Abstract
Inhibitory interneurons play important roles in the development of brain functions. In the visual cortex, functional maturation of inhibitory interneurons is essential for ocular dominance plasticity. However, roles of inhibitory interneurons in the development of orientation and direction selectivity, fundamental properties of primary visual cortex, are less understood. We examined orientation and direction selectivity of neurons in GAD67-GFP (Δneo) mice, in which expression of GABA in the brain is decreased in the newborn. We used in vivo two-photon calcium imaging to examine visual response of neurons in these mice and found that long-term decrease of GABA led to increase of response amplitude to non-preferred orientation of visual stimuli, which decreased orientation selectivity. In contrast, direction selectivity was not affected. These results suggest that orientation selectivity is decreased in mice with GABA down-regulation during development.
Highlights
Inhibitory interneurons are important for the development of many brain functions
We found that long-term decrease of GABA led to increase of response amplitude to non-preferred orientation of visual stimuli, and decrease of orientation selectivity, but had no effect on direction selectivity, which suggests that roles of GABA during development is different from those in acute
In summary, this study showed that long-term down-regulation of GABA increased response amplitudes to the non-preferred orientation of visual stimuli and decreased orientation selectivity (OI) without affecting DI, suggesting that GABA down-regulation has a relatively small impact on the development of direction selectivity
Summary
Inhibitory interneurons are important for the development of many brain functions. The functional maturation of inhibitory interneurons plays pivotal roles in activity-dependent ocular dominance plasticity in the visual cortex (Hensch et al, 1998; Fagiolini and Hensch, 2000; Iwai et al, 2003). Two studies (Atallah et al, 2012; Wilson et al, 2012) suggested that parvalbumin (PV) positive interneurons control response gain and slightly change the visual selectivity of excitatory neurons. Another study (Lee et al, 2012) suggested that PV positive interneurons markedly sharpen visual selectivity and that SOM and vasointestinal peptide positive interneurons have no significant effect. Despite of these inconsistencies, these previous works agreed that effects of inhibitory interneurons on the direction selectivity are similar to those on orientation selectivity when groups of interneurons are manipulated
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