A scientific theory of Ars Memoriae: Spatial view cells in a continuous attractor network with linked items

Abstract

The art of memory (ars memoriae) used since classical times includes using a well-known scene to associate each view or part of the scene with a different item in a speech. This memory technique is also known as the 'method of loci'. The new theory is proposed that this type of memory is implemented in the CA3 region of the hippocampus where there are spatial view cells in primates that allow a particular view to be associated with a particular object in an event or episodic memory. Given that the CA3 cells with their extensive recurrent collateral system connecting different CA3 cells, and associative synaptic modifiability, form an autoassociation or attractor network, the spatial view cells with their approximately Gaussian view fields become linked in a continuous attractor network. As the view space is traversed continuously (for example by self-motion or imagined self-motion across the scene), the views are therefore successively recalled in the correct order, with no view missing, and with low interference between the items to be recalled. Given that each spatial view has been associated with a different discrete item, the items are recalled in the correct order, with none missing. This is the first neuroscience theory of ars memoriae. The theory provides a foundation for understanding how a key feature of ars memoriae, the ability to use a spatial scene to encode a sequence of items to be remembered, is implemented.3

The storage and recall of memories in the hippocampo-cortical system

“…This type of representation is much more appropriate for a human memory system than that in rodents, because a human can remember where an object or person has been seen based just on looking at the place, without necessarily ever having been at that place (Rolls 2017 ); for example, you may remember where you have seen a lecturer in a lecture theatre, without ever having visited the precise place where the lecturer is standing. Moreover, some spatial view neurons respond to particular combinations of object and place, such as that object 1 is in place 1 on a screen (Rolls et al 2005 ) or that reward 1 is at place 1 on a screen (Rolls and Xiang 2005 ) and thus seem to encode what is necessary for an object-place memory representation system in the brain (Rolls 2016a , 2017 ; Rolls and Xiang 2006 ). Further, some of these neurons reflect the completion during recall of a whole memory from a part, for example, of the spatial location at which an object has previously been shown (Rolls and Xiang 2006 ).…”

“…The hippocampal processes described here for primates include recalling objects from spatial view recall cues. The theory has been developed that exactly this type of recall is involved in the “art of memory” used since classical times (Rolls 2017 ). Simonides of Ceos lived to tell the story of how, when a banquet hall collapsed in an earthquake, he could identify all the victims by recalling who had been sitting at each place at the table (Cicero 55 BC ).…”

“…The new theory (Rolls 2017 ) is that this type of memory, ars memoriae , is implemented in the CA3 region of the hippocampus in which, in primates, spatial view cells can be found that allow a particular view to be associated with a particular object in an event or episodic memory. Given that the CA3 cells, with their extensive recurrent collateral system connecting different CA3 cells and with their associative synaptic modifiability, form an autoassociation or attractor network, the spatial view cells with their approximately Gaussian view fields become linked in a continuous attractor network.…”

“…Given that each spatial view has been associated with a different discrete item, the items are recalled in the correct order, with none missing. The theory provides a foundation for understanding the implementation of the key feature of ars memoriae , namely the ability to use a spatial scene to encode a sequence of items to be remembered (Rolls 2017 ).…”

“…This must be kept separate from, for example, what happened the day before that. Episodic memory almost always has a spatial component (Dere et al 2008 ; Rolls 2017 ) and a spatial representation in the hippocampus can be updated by self-motion to produce path integration (McNaughton et al 1996 ; Robertson et al 1998 ; Rolls 2016a ; E.T. Rolls and S. Wirth in preparation).…”