Surround Modulation Properties of Tectal Neurons in Pigeons Characterized by Moving and Flashed Stimuli.

Xiaoke Niu,Minjie Zhu,Shuman Huang,Li Shi,Zhizhong Wang

doi:10.3390/ani12040475

Xiaoke Niu, Minjie Zhu + Show 3 more

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https://doi.org/10.3390/ani12040475

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Abstract

Simple SummarySurround modulation is a basic visual attribute of sensory neurons in many species and has been extensively characterized in mammal primary visual cortex, lateral geniculate nucleus, and superior colliculus. Little attention has been paid to birds, which have a highly developed visual system. We undertook a systematic analysis on surround modulation properties of tectal neurons in pigeons (Columba livia). This study complements existing studies on surrounding modulation properties in non-mammalian species and deepens the understanding of mechanisms of figure–background segmentation performed by avians.Surround modulation has been abundantly studied in several mammalian brain areas, including the primary visual cortex, lateral geniculate nucleus, and superior colliculus (SC), but systematic analysis is lacking in the avian optic tectum (OT, homologous to mammal SC). Here, multi-units were recorded from pigeon (Columba livia) OT, and responses to different sizes of moving, flashed squares, and bars were compared. The statistical results showed that most tectal neurons presented suppressed responses to larger stimuli in both moving and flashed paradigms, and suppression induced by flashed squares was comparable with moving ones when the stimuli center crossed the near classical receptive field (CRF) center, which corresponded to the full surrounding condition. Correspondingly, the suppression grew weaker when the stimuli center moved across the CRF border, equivalent to partially surrounding conditions. Similarly, suppression induced by full surrounding flashed squares was more intense than by partially surrounding flashed bars. These results suggest that inhibitions performed on tectal neurons appear to be full surrounding rather than locally lateral. This study enriches the understanding of surround modulation properties of avian tectum neurons and provides possible hypotheses about the arrangement of inhibitions from other nuclei, both of which are important for clarifying the mechanism of target detection against clutter background performed by avians.

Highlights

The fundamental nature of surround modulation has been fairly described in mammal primary visual cortex (V1), lateral geniculate nucleus (LGN), and superior colliculus (SC), and the existing studies have concluded that the surround modulation in V1 and LGN was selective to visual features, such as orientation and spatial frequency [20,21]
We recorded a total of 244 multi-units (Table 1) with an obvious classical receptive field (CRF) border from the middle layer OT of 17 pigeons
The results of our study showed that surround suppression was more intense when the surrounding of CRF of tectal neurons was fully stimulated compared to partially stimulated, which may be used to explain the habitation of birds who are more likely to focus on small targets in a cluttered scene

Summary

Introduction

The visual response to classical receptive field (CRF) stimuli can be modulated by the extra-classical receptive field (eCRF), where stimulating alone cannot elicit spikes [1,2,3]. This phenomenon is called “surround modulation”, which is generally suppressive [4,5,6,7,8,9,10,11,12,13]. As far as we know, there lacks detailed and systematic analysis of surround modulation properties of tectal neurons in pigeons

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