Neural bases of the interaction between frames of reference and spatial relations

The capacity to judge if an object is closer than another to our body or it is
on our right or left requires the combination of two basic spatial dimensions:
an egocentric frame of reference (the body) where to anchor metric (coordinate
relations, e.g. the keys are 10 cm away from my hand) or abstract spatial
relations (categorical relations, such as right/left, above/below). The same is
when we judge the position of an object independently from our body but with
respect to another element in the environment, in such cases we anchor metric
or abstract spatial relations to an allocentric frame of reference (e.g. the
keys are on the table, or close to the mug). Even if egocentric/allocentric
reference frames and categorical/coordinate spatial relations are strictly
connected and seem to serve similar adaptive purposes (egocentric and
coordinate information are particularly useful for action-oriented tasks,
whereas allocentric and categorical information for perception-oriented tasks,
Kosslyn, 1994; Milner & Goodale, 1995, 2008), they have mostly been studied
separately. As a consequence, several studies focused on the intrahemispheric
brain differences of egocentric and allocentric reference frames without
considering the role of the kind of spatial relation required (categorical vs.
coordinate), whereas other studies focused on the brain lateralization of
categorical and coordinate spatial relations without considering the role of
the frames of reference. However, no study has focused on the differences in
the neural underpinnings of the combinations of these two spatial dimensions.
Furthermore, no study has explored their combined role in visuo-perceptual and
visuo-motor tasks. Therefore, identifying these brain areas will help to paint
a more complete and complex picture of human visuospatial processing than that
offered by current theories (e.g. the two-streams hypothesis by Milner &
Goodale, 1995, 2008) and may provide crucial neuroimaging evidence which serve
to support assessment of visuospatial deficits within a neuropsychological
diagnosis and rehabilitation context.

The main aim of this study is to identify the neural correlates of four kinds
of spatial representations, i.e. egocentric coordinate, egocentric categorical,
allocentric coordinate, and allocentric categorical, in both visuo-perceptual
and visuo-motor tasks. We will look for: an extensive activation of right
dorsal areas when egocentric coordinate representations are used to guide the
movement on-line; an extensive activation of left ventral areas when
allocentric categorical representations are used for visuo-perceptual tasks;
finally, we look for an activation of dorsal along with some ventral areas when
allocentric coordinate and egocentric categorical representation are used for
visuo-motor and visuo-perceptual tasks respectively.

This study is a within-subjects experiment carried out with neuroimaging
techniques (functional MRI). Participants will perform four different spatial
tasks in two scanning sessions: visuo-perceptual response and visuo-motor
response.

There are no known risks associated with fMRI acquisition. The technique does
not require administration of any contrast agent or ionizing radiation. The
Utrecht group has ample experience with fMRI scanning (300 sessions per year on
the 7 tesla MRI scanner). The fMRI procedure is painless. Slight discomfort may
occur due to peripheral nerve stimulation during scanning, or due to lying
still with the head and part of the body confined in a tunnel-like device.
The results of this study are important for developing a more complete and
complex model of human visuo-spatial processing. Individual subjects in this
study are not expected to have any benefits from the outcome of this
study.javascript:saveABR('K')