Recall of semantically related word-lists in two patients with herpes simplex encephalitis

ObjectiveThe aim of the present study is to provide further insight into semantic processing in Working Memory (WM) in two amnesic patients with extensive medial temporal lobe (MTL) by adopting a short length word-lists recall task.BackgroundIt is still unclear whether the medial temporal lobe structures and especially the hippocampus is recruited in semantic processing in the context of WM.Materials & methodsTwo severely amnesic patients with extensive MTL damage due to herpes simplex encephalitis (HSE) and a control group (n = 36) underwent an experimental task involving the immediate free recall of 9 word-lists in three different conditions: 1. semantically related words clustered according to semantic category (SRC), 2. semantically related words non-clustered (SRnC), 3. semantically unrelated words (SU). Additionally, standard cognitive measures were administered [Digit Span Forward & Backward, Greek Verbal Learning Test (GVRT), Verbal Fluency Test (VFT), Logical Memory I & II (LM-I & LM-II) of Wechsler Memory Scale (WMS)].ResultsBoth patients obtained normal performance in WM tests (Digit Span Forward & Backward), but were impaired in GVRT, VFT, LM-I and LM-II. With regard to the word-list task, the number of words recalled by both patients' did not differ from controls. However, semantic facilitation effects were not recorded in patients' performance for the SRC and SRnC conditions (SRC = SRnR = SU), unlike controls (SRC > SRnC > SU).ConclusionsOur results suggest that the effects of semantic facilitation in short length word-lists recall are diminished to a certain degree in HSE patients that suffer from MTL damage.