Noise destroys feedback enhanced figure-ground segmentation but not feedforward figure-ground segmentation

Hans Supèr,August Romeo,Marina Arall

doi:10.3389/fphys.2012.00274

Abstract

Figure-ground (FG) segmentation is the separation of visual information into background and foreground objects. In the visual cortex, FG responses are observed in the late stimulus response period, when neurons fire in tonic mode, and are accompanied by a switch in cortical state. When such a switch does not occur, FG segmentation fails. Currently, it is not known what happens in the brain on such occasions. A biologically plausible feedforward spiking neuron model was previously devised that performed FG segmentation successfully. After incorporating feedback the FG signal was enhanced, which was accompanied by a change in spiking regime. In a feedforward model neurons respond in a bursting mode whereas in the feedback model neurons fired in tonic mode. It is known that bursts can overcome noise, while tonic firing appears to be much more sensitive to noise. In the present study, we try to elucidate how the presence of noise can impair FG segmentation, and to what extent the feedforward and feedback pathways can overcome noise. We show that noise specifically destroys the feedback enhanced FG segmentation and leaves the feedforward FG segmentation largely intact. Our results predict that noise produces failure in FG perception.

Highlights

The task known as Figure-ground (FG) segmentation is the assignment of visual elements to either objects or background, and constitutes a primary step in visual perception
Visual features are detected by neurons by means of their feedforward defined classical receptive field, whereas contextual influences beyond the classical receptive field have been interpreted as the neural substrate of FG segmentation
The findings are in agreement with the results of a recent computational modeling study showing that feedback enhances FG segmentation (Supèr and Romeo, 2010, 2011; Supèr et al, 2010, see Supèr and Lamme, 2007a)

Summary

Introduction

The task known as Figure-ground (FG) segmentation is the assignment of visual elements to either objects or background, and constitutes a primary step in visual perception. In the primary visual cortex (V1), feedback projections covering large parts transmit extra-classical receptive field information (Angelucci et al, 2002), and are considered to be critical for FG segmentation (Lamme and Roelfsema, 2000). The findings are in agreement with the results of a recent computational modeling study showing that feedback enhances FG segmentation (Supèr and Romeo, 2010, 2011; Supèr et al, 2010, see Supèr and Lamme, 2007a) This enhancement was seen to occur by a change in cortical state (Le Masson et al, 2002; Supèr and Lamme, 2007a), i.e., a change in the firing pattern from a bursting into a tonic mode (Sherman, 2001). The results of our study predict that noise produces failure in FG perception

Methods

Results

Conclusion