On the Specific Role of the Occipital Cortex in Scene Perception

In recent years there has been mounting scientific excitement about the perception of scenes containing more realistic and complex stimuli than simple objects or drawings. Visual recognition of scenes is a fast, automatic and reliable process. Experimental studies have shown that complex natural scenes can be categorized in a very short time (under 150 ms [1]), suggesting a simple and efficient coding process. Many studies have attested to the importance of the Fourier components of images in scene categorization. In terms of signal representation, an image can be expressed in the Fourier domain as amplitude and phase spectra [2-5]. The amplitude spectrum highlights the dominant spatial scales (spatial frequencies) and the dominant orientations of the image, while the phase spectrum describes the relationship between spatial frequencies. It is now well established that the primary visual cortex is mainly dominated by complex cells which respond preferentially to orientations and spatial frequencies [6-8]. Simulation and psychophysical experiments have shown that information from low/medium frequencies of the amplitude spectrum is sufficient to enable scene categorization [9, 10]. These data support current influential models of scene perception [11-14].