Chapter 11: Learning, Memory, and Amnesia

Sensory Memory

Initial stage that holds virtually all incoming information for fractions of a second

Short-term Memory

Holds five to seven items for about 15–20 seconds.

Long-term Memory

Can hold a large amount of information for years or even decades

The Case of H.M.

• H.M. suffered from severe, intractable epilepsy​

• Foci in both medial temporal lobes​

• Received bilateral medial temporal lobectomy.

Retrograde Amnesia

Inability to recall memory from the past

Anterograde Amnesia

Inability to form new memories

Mirror-Drawing Test

-H.M. displayed substantial savings with no conscious recall of previous practice.

-H.M.’s performance improved with practice although he had no recollection of doing this task. Suggests that H.M was capable of forming certain kinds of memories.​

Contributions of H.M.

• Medial temporal lobes are important for memory (especially the hippocampus).​

• H.M.’s short-term memory (STM) was intact, however, he seemed unable to transfer information from STM to LTM. This suggested that there were different modes of memory storage (STM vs. LTM).

Explicit Memory

Conscious Memory

Implicit Memory

Unconscious Memory

Semantic Memory

Memory for general facts

Episodic Memory

Memory for experience of specific life events

Episodic memories and time travel

• Suffers from severe amnesia for personal experiences, unable to recall personal events for more than a minute or two into the past.​

• While understanding the concept of time, cannot mentally "time travel" to imagine future events or recall past ones, impacting his ability to plan for the future.​

Post-traumatic Amnesia

Amnesia that occurs after a closed-head TBI

Consolidation

Process by which a new, fragile memory becomes stronger (less suspectable to disruption) over time.

Hebb’s Theory of Memory Consolidation

Memories stored temporarily by neural activity in closed circuits, susceptible to disruption but eventually inducing structural synaptic changes for long-term storage.​

Electroconvulsice shock (ECS)

• ECS involves administering an intense, brief, diffuse, seizure-inducing current to the brain through large electrodes attached to the scalp.​

• The use of ECS in memory studies is based on the idea that it can disrupt neural activity, erasing memories not yet converted into structural synaptic changes.​

• The duration of retrograde amnesia induced by ECS offers an estimate of the time required for memory consolidation.​

Current View on Memory Consolidation

• Believed to continue for a long time, potentially indefinitely. Memory becomes more resistant to disruption over time, with repeated activation strengthening and updating the memory and its connections.​

Reconsolidation

Each retrieval of a long-term memory places it temporarily into short-term memory where it is vulnerable to posttraumatic amnesia until reconsolidated.

Hippocampal Place Cells

• These cells fire when a something is placed in a specific location (in the place field), but only after something becomes familiar with that location. ​

• Each place cell has a place field in a different part of the environment. ​

• Firing of place cells will also indicate where the something “thinks” it is.

Grid Cells

Discovery of these in the entorhinal cortex revealed neurons with hexagonal, evenly spaced place fields, mapping the environment's surface

Border Cells

(fire when rat approaches a border or boundary), contributing to spatial orientation and awareness of environment boundaries.​

Head Orientation cells

Tuned to head position

Cognitive Map

The hippocampus is instrumental in spatial learning and memory but also responds to more than spatial cues.

Time Cells

Involved in coding the temporal aspects of experiences.​

Social Space

Social Organization

Concept Cells

Cells that respond to ideas of concepts

Infatile Amnesia

Common phenomenon where early childhood events are not explicitly remembered.