Keep your head on straight: Facilitating sensori-motor transformations for eye-hand coordination.
Humans generally tend to hold the head vertically while performing coordinated whole-body actions (i.e. skiing, gymnastics, walking or driving). During the task of aligning the hand to a target, the CNS compares target and hand in both visual and kinesthetic reference frames (rather than combining both sensory inputs into a single reference frame); some missing information in one modality is ‘reconstructed’ using information from the other.
In this study, subjects were asked to reach a visual target with an unseen hand, and with the head either upright or tilted. The main result was a striking difference in the effect of a sensory conflict on movements performed to align the unseen hand with a visual target, whether the target orientation was memorized with the head upright or tilted. Furthermore, results showed that responses when the head was tilted relied more on visual information, contrarily to upright head.
These results agree with previous work, showing that when the head is tilted to the side, the CNS gives greater weight to visual versus proprioceptive information that was available (hand during motor planning), compared to when the head is upright. This suggests that the reason humans tend to keep their head upright may also have to do with how the brain stores spatial information between reference frames and between sensory modalities, rather than only being tied to the specific problem of stabilizing visual and vestibular inputs. > From: Tagliabue et al., Neuroscience 248 (2013) 88–94. All rights reserved to Elsevier Ltd.
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