Minimal Phrase Composition Revealed by Intracranial Recordings

Abstract

The ability to comprehend phrases is an essential integrative property of the brain. Here, we evaluate the neural processes that enable the transition from single-word processing to a minimal compositional scheme. Previous research has reported conflicting timing effects of composition, and disagreement persists with respect to inferior frontal and posterior temporal contributions. To address these issues, 19 patients (10 male, 9 female) implanted with penetrating depth or surface subdural intracranial electrodes, heard auditory recordings of adjective-noun, pseudoword-noun, and adjective-pseudoword phrases and judged whether the phrase matched a picture. Stimulus-dependent alterations in broadband gamma activity, low-frequency power, and phase-locking values across the language-dominant left hemisphere were derived. This revealed a mosaic located on the lower bank of the posterior superior temporal sulcus (pSTS), in which closely neighboring cortical sites displayed exclusive sensitivity to either lexicality or phrase structure, but not both. Distinct timings were found for effects of phrase composition (210-300 ms) and pseudoword processing (;300-700 ms), and these were localized to neighboring electrodes in pSTS. The pars triangularis and temporal pole encoded anticipation of composition in broadband low frequencies, and both regions exhibited greater functional connectivity with pSTS during phrase composition. Our results suggest that the pSTS is a highly specialized region composed of sparsely interwoven heterogeneous constituents that encodes both lower and higher level linguistic features. This hub in pSTS for minimal phrase processing may form the neural basis for the humanspecific computational capacity for forming hierarchically organized linguistic structures.

Shared functional specialization in transformer-based language models and the human brain

“…For example, analyzing the encoding weights for transformations (Fig. 5) revealed that posterior temporal areas assign higher weights to heads at earlier layers (positive values along PC1) with shorter look-back distance (negative values along PC2), consistent with previous work suggesting that posterior temporal areas perform early-stage syntactic (and lexico-semantic) processing (Hickok & Poeppel, 2000Flick & Pylkkänen, 2020;Murphy et al, 2022). Headwise correspondence in posterior temporal cortex was high for the ccomp and dobj dependencies (Fig.…”

Integrity of the Left Arcuate Fasciculus Segments Significantly Affects Language Performance in Individuals with Acute/Subacute Post-Stroke Aphasia: A Cross-Sectional Diffusion Tensor Imaging Study

“…Therefore, consistent with these findings, our results support the relationship between damage to the left PSAF and comprehension and repetition deficits in acute/subacute PSA. Given the importance of the temporal and parietal lobes for phrase comprehension and sentence syntactic processing [ 54 , 62 ] and its anatomical connection between these two areas, we inferred that the PSAF might play an important role in higher-order language functions (e.g., syntax), which was expected to be verified in future research.…”

“…In the DTI studies by Ivanova and colleagues [ 15 , 44 ], the FA value and volume measurements of the PSAF were significantly related to some lexical-semantic and syntactic language abilities, including auditory comprehension. Based on these previous reports and two recent studies that demonstrated that the pSTG, pMTG, and the posterior superior temporal sulcus (pSTS) were crucial for sentence comprehension and phrase comprehension [ 54 , 62 ], it is not novel to state that damage to the temporal cortical language areas and the left PSAF significantly affected auditory comprehension ability.…”

The spatiotemporal dynamics of semantic integration in the human brain

“…Recruitment of pSTS was earliest (approximately 200 ms), and may pertain to composition-related demands or lexical search effort (Fig. 5–7), indexing greater engagement of compositional processing due to semantic narrowing demands (Flick and Pylkkänen, 2020; Matchin and Hickok, 2020), in particular given previous intracranial work implicating this region in basic semantic composition and lexicality (Murphy et al, 2022b). ATL engagement is in line with its apparent role in conceptual processing and entity-related (e.g., common object) representations (Thye et al, 2021; Turken and Dronkers, 2011).…”

“…Portions of fronto-temporal cortex were engaged for all aspects of language semantics, but become rapidly dedicated to certain processes at distinct times. Previous intracranial work has implicated pSTS in the initial construction of meaningful phrases, and IFS in the later evaluation of these phrases in the service of phrase-picture matching (Murphy et al, 2022b). Our results further highlight the role of pSTS-IFS in semantic composition demands, with early narrowing effects in pSTS (onset ∼ 250 ms) being followed by effects for all compositional processes in IFS (∼ 500 ms) (Fig.…”