Cortical cell orientation selectivity fails to develop in the absence of ON-center retinal ganglion cell activity

Abstract

Neuronal activity is necessary for the normal development of visual cortical cell receptive fields. When neuronal activity is blocked, cortical cells fail to develop normal ocular dominance and orientation selectivity. Patterned activity has been shown to play an instructive, rather than merely permissive, role in the segregation of geniculocortical afferents into ocular dominance columns. To test whether normal patterns of activity are necessary to instruct the development of cortical orientation selectivity, we studied ferrets raised without ON-center retinal ganglion cell activity. The ON-center blockade was produced by daily intravitreal injections of DL-2-amino-4-phosphonobutyric acid (APB). Effects of this treatment on the development of orientation selectivity in primary visual cortex were assessed using extracellular electrode recordings and optical imaging. In animals raised with an ON-center blockade starting after visual cortical cells are visually driven but still poorly tuned for orientation, cortical cell responsivity was maintained, but no maturation of orientation selectivity was seen. No recovery of orientation tuning was seen in animals treated with APB during the normal period of orientation development and then allowed several months of development without treatment. These results suggest that patterns of neuronal activity carried in the separate ON- and OFF-center visual pathways are necessary for the development of orientation selectivity in visual cortical neurons of the ferret and that there is a critical period for this development.

Fig. 1.

Eye diameter and body weight of developing ferrets. A, Eye diameter measured from postmortem normal ferrets. These eye diameters were used to calculate the amount of APB to be injected to produce the desired vitreal concentration (see Materials and Methods). B, Ferret growth rates were unaffected by APB injections. Round symbols show weights of ferrets undergoing APB injections (n = 42).Square symbols show the mean weights of normal age-matched controls (n = 5). Error bars indicate the SD.

Fig. 2.

Intravitreal APB injections silence ON-center activity in ferret LGN but leave OFF-center activity intact.A, PSTHs showing ON-center responses recorded in PND 28 ferret LGN lamina A. Left, Response before eye injection. Right, Response at the same location after the injection of APB sufficient to produce a vitreal concentration of 700 μm APB into the contralateral eye. B, PSTHs showing OFF-center responses recorded in PND 28 ferret LGN lamina A1. Left, Response before eye injection.Right, Response at the same location after the injection of APB sufficient to produce a vitreal concentration of 700 μm APB into the ipsilateral eye. C, PSTHs showing responses in ON (left) and OFF (right) leaflets in lamina A of the LGN from an animal treated with binocular 700 μm APB at PND 28–50.

Fig. 3.

ON-center blockade starting at PND 21 prevents the development of cortical orientation maps. A, No orientation-specific activity is seen in optical imaging of visual cortex in a ferret treated with 350 μm APB at PND 21–48. Responses to four different orientations of moving square wave gratings (see Materials and Methods) are shown. 0° is horizontal. For each map, caudal is up, and medial is to theleft. Scale bar, 1 mm. B, No orientation-specific activity is seen in optical imaging of visual cortex in a ferret treated with 700 μm APB at PND 21–52. All conventions as in A. C, Normal PND 51 orientation activity maps are shown for comparison. All conventions as in A.

Fig. 4.

Controls to rule out retinal damage from injections. A, Nissl-stained sections through retina from a ferret receiving daily intravitreal injections of 700 μm APB at PND 21–52 (left) and normal age-matched control (right) appear identical.gcl, Ganglion cell layer; ipl, inner plexiform layer; inl, inner nuclear layer;opl, outer plexiform layer; onl, outer nuclear layer. Scale bar, 50 μm. B, PSTHs of LGN activity recorded on PND 52 in lamina A of a ferret treated with 700 μm APB at PND 21–50. Both ON- and OFF-center activity appear normal. C, Normal layout and intensity of orientation maps (Chapman et al., 1996; Chapman and Bonhoeffer, 1998) is seen in visual cortex of a ferret treated with 0.9% daily intravitreal injections matched in volume to APB injections. All conventions as in Figure 3A.

Fig. 5.

Total ON-center blockade started at PND 28 prevents orientation selectivity development; part-time blockade reduces or delays development. A, No orientation-specific activity is seen in optical imaging of visual cortex in a ferret treated with 700 μm APB at PND 28–52.B, Faint orientation activity maps with normal layouts are seen in ferrets treated with 350 μm APB at PND 28–50. All conventions as in Figure 3A.

Fig. 6.

ON-center blockade prevents development of orientation selectivity in single cells. Orientation selectivity distributions for single cells recorded in animals treated with 700 μm APB starting at PND 28 are compared with those from normal postnatal week 4 (PNW4) ferrets, normalPNW7-adult ferrets, and ferrets treated with intra-cortical TTX infusion starting at PND 28 (data from all animals other than APB-treated are from Chapman and Stryker, 1993). Cumulative percentages of cells at each OSI are shown. The distribution for APB-treated animals is statistically indistinguishable from those for normal postnatal week 4 or TTX-treated animals (Mann–WhitneyU test; p > 0.25).

Fig. 7.

Critical period for orientation selectivity development. A, Orientation selectivity is unaffected by ON-center activity blockade begun after orientation selectivity is mature. Normal layout and intensity of orientation maps (Chapman et al., 1996; Chapman and Bonhoeffer, 1998) is seen in visual cortex of a ferret treated with 700 μm APB at PND 42–75.B, There is no recovery from the effects of blocking ON-center activity during the period of orientation maturation. No orientation-specific activity is seen in optical imaging performed on PND 100 in visual cortex of a ferret treated with 700 μmAPB at PND 28–50. All conventions as in Figure3A.