Memory, learning in the nervous system

Main

Memory and learning are complex processes that engage a wide range of brain regions. Learning involves the acquisition of new information or skills, while memory refers to the retention and retrieval of what has been learned. The capacity for learning and memory is one of the key functions of the nervous system.

The process of learning and memory formation involves several stages:

1. Encoding: New information is acquired and processed by the brain.

2. Consolidation: The information is strengthened and stabilized in the brain over time, often through repeated activation of neural pathways.

3. Storage: The information is maintained in the brain over an extended period, from hours to years. Memories are initially stored in the hippocampus but become distributed to the cortex for long-term storage over a period of weeks to years.

4. Retrieval: The stored information is accessed and brought back into conscious awareness. Memories are not static but can be modified or distorted with repeated retrieval or as new information is learned.

Emotional arousal can enhance memory by engaging the amygdala and promoting the release of stress hormones.Tips for effective learning and memorization:

• Engage multiple senses when learning new material

• Relate new information to existing knowledge

• Practice active recall and self-testing

• Space out study sessions over time

• Get sufficient sleep to promote memory consolidation

Terms

• Declarative memory: Memory for facts and events that can be consciously recalled, also known as explicit memory.

• Nondeclarative memory: Memory for skills, habits, priming, and simple forms of associative and nonassociative learning that do not require conscious recall, also known as implicit memory.

• Short-term memory: The temporary storage of information, lasting on the order of seconds to minutes.

• Long-term memory: The more permanent storage of information that can last days, weeks, years, or a lifetime.

• Synaptic plasticity: Changes in the strength of connections between neurons that are thought to underlie learning and memory.

Analogy

Learning and memory in the nervous system can be compared to writing and storing files on a computer. Short-term memory is like the RAM on a computer, providing a temporary workspace. Long-term memory is analogous to the hard drive, allowing files (memories) to be stored indefinitely. Repeatedly accessing and editing files makes them easier to retrieve, just as repeated activation of neural pathways strengthens synaptic connections and makes memories easier to recall.

Misconception

A common misconception is that memory is stored in a single location in the brain, similar to files in a computer. In reality, memories are distributed across many brain regions and involve changes in the strength of connections between neurons. Amnesia resulting from brain damage is often more pronounced for forming new memories (anterograde amnesia) than recalling old ones (retrograde amnesia), highlighting that the substrates for forming and storing memories are at least partially distinct.

History

1. 1880s-1890s: Hermann Ebbinghaus conducts pioneering studies on memory, discovering the forgetting curve and spacing effect.

2. 1920s: Karl Lashley searches for the "engram," the physical trace of memory, but concludes memories are widely distributed in the brain.

3. 1940s-1950s: Donald Hebb proposes that synaptic connections are strengthened with repeated use, coining the phrase "neurons that fire together wire together".

4. 1960s-1970s: Brenda Milner shows that the hippocampus is critical for forming new memories in patient H.M.

5. 1970s-2000s: Eric Kandel and colleagues elucidate the molecular basis of learning and memory in the sea slug Aplysia.

How to use it

1. A medical student can improve retention of anatomical terms by creating flashcards with images and self-testing regularly over several weeks leading up to an exam.

2. A person learning a new language can facilitate vocabulary acquisition by associating new words with mental images and using spaced repetition software to review the words at increasing intervals.

3. An individual with mild cognitive impairment can engage in mentally stimulating activities, physical exercise, and social interaction to promote synaptic plasticity and slow age-related memory decline.

Facts

• The hippocampus can generate around 1,400 new neurons per day in young adults.

• The brain's capacity for learning and memory declines with age, but engaging in mentally stimulating activities can help maintain cognitive function.

• Chronic stress can impair memory by causing atrophy of the hippocampus and prefrontal cortex.

• Retrieval practice, or the "testing effect," is a powerful strategy for enhancing long-term retention.

• Mnemonic devices, such as acronyms or visual imagery, can aid in the encoding and retrieval of information.