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.

Effect of aversive learning on discrimination of faces

In her Msc thesis, Lea Kampermann shows that humans can perceptually discriminate faces better, when these are paired with an aversive outcome. This effect was specific to the face, which was paired with an aversive outcome and was not observed for the one which was kept neutral throughout the experiment. Furthermore the effect was strongest when these faces were presented at shorter durations (~.6 s) allowing participants to make no more than two fixations per trial.

Her thesis contains also a detailed account on the methodology for generating face-stimuli that are perceptually calibrated to form a two-dimensional similarity gradient with equal perceptual steps between faces. The methodology is an extension of work from Yue et al. (Vision Research, 2012). If you wish to use these stimuli for your experiment they are available upon request.

Perceptually calibrated set of faces according to a simple primary visual cortex forming a circular similarity gradient. Details on their production can be read in Msc Thesis of Lea (please contact any of us for a pdf) .