Talking Faces by Solsken

The overarching theme of our research is to understand how the circuits in the mammalian brain make sense of incoming sensory information as meaningful collections of objects and background.

We use behavioral, electrophysiological, optical and viral targeting approaches to study this question.

Drawing of Ibn al-Haytham
Ibn al-Haytham (public domain)

One thousand years ago, Ibn al-Haytham (Alhazen) wrote in his Book of Optics that any perceptual act beyond the passive apprehension of light requires judgement, because the information received by the eyes is typically ambiguous. It is quite remarkable that this Arab polymath, without any notion of modern technology (computers, virtual reality, movies…), understood that perception requires a series of judgements that happen so fast that we are typically unaware of them!

Necker cube

You can see this process in action when you stare at the Necker cube on the right. Notice that your perception flips back and forth between alternative interpretations: sometimes you see the blue surface as the front of the cube, and at other times, as the back of the cube. This example demonstrates how perception is a constructive process that happens in your brain – the visual information on your screen does not change.

Such computations are important beyond the visual system. Consider the myriad possible soundscapes that you may encounter. The brain must reconstruct these from the vibrations of your ear drums – a daunting task! This problem has famously been compared by Albert Bregman to trying to understand the location and movement of boats on a lake by only looking at the motion of water in two narrow channels on the side of the lake. One important strategy that the brain uses is to compare the sounds that arrive at each ear (binaural hearing). In prior work we have studied how neural coincidence detection contributes to binaural computations.

In our laboratory we study the neural mechanisms that underlie such processes of perceptual organization. We employ a range of methods, including high-channel count electrophysiology, optical methods including optogenetics, and viral targeting approaches in behaving animals.

Our long-term goal is to reveal fundamental insights into the organization and function of these neural circuits in the brain, at a mechanistic level. This knowledge is required to better understand conditions in which perceptual organization fails, such as schizophrenia or agnosia.

Border ownership assignment

A recent interest in our lab is the circuit in the brain that assigns visual borders to foreground areas. The result of this assignment is that borders in visual scenes are perceived to be owned by foreground objects (border ownership). Rudiger von der Heydt and colleagues discovered that neurons in early visual areas are often selective for border ownership. Because these signals appear within ~20 milliseconds after response onset, it is thought that they may drive the segmentation of visual scenes into objects and background.

We recently discovered that border ownership signals in visual cortical area V4 are organized in columns in which they are computed first by neurons in deep layers. This supports the hypothesis that this computation relies on feedback from higher areas.

Neuron in area V4 selective for border ownership

Border ownership column

Deep layer neurons carry earliest border ownership signals

Modified from Franken and Reynolds, eLife (2021)

Selected literature

Bregman, A. S. (1981). Asking the ‘‘what for’’ question in auditory perception. In M. Kubovy, & J. Pomerantz (Eds.), Perceptual organization (pp. 99–118). Hillsdale, NJ: Routledge.

Franken, T.P., Reynolds, J.H. (2021) Columnar processing of border ownership in primate visual cortex eLife 10:e72573.

Franken, T.P., Bondy, B.J., Haimes, D.B., Goldwyn, J.H., Golding, N.L., Smith, P.H., Joris, P.X. (2021) Glycinergic axonal inhibition subserves acute spatial sensitivity to sudden increases in sound intensity eLife 10:e62183

Franken, T.P., Roberts, M.T., Wei, L., Golding, N.L., and Joris, P.X. (2015). In vivo coincidence detection in mammalian sound localization generates phase delays. Nature Neuroscience. 18(3): 444-452.

Vormstein-Schneider, D., Lin, J.D., Pelkey, K.A., Chittajallu, R., Guo, B., Arias-Garcia, M.A., Allaway, K., Sakopoulos, S., Schneider, G., Stevenson, O., Vergara, J., Sharma, J., Zhang, Q., Franken, T.P., Smith, J., Ibrahim, L.A., M Astro, K.J., Sabri, E., Huang, S., Favuzzi, E., Burbridge, T., Xu, Q., Guo, L., Vogel, I., Sanchez, V., Saldi, G.A., Gorissen, B.L., Yuan, X., Zaghloul, K.A., Devinsky, O., Sabatini, B.L., Batista-Brito, R., Reynolds, J., Feng, G., Fu, Z., McBain, C.J., Fishell, G., Dimidschstein, J. (2020) Viral manipulation of functionally distinct interneurons in mice, non-human primates and humans. Nature Neuroscience. Aug 17. PubMed PMID: 32807948.

Wagemans, J. (Ed.) The Oxford handbook of perceptual organization (2015). Oxford, UK: Oxford University Press.

Zhou, H., Friedman, H.S., von der Heydt, R. (2000). Coding of border ownership in monkey visual cortex. J Neurosci. 20(17):6594-6611.