A morphological basis for orientation tuning in primary visual cortex

Nat Neurosci. 2004 Aug;7(8):872-9. doi: 10.1038/nn1287. Epub 2004 Jul 18.


Feedforward connections are thought to be important in the generation of orientation-selective responses in visual cortex by establishing a bias in the sampling of information from regions of visual space that lie along a neuron's axis of preferred orientation. It remains unclear, however, which structural elements-dendrites or axons-are ultimately responsible for conveying this sampling bias. To explore this question, we have examined the spatial arrangement of feedforward axonal connections that link non-oriented neurons in layer 4 and orientation-selective neurons in layer 2/3 of visual cortex in the tree shrew. Target sites of labeled boutons in layer 2/3 resulting from focal injections of biocytin in layer 4 show an orientation-specific axial bias that is sufficient to confer orientation tuning to layer 2/3 neurons. We conclude that the anisotropic arrangement of axon terminals is the principal source of the orientation bias contributed by feedforward connections.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / physiology*
  • Female
  • Image Processing, Computer-Assisted
  • Male
  • Models, Neurological
  • Orientation / physiology
  • Tupaiidae / anatomy & histology*
  • Tupaiidae / physiology
  • Visual Cortex / anatomy & histology*
  • Visual Cortex / physiology
  • Visual Pathways / anatomy & histology*
  • Visual Pathways / physiology
  • Visual Perception / physiology*