Abstract

Visual short-term memory (vSTM) capacity represents the maximum number of visual items that can be perceived and stored into vSTM. One way to measure it is by using simple psycho-physical experiments together with the theory of visual attention (TVA) computational framework in which visual processing is conceived as a race between objects to be consciously perceived and stored into vSTM. The neural theory of visual attention (NTVA), which gives an interpretation of the TVA at both the cellular and systemic level, suggests that recurrent loops between posterior thalamus and visual cortices are relevant for vSTM capacity. Nevertheless, no clear evidence for the role of posterior thalamus and its connection to visual cortices in vSTM capacity has been found thus far. This thesis investigated the role of posterior thalamo-cortical connectivity in vSTM capacity in healthy young individuals as well as in two populations that have shown to exhibit both vSTM capacity impairments and posterior cortical and subcortical white matter damages: healthy aging and premature birth. We found that vSTM capacity in healthy young adults was significantly associated with the tracts connecting posterior thalamus to occipital cortices and their microstructure. However, this association was modified in elderly individuals and in young adults born prematurely, in which the recruitment of additional, cortico-cortical, tracts, takes place. Together, these findings bring the first structural evidence for the NTVA model with respect to the relevance of posterior thalamo-cortical tracts for vSTM capacity and show how alterations of these tracts affect vSTM capacity.