Mirror writing occurs in healthy children, in various pathologies and occasionally in healthy adults. There are only scant experimental data on the underlying brain processes.Eight, right-handed, healthy young adults were scanned (BOLD-fMRI) before and after practicing left-hand mirror-writing (lh-MW) over seven sessions. They wrote dictated words, using either the right hand with regularly oriented writing or lh-MW. An MRI compatible stylus-point recording system was used and online visual feedback was provided.Practice resulted in increased speed and readability of lh-MW but the number of movement segments was unchanged. Post-training signal increases occurred in visual, right lateral and medial premotor areas, and in right anterior and posterior peri-sylvian areas corresponding to language areas.These results suggest that lh-MW may constitute a latent ability that can be reinstated by a relatively brief practice experience. Concurrently, right hemisphere language processing areas may emerge, reflecting perhaps a reduction in trans-hemispheric suppression.
Bibliographical noteFunding Information:
Almost a century ago this notion and suggest that the acquisition of grapho-motor programs for rh-CW may generate a ‘dormant’ mirror representation for lh-MW in the right hemisphere; this would imply that handwriting (in right handers) is not necessarily unique left hemisphere ability. This conclusion is supported by the increase in the right hemisphere premotor and M1 activation associated with lh-MW training. The results reported by Orton (1928) proposed that engrams or visual representation of letters and words are stored in the dominant hemisphere with their mirror counterparts stored in the non-dominant hemisphere (usually the right hemisphere). Corballis and Beale (1970), Corballis and Beale (1976) , following Noble (1966), Noble (1968) , suggested that the reversal of engrams need not be restricted to visual input, and applies to motor acts as well. Inter-manual reversal of learned movement was described by Milisen and Van Riper (1939) in monkeys. Subsequent work in monkeys ( Achim & Corballis, 1977 ) suggested a role for the anterior commissure in interhemispheric reversal. Expanding Orton’s theory, one may assume that motor aspects of handwriting or ‘grapho-motor programs’ are similarly mirrored in the non-dominant (right) hemisphere. Our results are compatible with Zaman et al. (2002) suggest that even with no prior training lh-MW is associated with bilateral activation of sensory motor cortex pre-motor and parietal areas in right handed as well as left handed adults irrespective of the hand executing the writing movements. We propose that the right hemisphere pre-motor and motor cortices are possible sites in which the dormant, rudiments of mirror writing skills are represented. In line with Orton’s proposal one may conjecture that these dormant graph-motor representations of handwriting were generated during early stages in the acquisition of handwriting skills but were perhaps suppressed by the right hand committed representations of handwriting in the left hemisphere (see also, Angelillo et al., 2010; Schott, 2007 ).
- MRI compatible kinematics recording
- Mirror writing
- Real-time visual feedback device
ASJC Scopus subject areas
- Language and Linguistics
- Experimental and Cognitive Psychology
- Linguistics and Language
- Cognitive Neuroscience
- Speech and Hearing