Learning enhances the relative impact of top-down processing in the visual cortex

Nat Neurosci. 2015 Aug;18(8):1116-22. doi: 10.1038/nn.4061. Epub 2015 Jul 13.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Association Learning / physiology*
  • Behavior, Animal / physiology
  • Calcium
  • Female
  • GABAergic Neurons / physiology
  • Interneurons / physiology
  • Laser Scanning Cytometry
  • Male
  • Mice
  • Neurons / physiology*
  • Somatostatin / metabolism*
  • Visual Cortex / cytology
  • Visual Cortex / physiology*
  • Visual Pathways / physiology*
  • Visual Perception / physiology*


  • Somatostatin
  • Calcium