Selim Onat

My main occupation is Neuroscience.

In the past, I have been interested on how the visual system processes natural scenes. To this end, I have recorded naturalistic movies using micro-cameras carried by cats while they were actively exploring a natural environment. I used these movies to train neuronal networks in an unsupervised manner and compared learnt features to the known properties of neurons in visual cortex. I also used these videos as stimuli during physiological recordings to gain insights on the principles of natural signal processing in the visual cortex.

Recently, I started working on how humans make generalizations based on what they have previously learnt. To this end, I am using a variety of methodologies including fMRI (1), autonomous (2), as well as eye-movement recordings (3). This research emanates from the well-established field of "stimulus generalization" following mainly the "lineage" of Hovland, Hull and Roger Shepard (4), and including the more recent computational work of Josua Tenenbaum (5). Furthermore, it integrates work on anxiety disorders, as it is believed that these mechanisms are impaired in people suffering from anxiety problems.

Real-Time Halftoning with Perfect Circles

How to transform an image in real-time into an array of perfect circles (or other geometrical shapes) with their diameters proportional to the local image brightness below the circle?

This is classically known as halftoning and one of the most ancient digital image manipulation methods, still used today in printing business.

I managed to do this using Quartz Composer, here is an example video. In this video, the resolution i.e. the number of circles used, changes over time. Video starts with black and white circles, continues with circles colored with original pixel values and finishes with random colored circles. It is all done in real time without any noticeable delay.


Perfect for VJing purposes. When real-timing is not necessary the content of the video can be a political figure for example...

Halftoning AngelaMerkel from sonat on Vimeo.

The concept can be generalized to other politicians or other half-toning shapes...

Halftoning Politicians from sonat on Vimeo.

Halftoning AngelaMerkel Hearts from sonat on Vimeo.

Cross modal integration with auditory modality could be implemented by adding a noise to the diameter of the circles that is proportional to the amplitude of the instantaneous sound signal..