Proper names play a central role in day-to-day language, and are critical for social functioning. Linguistic, neuropsychological, and philosophical theories often argue that proper names have a special status in language (Kljajevic & Erramuzpe, 2018). While common nouns and verbs refer to categories of objects and events/states respectively, proper nouns refer to unique entities. It is suggested that they are directly referential expressions, and do not name things like common nouns do (Semenza & Zettin, 1989). In other words, it is argued that proper nouns lack meaning in the sense in which common nouns have meaning. Linguistically, they often follow different morpho-syntactic rules (Van Langendonck, 2007). They are more susceptible to forgetting relative to common nouns, controlling for phonological form and frequency (Cohen & Burke, 1993). Cases of patients with proper name anomia (Fukatsu et al., 1999; Martins & Farrajota, 2007; Semenza, 1997), with relatively spared common naming, seem to corroborate this special status of proper names. With this backdrop, one might expect proper names to have clearly distinct neuroanatomical correlates when compared to common names. The search for the neural basis of proper names, however, has revealed areas that are consistently associated with the semantic system and common names. This is surprising given that proper names are expected to be mostly or entirely separate from ‘common’ semantic memory in the above view.
Within the semantic system, angular gyrus (AG) is a central region suggested to be a multimodal or integrative hub (Binder & Desai, 2011; Bonner et al., 2013; Fernandino et al., 2016; Seghier, 2013) that is activated for all types of common nouns, verbs, and sentence stimuli (Binder et al., 2009). AG is found to be activated for proper names as well (Gorno-Tempini et al., 1998; Sugiura et al., 2006; Sugiura et al., 2009). Cases of proper name deficits are also reported with damage to AG (Martins & Farrajota, 2007).
Another region associated with proper names is the anterior temporal lobe (ATL), with many studies suggesting that it has a special role in proper name and person attribute retrieval (Abel et al., 2015; Grabowski et al., 2001; Mehta et al., 2015; Wang et al., 2017). A review of patient studies by Gainotti (2007) suggested distinct roles of the left and right ATL. Damage to the left ATL was associated with proper name retrieval deficits, while that to the right ATL resulted in a loss of familiarity and loss of specific information about a person. With regard to common names, bilateral ATL is also a putative semantic hub where all types of concepts are integrated (Ralph et al., 2017; Rice et al., 2015).
Two other regions with semantic-hub-like characteristics are the posterior cingulate complex1 (PCC) and the medial temporal lobe (MTL) (Fernandino 2016). These are also regions associated with proper names in neuroimaging studies (Gorno-Tempini et al., 1998; Sugiura et al., 2006; Sugiura et al., 2009; Wang et al., 2017).
One possibility is that proper and common names appear to rely on the same regions only under a broad definition of “region.” All of these hub areas have multiple subdivisions that have distinct connectivity and potentially different functional roles. One subdivision of angular gyrus, for example, might specialize in common names while the other in proper names. This may appear to be the same area only when using a general anatomical label and comparing different studies.
Another dimension in processing of proper names is the distinction between people and places. Some theories (Morton et al., 2021) suggest that an anterior-temporal network involving the ATL, inferior frontal/orbitofrontal cortex, and amygdala, due to its role in processing of social stimuli, is associated with names of people. A posterior-medial network, consisting of AG, PCC, and parahippocampal cortex represents situation models and hence is associated with representation of places. Both networks are functionally and anatomically connected to the hippocampus, which may represent domain-general conceptual content.
An additional possibility is that some proper names are special due to their association with rich autobiographical information. Three semantic hubs discussed above — AG, PCC, and MTL — are also part of the autobiographical memory network (Cabeza & St Jacques, 2007; Rissman et al., 2016; Svoboda et al., 2006). Areas within this network may respond specifically to personally familiar entities, reflecting autobiographical or episodic memory-related processes.
In this study, we investigated whether distinct hubs, or distinct subdivisions within hubs, show a preferential response for (1) proper vs. common names, (2) people vs. places, and (3) personally familiar vs. famous people and places. We presented both proper and common names to the same group of participants, avoiding the issue of anatomical variability between different groups of participants and the resulting loss of spatial precision. Proper names were presented in a 3 x 2 design, with personally familiar, famous, and unfamiliar names crossed with people and places. We are especially interested in the response of the four hubs discussed above: AG, ATL, PCC, and MTL. Using the Human Connectome Project (HCP) atlas (Glasser et al., 2016), we identified five subdivisions within each of these four regions, which were probed for their response to proper and common names.
1We use the term ‘posterior cingulate complex’ as a stand-in for an area including posterior cingulate, retrosplenial cortex, and precuneus.