CNR - Institute of Neuroscience CNR
Institute of Neuroscience


The developmental refinement of retino-geniculate connectivity

The developmental refinement of retino-geniculate connectivity


Historically, it has been thought that eye-specific projections emerge during development from an immature state where axons serving the two eyes are initially intermingled in both geniculate (LGN) and cortex, and that they segregate during development by an activity-dependent, competitive process following a Hebbian learning rule (Hebb, 1949) where "neurons that fire together, wire together" (Katz and Shatz, 1996). Recently, however, new data have brought this view into question. Therefore the basic intellectual scaffolding underlying our understanding of the development of eye-specific connections is now open to debate. In particular, questions remain about the initial state of ocular dominance columns early in development, about whether retinal activity actually drives eye-specific segregation during normal development, and about what features of activity are important for normal versus abnormal development of connections.

Signaling cascades involved in eye specific map refinement - roles for BDNF and ERKs

The molecular mechanisms underlying eye-specific segregation remain still largely unclear. We have shown that BDNF is a critical signal for the formation of the eye specific layers in the LGN and its mechanism of action is different from that of electrical activity (Menna et al., 2003). We have also examined the role of ERK pathway in the establishment of a proper retino-geniculate connectivity. We have been focalized specifically on the localization of its action along the retino-thalamic circuitry. Our work clearly demonstrates that the blockade of ERK pathway prevents the eye-specific segregation in the dLGN providing evidence that ERK is required for the proper development of retino-geniculate connections (Naska et al., 2004).

Role for retinal activity in the formation of eye specific map in rat dLGN

We are currently investigating how spontaneous retinal activity drives the refining of retinal projections to the dLGN and which information retinal activity provides for this process.


  • Naska S, Cenni MC, Menna E, Maffei L (2004) ERK signaling is required for eye-specific retino-geniculate segregation. Development 131:3559-70.
  • Caleo M, Cenni MC (2004) Anterograde transport of neurotrophic factors: possible therapeutic implications. Mol. Neurobiol. 29:179-96.
  • Menna E, Cenni MC, Naska S, Maffei L (2003) The anterogradely transported BDNF promotes retinal axon remodeling during eye specific segregation within the LGN. Mol. Cell. Neurosci. 24:972-83.



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Maria Cristina Cenni

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