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Many pathways in the developing visual system are restructured and become highly organized even before vision occurs. Yet the developmental processes underlying the remodeling of visual connectivity are crucially dependent on retinal activity. Surprisingly, the immature and light-insensitive retina spontaneously generates a pattern of rhythmic bursting activity during the period when the connectivity patterns of retinal ganglion cells are shaped. Spatially, the activity is seen to spread across the retina in the form of waves that bring into synchrony the bursts of neighboring cells. Waves are present in the developing retina of higher and lower vertebrates, which suggests that this form of activity may be a common and fundamental mechanism employed in the activity-dependent refinement of early patterns of visual connections. Unraveling the cues encoded by the waves promises to provide important insights into how interactions driven by specific patterns of activity could lead to the modification of connectivity during development.
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Spontaneous retinal waves Multielectrode recordings The following movies show multielectrode recordings of waves taken at two different ages in ferret retinae (Meister et al., 1991). Each circle within the hexagonal array represents one ganglion cell, and the intensity of the circle is proportional
to the burst rate of the cell. The total width of the hexagonal array is about 500 um. Each frame is taken at 0.5 second intervals. Waves are present at postnatal day zero (P0): By P30, just before eye-opening, the waves are replaced by adult-like background maintained activity, as shown by a 15 second sequence (MOV file). Optical imaging Optical imaging of ferret waves (MOV file) taken at P2 using the
fura-2 calcium indicator (Feller et al., 1996). The field of view in this image
is 1.4 mm by 1.2 mm. The entire sequence lasts 34 seconds. The first image is
the background image; subsequent frames are produced by subtracting the current
image from the previous image. Rises in intracellular calcium are indicated by
decreasing intensity. Optical imaging of P0 mouse waves [spiralcollision (MOV files)]
taken using the fura-2 calcium indicator. The first frame is the background
image. The optic disc can be seen (as a hole) in the top left of the first frame.
Subsequent frames are subtracted from the previous frame. The field of view
is approximately 4 mm2. One frame is taken every two seconds. Rises
in intracellular calcium are indicated by increasing intensity. Acknowledgements Thanks to Marla Feller for providing the movie of ferret waves.
Burst 1 (MOV file)
Burst 2 (MOV file)
Burst 3 (MOV file)
Burst 4 (MOV file)
Burst 5 (MOV file)