The perception of complex motion patterns, which requires integration of multiple moving elements, is impaired in a range of developmental disorders. In the brain, processing of complex motion signals is handled by a dedicated visual pathway that includes primary visual cortex (V1) and a higher order motion area. Very little is known about the mechanisms that determine its development, as is the case for most higher level visual functions. Here, we will test one factor likely to play a major role in its development, visual experience. We will investigate when visual experience is required for the motion pathway to develop, and what kind of visual experience is required. We will perform these experiments in the ferret, which has become a major animal model for visual development because of its relative immaturity at birth. The ferret?s motion pathway includes V1 and area PSS, a higher order visual area. We will investigate the influence of visual experience on this pathway in 2 sets of experiments. In the first set of experiments, we will investigate during which time visual experience is required for the motion pathway to develop normally. To this end, we will raise animals either normally, or withhold visual experience for certain time periods. We will then investigate how lack of visual experience impacts the pathway?s function by measuring direction selectivity in V1 and PSS, and signatures of motion integration in V1 and PSS. These experiments will be performed using extracellular recordings in PSS, and two-photon imaging combined with retrograde tracers in V1 to selectively study the responses of PSS- projecting V1 neurons. We will also perform behavioral experiments in adult animals to investigate whether there are lasting consequences on motion perception. We expect to find 2 critical periods during which vision is required, an initial period for the development of direction selectivity, and a later period for motion integration. This would demonstrate that visual experience has a sustained impact on the developing visual system. In a second set of experiments, we will test which kinds of visual experience are required for motion pathway development by testing the impact of different kinds of visual experience on the immature motion pathway. More precisely, we will determine whether complex motion stimuli containing multiple moving elements, simple moving stimuli containing only one moving element, or static stimuli can enhance immature direction selectivity and motion integration. We expect to find that only simple motion, but not static stimuli, can enhance direction selectivity. We also expect to find that complex motion, but none of the other stimuli can enhance motion integration. These findings would demonstrate that different visual functions require different kinds of visual experience for their development. In summary, our experiments would be a systematic investigation of how visual experience impacts the development of an important higher vision pathway. They would contribute important insights into the mechanisms shaping the development of higher visual cortex, and may help identify reasons for the deficits in motion processing observed in a range of developmental disorders.
Deficits in global motion perception have been observed in a range of developmental disorders. Here, we investigate how visual experience impacts the development of the motion pathway, which handles these complex motion computations. This will result in a better understanding of the factors influencing the development of the motion pathway, and in general provide much needed insights into the development of higher visual functions.
