Lecture 5 - Cellular basis of learning & memory (I) Flashcards
What is learning?
What is memory?
Learning - acquire and process information from the environment - changes the nervous system (synaptic structure and function)
Memory is our ability to encode, store, retain and subsequently recall information and past experiences in the human brain.
What is encoding?
What are the two important factors for successful encoding?
Encoding is the conversion of an item of interest into a construct that can be stored within the brain, and then recalled later from short-term or long-term memory
Attention and emotion are two important factors for the successful encoding
Attention (regulated by thalamus and frontal lobe) - a memorable event causes neurons to fire more frequently, increasing the likelihood it is encoded as a memory
Emotion (processed on an unconscious pathway in the brain leading to the amygdala) tends to increase attention
What is an engram?
An engram is a hypothetical biophysical or biochemical change in the neurons of the brain, hypothetical in the respect that no-one has ever actually seen, or even proved the existence of, such a construct.
What is consolidation?
Consolidation is the processes of stabilizing a memory trace after the initial acquisition.
- Synaptic consolidation (which occurs within the first few hours after learning or encoding)
- System consolidation (where hippocampus-dependent memories become independent of the hippocampus over a period of weeks to years).
What is memory re-consolidation?
Memory re-consolidation is the process of previously consolidated memories being recalled and then actively consolidated all over again, in order to maintain, strengthen and modify memories that are already stored in the long-term memory.
Several retrievals of memory may be needed for long-term memories to last for many years, depending on the depth of the initial processing. However, these individual retrievals can take place at increasing intervals, in accordance with the principle of spaced repetition.
What is storage?
How are long-term memories stored after consolidation?
Storage is the more or less passive process of retaining information in the brain, whether in the sensory memory the short-term memory or the more permanent long-term memory.
After consolidation, long-term memories are stored throughout the brain as groups of that are primed to fire together in the same pattern that created the original experience, and each component of a memory is stored in the brain area that initiated it.
They may even be encoded redundantly, several times. in various parts Of the cortex. So that, if one engram (or memory trace) is wiped out, there are duplicates, or alternative pathways, elsewhere, through which the memory may still be retrieved.
What is forgetting?
Forgetting, is perhaps the temporary or permanent inability to retrieve a piece of information or a memory that had previously been recorded in the brain.
Unlike amnesia, forgetting is usually regarded as a normal phenomenon involving specific pieces of content, rather than relatively broad categories of memories or even entire segments of memory.
What is recall or retrieval of memory?
Recall or retrieval of memory refers to the subsequent re-accessing of events or information from the past, which have been previously encoded and stored in the brain. In common parlance, it is known as remembering. During recall. the brain “replays” a pattern of neural activity that was originally generated in response to a particular event, echoing the brain’s perception of the real event.
Memory retrieval requires re-visiting the nerve pathways the brain formed when encoding the memory and the strength of those those pathways determines how quickly the memory can be recalled. Recall effectively returns a memory from long-term to short-term or working memory where it can be accessed, in a kind of mirror image of the encoding process. It is then re-stored back in long-term memory, thus re-consolidating and strengthening it.
What are the types of memory?
Sensory memory
Short-term memory (working memory)
Long term memory
- implicit memory - procedural memory
- explicit memory - declarative memory - episodic or semantic memory
What are the characteristics of sensory memory?
Large capacity but rapid decay
Sensory association areas involved
Responsible for recency effect
What are the characteristics of short-term memory (working memory)?
Lasts for seconds to minutes
Severely limited capacity
• magical 7 ± 2 - hold for digits, letters, etc.
Available to conscious awareness
Prefrontal cortex involved
What are the characteristics of intermediate memory?
Lasts for hours and days
May be transferred to LTM through rehearsal
Example: remembering where you parked your car
What are the characteristics of declarative (explicit) memory?
Conscious recollection
More conscious effort
Easy to form and are easily forgotten
No limit for storage
What are the characteristics of nondeclarative (implicit) memory?
Without conscious recollection
Direct experience
Require repetition and practice over a longer period of time and are less likely to be forgotten
Limit for storage/varies with age
Where are memories located?
Deep inside the medial temporal lobe is the region of the brain known as the limbic system, which includes the hippocampus, the amygdala, the cingulate gyrus, the thalamus, the hypothalamus, the epithalamus, the mammillary body and other organs, many of which are of particular relevance to the processing of memory.
Another sub-cortical system (inside the cerebral cortex) which is essential to memory function is the basal ganglia system, particularly the striatum (or neostriatum) which is important in the formation and of procedural memory.
