The contribution of the left anterior temporal lobe in lexical-semantic processing

A renewed debate on the role of the left anterior temporal lobe (in particular the anterior superior temporal gyrus, aSTG) in speech perception is based on a diverse functional engagement of this brain region, such as in speech intelligibility (Scott et al., 2000), in lexical-semantic processing (Kotz et al., 2002, 2003a; Scott et al., 2003), in local syntactic processing (Donkers et al., 1994; Kotz et al., 2003b; Meyer et al., 2000; Friederici et al., 2003) as well as in semantic integration (e.g., Stowe et al., 2000). fMRI and ERP lesion experiments on lexical-semantic processing reveal that the aSTG is activated and respectively causing deficits in the case of aSTG lesions. This is shown in fMRI when discriminating between words and pseudowords (Kotz et al., 2002), but is not shown in the case for semantic integration at the word (Kotz et al., 2002) and sentence level (Friederici et al., 2003). Here the posterior STG might play a crucial role. These data are confirmed by lesion data. Patients with left aSTG lesions showed semantic integration at the word and sentence level, even though these processes are temporally delayed. These results indicate that the left anterior temporal lobe may play a role in mapping initial phonetic information to lexical representation during word recognition, but only indirectly in semantic priming and semantic integration (see also McNellis & Blumstein, 2001).