CNR - Institute of Neuroscience CNR
Institute of Neuroscience
 

Project

Role of the corpus callosum in cortical development and plasticity

The corpus callosum is the largest white matter tract in the brain and mediates most of interhemispheric communication. Callosal fibers are involved in many cortical functions requiring either integration of information across hemispheres, or independent function of the two sides of the brain. In particular, in the visual cortex, commissural connections serve to bind together the separate representations of the two halves of the visual field in the two hemispheres. Our group studies the role of callosal connections in development and plasticity of the visual cortex.

In a first set of experiments, we have addressed the role of callosal input activity in the developmental maturation of the rodent visual cortex. Our results demonstrate that a transient unilateral silencing of rat striate cortex during postnatal development has lasting effects on visual function and plasticity. Indeed, visual abilities are permanently reduced in the blocked hemisphere, and the critical period for ocular dominance plasticity persists into adulthood. Remarkably, these effects extend equally to the contralateral uninjected side, revealing a role for interhemispheric connections in cortical development (Caleo et al., J Neurosci 2007). The crucial role of callosal projections in cortical maturation is confirmed by analysis of mice with conditional deletion of the AP2γ transcription factor. These animals have a reduced callosal connectivity that is associated with impaired development of visual function and prolongation of the sensitive period for ocular dominance plasticity (Pinto et al., 2009).

 

Ongoing experiments are assessing the role of the corpus callosum in experience-dependent cortical plasticity. First, we have shown that callosal projections contribute to normal binocularity in the rat visual cortex by providing mainly input from the ipsilateral eye (Restani et al., 2009). Second, we are using the paradigm of monocular deprivation by eyelid suture to examine callosal contribution to plasticity. Following monocular deprivation, cortical neurons exhibit a shift of ocular dominance towards the open eye. This shift appears to be generated by two different processes: down-regulation of the deprived input (depression) and up-regulation of the open eye input (potentiation). Our results demonstrate that callosal connections play a key role in functional weakening of deprived eye inputs during ocular dominance plasticity (Restani et al., 2009; Figure 1).

Publications

  • Restani L, Cerri C, Pietrasanta M, Gianfranceschi L, Maffei L, Caleo M (2009) Functional masking of deprived eye responses by callosal input during ocular dominance plasticity. Neuron 64:707-18.
  • Pinto L, Drechsel D, Schmid MT, Ninkovic J, Irmler M, Brill MS, Restani L, Gianfranceschi L, Cerri C, Weber SN, Tarabykin V, Baer K, Guillemot F, Beckers J, Zecevic N, Dehay C, Caleo M, Schorle H, Götz M (2009) AP2gamma regulates basal progenitor fate in a region- and layer-specific manner in the developing cortex. Nat. Neurosci. 12:1229-37.
  • Caleo M, Restani L, Gianfranceschi L, Costantin L, Rossi C, Rossetto O, Montecucco C, Maffei L (2007) Transient synaptic silencing of developing striate cortex has persistent effects on visual function and plasticity. J. Neurosci. 27:4530-40.

Collaborations

 

PI photo

Matteo Caleo

Contact information

email  E-mail

email  +39-050-3153195

Participating staff

Laura Restani, PhD

Chiara Cerri

Marco Mainardi

Marta Pietrasanta