I want to have different perspectives on forgetting in my narrative so embarked upon a research journey.
In Douwe Draaisma’s Metaphors of Memory: A History of Ideas about the Mind, he traces the history of theories on memory by looking at the metaphors that have been used to describe memory.
- In 1930s, Freud expresses the functions of memory in terms of the ‘mystic writing pad’ toy where information can be written and disappears, with lasting traces building up on the wax underneath.
- Plato compares memory to wax tablet. Socrates compares it to an aviary. Augustine compares it to a treasure house…
- In the medieval times, they compare it to a library.
- 17th century, they compare it to phosphorescence which is when the material retains an afterglow after absorbing bright light.
- It goes on and on, metaphors of the memory reflect the technological and scientific innovations that happen, memories get compared to stuff like holograms, computers and then eventually- networks.
The neuroscience of memory is complicated. I read all of this https://nba.uth.tmc.edu/neuroscience/s4/chapter07.html
and decided to focus more on the neuroscience of ‘forgetting’ since my theme and narrative is more related to this area. But I need to communicate some general ideas in a simple way as to not overwhelm my narrative with information.
Memories are stored as chemical changes in synapses (junctions between neurons). A memory can involve thousands of synapses and each synapse can involve thousands of memories.
Different brain areas support different types of memories which can be connected by neuronal networks. systems of memory are nested and not independent of each other.
Working Memory- short term memory. Mostly stored in pre-frontal cortex. When the pattern of activated neurons can be recreated after the stimulus input- temporarily- as the biophysical neural changes in the brain are temporary.
Long term Memory- stored in hippocampus, medial temporal lobe, reveals itself cortex over time. Consolidated memory as structural changes have occurred in the brain. Changes in protein synthesis (biological process by with cells build their proteins) and gene expression created long term changes in synaptic strength.
Episodic Memory– memory for personally experienced past events
Procedural Memory- memory for both mental and physical actions (playing the piano etc.)
Semantic Memory- memory for facts and details not tied to personal experience
Recalling past events is when an association triggers neural signalling that results in a reconstruction of a memory.
Engrams- memory traces whereby memories are stored as biophysical neural changes in the brain in response to experience.
Controversy about whether engrams (aftereffects of experiences in brain)= memory vs memory= memory revealed in behaviour/thought
The brain actively works to forget, in order to narrow details down, getting rid of out-dated stuff, to the essential information that will aid decision making. There are brain mechanisms that function to create memory loss. One mechanism is Long-term Depression, where synaptic connections between neurons are weakened. Another mechanism is the formation of new neurons (neurogenesis) which remodels the hippocampal circuits and overwrites older memories in those circuits.
Long-term Potentiation
Synaptic process in the cortex in which synaptic connections become strengthened. Triggered by high-frequency stimulation of the synapses. Formation of new memories. More receptors and more neurotransmitters creating closer bond between two neurons.
Long-term Depression
Synaptic process in cortex in which synaptic connections become weakened. Triggered by low-frequency stimulation of the synapses. Less receptors and neurotransmitters leading to weakened bond between two neurons.
Transcience
Word for neurobiology of forgetting. As opposed to neurobiology of remembering which is persistence.
Theory of Passive Forgetting-
Why it happens:
- loss of context cues across time that make retrieval difficult,
- interference during retrieval from other similar memories accumulated across time
- the “natural” decay of memory traces from the general instability of biological materials and the passage of time
Theory of Active Forgetting-
Why it happens
- neurogenesis based forgetting which is when formation of new neurons overwrite the hippocampal circuitry holding older memories. Really old memories are not affected as they have been moved to cortex (systems consolidation: process by which storage of memory is moved from the hippocampus to the cortex
- interference based forgetting- proactive and retroactive interference from other competing information before or after the experience accelerates decay of engrams
- intrinsic forgetting- ‘forgetting cells’ release dopamine onto engram cells, activating the protein Rac1, creating memory erasure. Thought to happen because cells reverse structural changes that made the engram. Consistently erode newly acquired memories unless they are reinforced.
- Motivated forgetting- cognitive mechanisms are voluntarily engaged to weaken memory traces often because the memory is unpleasant
- Retrieval-induced forgetting is when some aspects of of the recalled memories causes suppress recall of other aspects of the memory
Forgotten memories can have remnants that have been re-worked and changed scattered all over the sypnatic network.
Psychological process of Memory
Three basic stages in memory:
Encoding: the perceptual experience being transformed into a code in the brain, it is selective and interpretative of reality.
Storage: The representation of the memory in the brain when it is not being recalled. It is liable to change by entry of new memories or lose accessibility with neglect.
Retrieval: When the information is recalled, or more accurately- reconstructed.
Psychological Theories of Forgetting
Trace Decay- The theory that memories automatically decay over time if not recalled. The longer the time. the more the memory trace decays.
Displacement theory– Forgetting in short term memory due to limited capacity, new information pushing out old information.
Interference- All memories interfere with the recall of other memories
Proactive Interference- when old memories inhibits the recall of new memories
Retroactive Interference- new information replaces older information
Output Interference- the act of recalling specific information inhibits retrieval of other parts of the original information.
Retrieval Failure/Cue-dependent Forgetting- the failure to remember memories in the absence of memory cues.
Blocking- When the brain has partial recall and tries to retrieve information but another similar or related memory blocks it. Cause of the tip-of-the-tongue phenomenon.
Lack of Consolidation- Disruption during the consolidation process in which recently formed memories become stablised long term memories, thus causing new memories to be lost.
Encoding failure/ Absentmindedness- ineffective encoding of memories due to lack of attention, priority or commonality, causing difficulty or failure in retrieval.
Amnesia- Inability to recall memories due to Types of amnesia include Retrograde Amnesia (inability to recall information before the onset of amnesia) and Anterograde amnesia (inability to form and recall new memories).
Repression- memories that are actively suppressed in the brain, often due to being unpleasant.
I think I will have a spread on types of forgetting in diagram and another spread on neuroplasticity with analogical illustrations.
Something about Lost 