Eye movements while viewing coarse and fine image information B Nordhjem1, C K Petrozzelli1, N Gravel2, R Renken3, F Cornelissen1 |
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1Laboratory of Experimental Ophthalmology, University Medical Center Groningen, Netherlands |
| Neurons in early visual regions show selectivity for different spatial frequencies (SF) and also many extrastriate areas show SF preferences. Yet, it is still unclear how we extract information from different SF in order to support high-level image recognition. Eye-movements are an integral part of normal visual behaviour and their characteristics may provide clues towards the sampling processes taking place during natural viewing. Here, observers freely viewed images of objects, faces, and natural scenes while their eye-movements were tracked. The original image and two manipulated versions were shown: either the low SF or high SF were kept intact, while the remaining frequencies were phase-scrambled. In line with coarse-to-fine models, we expected a bias towards relatively short-fixations and long-saccades when viewing low-SF-intact images (LSFi) and towards long-fixations and short-saccades for high-SF-intact images (HSFi). Contrary to this, fixations on LSFi were longer compared to those on HSFi. Saccade amplitude did overall not depend on SF scrambling. Fixations were biased towards the centre of LSFi, while on HSFi these were more distributed. This suggests the sampling of larger regions for low SF compared to high SF information. Our results have implications for the interpretation of fixations and saccades within the coarse-to-fine framework. |
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