Neural basis of semantic control

Every form of semantically-driven human behaviour is supported by ‘semantic control’, which refers to executive processes that regulate access to semantic knowledge. In verbal and nonverbal tasks, semantic access needs to be ‘regulated’ in a time and context specific fashion to allow appropriate behaviours. In general terms, semantic control is known to be supported by frontal-parietal-temporal brain areas. Nevertheless, the specific networks and the exact contribution of each area in the networks to semantic control remain to be determined yet. Addressing these challenging questions is crucial to understand how semantic control is implemented in the brain and, therefore, healthy and pathological functioning during everyday verbal and nonverbal semantic activities (e.g. speaking, object use). Besides advancing our general understanding, these questions are also important to guide clinical research and practice, since different parts of the network can be affected by brain damage. The overall goal of this project was to reveal the brain areas and the neural networks underpinning semantic control and to provide new evidence on their functional specialization. To do so, we adopted a multimethod approach that ultimately provided convergent evidence on these key issues. In fact, by carrying out functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) studies we have been able to localize the brain structures and the networks engaged in semantic control and to test whether a brain region revealed by fMRI would have had a necessary role for semantic control.

Work completed
-Implementation of the experimental paradigms for the project (including task design, creation and rating of the stimuli, and programming of the task).
-Acquisition and analysis of pilot data for both fMRI and TMS studies.
-FMRI and TMS data acquisition and analysis.
-Presentation of results at international conferences.
-Preparation of manuscripts for publication.

Main results
The research objective of this research proposal was to reveal the brain areas and the networks underpinning semantic control and to provide new evidence on their functional specialization. The main results of the project can be summarised as follows: (1) Different functional networks support different cognitive processes for the integration of semantic information during language processing; (2) A language-semantic control network (LSN) and two visual attentional networks (VANs) were likely reflecting semantic-specific and domain-general control processes respectively, jointly recruited to integrate meaning during the task; (3) A left fronto-parietal network (LFPN) was sensitive to context integration rather than to semantic integration demands. This network might be crucial to buffer and integrate episodic information (e.g. who, where, when) presented in the narrative; (2) Contrary to previous claims, our results suggest that the default mode network (DMN) does not support semantic processing; (5) FMRI and TMS results together revealed that the Angular Gyrus (AG), an overlapping region between SLN, DMN and LFPN, is crucial for episodic retrieval rather than semantic processing.

Exploitation and dissemination
Conference Presentations:
Branzi, Pobric,... & Lambon-Ralph (2018). The contribution of the left angular gyrus in combinatorial processes during narrative reading. BNS, London (UK).
Branzi, Humphreys,... & Lambon-Ralph (2017). Reconfiguration of the semantic and default mode networks induced by variations of semantic context during comprehension of written narratives. SNL, Baltimore (USA).
Branzi, Humphreys,... & Lambon-Ralph (2017). Reconfiguration of the semantic and default mode networks induced by variations of semantic context during comprehension of written narratives. BNS, London (UK).
Branzi, Biau,... & Costa (2017). Bilingual lexical access is triggered by the intention to speak: behavioral and ERP/EEG evidence. Dutch Neuroscience meeting, Lunteren (The Netherlands).
Branzi, Biau,... & Costa (2017). Bilingual lexical access is triggered by the intention to speak: behavioral and ERP/EEG evidence. CNS, San Francisco (USA). Poster Presentation.
Branzi, Martin,... & Paz-Alonso (2016). Proactive and reactive control during bilingual lexical access is driven by different portions within the prefrontal cortex. SNL, London (UK).
Martin, Branzi, & Bar (2016). Prediction is production: ERP evidence in sentence comprehension. SNL, London (UK).
Branzi, Martin,... & Paz-Alonso (2016). Proactive and reactive control during bilingual lexical access is driven by different portions within the prefrontal cortex. AMLAP, Bilbao (Spain).
Martin, Branzi, & Bar (2016). Prediction is production: ERP evidence in sentence comprehension. AMLAP, Bilbao (Spain).
Branzi, Paz-Alonso,... & Carreiras (2016). Proactive and reactive control during bilingual lexical access is driven by different portions within the prefrontal cortex. CNS, New York (USA).

Manuscripts:
Branzi, Humphreys,... & Lambon-Ralph (In prep.). When the semantic context change: revealing the functional networks during processing of written narratives using Independent Component Analysis.
Branzi, Pobric,... & Lambon-Ralph (In prep). The contribution of the left angular gyrus in combinatorial processes during narrative reading.
Martin, Branzi, & Bar (2018). Prediction is Production: The missing link between language production and comprehension. Scientific Reports, 8, 1079.
Branzi, Calabria,... & Costa (2018). On the bilingualism effect in task-switching. Bilingualism: Language and Cognition, 1-14.
Canini,... Branzi, Costa, & Abutalebi (2016). Semantic interference and its control: A functional neuroimaging and connectivity study. Human Brain Mapping. 37, 4179-4196.
Branzi, Calabria,... & Costa (2016). On the overlap between bilingual language control and domain-general executive control. Acta Psychologica, 166, 21-30.

Damage to different brain regions can be potentially responsible for different semantic impairments in stroke patients. However, the establishment of a causal link between neural structures and behaviour is not trivial in clinical settings. In fact, lesions rarely honor areal boundaries and typically damage not only cortex, but also white matter. Therefore, the locus of the lesion responsible for an observed impairment is quite difficult to determine. With fMRI and TMS techniques we establish causal links between a specific area and behavior in healthy participants and use this information to design neuropsychological interventions tailored to patients’ needs. Recently, the use of neurostimulation for cognitive rehabilitation in stroke aphasia patients has gained attention. Some studies in fact have been able to demonstrate a positive effect of long-term neurostimulation on behavioural performance after structural brain damage. To that end, however, it is first necessary to determine the brain structures relevant for the specific semantic behaviours that need to be rehabilitated in healthy populations. The findings from the present project provide this important information, especially in relation to verbal aspects of semantic cognition. For this reason, the results from this project will be particularly useful for guiding current and future interventions for the rehabilitation of stroke patients, especially those that will use neurostimulation as rehabilitative tool.

Periodic Reporting for period 1 - NBSC (Neural basis of semantic control)

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