Specialized circuits from primary visual cortex to V2 and area MT

Neuron. 2007 Sep 6;55(5):799-808. doi: 10.1016/j.neuron.2007.07.037.


Primary visual cortex recombines inputs from magnocellular (M) and parvocellular (P) streams to create functionally specialized outputs. Understanding these input-output relationships is complicated by the fact that layer 4B, which provides outputs to dorsal visual areas, contains multiple cell types. Using a modified rabies virus that expresses green fluorescent protein, we show that layer 4B neurons projecting to MT are a majority spiny stellate, whereas those projecting to V2 are overwhelmingly pyramidal. Regardless of cell type, MT-projecting neurons have larger cell bodies, more dendritic length, and are deeper within layer 4B. Furthermore, MT-projecting pyramidal neurons are located preferentially underneath cytochrome oxidase blobs, indicating that MT-projecting neurons of both types restrict their dendrites to M-recipient zones. We conclude that MT-projecting layer 4B neurons are specialized for the fast transmission of information from the M pathway, while V2-projecting neurons are likely to mediate slower computations involving mixed M and P signals.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Axonal Transport / physiology
  • Brain Mapping / methods
  • Cell Shape / physiology
  • Dendrites / physiology
  • Dendrites / ultrastructure
  • Electron Transport Complex IV / metabolism
  • Genetic Vectors / genetics
  • Green Fluorescent Proteins / genetics
  • Interneurons / cytology
  • Interneurons / physiology
  • Macaca
  • Neurons / cytology*
  • Neurons / physiology
  • Pyramidal Cells / cytology
  • Pyramidal Cells / physiology
  • Rabies virus / genetics
  • Staining and Labeling / methods
  • Temporal Lobe / cytology*
  • Temporal Lobe / physiology
  • Visual Cortex / cytology*
  • Visual Cortex / physiology
  • Visual Pathways / cytology*
  • Visual Pathways / physiology
  • Visual Perception / physiology*


  • Green Fluorescent Proteins
  • Electron Transport Complex IV