Topographically localised modulation of tectal cell spatial tuning by complex natural scenes

The tuning properties of neurons in the visual system can be contextually modulated by the statistics of the area surrounding their receptive field, particularly when the surround contains natural features. However, stimuli presented in specific egocentric locations may have greater behavioural relevance, raising the possibility that the extent of contextual modulation may vary with position in visual space. To explore this possibility we utilised the small size and optical transparency of the larval zebrafish to describe the form and spatial arrangement of contextually modulated cells throughout an entire tectal hemisphere. We found that the spatial tuning of tectal neurons to a prey-like stimulus sharpens when the stimulus is presented against a background with the statistics of complex natural scenes, relative to a featureless background. These neurons are confined to a spatially restricted region of the tectum and have receptive fields centred within a region of visual space in which the presence of prey preferentially triggers hunting behaviour. Our results suggest that contextual modulation of tectal neurons by complex backgrounds may facilitate prey-localisation in cluttered visual environments.Significance statementVisual neurons can have their responses contextually modulated by the statistics of the area surrounding the receptive field. However, the spatial organisation of these neurons throughout the visual system is virtually unknown. Here we give the first demonstration that zebrafish tectal cells exhibit contextual modulation when stimuli are presented against a complex background. We find these contextually modulated cells are topographically restricted to a region visual space where hunting routines are preferentially triggered. Furthermore, we show that the circuits that support contextual modulation develop independently of visual experience. These results suggest that the tectum contains hard-wired circuits that support contextual modulation and that this may improve the accuracy of prey localisation at the onset of hunting routines in cluttered visual environments.