| First Author | Makino H | Year | 2015 |
| Journal | Nat Neurosci | Volume | 18 |
| Issue | 8 | Pages | 1116-22 |
| PubMed ID | 26167904 | Mgi Jnum | J:358668 |
| Mgi Id | MGI:6214486 | Doi | 10.1038/nn.4061 |
| Citation | Makino H, et al. (2015) Learning enhances the relative impact of top-down processing in the visual cortex. Nat Neurosci 18(8):1116-22 |
| abstractText | Theories have proposed that, in sensory cortices, learning can enhance top-down modulation by higher brain areas while reducing bottom-up sensory drives. To address circuit mechanisms underlying this process, we examined the activity of layer 2/3 (L2/3) excitatory neurons in the mouse primary visual cortex (V1) as well as L4 excitatory neurons, the main bottom-up source, and long-range top-down projections from the retrosplenial cortex (RSC) during associative learning over days using chronic two-photon calcium imaging. During learning, L4 responses gradually weakened, whereas RSC inputs became stronger. Furthermore, L2/3 acquired a ramp-up response temporal profile, potentially encoding the timing of the associated event, which coincided with a similar change in RSC inputs. Learning also reduced the activity of somatostatin-expressing inhibitory neurons (SOM-INs) in V1 that could potentially gate top-down inputs. Finally, RSC inactivation or SOM-IN activation was sufficient to partially reverse the learning-induced changes in L2/3. Together, these results reveal a learning-dependent dynamic shift in the balance between bottom-up and top-down information streams and uncover a role of SOM-INs in controlling this process. |
