Murat Aytekin

Posdoctoral Researcher
Auditory Neurethology Laboratory
University of Maryland
College Park, MD 20742

Contact Information
Degrees, Positions
Publications
Research Interests
Resume

Music
Conflict Resolution

THIS PAGE WILL NOT BE UPDATED PLEASE SEE MY NEW PAGE AT www.murataytekin.org

We have to remember that what we observe is not nature in itself but nature exposed to our method of questioning

Werner Karl Heisenberg

Contact Information

E-mail: aytekin@umd.edu
Telephone: 301-405-0374 (batlab)

Degrees, Positions

Bachelors in Electronics and Telecommunication Engineering	Yildiz Technical University, Istanbul-TURKEY	1994
Masters in Telecommunication	Yildiz Technical University, Istanbul-TURKEY	1998
Ph.D. in Neurosciences and Cognitive Sciences	University of Maryland, College Park	2007
Post Doctoral Fellow	Institute for System Research, Univ. of Maryland	2007-

Research Interests

The big picture

My research interests are driven by a single question: what makes biological systems different from the other artificial and natural systems? Pursuit of this question is essential to understand cognition, consciousness and "self" -- terms that are still mysterious to us. Even the most “intelligent“ robots are only crude models of their living counterparts. Due to lack of sufficient complexity a robot is incapable of generating “meaning” from its experiences: It is perfectly happy if it is sitting on the surface of the Mars digging its wheels to the sand without moving an inch, or exposing a rock surface for evidence of life (can’t say the same for the engineers in the mission room, however). The “meaning” of the robot’s actions are to its observers (or designers) that are outside of it. In fact we can probably argue that the robot and the user together make a system that fits to criteria of “being intelligent” in the sense that a living system would. Hence, we are missing something/s that are essential and fundamental in the making of living systems.

Why should we care? We should because, at the most, our ever growing demand for systems that are capable of functioning in complex environments require engineering solutions that will most likely be very similar to biological systems in terms of their functional structure. At the least, they can be a source of inspiration to learn and built systems that can generate, gather, categorize information and learn, infer and adapt to continue to function.

The symptom I have given above is well known and one of the most debated issues in artificial intelligence, psychology and other related areas. A good term for it is “the grounding problem” as in symbol grounding in psychology, and linguistics. Understanding how living systems build symbols that represent their experiences is one of the key steps to cross the gap between a living-engineered system and a robot. A second step is figuring out "what a living system is". Surprisingly, the first question seems to be easier to answer since it lends itself to experimental questioning (see my dissertation work or the book). The second question, however, require new approaches and lots of questioning of our standard assumptions. Some new approaches have been introduced under variety of disciplines; such as general system theory, relational biology and complexity theory. A single theme that emerges from these efforts is that the living systems are complex. A complete description of a complex system cannot be obtained by reductionist approaches. For the similar reasons theories of classic physics are also not sufficient (a good discussions of these issues can be found in Robert Rosen’s Life Itself).

My current and future research goal is to understand the functional organization of living systems, learning more about them from the perspective of complex systems. Concepts such as, emergence, self-reference, agency, adaptation, evolution and organizational closure and how they relate to living systems are among my interests. Organizational closure carries particular importance, for, it has been claimed to be a necessary, if not sufficient, for a system to be living. Interesting conclusions follow from this statement on the computability of the living systems (see Life Itself). Amongst my interests are the origin and the meaning of terms such as measurement (sensing), information, anticipation, decision, all of which only meaningful within a living system, can be listed. In addition, I put significant effort to understand the mathematical concepts; circular hierarchy, non-well founded set theory and category theory, for their relation to the concept I listed above.

Current Research in Echolocation and Spatial Perception

My current research involves experiments that are designed to understand adaptive control of sonar vocalization by echolocating bats, as they track an approaching prey in space in the presence of multiple interfering objects. The time-frequency structure as well as the temporal patterns of sonar vocalizations, combined with measurements of the sonar beam patterns reveal clues on how bats build and maintain spatial representation of their environment, control flow of spatial information and spatial attention.

I also participate in a project that aims to understand integration of the information received from consequent sonar vocalizations to discriminate objects by echolocating bats.

Past Research

As being a biological airborne sonar system a bat accomplishes target detection, identification, localization, tracking and finally capturing or avoiding. Engineered radar/sonar systems designed to realize only a subset of these functions in a limited capability. Bats seem to be very adaptive to the changing environmental conditions in degree to which engineered systems currently cannot achieve. In order to design systems that can be capable behaving in complex environments, bats could be ideal model system to study.

My research in bat echolocation is mainly in two related directions: Bats monitor their environment by making ultrasonic vocalizations and listening to echoes reflected from objects in the scene. Localizing the position of an object is essential for bats’ survival. Echoes acoustically interact with the head and external ear in a direction-dependent sense. The transformation as a result of this interaction creates the physical cues necessary to localize the source of the echo. The direction dependent transformations can simply be modeled as time-independent transfer functions of linear systems. The project I was involved in aims to measure and analyze these transfer functions, also known as head related transfer functions (HRTF), to understand more about sound localization by bats. I investigated the cues for sound localization that are likely to be used by evaluating frequency structure of the HRTFs. Hypothesis as a result of these investigations are tested via psychoacoustical experiments involving echolocating bats. Some interesting results of this research can be found here.

I was also employing computational methods to understand how the auditory system might compute sound localization. An example of these efforts is a binaural model for sound localization based on the bat HRTF to show that bats can use interaural level difference (ILD) cues to localize sound sources. Pursuing this avenue brought up an interesting question which motivated the computational part of my research. How an initially naïve, - unfamiliar to spatial nature of the sound - animal could learn to localize sound sources? Unlike the common approaches in sound localization modeling that assume availability of the acoustic cues for sound location, my approach attempted to circumvent the need for this assumption and ground the problem of auditory space learning. This approach employs sensorimotor contingencies for the learning of the auditory space. More detail about this approach and its motivation can be found here (see also a related lay language paper here).

The second set of studies aimed to understand the spatial properties of the bats' outgoing sonar calls. The goal of these studies was to measure the sonar beam profile across the frequency range of 20 kHz to 100 kHz from a freely behaving echolocating bat. Unlike the earlier studies on this species this study employs a different approach which allows sonar beam pattern measurements without requiring restraining of the bat and electrical stimulation of the brain stem to elicit sonar vocalizations. My preliminary studies suggest that the outgoing ultrasound beamshape of a bat was not constant but varies from vocalization to vocalization. Follow up studies are focusing on how the sonar beamshape changes and whether or not this change is controlled by the bat and if so what are the implications for echolocation.

Publications

BOOKS

M. Aytekin, Hearing Where Things Are: Sound localization by echolocating bats, VDM-Verlag, Saarbrucken-Germany. ISBN: 978-3-639-09933-1

JOURNALS

M. Aytekin, C.F. Moss and J. Z. Simon (2008), A sensorimotor Approach to Sound Localization, Neural Computation, Vol. 20, No. 3: 603–635. [PDF]

M. Aytekin, E. Grassi, C.F. Moss and M. Sahota (2004), The Head-related Transfer Function Reveals Binaural Cues For Sound Localization J. Acoust. Soc. Am. 116(6). [PDF]

CONFERENCE

Talks

M. Aytekin, C.F. Moss and J. Z. Simon (2007), Sound localization by echolocating bats: Are auditory signals enough?, 154^th ASA Meeting, New Orleans, LA

Posters

M. Aytekin, C.F. Moss “A sensorimotor model of sound localization in the echolocating bat, Eptesicus fuscus” ARO 2005 Mid-winter Meeting.

B. Falk, T. Williams, M. Aytekin, K. Ghose and C.F. Moss "Texture discrimination by echolocation: acoustics and behavior" Society for Neuroscience, 2005 Annual Meeting.

M. Aytekin, C.F. Moss “Interaural Level Difference Based Sound Localization by Bats” Society for Neuroscience, 2004 Annual Meeting.

M. Aytekin, C.F. Moss “Sound localization with binaural cues in echolocating bat, Eptesicus fuscus” 1^st International Conference on Acoustic Communication by Animals.

M. Aytekin, C.F. Moss “A Neural Network Sound Localization Model of Echolocating Bat, Eptesicus fuscus” ARO 2002 Mid-winter Meeting

M. Aytekin, E. Grassi, M. Sahota, C.F. Moss "Acoustic transfer function of the echolocating bat, Eptesicus fuscus" ARO 2001 Mid-winter Meeting.

THESIS

"Direction of Arrival Estimation and Spatial-Temporal Filtering with Adaptive Sensor Arrays" (M.S. Thesis, Yildiz Technical University, 1998)

"Sound Localization by Echolocating Bats" (Ph.D. Thesis, University of Maryland , 2007)

My References

University of Maryland