Language processing from the perspective of electrical stimulation mapping

ABSTRACT

Electrical Stimulation (ES) is a neurostimulation technique that is used to localize language functions in the brain of people with intractable epilepsy and/or brain tumors. We reviewed 25 ES articles published between 1984 and 2018 and interpreted them from a cognitive neuropsychological perspective. Our aim was to highlight ES as a tool to further our understanding of cognitive models of language. We focused on associations and dissociations between cognitive functions within the framework of two non-neuroanatomically specified models of language. Also, we discussed parallels between the ES and the stroke literatures and showed how ES data can help us to generate hypotheses regarding how language is processed. A good understanding of cognitive models of language is essential to motivate task selection and to tailor surgical procedures, for example, by avoiding testing the same cognitive functions and understanding which functions may be more or less relevant to be tested during surgery.

KEYWORDS:

• Awake surgery
• language
• direct electrical stimulation
• cognitive neuroscience

Disclosure statement

No potential conflict of interest was reported by the authors regarding the materials or methods used in this study or the findings reported in this paper.

ORCID

Adrià Rofes http://orcid.org/0000-0002-4274-1734

Notes

1. Differently from the model by Whitworth et al. (2014), we referred to lexical-semantics (instead of semantic system), included object concepts as a distinct function separate from lexical-semantics, and added a function for the representation and processing of lexical syntax that is shared by the output phonological and orthographic output lexica. The distinction between object concepts and lexical-semantics, as well as a separate level for lexical-syntax, are useful for explaining some of the DES findings.

2. Future work may consider ES studies of bilingual/multilingual questions (e.g., Borius, Giussani, Draper, & Roux, 2012; Fernández-Coello et al., 2017; Giussani et al., 2009; Mesgarani & Chang, 2012; Ojemann & Whitaker, 1978; Penfield & Roberts, 1959; Rodríguez-Fornells, Rotte, Heinze, Nösselt, & Münte, 2002). Here we chose not to include these studies because the questions investigated typically differ from those of monolingual studies. For example, from a cognitive perspective, bilingual studies have traditionally focused on answering whether two or more languages are realized in the same or different neural substrates (Macnamara, Krauthammer, & Bolgar, 1968; Penfield & Roberts, 1959). More recent studies have examined the possibility of inhibitory mechanisms that suppress one language, while allowing the production of a second language (e.g., Colomé, 2001; Dijkstra, Timmermans, & Schriefers, 2000; Green, 1998; Mosca & de Bot, 2017).

3. Here “writing” refers to the processes that involve lexical-semantics, orthographic output lexicon, graphemic buffer, including graphic motor programming. Note that researchers may refer to “writing” as motor aspects (graphic motor programming) and to “spelling” as the cognitive processes needed to write a word (e.g., orthographic output lexicon, graphemic buffer).

Additional information

Funding

Funding was provided by the GBHI (Global Brain Health Institute) to AR; by the PAT (Provincia Autonoma di Trento) and Fondazione CaRiTRO (Cassa di Risparmio di Trento e Rovereto) to GM.