| Summary: | Introduction: In acquired dysgraphia, the spelling network is disrupted, typically causing difficulty in correctly spelling some words more than others. Various studies have demonstrated that training can be effective for recovery (e.g., Beeson et al., 2002; Rapp, 2005). However, little is known regarding the neural basis of this recovery. Studying the neural changes associated with recovery can improve understanding of how the damaged brain responds to behavioral treatment, and will be relevant to the development of neuro-targeted therapies. In this study we specifically evaluate the possibility that treatment results in greater normalization of activation, such that improvement in the spelling of low accuracy words results in neural responses that resemble those of high accuracy words.
Methods: Participants were 3 individuals with chronic dysgraphia subsequent to stroke (time post-stroke at least two years). We identified individualized sets of 40 TRAINING words (25 - 80% letter accuracy) and 30 KNOWN words (100% letter accuracy). We carried out a CART based treatment (Beeson, 1999) over approximately a 3 month period. Training was completed when at least 90% letter accuracy was achieved for the TRAINING items. To track neural changes associated with spelling training, we performed an fMRI study of spelling (Rapp and Lipka, 2010) at pre- and post-training time points. The fMRI protocol was designed so that each participant processed the spelling of their individualized sets of KNOWN and TRAINING words during scanning.
The data analysis examined the neural response to TRAINING and KNOWN words to identify regions in which the activation differences between neural responses to TRAINING and KNOWN words was significant at pre-training but not significant at post-training – i.e. the training response became more normalized after training. Cluster-size correction for multiple comparisons (p < 0.05) was applied.
Results:
1) For all participants we identified brain areas associated with a normalized response for the TRAINING words at the post-training time point.
2) For all participants we identified an up-regulation of the TRAINING response (i.e., the TRAINING neural response was initially low and then increased post-training); whereas in only one participant did we also observe a down-regulation of the training response (i.e., the TRAINING neural response was initially high, but then decreased post-training).
3) Although the areas associated with the normalized TRAINING response were different in each individual, they all include areas typically associated with the spelling system (Purcell et al. 2011), including the right homologues of typically left hemisphere spelling regions. Across the participants, the following areas of normalization were observed: bilateral superior temporal gyrus, inferior frontal gyrus, and the bilateral inferior temporal/fusiform gyrus.
Discussion: We found that the predominant BOLD response to training involved an up-regulation of the neural response to spelling the TRAINING items. In addition, we found individual differences in the neurotopography of the normalization response patterns although all were with within brain areas that form a part of the spelling network(Purcell et al. 2011). This work provides evidence regarding one aspect of the multiplicity of neural responses associated with recovery of spelling in individuals with acquired dysgraphia.
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