Running Head: LETTER WRITING AND LETTER PERCEPTION

letter representation capable of unifying the concept of the letter ‘a’ along its many 195 dimensions. One such study, sought to localize brain areas that correspond to an abstract 196 representation of letters (Rothlein and Rapp 2014). Here, the term abstract refers to neural 197 representation in an amodal and symbolic sense, meaning that the abstract letter representation 198 exists independently of sensorimotor input and is not based on experience with writing letters. 199 They conclude that an amodal and abstract letter representation exists in the L-FuG and may 200 LETTER WRITING AND LETTER PERCEPTION 10 work in concert with modality-specific brain regions responsible for letter writing, letterform, 201 and lettersound. 202 An orthographic localizer task and a symbol detection task were administered to right203 handed adults during fMRI scanning. In the orthographic localizer task blocks, participants 204 passively viewed words, consonant strings, and checkerboard rectangles. Brain areas that showed 205 increased neural activity to words and consonant strings than to checkerboard rectangles were 206 chosen as orthographic ROIs. In the symbol detection task blocks, participants viewed 12 upper207 and lower-case letters and 4 non-letter symbols, for a total of 28 visual stimuli types, and were 208 asked to press a button when they saw one of the non-letter symbols. In this study, the 209 participants were not asked to write letters, were not presented with any auditory stimuli, but did 210 visually perceive letters. 211 Only the orthographic ROIs were investigated further for sensitivity and selectivity to 212 each of the 4 dimensions of interest: letter writing, letterform, lettersound, and abstract letter 213 identity. Modality-specific letter representations included motor programs for letter writing, 214 visual-motor properties associated with the shape trajectory of distinct letterforms, and 215 phonological properties of lettersound. Motor programs for writing letters were said to be 216 represented in brain areas that responded similarly for letter pairs that scored similarly on a 217 ‘stroke-feature metric’ developed by Rapp and Caramazza (1997) (e.g., T vs. L). Letterform 218 representations were defined as brain areas that responded similarly for letter pairs that have 219 been empirically shown to be similar in form (e.g., o vs. O, or b vs. d). Lettersound 220 representations were defined as brain areas that responded similarly for letter pairs that have 221 been empirically shown to have confusable letter names (e.g., b vs. e). Abstract letter identity 222 representations were defined as brain areas that responded similarly for letter pairs that were of 223 LETTER WRITING AND LETTER PERCEPTION 11 the same letter category, but of different letter case (e.g., A vs. a). An area was labeled sensitive 224 to a certain dimension if it responded similarly for letter pairs that shared that feature dimension. 225 An area was labeled selective for a certain dimension if it responded similarly for letter pairs that 226 shared only that the feature dimension. 227 Letters that require similar letter writing motor plans showed similar response patterns in 228 L-IPS, demonstrating sensitivity to motor plans. Letters that have similar lettersounds showed 229 similar response patterns in L-MTG, demonstrating sensitivity to lettersound. Areas that 230 responded similarly for upperand lower-case letters of the same letter category included 231 premotor regions (including: R-IFG, L-MFG), visual processing areas (including: bilateral FuG), 232 and a parietal region (L-IPS), demonstrating sensitivity to abstract letter identity. Only one brain 233 region was identified for which all participants demonstrated selective activation for upperand 234 lower-case letters: the L-FuG. Results are interpreted as evidence that, although some aspects of 235 letter representation are sensitive to modality-specific features, an abstract letter representation 236 also exists in the L-FuG that is amodal and independent of sensory and motor systems. 237 238 Summary 239 Looking back to the three previously discussed studies (Longcamp et al. 2014; Kadmon 240 Harpaz et al. 2014; Gimenez et al. 2014) is helpful in understanding the implications of the 241 results from the Rothlein and Rapp (2014) study on the debate concerning the neural 242 representation of letters. Longcamp et al. (2014) and Kadmon Harpaz et al. (2014) are studies in 243 which participants were asked to write letters and in which motor (L-PMC, SMA) and premotor 244 (L-PMd) areas were said to support letter writing; however, they differ in a crucial way. 245 Participants in the Longcamp et al. (2014) study were able to visually perceive each letter as they 246 LETTER WRITING AND LETTER PERCEPTION 12 wrote it, but participants in the Kadmon Harpaz et al. (2014) study were not. Of the studies 247 reviewed, the only other study in which participants visually perceived letters was Rothlein and 248 Rapp (2014). Thus, it is not surprising that only Longcamp et al. (2014) and Rothlein and Rapp 249 (2014) indicate a role for the L-FuG in letter representation. Further, the L-FuG was indicated as 250 being responsive to letter writing duration with visual feedback in Longcamp et al. (2014) and 251 the R-FuG was indicated as being responsive during a phonological processing task in children 252 that required visually perceiving pictures of objects in Gimenez et al. (2014), indicating that the 253 fusiform gyri are, in the least, modality-responsive. 254 In conclusion, there is relevant evidence supporting a modality-specific distributed neural 255 activation profile during letter perception that reflects experience with letters, such as motor 256 plans associated with letter writing, characteristics of the shape trajectory of each letterform, and 257 phonological properties of lettersound. Importantly, the L-FuG indicated by Rothlein and Rapp 258 (2014) as the location of an abstract neural representation for letters has also been indicated as a 259 modality-responsive neural substrate in letter writing and phonological studies, in that it engages 260 preferentially for visual stimuli. Therefore, while the constitution of a shared neural 261 representation for letter writing and letter perception may include an abstract component in the 262 L-FuG, this area is part of a distributed neural network comprised of modality-responsive brain 263 regions related to a history of motor and sensory experiences with individual letters. 264 LETTER WRITING AND LETTER PERCEPTION References: 265 266 Broca MP. Remarques sur le siege de la facultè du langage articulé, suivies d’une obserevation 267 d’aphemie (Perte la parole). Bulletins et memoires de la Societe Anatomique de Paris, 235-238, 268 1861. 269 270 Exner S. Untersuchungen über die Localisation der Functionen in der Grosshirnrinde des 271 Menschen. Wilhelm Braumüller, Wien, 1881. 272 273 Gimenez P, Bugescu N., Black JM, Hancock R, Pugh K, Nagamine M, Hendren R, 274 McClandiss BD, Hoeft F. Neuroimaging correlates of handwriting quality as children learn to 275 read and write. 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