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

Declarative Memory Classifications

In addition to short-term memory and long-term memory, I think it is important to emphasize the category unconsolidated, hippocampus-dependent memory.  This category comprises much of what we consider memory in our daily activities.

It is important to keep in mind that amnesic patient HM, who had his hippocampuses removed, retained his functionality for short-term memory and his remote long-term memory, but could not form new long-term memories.


Link to — Short-Term Memory

Link to — Long-Term Memory


Short-term Memory

Cognitive psychologists subdivide short-term memory into two major components -- immediate memory and working memory. (Squire & Kandel; Memory, 84)

Short-Term Memory Mechanisms

Short-term memory can be mediated in at least two ways.

· Rehearsal of neural activity.

· Synaptic facilitation by a biochemical mechanisms.

Immediate Memory

Immediate memory refers to what can be held actively in mind that forms the focus of current attention and that occupies the current stream of thought. (Squire & Kandel; Memory, 84)

Capacity of immediate memory is quite limited (it can hold approximately 7 items), and unless its contents are rehearsed, it ordinarily persists for less than 30 seconds. (Squire & Kandel; Memory, 84)

Ordinarily, information will slip from your conscious mind within a few seconds, but immediate memory can be extended in time and its contents retained for many minutes if you rehearse actively.  This extension of immediate memory is called working memory. (Squire & Kandel; Memory, 84)

Immediate working memory, short-term post-distractional memory, and long-term consolidated memory seem to involve different brain mechanisms. (Calvin; Neil's Brain, 86)


Working Memory

Working memory is an extension of immediate memory by rehearsing. (Squire & Kandel; Memory, 84)

Working memory may consist of a relatively large number of temporary capacities, each a property of one of the brains specialized information processing systems. (Squire & Kandel; Memory, 85)

Multicomponent working memory model assumes a four component system, comprising (1) an attentional controller, the central executive, and three temporary storage systems:(2) the visuospatial's sketch pad, (3) the phonological loop, and (4) a more general integrated storage system, the episodic buffer. (Baddeley; Working Memory, 13)

Immediate memory and working memory are best thought of as a collection of temporary memory capacities that operate in parallel. (Squire & Kandel; Memory, 85)

One kind of working memory, the phonological loop, is concerned with language and temporarily stores spoken words and meaningful sounds. (Squire & Kandel; Memory, 85)

Another kind of working memory, the visuospatial sketch pad, stores visual images such as faces and spatial layouts. (Squire & Kandel; Memory, 85)

We use working memory to conceptualize immediately occurring events and long-term memory to direct the present and plan for the future. (Ratey; User's Guide to Brain, 131)


Unconsolidated, Hippocampus-Dependent Memory

Unconsolidated, hippocampus-dependent memory comprises much of what we consider memory in our daily activities. —  Don’t forget a 12:30P meeting for lunch.  Remember to stop by the grocery store. Remember what I did yesterday.  Remember that pleasant excursion in the park last Sunday, etc.

At a week-long conference or meeting -- must learn and remember the first names and faces of new associates.  A month later, the names and faces will be completely forgotten -- no long-term memory.

A college student crams for exams, hippocampus regurgitates answers on the exam; unused knowledge fades over succeeding months; relatively little long-term memory.

Memory for a recently encountered object would be distributed among area TE in the temporal lobe, area PG in the parietal lobe, and other areas. (Squire & Kandel; Memory, 88)

Medial temporal lobe is not the ultimate long-term repository of memory. (Squire & Kandel; Memory, 88)


Link to — Nonconsolidated Hippocampus-Dependent Memories


Consolidation of Memory

Consolidation of long-term memory is a process that depends crucially on structures in the medial temporal lobe. (Squire & Kandel; Memory, 88)


Long-term Memory

Long-term memory is encrusted in the molecular structures of synapses.  An activated long-term memory is a reactivated subset of neuronal pathways via efficacious synapses, closely conforming to an associative triggering cue.

Long-term memories are stored in the same distributed set of structures that receive, process, and analyze what is to be remembered. (Squire & Kandel; Memory, 88)


Research study — Memory is Susceptible to Social Influences


Emotional Memory

Vividly remember emotional events, special events, traumatic events, etc.

Vividly remember a wedding ceremony, birth of a child, etc.

Vividly remember occasion when first learned about the 9-11 episode.


Short-term Memory -- Widespread Local Modularity

A useful metaphor is object-oriented programming wherein processing functionality together with data are amalgamated in a functional module.


Recency Effect

Presented with a list of words, and required to repeat the words regardless of the order (free recall), can usually recall well the first words in the list (primacy effect) and the last words (recency effect), but not so well the words in the middle. (Fuster; Cortex and Mind, 118)

Recency effect is one of the most stable and reliable phenomena within the study of human memory. (Baddeley; Working Memory, 115)

Recency effect -- extending from seconds to years. (Baddeley; Working Memory, 104)




Return to — Declarative Memory

Return to — Declarative Memory as Reconstruction

Return to — Memory Consolidation