Page 157 - Read Online

on the semantic task. In sum, a double dissociation the sentence-level. However, all the studies and the
between the type of task (semantic versus syntactic) findings that we have discussed so far were rTMS
that was performed and the rTMS effects was found studies conducted on normal readers who were not
in this study and provided neuroscientific proof for experiencing any reading problems. In the second part
the hypothesis that the underlying working memory of our paper, we will address whether rTMS can also
resources in sentence comprehension were processed be successfully applied to research on individuals that
differently by the two hemispheres. [39] are known to have reading problems? In order to do so,
we will discuss TMS studies on dyslexia. In addition,
Processing of specific sentence types we will go one step further and address whether rTMS
So far, we have discussed general sentence can be used as a clinical intervention technique to
comprehension in normal readers. In contrast to overcome reading problems?
Manenti et al., [39] Cacciari et al. [42] were interested in
how readers process specific kinds of sentences. They TMS AND DYSLEXIA
investigated three neurolinguistic classes of sentences,
“literal”, “nonliteral” (i.e. metaphorical, idiomatic), and Dyslexia
“fictive” motion sentences, and wondered how these Dyslexia (also referred to as specific reading
different types of sentences affected the excitabilities disability) [45,46] occurs when a child or adult has
of the motor areas in the brain. Larger motor-evoked significant difficulty with the speed and the accuracy
potentials were found when individuals read literal, of word decoding, which may lead to decreased text
[47]
fictive, and metaphorical motion sentences than when comprehension. In addition, spelling difficulties are
they read idiomatic motion or mental sentences. common in dyslexia [Figure 1]. [48,49] Previous research
Cacciari et al. [42] found neuroscientific evidence for showed that dyslexia was stable, meaning that children
the hypothesis that the activity of the motor areas was who were identified as dyslexic were likely to continue
affected by the motor component of the verb when suffering from reading difficulties throughout their
reading fictive and metaphorical motion sentences. lives. [50,51] The exact prevalence of dyslexia worldwide
is unknown; however, in most studies, the prevalence of
In line with the study by Cacciari et al., [42] Scorolli dyslexia is estimated to be somewhere between 5% and
[52]
et al. [43] were also interested in the motor-cortex 10% of the population. There is no cure for dyslexia, but
involvement underlying sentence comprehension; phonics-based treatments seem to be most successful.
[53]
more precisely, the focus of their study was on the Furthermore, in recent years, several treatment variants
specific role of abstract versus concrete verbs in this using temporal-auditory, articulatory, or multisensory
process. As Scorolli et al. [43] had hypothesized, early exercising programs have been developed in order to
activation of the hand-related motor system was found help individuals with dyslexia. [54]
after reading phrases with concrete verbs, whereas
a delay in the same region was visible after reading TMS research on dyslexia
phrases with abstract verbs. [43] One of the first TMS studies on dyslexia was conducted
by Coslett and Monsul [55] who investigated the
Finally, in their TMS study on normal readers, Acheson hypothesis that the right-hemisphere mediated the
and Hagoort [44] were interested in the processing of reading of patients with acquired dyslexia. A 57-year-old
different kinds of sentences, namely, the so-called: man with (partially recovered) pure alexia participated
“ambiguous” and “unambiguous” sentences. More in the study. The participant’s task was to read aloud
precisely, they tested the hypothesis that the middle words that were presented briefly, while receiving TMS
temporal gyrus played a significant role in the selection on either the right or the left hemisphere. The results
and the integration of lexical-syntactic information of the study supported the right-hemisphere reading
whereas the inferior frontal gyrus was involved in hypothesis because stimulation of the right, but not the
the unification processes needed for the successful left, hemisphere affected oral reading. Moreover, this
understanding of sentences. Their results, [44] indeed, study showed that TMS could be used successfully to
supported the idea that the middle temporal gyrus was answer experimental research questions on dyslexia.
involved in the retrieval of lexical-syntactic information
and that the inferior frontal gyrus was involved in Word-level Sentence-level
the unification processes underlying the successful Normal reader reading It is easy to read this sentence
understanding of sentences.

So far, we have seen that rTMS has become a Reader with dyslexia reabing If is easy to reab fhis senfence
valuable neuroscientific tool for answering questions Figure 1: Examples of how a normal reader and a reader with dyslexia would
related to reading research, both on the word and read the same words and sentences

148 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 Neuroimmunol Neuroinflammation | Volume 2 | Issue 3 | July 15, 2015 149