Roles of the Default Mode and Multiple-Demand Networks in Naturalistic versus Symbolic Decisions

Abstract

The default mode network (DMN) is often associated with representing semantic, social, and situational content of contexts and episodes. The DMN may therefore be important for contextual decision-making, through representing situational constraints and simulating common courses of events. Most decision-making paradigms, however, use symbolic stimuli and instead implicate cognitive control regions, such as the multiple demand (MD) system. This fMRI study aimed to contrast the brain mechanisms underlying decision-making based on rich naturalistic contexts or symbolic cues. While performing an ongoing task, 40 human participants (25 female) responded to different sounds. For one sound, the stimulus-response mapping was fixed; responses for the other sounds depended on the visual context: either lifelike scenes or letter symbols, varying across participants. Despite minimal behavioral differences between the groups, posterior DMN regions showed increased activity during context-dependent decision-making using the naturalistic scenes only, compared with symbolic cues. More anterior temporal and frontal DMN regions showed a different pattern, with sensitivity to the need for contextual control, but not to the type of context. Furthermore, in the scenes group, widespread DMN regions showed stronger representation of not just the context but also the sound whose significance it modulated. In comparison, the MD system showed strong univariate activity for every decision, but, intriguingly, somewhat reduced activity in the case of a scene-based but demanding context-dependent decision. Depending on context, we suggest, either DMN or MD regions may play a prominent role in selection and control of appropriate behavior. SIGNIFICANCE STATEMENT Contextual knowledge is widely believed to be important for guiding real-world goal-directed behavior. Much remains to be understood, however, regarding the underlying brain mechanisms. Using a novel paradigm to contrast decisions based on richly meaningful naturalistic scenes with decisions based on symbolic cues, we find that both multiple demand regions and default mode regions may contribute to the cognitive control of behavior. Rich semantic context enhances representation not just of the context itself, but also of the contents of the decision that it controls. Dependence of a decision on naturalistic context can also reverse the common pattern of multiple demand regions responding more, and default mode regions responding less, to more difficult decisions.

Dynamic Subcortical Modulators of Human Default Mode Network Function

“…Given that the self condition, like rest, promotes an internal mental focus, this suggests that BF responses generally tracked the switch between internal and external cognitive states. While DMN cortical regions also exhibited switching responses during the rest to external task transitions, consistent with other recent studies (Crittenden et al 2015;Smith et al 2018Smith et al , 2021, they were less prominent than the BF's response and were more broadly defined by activity suppression. In the rodent study by Nair et al (2018), the transition between rest and external task states, especially the reengagement of DMN cortical activity during rest, was causally attributed to BF function.…”

A voice without a mouth no more: The neurobiology of language and consciousness

“…Results tend to support a proposal by which this involvement in tasks largely occurs when they benefit from memory guidance (Crittenden et al, 2015;Konishi et al, 2015;Murphy et al, 2019Murphy et al, , 2018Sormaz et al, 2018;Spreng et al, 2014;Vatansever et al, 2017). Some HOLISTIC Model 37 have even suggested that those memories take the form of contextually relevant situation models (Chen et al, 2017;Keidel et al, 2018;Ranganath and Ritchey, 2012;Smith et al, 2021Smith et al, , 2018.…”

Unraveling the functional attributes of the language connectome: crucial subnetworks, flexibility and variability

“…The specialization of such a network in the active controlled integration of exteroceptive information may lead to the provision of relevant information in working memory (Parr & Friston, 2017) in order to construct an internal representation of the external world that is relevant to the individual at a specific time. Second, the fronto-parietal network [FPN; close to the Multiple Demand Network (MDN): Smith et al, 2021, or to the Central Executive Network (CEN); Doucet et al, 2019] is a network involved in all processing requiring controlled attention directed toward internal cues and goals. This network operates for endogenous and top-down attentional redirection (Perrone-Bertolotti et al, 2020) and is engaged in verbal working memory and “fluid” cognition (Assem et al, 2020).…”