Abstract
We present a neural network model of the storage of episode representations in working memory (WM). Our key idea is that episodes are encoded in WM as prepared sensorimotor routines, i.e. as prepared sequences of attentional and motor operations. Our network reproduces several experimental findings about the representation of prepared sequences in prefrontal cortex. Interpreted as a model of WM episode representations, it has useful applications in an account of long-term memory for episodes and in accounts of sentence processing.






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Manuscript in preparation, Knott and Takac: Locomotion actions as sequentially structured sensorimotor routines.
In fact, even when the network is used for perception of episodes, the selection mechanism has an impact on the agent’s behaviour. The expected episode is a sequence whose first two items are planned attentional actions: during perception, these actions will actually be executed by the agent, with results that depend on the world as well as on the agent’s expectations and which might well result in revisions to the selected episode. The model thus allows for active perceptual operations during the process of selecting an episode, creating the structural coupling between its representational system and the environment that is characteristic of embodied systems (see, for example, [32]).
The most obvious kind of ‘attentional actions’ are overt movements, such as saccades. But attentional actions also involve cognitive operations, in particular top−down activation of semantic representations. These top−down activation operations can encode either the expected result of a forthcoming object classification process [34] or the category of properties of a desired search target [35, 36]. Our attentional actions represent objects in the sense that they represent expected or sought-for object categories.
Since WM representations are normally understood to be ‘maintained in the face of incoming perceptual stimuli’, we have to assume a special operation to remove the current episode representation from the dynamic episodic buffer before the next episode begins—an operation that probably involves an element of self-inhibition (see, for example, Mayr and Keele [39]). In previous work [19], we have considered the nature of this operation, but in the present study, we just use the end-of-episode signal to stand in for this operation.
If the predicted episode ranked among multiple episodes predicted by the VLMM with equal frequency, e.g. occupying 2nd–4th position, its rank would be the upper bound, i.e. 2.
Candidates were determined by top−down reconstruction, i.e. replayed as a temporal sequence in the aggregate SM signal layer.
The distributed model performed better by 3.7 % in total grammaticality, 0.2 % in compatibility, 0.8 % in matches, 0.09 in rank, and 5.1 % in rank base [37].
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Acknowledgments
This research was supported by NZ Marsden Fund, and partially supported by grants VEGA 1/0898/14 and KEGA 076UK-4/2013 for Martin Takac. We are grateful to Lubica Benuskova and Igor Farkas for helpful discussions.
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Takac, M., Knott, A. A Neural Network Model of Episode Representations in Working Memory. Cogn Comput 7, 509–525 (2015). https://doi.org/10.1007/s12559-015-9330-3
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DOI: https://doi.org/10.1007/s12559-015-9330-3