The purpose of this thesis is to study the functional anatomy of stereoscopic
vision. Although many studies have investigated the physiological mechanisms by
which the brain transforms the retinal disparities into three-dimensional
representations, the invasive nature of the techniques available have restricted
them to studies in non-human primates, whilst the research on humans has been
limited to psychophysical studies.
Modem non-invasive neuroimaging techniques now allow the investigation of the
functional organisation of the human brain. Although PET and fMRI studies have
been widely used, few researchers have explored the functional anatomy of
stereoscopic vision. Most of these studies appear to be pilot work, showing
inconsistency, not only in the areas sensitive to stereo disparities, but also in the
specific role that each of these possesses in the perception of depth.
In order to investigate the cortical regions involved in stereoscopic vision, four
fMRI studies were performed using anaglyph random dot stereo grams. Our results
suggest that the stereo disparity processing is widespread over a network of
cortical regions which include VI, V3A, V3B and B7. Functionally, the V3A
region seems to be the main processing centre of pure stereo disparities and the
V3B region to be engaged in motion defined purely by spatio-temporal changes of
local horizontal disparities (stereoscopic -cyclopean- motion).
Interregional connectivity was investigated with two approaches. Structural
Equation Modelling (SEM), as the classical technique for the analysis of effective
connectivity, was used to assess one connectivity model proposed to· explain the
cortical interaction observed in the first experiment. The implementation and
application of this technique permitted us to identify some of its weaknesses in
representing fMRI data. An extension of the SEM technique was introduced as a
Non-linear Auto-Regressive Moving Average with eXogenous variables
(NARMAX) approach. This can be thought of as an attempt to bring SEM
towards a non-linear dynamic system modelling technique which permits a more
appropriate representation of effective connectivity models using fMRI time
series
