Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Declarative Memory As Reconstruction

I have considered the words (reactivation/reenactment/regeneration/reconstruction/reconsolidation) to connote the process of invoking a declarative memory. My current view is that the word reconstruction is the most descriptive word for the process.

Memories are not stored in facsimile fashion; they must undergo a complex process of reconstruction during retrieval. (Damasio; Feeling of What Happens, 227)

Keep in mind that declarative memory is invoked by injecting a neural signals cue-pattern into the quiescent synaptic network to associatively activate the reconstructed active neural pattern of the memory.

 

Research study Overlapping Memory Trace Linking, but Not Recalling, Individual Memories

Link to Memories Retrieved

 

Declarative Memory is not simply a readout -- it involves a Mental Reconstruction of a Prior Event

Declarative memory is a reconstruction of a prior arrangement of synaptic connections over widely distributed areas of the brain. Tens or hundreds of millions of synaptic connections are involved. The specific arrangement of synaptic connections is not precise. Each time the memory is regenerated, a somewhat different set of neurons and synapses could be active, but enough of the original synaptic connections will be involved to result in approximately the same thought. Memories will tend to change and fade over time. Newly stored memories will typically utilize some of the same neurons and synapses used by older memories. The newly stored memories could modify the synapses used by older memories. This multiuse of the synapses forming memories will eventually lead to fading of memories as newer memories are formed with reused and modified combinations of synaptic connections.

A memory is a tiny bit different each time we remember it. (Ratey; User's Guide to Brain, 186)

The information we ultimately remember from an experience is not a high-resolution copy of the experience, however vivid it may have been, but rather a low-resolution transformation of the experience in which much of the original context has been lost to compression. (Hurley, Dennett, Adams; Inside Jokes, 111)

Human memory is subject to the distortion of memory reconstruction. (Mlodinow; Subliminal, 63)

Memory mistakes are all artifacts of the techniques our minds employ to fill in the inevitable gaps. (Mlodinow; Subliminal, 61)

Though our memory system is far from perfect, it is in most situations, exactly what evolution requires: it is good enough. (Mlodinow; Subliminal, 63)

In the evolutionary big picture, human memory is wonderfully efficient and accurate -- sufficient to have enabled our ancestors to generally recognize the creatures they should avoid and those they should hunt down. (Mlodinow; Subliminal, 63)

 

Memories Are Reactivated Via Associative Cues

Memories are retrieved by associative access through their component representations, by reconstruction from fragments. (Fuster; Memory in Cerebral Cortex, 199)

Memory is a replay of neural response patterns adequate to the performance, not some sequence or specific detail. (Edelman; Universe of Consciousness, 98)

During recall, neural activity does occur in cortical areas involved in the original processing. (Rolls & Treves; Neural Networks, 243)

The ability of autoassociative systems to reconstruct missing or noisy parts of the learned patterns. (Anderson; Associative Networks, 105)

Storage of short-term memories is inextricable from the reactivation of a long-term memories. (Fuster; Memory in Cerebral Cortex, 4)

Individuals with posttraumatic stress disorder (PTSD) typically report experiencing intrusive recollections, nightmares, and distress with physiologic arousal in response to reminders of trauma. (Vogt; Cingulate Neurobiology, 454)

Gestalts in Memory Reconstruction

The figurative smoothing out of memory is strikingly similar to a literal smoothing out that Gestalt psychologists in the 1920s had noticed in studies of people's memory for geometric shapes. (Mlodinow; Subliminal, 69)

 

Research study Hippocampal Learning and CA3 Output

 

Top-Down Activity Invokes Declarative Memories

Much of recollection works with top-down activity from higher centers feeding back upon upstream cortical areas to re-evoke the specific features of an image or idea. (Squire & Kandel; Memory, 107)

Memory cannot simply be equated with synaptic change, although changes in synaptic strength are essential for it. Each event of memory is dynamic and context-sensitive. Memory involves a repetition of a mental act that is similar to but not identical with previous acts. Memory is recategorical; it does not replicate an original experience exactly. Memory should be looked on as a property of degenerate nonlinear interactions in a multidimensional network of neuronal groups. Such interactions allow a non-identical "reliving" of a set of prior acts and events. Memories are necessarily associative and never identical. (Edelman; Wider than the Sky, 52-53)

Cells in high-order cortices forming the hierarchy of convergence zones are critical for the neural process of memory reenactment, but they are neither the "sole basis for" nor the "explicit site of" that neural process. There is no single basis or site for such a process. Each memory reenactment can utilize slightly different neural assemblies. (Domasio; Convergence Zone, 68)

Memory Is a Complex Process of Reconstruction

Our brains are belief engines, evolved pattern recognition machines that connect the dots and create meaning out of the patterns that we think we see in nature. (Shermer; Believing Brain, 59)

Patternicity -- the tendency to find meaningful patterns in both meaningful and meaningless noise. (Shermer; Believing Brain, 60)

Memories are not stored in facsimile fashion; they must undergo a complex process of reconstruction during retrieval. (Damasio; Feeling of What Happens, 227)

Retrieval Process

During retrieval, we usually seek a particular memory -- a particular fact, idea, or experience, often called the target memory or the target trace. (Baddeley, et.al.; Memory, 165)

The snippets of information that allow you to access a memory are known as retrieval cues, or simply cues. (Baddeley, et.al.; Memory, 165)

Traces of memory are believed to be linked up to one another by connections that are usually called associations or links. (Baddeley, et.al.; Memory, 165)

Associations are synaptic efficacy linkages between traces that vary in strength. (Baddeley, et.al.; Memory, 165).

Retrieval is a progression from one or more cues to a target memory, via associative connections. (Baddeley, et.al.; Memory, 165)

Memories automatically spread activation to other memories to which they are associated. (Baddeley, et.al.; Memory, 166)

The idea that traces have activation that spreads is central to many theories of memory, and provides a useful way of thinking about how to cues access memories. (Baddeley, et.al.; Memory, 166)

Retrieval is a progression from one or more cues to the target memory, via associative connections linking them together, through a process of spreading activation. (Baddeley, et.al.; Memory, 166)

 

Research study Retrieval of Knowledge Enhances Learning Not only does retrieval produce learning, but a retrieval event may actually represent a more powerful learning activity than an encoding event.

 

Retroactivation process uses the rich connectional patterns of feed-forward and feedback that characterize the architecture of cortical regions and subcortical nuclei. (Damasio; Making Images, 20)

 

Each event of memory is a dynamic and context-sensitive. Memory involves a repetition of a mental act that is similar to but not identical with previous acts. Memory is recategorical; it does not replicate an original experience exactly. (Edelman; Wider than the Sky, 52)

Remembering is an imaginative construction, built on a whole active mass of past experiences. (LeDoux; Synaptic Self, 177)

Memory cannot simply be equated with synaptic change, although changes in synaptic strength are essential for it. (Edelman; Wider than the Sky, 52)

Memory should be looked on as a property of degenerate nonlinear interactions in a multidimensional network of neuronal groups. Such interactions allow a non-identical "reliving" of a set of prior acts and events. (Edelman; Wider than the Sky, 52)

Memories are necessarily associative and never identical. (Edelman; Wider than the Sky, 53)

Memory is dynamically generated from the activity of certain selected subsets of circuits. Memory cannot be identified uniquely with any single specific set of synaptic changes. Memory is a replay of neural response patterns adequate to the performance, not some sequence or specific detail. Synaptic change is fundamental and essential for memory but not identical to it. Degeneracy in neural circuits allows for changes in particular memories as new experiences and changes in context occur. Dynamic changes linking one set of circuits to another within the enormously varied neuroanatomical repertoires of the brain allow it to create a memory. Structurally different circuits within the degenerate repertoires are able to produce a similar output, leading to repetition or variation. Associative properties of memory - an act can trigger another act, a word can trigger other words, or an image can provoke a narrative. Associative properties arise materially from the fact that each different member of the degenerate set of circuits used at different times has different alternative network connections. (Edelman; Universe of Consciousness, 98)

Memory capacity arises from combinations of synaptic alterations in reentrant circuits. (Edelman; Universe of Consciousness, 105)

Fundamental mechanism of memory is a change in synaptic strength. (Edelman; Bright Air, 103)

Memory is considered to be a form of recategorization. (Edelman; Bright Air, 104)

Recall involves the activation of some of the previously facilitated portions of global mappings. (Edelman; Bright Air, 102)

Categorization response is similar to a previous response, but at a later time the neurons and synapses contributing to that response will be different. In general, they are likely to have been altered by ongoing activity in the brain. (Edelman; Bright Air, 102)

Perceptual categories are not immutable and are altered by the ongoing behavior. Memory in this view results from continual recategorization. (Edelman; Bright Air, 102)

 

For further discussion of declarative memory involving the hippocampus:

Link to Declarative Memory Classifications

 

 

Return to Memory