Neural basis of visual deficits recovery: visual residual functions and multisensory integration.

The ability of integrating into a unified percept sensory inputs deriving from different sensory modalities, but related to the same external event, is called multisensory integration and might represent an efficient mechanism of sensory compensation when a sensory modality is damaged by a cortical lesion. This hypothesis has been discussed in the present dissertation. Experiment 1 explored the role of superior colliculus (SC) in multisensory integration, testing patients with collicular lesions, patients with subcortical lesions not involving the SC and healthy control subjects in a multisensory task. The results revealed that patients with collicular lesions, paralleling the evidence of animal studies, demonstrated a loss of multisensory enhancement, in contrast with control subjects, providing the first lesional evidence in humans of the essential role of SC in mediating audio-visual integration. Experiment 2 investigated the role of cortex in mediating multisensory integrative effects, inducing virtual lesions by inhibitory theta-burst stimulation on temporo-parietal cortex, occipital cortex and posterior parietal cortex, demonstrating that only temporo-parietal cortex was causally involved in modulating the integration of audio-visual stimuli at the same spatial location. Given the involvement of the retino-colliculo-extrastriate pathway in mediating audio-visual integration, the functional sparing of this circuit in hemianopic patients is extremely relevant in the perspective of a multisensory-based approach to the recovery of unisensory defects. Experiment 3 demonstrated the spared functional activity of this circuit in a group of hemianopic patients, revealing the presence of implicit recognition of the fearful content of unseen visual stimuli (i.e. affective blindsight), an ability mediated by the retino-colliculo-extrastriate pathway and its connections with amygdala. Finally, Experiment 4 provided evidence that a systematic audio-visual stimulation is effective in inducing long-lasting clinical improvements in patients with visual field defect and revealed that the activity of the spared retino-colliculo-extrastriate pathway is responsible of the observed clinical amelioration, as suggested by the greater improvement observed in patients with cortical lesions limited to the occipital cortex, compared to patients with lesions extending to other cortical areas, found in tasks high demanding in terms of spatial orienting. Overall, the present results indicated that multisensory integration is mediated by the retino-colliculo-extrastriate pathway and that a systematic audio-visual stimulation, activating this spared neural circuit, is able to affect orientation towards the blind field in hemianopic patients and, therefore, might constitute an effective and innovative approach for the rehabilitation of unisensory visual impairments.

Essays on European economic and monetary integration

This thesis focuses on two aspects of European economic integration: exchange rate stabilization between non-euro Countries and the Euro Area, and real and nominal convergence of Central and Eastern European Countries. Each Chapter covers these aspects from both a theoretical and empirical perspective. Chapter 1 investigates whether the introduction of the euro was accompanied by a shift in the de facto exchange rate policy of European countries outside the euro area, using methods recently developed by the literature to detect "Fear of Floating" episodes. I find that European Inflation Targeters have tried to stabilize the euro exchange rate, after its introduction; fixed exchange rate arrangements, instead, apart from official policy changes, remained stable. Finally, the euro seems to have gained a relevant role as a reference currency even outside Europe. Chapter 2 proposes an approach to estimate Central Bank preferences starting from the Central Bank's optimization problem within a small open economy, using Sweden as a case study, to find whether stabilization of the exchange rate played a role in the Monetary Policy rule of the Riksbank. The results show that it did not influence interest rate setting; exchange rate stabilization probably occurred as a result of increased economic integration and business cycle convergence. Chapter 3 studies the interactions between wages in the public sector, the traded private sector and the closed sector in ten EU Transition Countries. The theoretical literature on wage spillovers suggests that the traded sector should be the leader in wage setting, with non-traded sectors wages adjusting. We show that large heterogeneity across countries is present, and sheltered and public sector wages are often leaders in wage determination. This result is relevant from a policy perspective since wage spillovers, leading to costs growing faster than productivity, may affect the international cost competitiveness of the traded sector.