Cone inputs to murine striate cortex

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.The murine retina contains middle (M) and ultra-violet (UV) sensitive cone opsins, which could provide the mouse with a form of colour vision. These two cone opsins, however, are distributed in different regions of the retina; the M- and UV-cone opsins are more common in the superior and ventral retina, respectively, which complicates comparing their responses in the same areas of visual space, a logical requirement for colour vision. In addition, many murine cones seem to express both M- and UV-cone opsins [1,2], which is also a handicap for colour vision. Nevertheless behavioural studies indicate that mice have colour vision [3] and anatomical evidence exists for UV cone specific bipolar cells [4], another requirement for colour vision. We have also found evidence that some retinal ganglion cells receive inputs exclusively from UV-cones [5] supporting the latter anatomical findings. Therefore the question of colour vision in the mouse deserves further study. To do this, we have recorded responses fr