The language network is recruited but not required for non-verbal event semantics

Abstract

Consistent with longstanding findings from neuropsychology, several brain regions in left frontal and temporal cortex respond robustly and selectively to language [1]. These regions, often referred to as the "language network", respond more strongly to meaningful stimuli (like words and sentences) than to stimuli devoid of meaning (like pseudowords and Jabberwocky sentences) [2]. But are these regions selectively recruited in processing linguistic meaning? Or do they instead store and/or process complex semantic information independent of its format (sentences or pictures)? In Experiment 1, we scanned participants with fMRI while they performed a semantic plausibility judgment task vs. a difficult perceptual control task on sentences and line drawings that describe/depict simple agent-patient interactions. We found that the language regions responded more strongly when participants performed the semantic task compared to the perceptual task, for both sentences and pictures (although sentences elicited overall stronger responses). Thus, healthy adults engage language regions when processing non-verbal meanings. But is this engagement necessary for understanding pictorial depictions of events? In Experiment 2, we tested two individuals with global aphasia, who have sustained massive damage to perisylvian language areas and display severe language difficulties, together with a group of control participants. Individuals with aphasia were at chance on a task of matching the sentences and pictures. However, they performed close to controls in assessing the plausibility of pictorial depictions of agent-patient interactions. Taken together, these results indicate that the left fronto-temporal language system is recruited but not necessary for processing complex non-verbal meanings.

Behavioral correlates of cortical semantic representations modeled by word vectors

“…Although these brain regions, primarily the posterior and temporal cortices, are consistent with previous reports on the modeling of semantic representations (Huth et al, 2012;Nishida et al, 2020a), it may be argued that these regions do not encompass the entire language network, including the left inferior frontal and superior temporal cortices (Friederici and Gierhan, 2013). However, a recent study has clearly demonstrated that language network is not necessarily involved in semantic processing that requires no explicit linguistic processing (Ivanova et al, 2019). They reported that aphasia patients with physical damage to the language network manifested severely declined performance in semantic tasks with linguistic information, but performance equivalent to healthy controls in semantic tasks with nonlinguistic information.…”

The Domain-General Multiple Demand (MD) Network Does Not Support Core Aspects of Language Comprehension: A Large-Scale fMRI Investigation

“…In the remaining 484 localizer sessions, participants read the materials passively and performed a simple button-press task at the end of each trial (included to help participants remain alert). The language localizer has been shown to be robust to changes in the materials, modality of presentation, and task (Fedorenko et al, 2010;Fedorenko, 2014;Scott et al, 2017;Ivanova et al, 2019).…”

No evidence for functional distinctions across fronto-temporal language regions in their temporal receptive windows

“…Second, to avoid over-inclusiveness, the contrast should not identify functional networks that are distinct from the core language network and might be recruited during online comprehension for other reasons (e.g., task-demands, attention, episodic encoding, non-verbal knowledge retrieval, or mental state inference). Whereas there are many potential differences between the processing of sentences vs. nonwords that might engage such non-linguistic processes, the identified regions exhibit robust language-selectivity in their responses, showing little or no response to non-linguistic tasks (Fedorenko et al, 2011;Fedorenko et al, 2012a;Pritchett et al, 2018;Ivanova et al, 2019;Jouravlev et al, 2019; For a review, see Fedorenko and Varley, 2016). Moreover, these regions are internally synchronized with one another during naturalistic cognition, yet are strongly dissociated from other brain networks (Blank et al, 2014;Paunov et al, 2019; for evidence from inter-individual differences, see: Mineroff et al, 2018).…”

“…(Unlike previous reports from our group that had used an additional mask in the angular gyrus, we decided to exclude this region going forward because it does not appear to be a part of the core language network in either its task-based responses or its signal fluctuations during naturalistic cognition. See, e.g., Blank et al, 2014;Blank et al, 2016;Pritchett et al, 2018;Ivanova et al, 2019;Jouravlev et al, 2019;Paunov et al, 2019).…”

“…Language comprehension engages a cortical network of frontal and temporal brain regions, primarily in the left hemisphere (Binder et al, 1997;Bates et al, 2003;Fedorenko et al, 2010;Menenti et al, 2011). There is ample evidence that this "core language network" is language-selective and is not recruited by other mental processes (Fedorenko and Varley, 2016; see also Pritchett et al, 2018;Ivanova et al, 2019;Jouravlev et al, 2019), indicating that it either employs cognitively unique representational formats and/or implements algorithms distinct from those recruited in other cognitive domains. Nonetheless, the functional architecture of this network-i.e., the division of linguistic labor among its constituent regions-remains highly debated.…”