Observation of simple intransitive actions: the effect of familiarity.
BACKGROUND
Humans are more familiar with index - thumb than with any other finger to thumb grasping. The effect of familiarity has been previously tested with complex, specialized and/or transitive movements, but not with simple intransitive ones. The aim of this study is to evaluate brain activity patterns during the observation of simple and intransitive finger movements with differing degrees of familiarity.


METHODS
A functional Magnetic Resonance Imaging (fMRI) study was performed using a paradigm consisting of the observation of 4 videos showing a finger opposition task between the thumb and the other fingers (index, middle, ring and little) in a repetitive manner with a fixed frequency (1 Hz). This movement is considered as the pantomime of a precision grasping action.


RESULTS
Significant activity was identified in the bilateral Inferior Parietal Lobule and premotor regions with the selected level of significance (FDR [False Discovery Rate] = 0.01). The extent of the activation in both regions tended to decrease when the finger that performed the action was further from the thumb. More specifically, this effect showed a linear trend (index>middle>ring>little) in the right parietal and premotor regions.


CONCLUSIONS
The observation of less familiar simple intransitive movements produces less activation of parietal and premotor areas than familiar ones. The most important implication of this study is the identification of differences in brain activity during the observation of simple intransitive movements with different degrees of familiarity.
Department of Physiology, Faculty of Medicine, University of La Laguna, San Cristóbal de La Laguna, Spain ; Hospital Universitario de Canarias (Department of Neurosurgery), S/C de Tenerife, Spain.
Julio
J
Plata Bello
Cristián
C
Modroño
Francisco
F
Marcano
José Luis
JL
González-Mora
D000328:Adult; D001931:Brain Mapping; D005260:Female; D005385:Fingers / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D021641:Recognition, Psychology; D013933:Thumb / Q000502:physiology*; D055815:Young Adult