Preserved cumulative semantic interference despite explicit memory impairment

Several current models describe a role for implicit learning in continually re-tuning the language production system, claiming specific behavioral effects (e.g. syntactic priming, phonotactic learning, cumulative semantic interference) as demonstrations of implicit learning over various mappings. But because speaking is typically quite memorable, it can be difficult to distinguish true implicit learning from concomitant explicit memory for the learning events. This single-case study considers possible explicit memory contributions to two picture-naming paradigms where implicit learning is often claimed to underlie cumulative semantic interference in response times. Patient WRP is a 52-year-old male who has unilateral lesions to his left hippocampus, amygdala, and anterior to medial temporal lobe, resulting in ceteris paribus impaired recognition and recall of words, but fully intact linguistic processing and only mildly impaired semantics. After ruling out semantic refractory disorders as alternative sources of interference, we show that his naming latency patterns exhibit canonical and control-like cumulative semantic interference in both continuous and blocked-cyclic picture naming paradigms, leading to the conclusion that interference in both specifically reflects persistent implicit changes. Finally, we also consider an underappreciated role for explicit memory in typical laboratory picture naming experiments, which may explain some curious neuroimaging results for one of these paradigms