Current Alzheimer Research, 2009, 6, 000-000 1 1567-2050/09 $55.00+.00 ©2009 Bentham Science Publishers Ltd. Memory and Consciousness in Alzheimer’s Disease C. Souchay* and C.J.A. Moulin Leeds Memory Group, Institute of Psychological Sciences, University of Leeds, UK Abstract: Human memory can be split into familiarity and recollection processes which contribute to different aspects of memory function. These separate processes result in different experiential states. In this review, we examine how this dominant theoretical framework can explain the subjective experience of people with Alzheimer’s disease, the profile of their memory impairments and their inability to reflect on their performance metacognitively. We conclude with a brief overview of the brain regions supporting conscious experience of memory, and propose that the memory and awareness deficits seen in Alzheimer’s disease could be conceived of as a deficit in autonoetic consciousness. A future priority for research is to take these robust constructs into research programmes examining rehabilitation and pharmacological inter- vention. Keywords: Recollection, familiarity, awareness, metacognition. 1. OVERVIEW People with Alzheimer’s disease seem to have informa- tion which is inaccessible to recall, such as an inability to name the prime minister, but which is available for recogni- tion, such as correctly picking out Gordon Brown from a set of alternatives. Such a discrepancy between recall and rec- ognition has been cited as evidence of a specific form of memory deficit in AD since patients have memory for a word (recognising it as the correct answer), and yet they cannot retrieve it spontaneously, or recall it. Clinically, tests of recall are more sensitive to Alzheimer brain changes than are tests of recognition [1]. Considering this difference in recall and recognition, the relationship between consciousness and memory is in ques- tion. How is it that the patient cannot on the one hand report something, but know it when prompted? In this review we aim to illustrate that there exists a complex relationship be- tween consciousness and memory, and that in Alzheimer’s disease, this relationship breaks down, according to known patterns of neuropathology. We propose that Alzheimer’s disease results in a disconnection between medial temporal and frontal areas and that this leads to a specific deficit in recollection, which is characterised by certain subjective feelings, and evocative, associated and personal information coming to mind during memory retrieval (See Table 1). The concept of recollection is a relatively recent theoreti- cal development [2] and helps us understand other issues in memory and awareness more generally in Alzheimer’s. In short, the emergent view is that memory function is sup- ported by conscious states, and that a full understanding of memory function is only possible through understanding the experience of what comes to mind in memory [3]. We exam- ine to what extent consciousness and awareness influence memory function and real world behaviours. *Address correspondence to this author at the Leeds Memory Group, Insti- tute of Psychological Sciences, University of Leeds, LS2 9JT, UK; E-mail: c.souchay@leeds.ac.uk 2. MEMORY IN ALZHEIMER’S DISEASE In Alzheimer’s disease, memory impairment is the earli- est and most severe cognitive deficit. The commonest means of demonstrating this deficit is to evaluate the number of previously encountered items that can be recovered after a retention interval [1, 4, 5]. Such tests have been shown to be particularly sensitive at detecting pre-clinical changes in memory in people who develop Alzheimer’s disease [6-8]. Additionally, neuroimaging studies have converged on tem- poro-parietal and hippocampal areas as being particularly involved in Alzheimer’s disease. These regions are known to be crucial in learning of new information [9]. Convit et al. [10] demonstrated with volumetric MRI that atrophy in the medial occipito-temporal and the middle and inferior tempo- ral gyri are associated with progression to Alzheimer’s dis- ease. Similarly, pre-morbid volumetric measurements of the hippocampus predict progression [11]. Thus, a large literature points to the fact that people with Alzheimer’s have particular difficulties in retrieving material learnt in previous episodes, and this relates to underlying neuropathology. Cognitive Neuropsychologists see this memory deficit as episodic, relating to a specific study epi- sode. That is, people with Alzheimer’s disease have particu- lar difficulties in learning and recalling recently encountered information, as opposed to material encountered and ac- quired premorbidly. However, rather than considering the types of materials and tasks which delineate different forms of memory impairment, a contemporary focus is the experi- ential state during memory retrieval – the state of awareness associated with the act of remembering. Because this con- ceptualisation opens up new fields of research and has utility in understanding disorders such as Alzheimer’s disease, it is this emergent field that we review here. This subjective approach was developed by Tulving [12]. He classified memory on the basis of experience, arguing that without considering experience you could not investi- gate cognition [13]. ‘Self knowing’ or ‘autonoetic’ memory described a memory where the first person experience was of