Cognitive Rehabilitation Memory
“A memory is regarded as a reconstruction from many different chunks stored redundantly through the brain.” – Encarta
The Role of Memory in the Learning Process
- Memory – processes by which people and other organisms encode, store and retrieve information.
- Encoding- refers to the initial perception and registration of information.
- Storage is the retention of encoded information over time.
- Retrieval- refers to the processes involved in using stored information.
- Learning creates “new synapses” and/or strengthens old.
- The synaptic connections are the molecular equivalent of a chunk of newly learned material.
- As we learn, a protein called C-kinase is deposited among certain hippocampal neurons according to Daniel Alkon of the Marine Biological Laboratory, Woods Hole, Massachusetts.
- C-kinase cause the branches of the brain cells to narrow. When they have narrowed and formed new synapses, learning has occurred.
- However, unless learning is converted into long-term memory it will disappear. (Howard, 1994)
Forming a chunk of memory is like making a photograph. Capturing the picture (immediate memory), developing the film (short-term memory) and fixing the image permanently (long-term memory). (Howard, 1994)
Learning VS. Memory
- refers to the processes involved in the initial acquisition or encoding of information.
- refers to the storage and retrieval of the information acquired.
Types of Memory
Short-term Memory (working memory)
Iconic- Visual interpretation
Serial Position Effect: Primacy Effect / Recency Effect
3 Long-Term Systems: Episodic, Semantic, Procedural
Echoic- Auditory interpretatio
Memory Span Auditory / Visual sequential memory
Declarative vs. Nondeclarative
- Limbic System
- Episodic memory
- Skills, continuous chunks of memory
- Kinesthetic Sequences, tying shoes, riding a bike
- Unconscious Learning
- Implicit Memory
- Frontal Lobe/Cerebral Cortex
- Semantic memory
- Word Definitions
- Symbol Meanings
- Associations with dates, places and faces.
- Conscious Learning
- Explicit Memory
- “Experiences which are destined to be laid down as long-term memories are shunted down to the hippocampus where they are held in storage for 2-3 years. During this time the hippocampus replays the experiences back up to the cortex, and each rehearsal etches it deeper into the cortex. Much of the hippocampal replay is thought to happen during sleep.” (Carter, 1998)
- The brain has 100 trillion connections joining billions of neurons and each junction has the potential to be part of a memory.
- The capacity of the brain is effectively infinite, providing it is stored in the right way.
- Personal and meaningful memories can be in the billions while dry facts (from school) may fade quickly. (Carter, 1998)
The Chemistry of Learning
Memories are groups of neurons that fire together in the same pattern, the links between individual neurons, which bind them into one single memory are formed through a process called “Long-term potentiation” (LTP)
Cell 1 receives a significant stimulus, which causes it to fire and fast enough that it also sets off it’s neighboring cell 2. Cell 2 will be chemically changed from this process causing it’s receptors to surface. This cell will stay in a “standby” mode for perhaps days waiting for Cell 1 to fire again. Each time the two cells fire in synchrony the link between them is strengthened and they permanently bond. When a group of linked neurons fire it triggers a memory. (Carter, 1998)
The Neuronal Basis of Learning
- The consequence of the chemical exchange between these cells creates permanent reverberating structural changes in the efficiency of learning as well as the enlargement of the memory storage.
- Cajal (1911) & Hebb (1949) postulated that memory storage takes place in the same cortical region where information is processed.
- “Because there are so many available synapses, cognitive complexity and memory capacity is potentially unlimited. The neocortex alone contains anywhere from 1014 to 1017 synapses” (Joseph, 2001).
- As the number of neurons that come linked via perceptual and cognitive activity increases, so does the complexity in mental functioning which in turn is maintained via a vast system of interconnected memories and semi-independent neural networks (Buchel et al., 1999; Miltner et al., 1999; Quartz & Sejnowski, 1997).
- “Neural networks also allow for the addition of new associated memories-through correlated activity involving the same synapses, a new memory can be added to the neural network and /or circuit can be modified so as to accommodate new learning”(Joseph, 2001).
- Moreover, a new set of activated neurons can be added to the network so long as their activity and interconnections become linked to the previously established pattern of excitation associated with the specific neural network (Buchel et al., 1999; Enbert & Bonhoeffer, 1999; Miltner et al., 1999; Quartz & Sejnowski, 1997; Xu et al., 1998).
Memory Permanence & Stability Isolated Memories
- With decreased activation, the original neuronal circuit may decay as neurons and dendrites drop out, and the LPT diminishes. The result is memory loss or amnesia for specific events and experiences.
- Presumably it is because memories are stored in different neurons and in different regions of the brain, that different components may be retained or lost at different rates or as a consequence of different forms of interference, including brain damage and degeneration. (Joseph, 2001)
Theories of Memory
- “Localized models essentially suggest that particular memories are coded in terms of particular pathways, or neuronal circuits, and were given substance by Donald Hebb, who postulated the existence of a class of neurons whose connections were in the form of synapses which could be modified by experience, thus opening or closing unique pathways.”
- This method was a pre-curser to the Holographic Model. The Rival memory model suggests that, rather than there being a localization of memory circuits, the storage of information is a molar property of the mass of cortical cells, a ‘field’ rather than a ‘point’ representation being involved.
- The Holographic Model was the mathematical rationale for the Rival method, in the form of analogies with the non-localized storage of information on a photographic plate provided by the hologram.
- The hippocampal memory is important for spatial, verbal, auditory, cognitive and for recognition of experiences, or non-emotional memories.
- The hippocampus does NOT receive direct neocortical input. The data it does receive originates in the association areas and is transmitted to the entorhinal cortex or the amygdala before being relayed to the hippocampus.
- The hippocampus creates a cognitive map of an individuals environment and their movements.
- When the hippocampus has been damaged the ability to convert short term memories into long term memories becomes significantly impaired in humans. (Eichenbaum et al. 1994; Gloor, 1997; MacKinnon & Squire, 1989; Nunn, et al., 1999; Squire, 1992; Victor & Agamanolis, 1990).
- Lesions of the hippocampus can also disrupt time sense and temporal sequencing such as involving timing tasks (Meck et al. 1984). Memory for words, passages, conversations, and written material can be affected, especially with left hippocampal lesions.(Frisk & Milner, 1990; Squire, 1992).