Biology subjects

Humphreys, G. F.

Publications and source records attributed to Humphreys, G. F..

7 recordsLinked to original sources

bioRxiv2026

A lateral temporal network for transmodal combinatorial semantics: Convergent evidence from a multi-study investigation

This study integrates three literatures typically examined in isolation: single-concept semantics, combinatorial semantics, and theory of mind (ToM). We argue that these domains share overlapping computational principles and neuroanatomical networks. Here, we report three major investigations with converging methodological approaches: a meta-analysis of 410 neuroimaging studies, a large omnibus fMRI cross-study comparison (drawing on data from over 150 participants), and two targeted fMRI studies that integrate large language models with traditional psycholinguistic measures, allowing us to quantify combinatorial processing demands and predict brain activation. Across methods, convergent evidence identified a stable, bilateral ATL-STS-TPJ network supporting transmodal combinatorial semantic processing. In addition, the anterior temporal lobe (ATL) showed graded functional specialisation: ventral ATL responded equivalently to single-concept and combinatorial semantics, consistent with a domain-general semantic role, whereas lateral superior ATL was selectively recruited by combinatorial demands. Although ATL-STS-TPJ overlapped with ToM-related activation, targeted control analyses demonstrated that this overlap was eliminated when lexico-syntactic and semantic coherence demands were controlled. Together, these findings support a multimodal combinatorial semantic network centred on bilateral ATL-STS-TPJ with implications for theories of semantic and social cognition. On the basis of these results, we propose a unified theoretical framework of semantic processing.

neuroscience↗

bioRxiv2023

Mapping the task-general and task-specific neural correlates of speech production: meta-analysis and fMRI direct comparisons of category fluency and picture naming

Improving our understanding of the neural network engaged by different forms of speech production is a crucial step for both cognitive and clinical neuroscience. We achieved this aim by exploring two of the most commonly utilised speech production paradigms in research and the clinic, which have been rarely, if ever, compared directly: picture naming and category fluency. This goal was achieved in this two study investigation through a full ALE meta-analysis as well as a targeted fMRI study. Harnessing the similarities and differences between the two tasks offers a powerful methodology to delineate the core systems recruited for speech production, as well as revealing task-specific processes. The results showed that both tasks engaged a bilateral fronto-temporal speech production network, including executive and motor frontal areas, as well as semantic representational regions in the ATL, bilaterally. In addition, it was found that the extent of relative frontal lateralisation was task-dependent with the more executively-demanding category fluency task showing augmented left hemisphere activation. The results have implications for neurocomputational speech production models and the clinical assessment of speech production impairments. Open access: For the purpose of open access, the UKRI-funded authors have applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.

neuroscience↗

bioRxiv2022

The angular gyrus is engaged by autobiographical recall not object-semantics, or event-semantics: Evidence from contrastive propositional speech production

The angular gyrus (AG) has been implicated in a myriad of cognitive functions. Using the previously under-studied naturalistic task of propositional speech production, we investigated the engagement of the left posterior AG (pAG) by three forms of memory: 1) episodic/autobiographical memory, 2) object semantic-memory, and 3) event-semantic knowledge. We conducted an ALE meta-analysis, followed by an fMRI study. The meta-analysis showed that pAG is only engaged as part of the propositional speech network when the task carries an autobiographical component. This finding was supported by the fMRI results, which also showed that: 1) pAG was positively engaged during autobiographical memory retrieval; 2) pAG was strongly deactivated for definitions of object semantics and non-propositional speech; 3) pAG activation increased with the degree to which the event descriptions relied on autobiographical information; 4) critically, the pAG showed a different pattern to known semantic representation regions (e.g., ventral anterior temporal lobe (vATL)) thereby providing clear evidence that the pAG is not acting as a semantic hub. Instead, the pAG activation profile directly mirrored that found in the wider autobiographical retrieval network. We propose that information stored elsewhere in the episodic system is temporally buffered online in the pAG during autobiographical retrieval/memory construction.

neuroscience↗

bioRxiv2021

Couching the brain's multiple-demand and language-specific systems within a macroscale gradient of cortical connectivity

Semantic control is the capability to operate on meaningful representations, selectively focusing on certain aspects of meaning while purposefully ignoring other aspects based on ones behavioural aim. This ability is especially vital for comprehending figurative/ambiguous language. It remains unclear, at the topographical level, why/how regions involved in semantic control seem reliably juxtaposed alongside other functionally specialised regions in the association cortex. We investigated this issue by characterising how semantic control regions topographically relate to the default-mode network (associated with memory and abstract cognition) and multiple-demand network (associated with executive control). Topographically, we confirmed that semantic control areas were sandwiched by the default-mode and multi-demand networks, forming an orderly arrangement observed both at the individual- and group-level. Functionally, semantic control regions exhibited hybrid responses, fusing a preference for cognitively demanding processing (multiple-demand) and a preference for meaningful representations (default-mode) into a domain-specific preference for difficult operations on meaningful representations. When projected onto the principal gradient of human connectome, the neural activity of semantic control showed a robustly dissociable trajectory from visuospatial control, implying different roles in the functional transition from sensation to cognition. We discuss why the hybrid functional profile of semantic control regions might result from their intermediate topographical positions.

neuroscience↗

bioRxiv2021

The Coherent Default Mode Network is not involved in Episodic Recall or Social Cognition

Resting-state network research is extremely influential, yet the functions of many networks remain unknown. In part, this is due to typical (e.g., univariate) analyses testing the function of individual regions and not the full set of co-activated regions that form a network. Connectivity is dynamic and the function of a region may change based on its current connections. Therefore, determining the function of a network requires assessment at the network-level. Yet popular theories implicating the default mode network (DMN) in episodic memory and social cognition, rest principally upon analyses performed at the level of individual brain regions. Here we use independent component analysis to formally test the role of the DMN in episodic and social processing at the network level. As well as an episodic retrieval task, two independent datasets were employed to assess DMN function across the breadth of social cognition; a person knowledge judgement and a theory of mind task. Each task dataset was separated into networks of co-activated regions. In each, the co-activated DMN, was identified through comparison to an a priori template and its relation to the task model assessed. This co-activated DMN did not show greater activity in episodic or social tasks than high-level baseline conditions. Thus, no evidence was found to support hypotheses that the co-activated DMN is involved in explicit episodic or social processing tasks at a network-level. The networks associated with these processes are described. Implications for prior univariate findings and the functional significance of the co-activated DMN are considered.

neuroscience↗

bioRxiv2020

The convergence and divergence of episodic and semantic functions across lateral parietal cortex

Several decades of neuropsychological and neuroimaging research have highlighted the importance of lateral parietal cortex (LPC) across a myriad of cognitive domains. Yet, despite the prominence of this region the underlying function of LPC remains unclear. Two domains that have placed particular emphasis on LPC involvement are semantic memory and episodic memory retrieval. From each domain, sophisticated models have been proposed as to the underlying function, as well as the more domain-general assumption that LPC is engaged by any form of internally-directed cognition (episodic and semantic retrieval both being examples if this process). Here we directly address these alternatives using a combination of fMRI, functional connectivity and DTI white-matter connectivity data. The results show that ventral LPC (angular gyrus) was positively engaged during episodic retrieval but disengaged during semantic memory retrieval. In addition, the level of activity negatively varied with task difficulty in the semantic task whereas episodic activation was independent of difficulty. In contrast, dorsal LPC (intraparietal sulcus) showed domain general activation that was positively correlated with task difficulty. In terms of functional and structural connectivity, a dorsal-ventral and anterior-posterior gradient of connectivity was found to different processing networks (e.g., mid-angular gyrus (AG) connected with episodic retrieval). We propose a unifying model in which LPC as a whole might share a common underlying neurocomputation (e.g., multimodal buffering) with variations in the emergent, expressed cognitive functions across subregions arising from differences in the underlying white matter connectivity.

neuroscience↗

bioRxiv2019

Overarching principles and dimensions of the functional organisation in the inferior parietal cortex

The parietal cortex (PC) is implicated in a confusing myriad of different cognitive processes/tasks. Consequently, understanding the nature and organisation of the core underlying neurocomputations is challenging. According to the Parietal Unified Connectivity-biased Computation (PUCC) model two properties underpin PC function and organisation. Firstly, PC is a multi-domain, context-dependent buffer of time-and space-varying input, the function of which, over time, becomes sensitive to the statistical temporal/spatial structure of events. Secondly, over and above this core buffering computation, differences in long-range connectivity will generate graded variations in task engagement across subregions. The current study tested these hypotheses using a group ICA technique with two independent fMRI datasets (task and resting state data). Three functional organisational principles were revealed. Factor 1: inferior PC was sensitive to the statistical structure of sequences for all stimulus types (pictures, sentences, numbers). Factor 2: a dorsal-ventral variation in generally task-positive vs. task-negative (variable) engagement. Factor 3: An anterior-posterior dimension in inferior PC reflecting different engagement in verbal vs. visual tasks, respectively. Together the data suggest that the core neurocomputation implemented by PC is common across domains, with graded task engagement across regions reflecting variations in the connectivity of task-specific networks that interact with parietal cortex.

neuroscience↗