displays containing more than one object and were modulated by different spatial grouping principles. In particular, uniform connectedness was found to modulate these audiovisual interactions in time. The effect of sound timing on perceived speed was smaller when horizontal connecting bars were introduced along the path of apparent motion. When the objects in each apparent motion frame were not connected or connected with vertical bars, the sound timing was more influential compared to the horizontal bar conditions. Overall, our findings here suggest that the effects of sound timing on perceived speed exist in different spatial configurations and can be modulated by certain intramodal spatial grouping principles such as uniform connectedness.