Dynamic semantic cognition: Characterising coherent and controlled conceptual retrieval through time using magnetoencephalography and chronometric transcranial magnetic stimulation

Abstract

Distinct neural processes are thought to support the retrieval of semantic information that is (i) coherent with strongly-encoded aspects of knowledge, and (ii) non-dominant yet relevant for the current task or context. While the brain regions that support readily coherent and more controlled patterns of semantic retrieval are relatively well-characterised, the temporal dynamics of these processes are not well-understood. This study used magnetoencephalography (MEG) and dual-pulse chronometric transcranial magnetic stimulation (cTMS) in two separate experiments to examine temporal dynamics during the retrieval of strong and weak associations. MEG results revealed a dissociation within left temporal cortex: anterior temporal lobe (ATL) showed greater oscillatory response for strong than weak associations, while posterior middle temporal gyrus (pMTG) showed the reverse pattern. Left inferior frontal gyrus (IFG), a site associated with semantic control and retrieval, showed both patterns at different time points. In the cTMS experiment, stimulation of ATL at ∼150 msec disrupted the efficient retrieval of strong associations, indicating a necessary role for ATL in coherent conceptual activations. Stimulation of pMTG at the onset of the second word disrupted the retrieval of weak associations, suggesting this site may maintain information about semantic context from the first word, allowing efficient engagement of semantic control. Together these studies provide converging evidence for a functional dissociation within the temporal lobe, across both tasks and time.

The neurocognitive basis of knowledge about object identity and events: dissociations reflect opposing effects of semantic coherence and control

“…By contrast, TMS to AG particularly disrupted the efficient retrieval of strong associations [71]. Our recent MEG results are consistent with this functional distinction within temporoparietal cortex [40,41]. pMTG showed a more substantial oscillatory response in weak association trials, while AG (along with ATL) showed a larger response to pairs of words that were linked by a strong association.…”

“…Alternatively, manipulations of semantic control and judgements of thematic or event relations might rely on shared computational principles, explaining the similarity of largescale networks (beyond pMTG) that are implicated in these aspects of cognition [5,53]. We have suggested that pMTG might provide a dynamically updated conceptual 'context' which supports the tailored retrieval of currently relevant knowledge, even when this information is not the most strongly encoded within long-term memory [40]. This type of conceptual context would be expected to play a crucial role in the recovery of weakly instantiated knowledge that is important to the ongoing circumstances, but a less crucial role for dominant features or associations which are thought to be readily recovered within ATL without additional processing.…”

Conceptual and Perceptual Dimensions of Word Meaning Are Recovered Rapidly and in Parallel during Reading

“…To date, separate and complementary findings from a variety of time-resolved techniques provide partial and indirect support to the prediction made by the huband-spoke model. Chronometric TMSs and magnetoencephalography (MEG) findings indicate that ATL plays a crucial role in semantic processing 200-600 msec poststimulus onset (Teige et al, 2018;Jackson, Lambon Ralph, & Pobric, 2015;Lau, Gramfort, Hämäläinen, & Kuperberg, 2013). Although studies on the temporal features of word meaning access have traditionally focused on lateappearing ERPs, notably the N400 (Lau, Phillips, & Poeppel, 2008;Kutas & Federmeier, 2000), there is now evidence that semantic information is recovered much earlier in time.…”

The neural basis of semantic cognition in Mandarin Chinese: A combined fMRI and TMS study

“…Moreover, patients with damage on left IFG showed greater semantic deficits on similar tasks which require high executive control demands. These findings suggest that the prefrontal cortex is mainly associated with semantic control process (Corbett et al, 2009;Corbett, Jefferies, & Lambon Ralph, 2011;Jefferies, Patterson, & Ralph, 2008;Noonan et al, 2010;Novick, Kan, Trueswell, & Thompson-Schill, 2009;Soni et al, 2009;Teige et al, 2018).…”

“…For example, left IFG activation largely increases when participants identify words with weak associations or accessing words with ambiguous meaning (Badre, Poldrack, Paré-Blagoev, Insler, & Wagner, 2005;Noppeney, Phillips, & Price, 2004;. These findings suggest that the prefrontal cortex is mainly associated with semantic control process (Corbett et al, 2009;Corbett, Jefferies, & Lambon Ralph, 2011;Jefferies, Patterson, & Ralph, 2008;Noonan et al, 2010;Novick, Kan, Trueswell, & Thompson-Schill, 2009;Soni et al, 2009;Teige et al, 2018). These findings suggest that the prefrontal cortex is mainly associated with semantic control process (Corbett et al, 2009;Corbett, Jefferies, & Lambon Ralph, 2011;Jefferies, Patterson, & Ralph, 2008;Noonan et al, 2010;Novick, Kan, Trueswell, & Thompson-Schill, 2009;Soni et al, 2009;Teige et al, 2018).…”