Linear Pattern Associators

Readings

Human memory systems

• Short-term versus long-term memory: states versus weights
• Episodic or "flashbulb" memory, versus gradual, incremental, assimilation into an existing representation
• Characteristics of human episodic memory:
  • huge capacity
  • one-shot learning
  • impaired in amnesics
  • associated with the hippocampus & related brain structures
  • probably only accounts for a small fraction of what is learned
  • may be modelled well by associative memory models

Associative memory models

• Hebb's learning postulate
• neurobiological evidence: LTP, LTD
• the generalized Hebb-rule or outer-product rule
• a feed-forward linear pattern associator
• conditions for perfect recall
• hetero-associative (supervised) versus auto-associative (unsupervised) models
• recurrent versus feedforward auto-associative models
• performance measures:
  • memorization (recall & recognition rates)
  • generalization (pattern completion)
• Summed vector memories, matched filters
• Summary of major features:
  • one-shot learning
  • poor capacity