The function of the anterior temporal lobe: a review of the empirical evidence

Recent work on the anterior temporal lobe (ATL) has lead to substantively different theoretical branches, of its putative functions, that have in some part developed independently of one another. The ATL has dense connectivity with a number of sensory modalities. This has resulted in empirical evidence that supports different functionality dependent upon the variables under investigation. The main bodies of evidence have implicated the ATL as a domain-general semantic hub, whilst other evidence points to a domain-specific role in social or 'person-related' processing. A third body of evidence suggests that the ATLs underlie processing of unique entities. Primarily, research of the ATL has been based on lesion studies and from clinical populations such as semantic dementia or temporal lobe epilepsy patients. Although important, this neuropsychological evidence has a number of confounds, therefore techniques such as functional neuroimaging on healthy participants and the relatively novel use of non-invasive brain stimulation may be more useful to isolate specific variables that can discriminate between these different theories concerning 'normal' function. This review focuses on these latter types of studies and considers the empirical evidence for each perspective. The overall literature is integrated in an attempt to formulate a unifying theory and the functional sub-regions within the ATL are explored. It is concluded that a holistic integration of the theories is feasible in that the ATLs could process domain-general semantic knowledge but with a bias towards social information or stimuli that is personally relevant. Thus, it may be the importance of social/emotional information that gives it priority of processing in the ATL not an inherent property of the structure itself.