Andrea Greve PhD

Andrea Greve


Publications:
2010
  A Single-Trace Dual-Process Model of Episodic Memory
Greve, A, Donaldson, DI & van Rossum, MCW 2010, 'A Single-Trace Dual-Process Model of Episodic Memory: A Novel Computational Account of Familiarity and Recollection' Hippocampus, vol 20, no. 2, pp. 235-251. DOI: 10.1002/hipo.20606

Dual-process theories of episodic memory state that retrieval is contingent on two independent processes: familiarity (providing a sense of oldness) and recollection (recovering events and their context). A variety of studies have reported distinct neural signatures for familiarity and recollection, supporting dual-process theory. One outstanding question is whether these signatures reflect the activation of distinct memory traces or the operation of different retrieval mechanisms on a single memory trace. We present a computational model that uses a single neuronal network to store memory traces, but two distinct and independent retrieval processes access the memory. The model is capable of performing familiarity and recollection-based discrimination between old and new patterns, demonstrating that dual-process models need not to rely on multiple independent memory traces, but can use a single trace. Importantly, our putative familiarity and recollection processes exhibit distinct characteristics analogous to those found in empirical data; they diverge in capacity and sensitivity to sparse and correlated patterns, exhibit distinct ROC curves, and account for performance on both item and associative recognition tests. The demonstration that a single-trace, dual-process model can account for a range of empirical findings highlights the importance of distinguishing between neuronal processes and the neuronal representations on which they operate. (C) 2009 Wiley-Liss, Inc.


General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Greve, Andrea, Donaldson, David I. & van Rossum, Mark C. W..
Keywords: (episodic memory model, Hopfield network, recognition, recollection, familiarity, , , . )
Number of pages: 17
Pages: 235-251
Publication Date: 21 Jul 2010
Publication Information
Category: Article
Journal: Hippocampus
Volume: 20
Issue number: 2
ISSN: 1050-9631
Original Language: English
DOIs: 10.1002/hipo.20606
2009
  Dynamics and Robustness of Familiarity Memory
Cortes, JM, Greve, A, Barrett, AB & van Rossum, MCW 2009, 'Dynamics and Robustness of Familiarity Memory' Neural Computation, vol 22, no. 2, pp. 448-466. DOI: 10.1162/neco.2009.12-08-921
When presented with an item or a face, one might have a sense of recognition without the ability to recall when or where the stimulus has been encountered before. This sense of recognition is called familiarity memory. Following previous computational studies of familiarity memory, we investigate the dynamical properties of familiarity discrimination and contrast two different familiarity discriminators: one based on the energy of the neural network and the other based on the time derivative of the energy. We show how the familiarity signal decays rapidly after stimulus presentation. For both discriminators, we calculate the capacity using mean field analysis. Compared to recall capacity (the classical associative memory in Hopfield nets), both the energy and the slope discriminators have bigger capacity, yet the energy-based discriminator has a higher capacity than one based on its time derivative. Finally, both discriminators are found to have a different noise dependence.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Cortes, J. M., Greve, Andrea, Barrett, A. B. & van Rossum, M. C. W..
Keywords: (, , . )
Number of pages: 19
Pages: 448-466
Publication Date: 20 Oct 2009
Publication Information
Category: Article
Journal: Neural Computation
Volume: 22
Issue number: 2
ISSN: 0899-7667
Original Language: English
DOIs: 10.1162/neco.2009.12-08-921
  Optimal learning rules for familiarity detection
Greve, A, Sterratt, DC, Donaldson, DI, Willshaw, DJ & van Rossum, MCW 2009, 'Optimal learning rules for familiarity detection' Biological Cybernetics, vol 100, no. 1, pp. 11-19. DOI: 10.1007/s00422-008-0275-4
It has been suggested that the mammalian memory system has both familiarity and recollection components. Recently, a high-capacity network to store familiarity has been proposed. Here we derive analytically the optimal learning rule for such a familiarity memory using a signal- to-noise ratio analysis. We find that in the limit of large networks the covariance rule, known to be the optimal local, linear learning rule for pattern association, is also the optimal learning rule for familiarity discrimination. In the limit of large networks, the capacity is independent of the sparseness of the patterns and the corresponding information capacity is 0.057 bits per synapse, which is somewhat less than typically found for associative networks.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Greve, Andrea, Sterratt, D. C., Donaldson, D. I., Willshaw, D. J. & van Rossum, M. C. W..
Keywords: (, , . )
Number of pages: 9
Pages: 11-19
Publication Date: Jan 2009
Publication Information
Category: Article
Journal: Biological Cybernetics
Volume: 100
Issue number: 1
ISSN: 0340-1200
Original Language: English
DOIs: 10.1007/s00422-008-0275-4
2008
  Moderate hypoglycaemia after learning does not affect memory consolidation and brain activation during recognition in non-diabetic adults
Warren, RE, Sommerfield, AJ, Greve, A, Allen, KV, Deary, IJ & Frier, BM 2008, 'Moderate hypoglycaemia after learning does not affect memory consolidation and brain activation during recognition in non-diabetic adults' Diabetes/Metabolism Research and Reviews, vol 24, no. 3, pp. 247-252. DOI: 10.1002/dmrr.v24:3
General Information
Organisations: School of Philosophy, Psychology and Language Sciences.
Authors: Warren, Roderick E., Sommerfield, Andrew J., Greve, Andrea, Allen, Kate V., Deary, Ian J. & Frier, Brian M..
Keywords: (, , . )
Pages: 247-252
Publication Date: 1 Mar 2008
Publication Information
Category: Article
Journal: Diabetes/Metabolism Research and Reviews
Volume: 24
Issue number: 3
ISSN: 1520-7552
Original Language: English
DOIs: 10.1002/dmrr.v24:3
2007
  Dynamical effects on familiarity discrimination
Cortes, JM, Greve, A & Van Rossum, MCW 2007, Dynamical effects on familiarity discrimination. in AIP Conference Proceedings 887. American Institute of Physics, pp. 217-223. DOI: 10.1063/1.2709599
One process involved in recognition memory is familiarity discrimination. Familiarity distinguishes almost immediately after stimulus presentation whether the item was previously encountered (old) or novel. By using a formalism based on attractor neural networks, we discuss different dynamical processes affecting familiarity discrimination. First, we compare two different familiarity discriminators, the previously proposed energy (FamE) and the temporal derivative of the energy (FamS). This second measure relies on differences in the dynamics of the network when novel or old stimuli are presented. Contrarily to FamE, FamS depends on details of the dynamics of the network. As a result, and counterintuitively, famS is enhanced by random fluctuations in the neural activity. Finally, we present some preliminary results showing how familiarity discrimination is affected by activity dependent mechanisms at synaptic level, such as short?term depression and facilitation. These results allow formulating new models regarding optimal dynamics and familiarity discrimination.
General Information
Organisations: School of Informatics.
Authors: Cortes, J. M., Greve, A. & Van Rossum, M. C. W..
Number of pages: 7
Pages: 217-223
Publication Date: 2007
Publication Information
Category: Conference contribution
Original Language: English
DOIs: 10.1063/1.2709599
  Investigating the functional interaction between semantic and episodic memory: Convergent behavioral and electrophysiological evidence for the role of familiarity
Greve, A, van Rossum, MCW & Donaldson, DI 2007, 'Investigating the functional interaction between semantic and episodic memory: Convergent behavioral and electrophysiological evidence for the role of familiarity' NeuroImage, vol 34, no. 2, pp. 801-814. DOI: 10.1016/j.neuroimage.2006.07.043
Throughout our lives we acquire general knowledge about the world (semantic memory) while also retaining memories of specific events (episodic memory). Although these two forms of memory have been dissociated on the basis of neuropsychological data, it is clear that they typically function together during normal cognition. The goal of the present study was to investigate this interaction. One influence of semantic memory on episodic retrieval is 'Levels Of Processing'; recognition is enhanced when stimuli are processed in a semantically meaningful way. Studies examining this semantic processing advantage have largely concluded that semantic memory augments episodic retrieval primarily by enhancing recollection. The present study provides strong evidence for an alternative relationship between semantic and episodic memory. We employed a manipulation of the semantic coherence of to-be-remembered information (semantically related vs. unrelated word pairs) during an associative recognition memory test. Results revealed that associative recognition is significantly enhanced for semantically coherent material, and behavioral estimates (using the process dissociation procedure) demonstrated concomitant changes in the contribution of familiarity to retrieval. Neuroimaging data (event-related potentials recorded at test) also revealed a significant increase in familiarity based retrieval. The electrophysiological correlate of familiarity (the mid-frontal ERP old/new effect) was larger for semantically related compared to unrelated word pairs, but no difference was present in the electrophysiological correlate of recollection (the left parietal old/new effect). We conclude that semantic memory and episodic memory do indeed interact in normal functioning, and not only by modulating recollection, but also by enhancing familiarity.
General Information
Organisations: Institute for Adaptive and Neural Computation .
Authors: Greve, Andrea, van Rossum, M.C.W & Donaldson, David I..
Number of pages: 14
Pages: 801-814
Publication Date: 2007
Publication Information
Category: Article
Journal: NeuroImage
Volume: 34
Issue number: 2
ISSN: 1053-8119
Original Language: English
DOIs: 10.1016/j.neuroimage.2006.07.043

Projects:
ERP studies of memory (PhD)