Introduction Manual dexterity involves reaching and grasping for

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Introduction Manual dexterity involves reaching and grasping for
Alexander Romanowski1, Simone Kühn2, Christina Schilling1, Andreas Heinz1, Juergen Gallinat1
1
Department of Psychiatry and Psychotherapy, Charité – Universitätsmedizin Berlin, Berlin, Germany,
2
Department of Experimental Psychology and Ghent Institute for Functional and Metabolic Imaging,
Gent, Belgium
Introduction
Manual dexterity involves reaching and grasping for objects and is one of the most frequent
daily actions. In spite of the implicitness of grasping objects, it is a very complex and
demanding task. In order to execute goal-directed movements, as reaching with the hand at
stationary or moving objects, the brain must specify the position of the target in an egocentric
frame of reference by integrating external signals (e.g. visual and auditory stimuli) with
intrinsic congruent signals (proprioceptive, vestibular, motor) related to body, arm, head, and
eye position. Particularly, the fine-tuning of reaching for objects is coordinated by the
cerebellum. Region-of-interest-based studies have described handedness dependent
cerebellar volume asymmetry (Good 2001) and vermis lobules volumina differences
dependent on proficiency in basketball players compared to amateurs (Park 2004). Whole
brain voxel-based morphometry (VBM) studies report distinct local correlates in the
cerebellum only in highly trained typist (Cannonieri et al. 2007) and musicians (Gaser 2003),
but not golfers (Jäncke et al 2009). Dragansky et al. (2004) have reported no GM changes
induced by juggling in the cerebellum in their VBM studies. For the first time we used a
cerebellum-optimized VBM procedure to investigate cerebellar correlates of manual dexterity
in untrained adolescents.
Methods
Sixty five 14-year-olds (M 14.4 years; SD 0.32 years; 44 females) participated in this study
within the scope of the IMAGEN project (Schumann et al. 2010). Clusters of GM volume
associated with dexterity, measured with the Purdue Pegboard Dexterity Test (PPDT), were
identified in a whole brain analysis using optimized voxel-based morphometry (SPM8) as
well as in an optimized analysis of the cerebellum using the Spatially Unbiased Infratentorial
(SUIT) toolbox (Diederichsen, 2006).
Results
In the whole brain analysis of the study we found that higher performance in PPDT for the
right hand (RH) was associated with higher GM volume in the left SMA, right fusiform gyrus,
and left cuneus (Figure 1). There was no significant GM correlation with pegboard
performance of the non-dominant left hand. The correlation with bilateral pegboard
performance revealed higher GM volume in the right fusiform gyrus. The whole brain VBM
analysis revealed no significant structural correlates for the cerebellum. In the cerebellar
VBM employing SUIT we found that higher PPDT for RH performance was associated with
higher GM volume in right cerebellum crus VI. When correlating with pegboard performance
of the non-dominant left hand we likewise found a positive correlation with GM volume in
right cerebellum crus VI extending into crus I. The overlap of the clusters found for right-hand
and left-hand performance is displayed in Figure 2. The correlation with bilateral pegboard
performance revealed no significant structural correlate in the cerebellum. All findings are
corrected for multiple comparisons.
Conclusions
To our knowledge, the present study is the first one using cerebellum optimized VBM
procedure that shows evidence for distinct GM volume differences correlated with the
manual dexterity located in the right cerebellar lobule VI as well as in the left SMA, the right
fusiform gyrus and the left cuneus. The use of cerebellum optimized VBM (SUIT) revealed
substantial results that have not been detectable by means of standard VBM procedures.
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The data suggests that future research on morphological correlates of higher cognitive
functions might benefit from considering both cortical as well as cerebellar analyses.
Imaging Methods
Anatomical MRI
References
Cannonieri, G.C. (2007). 'Practice and perfect: length of training and structural brain changes in
experienced typists'. Neuroreport, vol.18, no. 10, pp. 1063-1066.
Diedrichsen, J. (2006). 'A spatially unbiased atlas template of the human cerebellum'. NeuroImage,
vol. 33, no.1 , pp.127-138.
Draganski, B. (2004). 'Neuroplasticity: Changes in grey matter induced by training'. Nature, Vol. 427,
no. 6972, pp. 311-312.
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Driemeyer, J. (2008). 'Changes in gray matter induced by learning--revisited'. PloS One, vol. 3, no. 7,
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Gaser, C. & Schlaug, G. (2003). 'Gray matter differences between musicians and nonmusicians'.
Annals of the New York Academy of Sciences, vol. 999, pp. 514-517.
Good, C.D. (2001). 'Cerebral Asymmetry and the Effects of Sex and Handedness on Brain Structure:
A Voxel-Based Morphometric Analysis of 465 Normal Adult Human Brains', NeuroImage, vol. 14, no.
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Jäncke, L. (2009). 'The architecture of the golfer's brain', PloS One, vol. 4, no. 3, e4785.
Park, J. (2010). 'Dynamic changes in the cortico-subcortical network during early motor learning',
NeuroRehabilitation, vol. 26, no. 2, pp. 95-103.
Schumann, G. (2010). 'The IMAGEN study: reinforcement-related behaviour in normal brain function
and psychopathology', Molecular Psychiatry, vol. 15, no. 12, pp.1128-1139.
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