Autobiographical memory and autoneotic consciousness in a case of semantic dementia

Investigations of retrograde amnesia have contributed to a better understanding of the cerebral structures involved in remote memory. Such studies have suggested that neocortical regions such as the anterior temporal lobe play a major role in both the storage and retrieval of remote episodic and semantic information. Semantic dementia (SD), characterised as a focal anterior temporal lobe atrophy, offers an opportunity to study episodic remote memory, especially in the absence of day-to-day memory dysfunctioning, which takes place in permanent amnesic syndromes. Few studies have investigated autobiographical retrograde amnesia in SD. We present the findings from a patient (AT) at the early stage of SD. First, we have compared episodic and semantic components of autobiographical memory using two specially designed fluency tasks. The results demonstrated good recall of autobiographical events from all time periods and poor retrieval of names of acquaintances, albeit to a lesser degree, with respect to recent life. Second, we have investigated strictly episodic autobiographical memory and autonoetic consciousness by means of a sophisticated autobiographical test and the Remember/Know procedure which used a more stringent criterion of episodicity. The results demonstrated a relatively good recall of autobiographical memories (whatever their nature) but poor retrieval of remote specific detailed memories compared to recent ones. Moreover, patient AT provided Remember judgements to the same extent as control subjects regardless of the time interval covered although his responses were not justified in terms of the actual contextual information retrieved beyond the last 5 years. These findings provide further evidence that strictly episodic recollection is restricted to the recent past in SD. These data are discussed according to their relevance to the episodic and semantic distinction and to models of long-term memory consolidation.