Language is the ability to acquire and use complex systems of communication, particularly the human ability to do so, and a language is any specific example of such a system. The scientific study of language is called linguistics.

Verbal memory is a term used in cognitive psychology that refers to memory of words and other abstractions involving language.

Classic models of language organization posited that separate motor and sensory language foci existed in the inferior frontal gyrus (Broca's area) and superior temporal gyrus (Wernicke's area), respectively, and that connections between these sites (arcuate fasciculus) allowed for auditory-motor interaction.

These theories have predominated for more than a century, but advances in neuroimaging and stimulation mapping have provided a more detailed description of the functional neuroanatomy of language. New insights have shaped modern network-based models of speech processing composed of parallel and interconnected streams involving both cortical and subcortical areas. Recent models emphasize processing in “dorsal” and “ventral” pathways, mediating phonological and semantic processing, respectively. Phonological processing occurs along a dorsal pathway, from the posterosuperior temporal to the inferior frontal cortices. On the other hand, semantic information is carried in a ventral pathway that runs from the temporal pole to the basal occipitotemporal cortex, with anterior connections.

Functional MRI has poor positive predictive value in determining critical language sites and should only be used as an adjunct for preoperative planning.

Cortical mapping and subcortical mapping should be used to define functional resection boundaries in eloquent areas and remains the clinical gold standard.

In tracing the historical advancements in our understanding of speech processing, Chang et al. hope to not only provide practicing neurosurgeons with additional information that will aid in surgical planning and prevent postoperative morbidity, but also underscore the fact that neurosurgeons are in a unique position to further advance our understanding of the anatomy and functional organization of language 1).

Human language organization models and language time course patterns are still predominantly derived from meta-analyses of numerous single publications, which only investigated scattered cortical regions. Moreover, there is not much literature available on the exact impact of repetitive navigated transcranial magnetic stimulation (rTMS) onset times on object naming. We, therefore, used a virtual lesion-based approach by mapping various cortical areas with rTMS to investigate the time course of object naming, and to specifically provide data on the pattern of rTMS language mapping results depending on different stimulation onset times. Ten healthy, right-handed subjects were enrolled, and rTMS in combination with an object-naming task was performed with different stimulation onset times (0 ms, 100 ms, 200 ms, 300 ms, 400 ms, and 500 ms). Subsequent to language mapping, all naming errors detected were systematically classified with respect to previous literature. The majority of errors was elicited within the opercular inferior frontal gyrus (opIFG) and ventral precentral gyrus (vPrG), and the spatial distribution of naming errors changed according to the time point of naming disruption by varying onset times. For instance, immediate rTMS onset led to a widespread cortical distribution of no responses, whereas performance and hesitation errors increased with higher stimulation onset times 2).

Mapping the language system has been crucial in preoperative evaluation especially when the area to be resected is near the relevant eloquent cortex. Functional magnetic resonance imaging (fMRI) proved to be a noninvasive alternative to the Wada test that can account not only for language lateralization but also for localization when appropriate tasks and MRI sequences are being used. The tasks utilized during the fMRI acquisition are playing a crucial role in which areas will be activated. Recent studies demonstrated that key language regions exist outside the classical model of “Wernicke-Lichtheim-Geschwind,” but sensitive tasks must take place in order to be revealed. On top of that, the tasks should be in the mother tongue for appropriate language mapping to be possible.

For that reason, in this study, Gkiatis et al. adopted an English protocol that can reveal six language critical regions even in clinical setups and we translated it into Greek to prove its efficacy in a Greek population. Twenty healthy right-handed volunteers were recruited and performed the fMRI acquisition in a standardized manner.

Results demonstrated that all six language critical regions were activated in all subjects as well as the group mean map. Furthermore, activations were found in the thalamus, the caudate, and the contralateral cerebellum.

Gkiatis et al. standardized an fMRI protocol in Greek and proved that it can reliably activate six critical language regions. They validated its efficacy for presurgical language mapping in Greek patients capable to be adopted in clinical setup 3).

Chang EF, Raygor KP, Berger MS. Contemporary model of language organization: an overview for neurosurgeons. J Neurosurg. 2015 Feb;122(2):250-61. doi: 10.3171/2014.10.JNS132647. Epub 2014 Nov 28. PubMed PMID: 25423277.
Sollmann N, Ille S, Negwer C, Boeckh-Behrens T, Ringel F, Meyer B, Krieg SM. Cortical time course of object naming investigated by repetitive navigated transcranial magnetic stimulation. Brain Imaging Behav. 2016 Jul 22. [Epub ahead of print] PubMed PMID: 27448161.
Gkiatis K, Garganis K, Benjamin CF, Karanasiou I, Kondylidis N, Harushukuri J, Matsopoulos GK. Standardization of presurgical language fMRI in Greek population: Mapping of six critical regions. Brain Behav. 2022 May 19:e2609. doi: 10.1002/brb3.2609. Epub ahead of print. PMID: 35587046.
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