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research. [10] By varying the intensity, stimulation modalities? After discussing the main findings of
frequency, and duration of rTMS, the researcher can TMS research on normal readers, we will look deeper
now transiently inhibit or block the function of a into the field of TMS and dyslexia. We will finish
specific cortical structure or enhance the excitability of our paper by answering the question whether rTMS
particular cortical areas under the coil. [10-12] Moreover, can be used as a future therapeutic modality for
in addition to the useful applications of rTMS in treating dyslexia.
basic cognitive neuroscience research, clinicians have
recently started to use it as a therapeutic technique. [13] The following methodology was used in the present
Later, in this paper, we will look into the possibility of review. Three databases (Medline, [21] Educational
using rTMS as a therapeutic intervention for treating Resources Information Center, [22] and Scopus [23] ) were
dyslexia. searched with a cut-off date of October 31, 2014. In
addition, the reference lists of all studies that were
First transcranial magnetic stimulation studies on language found in the databases were further checked in order
The first TMS study on language was conducted by to find additional suitable studies (also known as the
Pascual-Leone et al., [14] who induced speech arrest snowball method). [24] Two authors (van den Noort and
in presurgical patients with epilepsy. They were Struys) independently performed the literature search;
particularly interested in whether TMS could be used moreover, the study selection and data extraction
as an alternative to intracarotid amobarbital testing, were also independently conducted by two authors
also known as the WADA-test, [15] which is a test that is (van den Noort and Struys). The extracted data
clinically used to determine language representation in included the authors, the title, the journal in which
presurgical patients, but can lead to several substantial the study had been published, the publication year,
negative side effects (like seizures, encephalopathy, the number of participants involved in the study, the
strokes, etc.). [16] exact methodology used, the effects of TMS on normal
reading and in treating dyslexia that were found, and
In the last two decades, TMS studies on language have the conclusions that were drawn. In addition, Bosch
further focused on language representation issues; [17] was contacted in case of disagreement regarding the
moreover, the identification of language areas and study selection and/or data extraction, and in all cases,
an understanding of their underlying functions have a consensus was reached.
become key research topics. [18] TMS is used to either
inhibit or facilitate language processes and may operate TMS RESEARCH ON NORMAL READING
directly on a specific language-related cortex area or
indirectly via the intra-cortical networks. With TMS, First, we will discuss several influential TMS studies
reversible temporary lesions have been made in order involving normal readers and focusing on the processing
to investigate the cerebral cortical areas that are thought of words and Chinese characters. Then, we will move
to be responsible for language function. Interestingly, on to the sentence-level. Note that the processing
the TMS results differ from those predicted by classical of words/characters is a simplification of reading in
models of language organization: speech production daily life, where complete sentences and texts are
in the left inferior frontal region [19] and reception of processed. However, for reading research, these studies
language in the superior temporal gyrus. [20] RTMS are relevant because they give important insights into
over the left inferior frontal region was found to block how normal reading works, and as we will see later
speech output while speech arrest was obtained most in this paper, can explain what has gone wrong in
easily over the facial motor-cortex, a structure located individuals with dyslexia.
anterior to the central sulcus and superior to the
perisylvian fissure. Surprisingly, in general, the rTMS Word‑level
results show limited proof for aphasia as a result of Visual word recognition
impairment of the classical Broca’s left inferior frontal Before the advent of TMS, behavioral studies of visual
region [19] and of Wernicke’s superior temporal gyrus, [20] word recognition had already suggested that the left
whereas right-hemisphere or bilateral lateralization cerebral hemisphere was more critically involved
was often found. [18] in visual word recognition than the right cerebral
hemisphere. Participants showed slower reading times
Aim of the study and methodology used for longer words than for shorter words (a phenomenon
The aim of the present paper was to review the use of known as the “word-length reading effect”) when
TMS in the study of, as well as its role in developing the words were presented in the left-hemi-field, as a
a better understanding of, one specific language result, were processed in the right hemisphere (note
area, namely, reading. What are the contributions of that the human visual system is contra-lateral in
TMS to the understanding of the different reading nature [25] ), but this was not the case when the words

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