The role of the anterior temporal lobe in semantic processing: ERP patient evidence

Kotz, S. A., Hofmann, J., von Cramon, D. Y., and Friederici, A. D.
Max-Planck-Institute of Cognitive Neuroscience, Leipzig, Germany

A renewed debate on the role of the left anterior temporal lobe in speech perception has revealed a diverse functional engagement of this brain region such as in speech intelligibility (Scott et al., 2000), in lexico-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). To further investigate lexico-semantic processing (Experiment 1) and semantic integration (Experiment 2) we tested a group of patients with left anterior temporal lesions (Exp.1, N=11; Exp.2, N=6) and as a control group patients with extended right anterior temporal lesions (Exp.1, N=8; Exp.2, N=5) in an auditory word list lexical primed decision task (LDT; Exp.1) and an auditory semantic correctness judgment task (Exp.2). Patients with left anterior temporal lobe lesions showed no lexical N400 effect, but a delayed and reduced N400 semantic priming effect in the LDT, while patients with right anterior temporal lobe lesions showed a lexical N400 effect, but a strongly reduced N400 priming effect. Both patient groups showed a delayed N400 effect comparing semantically correct and incorrect sentences. 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).