Regional Specialization and Coordination Within the Network for Perceiving and Knowing About Others

Abstract

Seeing familiar faces prompts the recall of diverse kinds of person-related knowledge. How this information is encoded within the well-characterized face-/person-selective network remains an outstanding question. In this functional magnetic resonance imaging study, participants rated famous faces in 10 tasks covering 5 domains of person knowledge (social, episodic, semantic, physical, and nominal). Comparing different cognitive domains enabled us to 1) test the relative roles of brain regions in specific cognitive processes and 2) apply a multivariate network-level representational similarity analysis (NetRSA) to gain insight into underlying system-level organization. Comparing across cognitive domains revealed the importance of multiple domains in most regions, the importance of social over nominal knowledge in the anterior temporal lobe, and the functional subdivision of the temporoparietal junction into perceptual superior temporal sulcus and knowledge-related angular gyrus. NetRSA revealed a strong divide between regions implicated in "default-mode" cognition and the fronto-lateral elements that coordinated more with "core" perceptual components (fusiform/occipital face areas and posterior superior temporal sulcus). NetRSA also revealed a taxonomy of cognitive processes, with semantic retrieval being more similar to episodic than nominal knowledge. Collectively, these results illustrate the importance of coordinated activity of the person knowledge network in the instantiation of the diverse cognitive capacities of this system.

Keywords: cortical network; fMRI; face perception; representational similarity analysis; semantics.

Figure 1

(A) Top: Schematic representation of the experiment. Experimental blocks were preceded by 4s of instruction screen, and 6s fixation point. Each trial consisted of .5s face presentation and 2s fixation. Bottom: five domains of person knowledge and two questions per domain are noted in corresponding colours. (B) Data analysis schematic. ROI beta averages for each of the ten tasks were extracted from ROIs, correlated and subjected to RSA. [add ‘task→’ to top right panel]. [‘correlation matrix’ might be a bit vague]

Figure 2

Regional response to person knowledge access (average of experimental tasks > face control task). Bars show response estimate magnitude (beta value), error bars represent standard error of the mean (SE). Retrieving person knowledge activated extended system regions to variable extent, but core system did not show an increased response. Could we maybe space out the sub-networks (I want it visually clear that the core is donw, frontolateral is up etc, and it is not at the moment)

Figure 3

[asterisk are still not centred.] [lateral-frontal axis label seems uncentered] [labels for cog domain are un-aligned] Figure 3. Regional preference patterns. Percentage of total activation elicited by each cognitive domain. Stars denote significance threshold. Most regions are involved in most cognitive domains. Although patterns vary across components of the network, it can also be seen that regions that respond to episodic knowledge tend to respond to semantic access as well.

Figure 4

[straighten colourbar labels] [use more asterisks to indicate robustness of significance] [make blue line in A) black] [the IFG anf OFC labels on the network organisation models confused me]. [Y-label on model evidence] Figure 4. A) ROI clustering. First major division separates core together with IFG & OFC from the rest of the extended system (red vs (green + purple)). Within the extended system, a further division is evident between medial temporal regions and regions involved in the intrinsic system (purple, green). B) Schematic representation of clusters projected onto the brain. C) model comparison schematic. Competing models of network organisation were constructed, fitted to observed data for each participant, and compared in a paired samples t-test.

Figure 5

A) [random bar for ‘task couplet bar plot- either shift the asterisk of kill the bar]] Task similarity in core and extended system ROIs. Tasks are grouped according to the domain they were sampled from. Episodic and semantic knowledge retrieval tasks elicit differentiable patters from nominal, physical or social ones (dendrogram, left). B) fMRI pattern similarity matrix and models tested. [change range for b to .5 – .75.] [could add ***s to indicate greater significance]

Figure 6

[BIGGER] Figure 6. Cognition specific brain activations. Whole brain map highlights peripheral, domain specific cognitive systems that are recruited during diverse kinds of person-knowledge retrieval. Semantic knowledge did not elicit significant clusters of activity.