6 avril 2010
Charles Leek présentera "Functional Specialization in Supplementary Motor Area (SMA): Evidence from fMRI and visuo-spatial transformation deficits in Parkinson's disease"
- Intervenant : Charles Leek
- Laboratoire : Bangor University, Wales
- Date prévue : 6 avril 2010 à 13h
- Lieu : salle D32, 1er étage, bâtiment BSHM
- Titre : Functional Specialization in Supplementary Motor Area (SMA): Evidence from fMRI and visuo-spatial transformation deficits in Parkinson's disease
- Abstract : The Supplementary Motor Area (SMA) of the medial frontal cortex is typically associated with the planning, preparation and online control of visually-guided movement. However, this view has been challenged by recent evidence highlighting functional specialisation within the SMA. Leek & Johnston (2009, Nature Reviews Neuroscience, 10, 78-79) have suggested that one function of the anterior (pre-) SMA in humans is the computation of abstract visuo-spatial vector transformations. According to this hypothesis, pre-SMA should be involved in visual tasks that require the transformation or remapping of spatial locations (vectors) regardless of whether there is a motor component to the task (e.g., visual mental rotation). Here I present evidence from 3T fMRI and studies of visuo-spatial processing deficits in Parkinson's disease (PD) patients that tests this hypothesis. One known aspect of the underlying pathology of PD is the consequent effects of dopamine depletion in the basal ganglia upon functioning of medial frontal cortex. Thus, PD provides a good model for studying SMA dysfunction and its effects on visuo-spatial processing. The spatial vector transformation hypothesis predicts that PD patients, with impaired SMA function, are likely to exhibit deficits on tasks that require spatial vector transformations. The results showed that, as predicted, PD leads to impairments on transformational but not on non-transformational tasks. Further support for this hypothesis comes from 3T fMRI studies using similar tasks showing preferential activation in pre-SMA during spatial vector transformation. These findings support the vector transformation hypothesis and suggest that regions of the SMA are involved in highly abstract visuo-spatial computations that go beyond the preparation and planning of movement. Indeed, these findings suggest that the SMA supports abstract visuo-spatial processes that are potentially recruited in a wide range of visual and spatial tasks.
