Neuropsychologia 42 (2004) 426–433 Rapid publication Recognition memory for single items and for associations in amnesic patients Patrizia Turriziani a,c,∗ , Lucia Fadda a,b , Carlo Caltagirone a,b , Giovanni A. Carlesimo a,b a IRCCS Fondazione Santa Lucia, Laboratorio di Neurologia Clinica e Comportamentale, Via Ardeatina 306, Rome 00179, Italy b Clinica Neurologica, Università Tor Vergata, Rome, Italy c Dipartimento di Psicologia, Università di Palermo, Palermo, Italy Received 22 May 2003; received in revised form 15 October 2003; accepted 21 October 2003 Abstract Recognition memory performance reflects two distinct processes or types of memory referred to as recollection and familiarity. According to theoretical claims about the two types of memory, single item and associative recognition tasks can be used as an experimental method to distinguish recollection and familiarity processes. Associative recognition decisions can be used as an index of recollection while memory for single items is mostly based on familiarity judgement. We employed this procedure to examine a possible dissociation in the memory performance of amnesic patients between spared single item and impaired associative recognition. Twelve amnesic patients, six with damage confined to the hippocampus proper, and six with damage elsewhere in the brain, were recruited for the present study. The findings showed that hippocampal amnesics exhibit relative sparing of single item learning but are consistently deficient in the learning of all kinds of between-item associations. These results are consistent with the view that hippocampal formation contributes differently to declarative tasks that require recollective or familiarity processes. © 2003 Elsevier Ltd. All rights reserved. Keywords: Amnesia; Familiarity; Recollection; Hippocampus 1. Introduction Recognition memory, i.e., judgement of the prior occur- rence of what has been identified, is a fundamental man- ifestation of our ability to remember. A currently debated issue in the neurocognitive literature is whether recognition memory for single items (i.e., the representation of a unique event) can be dissociated from recognition memory for as- sociations between items (i.e., the specific conjunctions of events unique to particular experiences). According to the dual-process model of recognition (Mandler, 1980), recognition memory has two different bases. One of these processes involves what is known as contextual retrieval and requires recollection of the episodic context in which the item was encoded. The other process involves the feeling of familiarity, when increased fluent processing of a stimulus is attributed to recent experience of that stimulus (Jacoby & Dallas, 1981; Mandler, 1980). Critical for the purpose of the present investigation is the hypothesis that recollection and familiarity processes are ∗ Corresponding author. Tel.: +39-06-51501574; fax: +39-06-51501388. E-mail address: p.turriziani@hsantalucia.it (P. Turriziani). differently involved in single item and associative recogni- tion. Indeed, while memory for single items would be prin- cipally based on familiarity judgement, independent of the retrieval of the spatio-temporal context of the experience, associative recognition decisions would be mainly based on a recall-like or recollective retrieval process (Yonelinas, 2002). For example, using the remember-know procedure (Tulving, 1985), Honckley and Consoli (1999) showed that associative recognition decisions were accompanied by more “remember” responses and less “know” responses than item recognition decisions, thus suggesting that rec- ollection plays a more decisive role in associative than in single item recognition. Aggleton and Brown (1999) suggested a neurobiological basis for the recollection/familiarity distinction. Based on a wide review of animal studies and on a meta-analysis of published data on amnesic patients (Aggleton & Shaw, 1996), these authors proposed that the hippocampus proper (i.e., CA fields, dentate gyrus and subiculum) is decisive for recollection but not necessary for item familiarity. In- stead, item familiarity depends critically on the integrity of the cortex adjacent to the hippocampus, namely, the perirhinal, the entorhinal and parahippocampal cortices in the parahippocampal gyrus. Several convergent findings 0028-3932/$ – see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2003.10.003