Neurons in the primary visual cortex (V1) are sensitive to simple features of the visual scene such as contrast, spatial frequency or orientations. In higher mammals, they are organized into columns of orientationpreference, whereas such organization is absent in rodents. However, in both types of organization, neurons can be highly selective or poorly selective for a particular stimulus. In mouse V1, it has been shown that all stimuli are represented on the dendritic tree of single neurons. To

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... what extent this concept is applicable in higher mammals? In this review, we discuss possible models of integrating visual information from visual cortical neurons. In particular, how the modulation of the number of inputs and/or the frequency firing can explain the orientation selectivity in V1. Based on our findings and literature, we propose three different hypotheses namely the spatial summation, the temporal summation and the excitation-inhibition. In addition, we discuss the possible interactions between excitatory pyramidal neurons and inhibitory interneurons during stimulus processing. INTRODUCTION Modern technology in neuroscience has revealed a large amount of informative clues on how neural computations are performed in response to sensory stimulation. In particular, visual cortical neurons have been largely used as a model to investigate those computations. Optogenetic techniques, two-photon calcium imaging and electrophysiology shed light on the neuronal integration up to single cellular levels. In this opinion, we use the orientation selectivity as a paradigm to explain the synaptic integration of oriented inputs and their processing within the dendritic tree of visual neurons. Indeed, in relation to previous research work and results from electrophysiology, we discuss possible models of the integration of information