The left temporal pole is important for retrieving words for unique concrete entities

Abstract

Background: The neuroanatomical basis of lexical retrieval has been studied intensively. The current review focuses on the special case of proper nouns.

Aims: This article reviews a programme of research that has used both lesion‐deficit and functional‐imaging (PET) approaches to investigate the neuroanatomical basis for lexical retrieval of proper nouns. In lesion‐deficit studies we found that damage to the left temporal polar (TP) region leads to reliable and specific impairments in naming famous persons (e.g., “George Clooney”) and famous landmarks (e.g., “Golden Gate Bridge”). In functional‐imaging studies we found that when participants name famous persons and landmarks they produce specific activation (increases in regional cerebral blood flow) in the left TP region.

Main Contribution: These findings converge with lesion and functional‐imaging data from other laboratories to support the idea that the left TP region is important for the retrieval of names for unique concrete entities, persons and landmarks being typical examples of such categories of entities.

Conclusions: We have interpreted these results within a theoretical framework which suggests that left TP contains convergence regions that operate as intermediaries between conceptual knowledge retrieval and lexical retrieval for classes of unique concrete entities.

Keywords:

• Aphasia
• Anomia
• Proper nouns
• Visual naming
• Lesion
• Positron emission tomography

Notes

Supported by Program Project Grant NINDS NS19632.

1. The Patient Registry provides the pool of neurological patients for all the lesion studies from our laboratory presented in this article. The Registry contains a large number of patients with focal, stable brain lesions, who have been extensively characterised from both neuropsychological (Tranel, 2007) and neuroanatomical (Frank, Damasio, & Grabowski, 1997) perspectives.

2. Recovery, in both neurological and neuropsychological terms, can take place beyond 3 months, but the most substantial changes occur within the first 3 months following brain damage. Moreover, most of our patients are quite a bit farther out from their brain damage at the time of data collection, and the typical time since lesion onset in most of our language studies is on the order of several years (cf. Tranel, Manzel, Asp, & Kemmerer, 2008).

3. The rationale for using five as the criterion for “excess” in this context derives from the fact that this degree of difference (between lesion‐with‐deficit minus lesion‐without‐deficit) is highly unlikely to occur by chance (see detailed discussion in Damasio et al., 2004, p. 190). In fact, in calculations reported in Damasio et al. (2004), the difference of five corresponded to probabilities that were estimated to be smaller than 0.001 for various contrasts and categories, and we have used this threshold in several previous studies employing the same general method of lesion subtraction. The reader is also referred to a more recent discussion of this issue from a lesion probability sampling perspective, detailed in Rudrauf et al. (2008).

4. The effects of gender on naming performance have been directly explored (e.g., Grabowski, Damasio, Eichhorn, & Tranel, 2003). The effects are not zero, but they are small at group level and quite variable at individual level, and for the purposes of the current article gender will not be considered as an independent variable.

5. Lest this seem like a foregone conclusion, it should be noted that there have been a number of strong arguments for the notion that faces constitute a “special” class of stimuli, and have properties and processing requirements that make them different from all other classes of stimuli. Moreover, there are at least some empirical data that can be taken to support this position, including the specific and reliable activation of the “fusiform face area” by face stimuli in functional imaging experiments (for varying perspectives on this debate, see Gauthier, Tarr, Skudlarski, & Gore, 1999; Kanwisher, 2000).