Lecture 2B: Memory

Memory requires what three things?

Acquisition, retention, and the ability to retrieve information

• memory can break down at any point here

How is memory and behaviour connected?

Forming, keeping, and retrieving memories changes our behaviour and brains

With each thing that we experience, we store memory and it changes how we react and experience things in the future and it shapes who we are

Memory can be classified in three ways… explain:

1. Time

   1. Short-term

   2. Long-term

2. Content

   1. Explicit

      1. Facts (semantic)

      2. Events (episodic)

   2. Implicit

3. Process

   1. Encoding → Storage → Retrieval

Describe the processes of memory

1. Encoding - relies on attention so that the stimuli doesn’t become forgotten

   1. acquisition, registration, consolidation

   2. Environmental input is registered and turned into sensory input and forms a sensory memory

   3. Sensory memory can either be forgotten if no attention is applied, or it can become short-term memory

2. Storage

   1. Memories are either stored in short-term memory or moved into long-term memory

   2. Maintenance (doing stuff with the information to encode it and move it to LTM storage)

   3. If not maintained, it is forgotten through decay or displacement

   4. Memories in LTM can also be forgotten through interference or retrieval failure

3. Retrieval

   1. Going into your brain to find it and bring it back into the box of short-term memory

   2. Recognition: ability to judge whether or not item has been seen before

      1. recognition means that it is encoded in LTM somewhere

   3. Recollection: remembering contextual details and the encountering event

What is working memory?

Specific type of STM involving active and effortful maintenance and manipulation (applying higher order control onto the information)

Eg. Give someone a list of animals and tell them to list it back to me in alphabetical order (manipulating the STM before giving it back)

Describe primary/recency effects

You are more likely to remember things that you were presented first (primacy) and last (recency)

The stuff in the middle is the most likely to be forgotten

What is the timeframe for sensory memory, short-term memory, and long-term memory?

Sensory: milliseconds

STM: seconds to minutes

LTM: hours to days to years

what is amnesia?

mental state in which memory and learning are affected out of all proportion to other cognitive functions (only memory is impacted) - no perceptual, execF, attention problems

This never happens cause the cause of memory issues almost always impacts the attention, behaviour, etc…

Describe the two types of amnesia

1. Retrograde:

   1. loss of memory before the point of injury (loss of remote memory) or an arbitrary moment in time

   2. the amount of retrograde memory loss can be indicative of the severity of the brain injury

2. Anterograde:

   1. inability to form new memories after the point of injury/psychological trauma

It’s very unusual for a victim of a car crash to remember what happened at the point of contact

What can cause amnesia?

• TBI

• Herpes encephalitis

• Stroke

• Anoxia (lack of oxygen)

• Aneurysm

• Tumour

• Surgery

• Early stages alzheimers

Explain how HM’s case helps us understand the difference between explicit and implicit memory

• Had his medial temporal lobe excised (bilaterally) as a surgical intervention for his epilepsy

• Could not form new memories after surgery (global anterograde amnesia) - retrograde memories extended back 11 years (limited retrograde amnesia)

• no intervention was improving this (no memory test, specific stimulus material, or sensory modality)

• HOWEVER, he could learn new motor skills and perceptual tasks with practice (but could not remember ever doing the task before)

  • Improve mirror reading, word stem completion, and gollin figures

  • He was implicitly learning, but could not explicitly remember doing the task

This case study showed us that forming new conscious memories (explicit) is a different process from skill learning

What are the two forms of explicit memories? What case study helps us understand the two types?

KC case study:

• Motorcycle accident left him with a hematoma that impaired his memory (retrograde and anterograde amnesia)

• ALL episodic memories were lost, but he was still able to form new semantic memories

• Still had functioning short-term memory

Facts (semantic)

• General, undated knowledge that we have about the world and ourselves

• oriented to the present and represents general context-free facts

• memories for facts that are not based on personal experiences or episodes of your life

Events (episodic)

• Memories based on experiences of what you saw, heard, etc…

• Memory for events specific to time and place

• Past-oriented memory system, allowing mental time-travel through autonoetic awareness

What is the difference between explicit and implicit memories?

Explicit: conscious, intentional recollection of previous experience

• declarative

• factual

• memory

• Knowing WHAT

Implicit: unconscious/subconscious, non-intentional form of memory

• non-declarative

• Skills

• Habits

• Knowing HOW

What area of the brain is responsible for explicit memory

The medial temporal lobe (refer to HM case study)

Specifically, the hippocampus and the parahippocampus (mostly the hippocampus)

Is it just one area of the brain that controls memory formation and storage?

No! its a neural network

• frontal areas

• thalamic areas

• lymbic areas

• etc…

How is implicit learning mediated? What structures in the brain are responsible for this form of memory?

People with PD and Huntington’s exhibit impaired skill learning and even degeneration of already learned tasks

• Practicing doesn’t help them get better at things

• Things they have done their entire lives, they may no longer be able to do

PD and Huntington’s are characterized by degeneration of cells in the basal ganglia that produce dopamine

• thus, the basal ganglia, specifically the substantia nigra, have a role in implicit memory (skills, habits)

What areas of the brain are responsible for episodic memory formation

Ventral frontal lobe and medial temporal lobe

The uncinate fasciculus is a white matter communication tract that connects the frontal lobe with the medial temporal lobe

• this tract is important for the ability to retrieve episodic memories

Briefly describe the development of memory in children

0-2 y,o:

• no episodic memories formed, only semantic and implicit

• eg. babies before 2 can recite ABCs and learn skills, but do not have the ability to form and retrieve episodic memories

2-6 y.o:

• Paucity of recall (imperfect, but episodic memory formation begins)

6+ y.o:

• sudden increase in episodic memories that you can retrieve

• emergence of adult like memory

Not that our sense of self is developing during this whole process, as the brain matures (hippocampus and prefrontal areas)

How does emotion/trauma impact memory?

In general, highly emotional events (strong positive or negative ties) are easier to recall than neutral events

• As such, most people have a better recall of childhood trauma details

Note that PTSD is associated with lower hippocampal volumes (PTSD brain)

• results in difficulty retrieving old memories and forming new ones

• Is this because it never fully developed? Did it shrink? Does trauma decrease memory capacity? All unknown…

• Possibly more difficult to recall traumatic events, but this is not that common

• Is there a role in avoiding memories? emotional support? - Dissociation

how does dissociation impact memory formation?

Individuals who actively dissociate to remove themselves from traumatic situations are not encoding the information and often have reduced memories related to the events