Figure 1.

dLGN and cortical responses to natural movies through closed eyelids. A, Short movies were constructed that mimicked the spatiotemporal visual stimulation resulting from a typical neonatal ferret head movement. Temporal parameters for the movies were based on video footage of ferret kits (P18-24) behaving in their home cage environment (see Materials and Methods). In each movie, this behavior was simulated with a sequence of digital images from the home cage, each image representing a rotation of 10°. To record spontaneous activity, a blank screen at the mean luminance of the digital images (blank) was presented for 5.5 sec at the start of each movie sequence. For analysis, each movie sequence was divided into two parts, the spontaneous period and the movie period. The movie period encompassed the simulated head movement and ended four frame lengths (i.e., 0.44 sec) into the final frame. The spontaneous period matched the movie period in length but was taken from the middle of the blank. B, Examples of dLGN responses when movie stimuli were presented to the closed eyelids. Raster plots are shown for three different dLGN cells recorded 9 d before the eyes open. Each dot represents a single spike. All of the cells show modulated responses during the movie period but not during the spontaneous period (indicated by shaded regions). Stated at the top of each raster are the age, the cell type, and the movie code. C, Movie responses through closed eyelids for three different cortical cells recorded at P24. As in the dLGN, cortical cells respond strongly during the movie period but not the spontaneous period. Phase-locked spikes between 0 and 1 sec of the movie rasters are responses to the onset of the blank screen. Phase-locked spikes between 6 and 7 sec are responses to the onset of the first frame of the movie. None of these spikes were part of the spontaneous period or movie period and, therefore, were not included in any analyses.