Design of Web Agents Inspired by Brain Research
Maya Dimitrova, Hiroaki Wagatsuma * and Yoko Yamaguchi*
Institute of Control and System Research – Bulgarian Academy of Sciences
* Laboratory for Dynamics of Emergent Intelligence, RIKEN Brain Science Institute, Japan
30/09/2007 ADBIS'07 Varna 2
Content1. Introduction2. Information retrieval studies based on cognitive
heuristics (problem definition)3. Theta phase coding in the brain and episodic
memory 3.1. The Theta phase model3.2. Relevance to episodic/autobiographical memory4. Autobiographical memory in Web context: An
example5. Conclusions and future work
30/09/2007 ADBIS'07 Varna 3
Introduction
Modeling agents’ own experience – their reconstructed past - is essential to optimize agent behavior (i.e. agents for Web knowledge search, retrieval and presentation)
We propose to base this optimization on recent studies and models of the brain – focusing on the generality of processing in the animal and human, not on their difference
We have focused on “episodic” memory and the underlying hippocampal mechanisms of processing as closest to the “story-telling” approach of agent design
30/09/2007 ADBIS'07 Varna 4
Information retrieval studies based on cognitive heuristics
Problem statement:- Current Web page classifiers perform excessive amount of
processing to reach simple classificatory results- Whenever the classificatory task is multi-dimensional, agent
performance deteriorates dramatically- There is the database or storage problem – where models have
always been least analogous to human memory- Human memory processing is fast, heuristical and much more
efficient in the multi-dimensional case, than in the sequential processing case (contrary to the machine) etc. (recent finding)
- There is always a point in looking into recent brain studies – for their fast and accelerated development as empirically-based science
30/09/2007 ADBIS'07 Varna 5
Information retrieval studies based on cognitive heuristics (2)
The current study:- Presents the main ideas of the Theta phase precession
theory as proposing a memory model, different from the mainstream rate-coding models
- Operationalizes “episodic memory” for the purpose of design of memory-optimized Web search agent
- Provides an example to illustrate the described process in a human Web search process and some relevant conclusions for agent future development
30/09/2007 ADBIS'07 Varna 6
The agent (1)
In earlier work we designed a Java-servlet (a wrapper to a search engine) to diagnose the level of expertise and detail of a corpus of on-line available Web pages
Weak point – what to store in the database and in what form
Example of classified documents on one criterion
Example of classified documents on two criteria
Legend
- expert level
- detail ∆ - illustration Ω - explanation
..
.
Ω
..
.
∆
∆
∆
Ω
Results of the online classification on a specific criterion
Types (sample, test set) of documents
Document of type
Document of type
Document of type ∆
Document of type Ω
..
.
Classifier
(heuristics and methods for
classification)
Process of comparison for validity of the results
Adjustment of the parameters of the classifier
Lexical Database
30/09/2007 ADBIS'07 Varna 7
The agent (2)
It employed pattern classification based on syntactic analysis for diagnosing the amount of detail
And cognitive heuristics based on memory research for the expert level of the text
Example of classified documents on one criterion
Example of classified documents on two criteria
Legend
- expert level
- detail ∆ - illustration Ω - explanation
..
.
Ω
..
.
∆
∆
∆
Ω
Results of the online classification on a specific criterion
Types (sample, test set) of documents
Document of type
Document of type
Document of type ∆
Document of type Ω
..
.
Classifier
(heuristics and methods for
classification)
Process of comparison for validity of the results
Adjustment of the parameters of the classifier
Lexical Database
30/09/2007 ADBIS'07 Varna 8
The agent (3)
In following history of interaction, optimization is needed much the way natural cognitive systems perform - learn, abstract, remember and forget
We use the ‘autobiographical memory’ metaphor to apply to such kind of Web agents and the Theta phase precession theory to model it
Example of classified documents on one criterion
Example of classified documents on two criteria
Legend
- expert level
- detail ∆ - illustration Ω - explanation
..
.
Ω
..
.
∆
∆
∆
Ω
Results of the online classification on a specific criterion
Types (sample, test set) of documents
Document of type
Document of type
Document of type ∆
Document of type Ω
..
.
Classifier
(heuristics and methods for
classification)
Process of comparison for validity of the results
Adjustment of the parameters of the classifier
Lexical Database
30/09/2007 ADBIS'07 Varna 9
Current MATLAB GUI versionof the agent interface
The difference of the MatLab version from the Java version is that the Java-servlet processed also the hyperlink structure of the Web page
The current version is simplified for algorithmic and modeling reasons
30/09/2007 ADBIS'07 Varna 10
Assumptions of the current study:
Assumptions:- User interaction with the present-day Web is an
autobiographical experience (remembering sequences of events like personal-life episodes)
- Memorizing events in a human-like memory system undergoes constant synthesis as any other learning process and therefore can be implemented in autonomous agent on the Web
30/09/2007 ADBIS'07 Varna 11
Operational definitions in the current study:Definition of Episodic Memory: - The system of processing episodes of Web search and
transforming them into autobiographical events of successful/unsuccessful Web navigation to reach the needed goal
- Every Web page viewed by the user is a complex perceptual and semantic stimulus, i.e. an episode of Web search
- What is stored in episodic memory from the rapid viewing of a succession of pages is a set of fragments of the search episode rather than the entire pages and their exact order of viewing
30/09/2007 ADBIS'07 Varna 12
Hypotheses of the current study:
- The theoretical hypothesis is that episodic memory extracts meaningful cues from the fragments of the page-retrieval episodes, rather than random perceptual or semantic cues
- “Meaningful” we define as having anticipatory value (i.e. useful in the future)
- The tested hypothesis is that the mechanisms of event synthesis from fragments of page-retrieval episodes are the same in personally-significant and neutral situations, that is – universal for learning per se
- These effects are reproduced by both the human and the agent in the current study
30/09/2007 ADBIS'07 Varna 13
Theta phase coding in the brain and episodic memory
Theta phase theory models rhythmic patterns of activity of assemblies of neurons in the brain and their role in complex cognitive tasks (theta rhythm 4-10 Hz)
Theta phase modulation is associated with learning and memory in rats and humans A mechanism of pattern compression has been observed in hippocampal neuron assemblies, which is called theta phase precession
Modelling hippocampal nerve cirquit by the Theta phase precession theory (Yamaguchi, Yamaguchi et al.) reinstates complex learning effects observed in human episodic memory like object-context integration, single-trial learning and time-space contextualization
30/09/2007 ADBIS'07 Varna 14
Neuro-realistic model of episodic encoding and retrieval
(a) Main modules of the hippocampus – ECII, ECIII, CA3, CA1, DG
(b) Entorhinal input, emerging from the sensory system and representing the vector time series produced by behavior
(c) when the rat runs to the right, the phase shift in firing within each theta rhythm cycle occurs in place cells 1 to 4, which are activated sequentially
30/09/2007 ADBIS'07 Varna 15
Properties of the phase model
(The recurrent connections in the CA3 layer of the hippocampus form asymmetric connections so that units with prior activations are connected to those with subsequent activations
These activations are a consequence of the coincidence between their phase differences and the time window of the asymmetric synaptic plasticity
30/09/2007 ADBIS'07 Varna 16
Model of hippocampal nerve circuit
(a) mechanism of theta phase coding (b) phase shift in firing within each theta rhythm cycle
30/09/2007 ADBIS'07 Varna 17
Relevance to modeling memory: Partial cuing triggers pattern completion in the CA3 and its
transmission to the CA1 and EC. Thus a stored pattern in the hippocampus can be sent to the cortical area to replay the input pattern
The temporal difference between encoding and retrieval in the network parallels behavioral tests
The retrieval is ten times faster than the behavioral input in the encoding stage and the retrieval time scale is similar to that of the compressed pattern of theta phase precession
The retrieved activity can cause further synaptic plasticity in other cortical areas for memory consolidation or memory transfer from the hippocampus to the cortex
30/09/2007 ADBIS'07 Varna 18
Importance of theta phase precession theory to the present study:
The emergence of rhythmic patterns in the absence of memory to cause its formation is a plausible candidate for a neural correlate of the formation of complex and durable cognitive effects governing future behavior i.e. autobiographical memories
We have aimed to give a relevant example to illustrate these effects
30/09/2007 ADBIS'07 Varna 19
How to find an Art Gallery on the Web with incomplete initial information?
Participants:- Motivated- NeutralSearch goal:- Example of new concept learning, similar to
artificial concept learning: “Kurenai Kai”Search task:- Google search from incomplete initial information
(The name of the gallery “Kurenai Kai” not known apriory)
30/09/2007 ADBIS'07 Varna 20
Results and discussion:
User Searches Time Random Meaningful Approximate
Motivated 23 3-5 30 min Neutral 19 3-5 30 min
Table 1. User performance on Web search with incomplete initial information about the search goal
Our study of Web search has replicated the mechanism of performance of the theta phase precession model :- The Web paths resemble random search until a meaningful path is composed-We observe that meaningful paths are composed, rather than encountered
30/09/2007 ADBIS'07 Varna 21
Web search: “Kurenai Kai”
Left path represents the nature of the search with incomplete initial information Right path represents the shortest path with well-remembered concept term
30/09/2007 ADBIS'07 Varna 22
Remembering meaningful fragments of search episodes
Left path represents episodic memory guided retrieval based on a set of meaningful cues and “insight”The pages to the right represent the mappings to the respective initial cues (none of them are identical)
30/09/2007 ADBIS'07 Varna 23
Conclusions from the Web search study:
Users base subsequent retrieval of the search path on remembering the ‘events’ of their search, which are the meaningful fragments of knowledge inside the Web pages, not the exact ‘page-retrieval’ episodes
We propose that the autonomous Web agent behaves in analogy with the event-based (autobiographical) strategy that Web users are applying for retrieval of useful information, which is some state of knowledge with anticipatory value (useful in the future)
Next will be tests of the agent for optimized storage of fragments of knowledge contained in the Web page, rather than of snapshots of sequences of Web pages
30/09/2007 ADBIS'07 Varna 24
Fragment extraction and recombination
of textual elements as a
process of encoding
search events
Agent reinstatement of the search task
30/09/2007 ADBIS'07 Varna 25
Temporal evolution of episodic events by the neuro-cognitive agent
30/09/2007 ADBIS'07 Varna 26
Conclusions and Future WorkWe presented one approach towards the design of
Web agents based on recent knowledge from brain research
We have tried to demonstrate how the theoretical framework of theta phase coding endows real-time process of memory formation of Web search experiences and the retrieval process of effective routes to the targets through the experienced sites
The proposed approach focuses on bridging the gap between neuroscience and Web technologies
It is currently being applied to retrieval of cardiological knowledge from the Web
30/09/2007 ADBIS'07 Varna 27
AcknowledgementThis work is supported by:
NSRF of the Bulgarian Ministry of Education and Science as part of the Research Project
MI - 1509/2005
”Multimodal User and Sensor Interface in a Computer-Aided System for Cardiological
Diagnosis and Intervention”
30/09/2007 ADBIS'07 Varna 28
Thank you for your attention