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were presented in the right-hemi-field, and as a result, Chinese character recognition remained? Therefore,
were processed in the left-hemisphere (a phenomenon an intriguing study on human foveal splitting with
known as “length-independent reading”), proving the rTMS was conducted by Hsiao et al., [32] in which
[26]
hypothesis that the left cerebral hemisphere is more not words, but Chinese characters were used as
critically involved in visual word recognition. stimuli. As in Skarratt and Lavidor’s rTMS study, [27]
Hsiao et al. [32] conducted rTMS on the right and
Skarratt and Lavidor [27] were the first to test these the left occipital cortexes. Hsiao et al. [32] found
behavioral findings [26] with rTMS. They were neuroscientific proof for the split fovea theory. [30]
particularly interested in how expert readers were Moreover, with respect to visual word recognition,
able to identify arrays of several letters quickly and they showed that fovea splitting was not a unique
in parallel. They found that left occipital cortex rTMS characteristic of European languages, but could also
disrupted processing in the right visual hemi-field be found in Chinese, which belongs to a completely
of experts, resulting in the previously-discussed different language family and uses characters instead
word-length reading effect. RTMS of the right occipital of Arabic letters. [32]
cortex, however, did not disrupt the processing of right
visual hemi-field words in experts nor did it affect the In their TMS study, Stoeckel et al. [33] were
word-length reading effect that was already visible in particularly interested in the supramarginal gyrus.
the left visual hemi-field. To conclude, Skarratt and Previous neuroimaging research had shown that the
Lavidor’s study [27] were the first to demonstrate that supramarginal gyrus played a role in visual word
TMS-induced impairment in the left-hemisphere led to recognition. [34] Stoeckel et al. [33] were the first to use
a word-length reading effect, providing neuroscientific the TMS technique to investigate the role of the
evidence for the hypothesis that the left-hemisphere is supramarginal gyrus in word recognition. They used
more specialized in word recognition [Table 1]. three different tasks: a phonological, a semantic, and
a visual control task. Their results showed that the
In addition, several studies have tested these visual supramarginal gyrus contributed to reading, regardless
hemi-field word processing findings [26,27] by using of the specific task requirements. The supramarginal
foveally-presented lexical stimuli [28,29] and have gyrus automatically seemed to compute the sound of
revealed that the different right and left-hemispheric the word, even when it was not needed for the task. [33]
processing styles have contra-lateral influences on Thus, the visual perception of words automatically
the responses driven by the right and the left halves seemed to activate the auditory representation of their
of the lexical stimuli (also known as the split fovea spoken forms. [33]
theory). [30] In sum, research has shown the importance
of human foveal splitting for the visual recognition of Nakamura et al. [35] further investigated the above issue
words, [31] but the question of what would happen in by conducting TMS on both the left superior temporal

Table 1: TMS findings on word‑reading in normal readers
Study Participants Brain area Main finding
Skarratt and Twelve right‑handed, Occipital A word‑length effect was found after rTMS had been conducted on
Lavidor [27] healthy, volunteers cortex the left occipital cortex. Evidence was found for the hypothesis that
the left‑hemisphere was more specialized in word recognition
Hsiao et al. [32] Eight right‑handed, Occipital The findings of the Chinese character study confirmed the split
healthy, volunteers, who cortex fovea hypothesis. Moreover, it showed that fovea splitting was not
were all native speakers of solely found for reading in European languages, but seemed to be a
Chinese universal processing constraint
Stoeckel et al. [33] Twenty‑two right‑handed, Supramarginal The authors found that the supramarginal gyrus clearly contributed
healthy volunteers, who gyrus to reading; moreover, a conclusion was that the supramarginal gyrus
were all native English automatically computed the sound of a word and that this occurred
speakers even when it was not really required to perform the task
Nakamura et al. [35] In total, 30 healthy, native Superior A clear double dissociation was discovered; the repetition priming
Japanese speakers temporal gyrus during the pronunciation task was eliminated when TMS was
and inferior conducted on the left inferior parietal lobe, but not when it was
parietal lobe conducted on the left superior temporal gyrus, whereas the priming
during the lexical decision task was eliminated when the left superior
temporal gyrus, but not the left inferior parietal lobe, was stimulated
Tomasino et al. [36] Twenty right‑handed, Primary The authors showed that the primary motor‑cortex was critically
healthy men, who were all motor‑cortex involved in processing action verbs, but that this was only the case
native speakers of German when participants were simulating the corresponding movement
Hoffman et al. [37] Thirteen right‑handed, Ventrolateral The results suggested that the ventrolateral prefrontal cortex worked
healthy, native speakers of prefrontal as a kind of executive regulator in the processing of abstract words.
English cortex However, this was less the case when abstract words were presented
in a specific context and when concrete words were processed
rTMS: rapid‑rate transcranial magnetic stimulation; TMS: transcranial magnetic stimulation

146 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 147