Gordon Smith, Massachusetts Institute of Technology

Abstract:
Early developmental events are critical for defining and constraining future capabilities, yet our understanding of the structure and plasticity of cortical circuits during early development remains poor. By using cutting-edge imaging approaches in the ferret, I have been able to examine the early development of the large-scale distributed functional networks that are a hallmark of visual cortical organization in higher mammals. Through a combination of wide-field and 2-photon calcium imaging, my results demonstrate that correlations in ongoing spontaneous activity reflect highly organized long-range networks in the early cortex, prior to the formation of long-range horizontal connectivity. Furthermore, chronic in vivo imaging experiments show that early correlations in spontaneous activity are predictive of future visually-evoked responses, well before those correlated networks can be engaged by visual stimuli. In addition, computational modeling shows that purely local connectivity, if anisotropic and heterogeneous, is sufficient to explain the presence of long-range correlations in the early cortex prior to the emergence of long-range connections. Together, these results reveal surprising and fundamental features of early cortical circuits and suggest that the large-scale correlations generated through local connectivity during early development may form the basis for large-scale distributed networks in the mature visual cortex.