Working Memory Model (Covington)
(Damasio, Self Comes to Mind, 142)
My working memory model combines the working memory model of Baddeley together with the functionality of Damasio's Convergence-Divergence Zone architecture, and aspects of Cowan’s Attention and Memory model, together with some Neural Networks functionality provided by Rolls & Treves.
The Central Executive contains a number of Convergence-Divergence Regions (CDRs) and Convergence-Divergence Zones (CDZs).
CDRs and CDZs receive feedforward connections from areas located earlier in the signal-processing chains, as well as reciprocal feedback projections to those areas. (Damasio; Self Comes to Mind, , 144)
The Central Executive is principally in the frontal cortex but also has projections and functionality widespread through the cortex.
Backprojection architecture could implement semantic priming by using backprojecting neurons to provide a small activation of just those neurons that are appropriate for responding to the semantic category of input stimulus. (Rolls & Treves; Neural Networks, 244)
Attention could operate from higher to lower levels, to selectively facilitate only certain pyramidal cells by using backprojections. (Rolls & Treves; Neural Networks, 244)
Backprojections could produce many of the top-down influences that are common in perception. (Rolls & Treves; Neural Networks, 244)
Short-Term Memory Systems
There are a number of different short-term memory systems, each implemented in a different cortical area. (Rolls & Treves; Neural Networks, 245)
The particular systems considered here implements short-term memory by subpopulations of neurons that show maintained activity in the delay, while a stimulus or event is being remembered. (Rolls & Treves; Neural Networks, 245)
The short-term memories may operate as autoassociative attractor networks. (Rolls & Treves; Neural Networks, 246)
Autoassociation could be implemented by associatively modifiable synapses between connected pyramidal cells within an area, or between adjacent cortical areas in a hierarchy. (Rolls & Treves; Neural Networks, 246)
The Episodic Buffer includes the hippocampal CA3 area, with its associative memory capability, together with long-term memory widely distributed throughout the cortex.
A theory of the hippocampus in which the CA3 neurons operate as an autoassociation memory to store episodic memories including object and place memories, and the dentate granule cells operate as a preprocessing stage by performing pattern separation so that the mossy fibers could act to set up different representations for each memory to be stored in the CA3 cells. (Rolls; Memory, Attention, and Decision-Making, 37)
The Visuospatial Sketchpad includes the image areas of the occipital cortex and the association areas of the parietal cortex and temporal cortex.
One short-term memory system is in dorsolateral prefrontal cortex, Brodmann area 46. This is involved in remembering the locations of spatial responses. (Rolls & Treves; Neural Networks, 246)
The Phonological Loop includes the functionality of Broca’s area and Wernicke’s area.
Another short-term memory system is human auditory-verbal short-term memory, which appears to be implemented in the left hemisphere at the junction of the temporal, parietal, and occipital lobes. (Rolls & Treves; Neural Networks, 247)
Complemented by other Neural Network Models
My working memory model would be complemented by other neural network functionality:
• Attention and Memory model of Nelson Cowan
• Perception Action Cycle of Joaquin Fuster
• Bayesian inference functionality
Cortical Sequences of Activity States during Working Memory
Research studies have identified cortical sequences of activity states during working memory tasks. Navigation, memory and choice information may be combined in the sequences such that the identity of the active sequence reflects choice-related information for working memory and movement planning.
Research study — Parietal Cortex Decision-Making
Return to — Working Memory
Return to — Scientific Understanding of Consciousness