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New article "The Visual Input to the Retina during Natural Head-Free Fixation" published in The Journal of Neuroscience, 34(38): 12701-12715
pdf Abstract Head and eye movements incessantly modulate the luminance signals impinging onto the retina during natural intersaccadic fixation. Yet, little is known about how these fixational movements influence the statistics of retinal stimulation. Here, we provide the first detailed characterization of the visual input to the human retina during normal head-free fixation. We used high-resolution recordings of head and eye movements in a natural viewing task to examine how they jointly transform spatial information into temporal modulations. In agreement with previous studies, we report that both the head and the eyes move considerably during fixation. However, we show that fixational head and eye movements mostly compensate for each other, yielding a spatiotemporal redistribution of the input power to the retina similar to that previously observed under head immobilization. The resulting retinal image motion counterbalances the spectral distribution of natural scenes, giving temporal modulations that are equalized in power over a broad range of spatial frequencies. These findings support the proposal that “ocular drift,” the smooth fixational motion of the eye, is under motor control, and indicate that the spatiotemporal reformatting caused by fixational behavior is an important computational element in the encoding of visual information. |
New article "Motion Parallax from Microscopic Head Movements during Visual Fixation" published in Vision Research
M.Aytekin and M.Rucci (2012) http://dx.doi.org/10.1016/j.visres.2012.07.017 Abstract Under normal viewing conditions, adjustments in body posture and involuntary head movements continually shift the eyes in space. Like all translations, these movements may yield depth information in the form of motion parallax, the differential motion on the retina of objects at different distances from the observer. However, studies on depth perception rarely consider the possible contribution of this cue, as the resulting changes in viewpoint appear too small to be of perceptual significance. Here, we quantified the parallax present during fixation in normally standing observers. We measured the trajectories followed by the eyes in space by means of a high-resolution head-tracking system and used an optical model of the eye to reconstruct the stimulus on the observer’s retina. We show that, within several meters from the observer, relatively small changes in depth yield changes in the velocity of the retinal stimulus that are well above perceivable thresholds. Furthermore, relative velocities are little influenced by fixation distance, target eccentricity, and the precise oculomotor strategy followed by the observer to maintain fixation. These results demonstrate that the parallax available during normal head-free fixation is a reliable source of depth information, which the visual system may use in a variety of tasks. |
Our new article "Spatial perception and adaptive sonar behavior" published in JASA
Spatial perception and adaptive sonar behavior
Murat Aytekin, Beatrice Mao, and Cynthia F. Moss, "Spatial perception and adaptive sonar behavior" J. Acoust. Soc. Am. 128, 3788 (2010), DOI:10.1121/1.3504707 Here is the abstract: Bat echolocation is a dynamic behavior that allows for real-time adaptationsin the timing and spectro-temporal design of sonar signals in response to a particular task and environment. To enable detailed, quantitative analyses of adaptive sonar behavior, echolocation call design was investigated in big brown bats, trained to rest on a stationary platform and track a tethered mealworm that approached from a starting distance of about 170 cm in the presence of a stationary sonar distracter. The distracter was presented atdifferent angular offsets and distances from the bat. The results of this study show that the distance and the angular offset of the distracter influence sonar vocalization parameters of the big brown bat, Eptesicus fuscus. Specifically, the bat adjusted its call duration to the closer of two objects, distracter orinsect target, and the magnitude of the adjustment depended on the angular offset of the distracter. In contrast, the bat consistently adjusted its call rate to the distance of the insect, even when this target was positioned behind the distracter. The results hold implications for understanding spatial information processing and perception by echolocation.
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Group Anadolu performed Turkish Folk Music in the 29th Washington Folk Festival
On last Saturday, the 5th of June, I as a member of Group Anadolu, under the leadership of Husnu Aydogdu, performed in the Washington Folk Festival. Our group on that day consisted of Husnu Aydogdu, myself, Suphi Maruf, Sarah Olmstead (please take a look at her fundrasing page ), Alkan Donmez and Greg BenAvram. It was a great festival and we enjoyed playing to a large group of audience. |
Starting a new position in Boston University
I am joining APLAB directed by Dr. Michele Rucci as a postdoctoral researcher. The main focus of the laboratory is the role of the eye movements in visual perception, performance and development using psychophysical, computational and neuromorphic robotics methods. This focus well overlaps with my interest that is understanding the involvement of sensorimotor interactions in the development of perception and emergence/occurrence of percepts (a phenomenological approach to perception). More on my thoughts on this direction can be found:
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Got Married!
On May 3rd, 2009 Monika Megyesi and I are finally got married after 7 years of dating. The event took place at the home of Mary and Tilden Edwards. The ceremony performed by our dear friend Tilden H. Edwards, Jr, founder and senior fellow of Shalem Institute for Spirutual Formation, an Episcopal priest
and the author or editor of six books related to the spiritual life, in the presence of the family. Our 7-year journey together has been filled with joy and struggles of learning to live together and becoming more than we could ever be separately, thanks to our different background and experiences that helped enrich eachother's identity. The event was reflecting this fact: an Hungarian girl with Jewish decent, born in Romania and imigrated to Hungary, an expert in conflict management and a Muslim, Turkish boy, an engineer turned neuroscientist, married, on the other side of the world (USA), by an Episcopal priest whose love of God and people transcends beyond the construct of any individual religion and philosophy.  |
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