SPEAKERS: Claudia Lunghi, Paola Binda and Concetta Morrone
TITLE: “Development and plasticity of the human visual system”
Abstract: The visual system is model system for understanding the experience-dependent development of the central nervous system early in life, and its plasticity in the adult. This line of work traces back to the work of Nobel Laureates Hubel and Wiesel on “Monocular Deprivation”, introducing the concept of a “critical period” early in life, within which neural circuits are particularly sensitive to (abnormal) experience. This work is at the basis of the research by Prof. Maria Concetta Morrone, who will introduce the main topics and techniques – primarily non-invasive measures of visual performance and brain activity, in both adults and infants, including neuroimaging experiments performed on 3-week old babies. While the plasticity potential of the human brain peaks at birth and declines thereafter, Dr. Claudia Lunghi will show that the adult visual system retains a degree of plasticity. It still responds to Monocular Deprivation with a change of ocular dominance. Albeit transient, this effect reflects a reorganization of the adult visual cortex, which appears to co-vary with two variables: physical activity (boosting plasticity) and body weight (lower plasticity accompanying higher BMI). Importantly, preliminary findings suggest that this reorganization may open a new window of opportunity for treating Amblyopia even in adult individuals. The consequence of Monocular Deprivation in the adult visual cortex are seen both with electrophysiology and with neuroimaging techniques, which suggest that one of the key factors is a decrease of GABAergic inhibition. Dr. Paola Binda will illustrate fMR imaging experiments performed at ultra-high Magnetic field (IMAGO7 Center), where we measure the change of visual response before and after deprivation and relate it to the tuning properties of visual neurons and their level of excitability. Cortical excitability is also reflected in an easily monitored variable: the diameter of the eye pupil. We find that its variations are surprisingly indicative of an individual’s plasticity potential, and reflect inter-subject variability on subtle aspects of visual performance. This might be exploited to obtain objective indices of anomalies in vision and its development, a possibility we are beginning to explore in the context of the Autistic Spectrum Disorders, finding that an individual’s position along the Spectrum is tightly correlated with pupil behavior during performance of a visual task.