MEMORY AND AMNESIA

Brain damage can cause several distinct disorders of explicit memory a s well as several disorders of implicit memory. Organic amnesia is the best studied explicit memory disorder. It is a syndrome that can be c aused by lesions in (a) the medial temporal lobes, (b) the midline die ncephalon, or (c) the basal forebrain. It remains unresolved whether o ne or several functional deficits underlie the syndrome, how these def icits should be characterised, and what is the exact location of the c ausal lesions. There is good evidence that amnesics encode information normally so their deficit(s) must be of storage or retrieval processe s. If storage is disrupted, then one would expect item-specific implic it memory for certain kinds of novel information to be disrupted in am nesics. Current evidence is unable to indicate conclusively whether or not this prediction is met mainly because indirect memory test perfor mance depends on explicit as well as implicit memory. Storage deficits should also result in accelerated forgetting in amnesic patients. Stu dies are described which reveal accelerated loss of free recall, but n ot recognition, for stories and semantically organised word lists in a mnesics at delays between 15 s and 10 min. This suggests that amnesia involves a storage deficit for complex contextual associations that po ssibly occurs in conjunction with one or more other functional deficit s.