Introduction to Memory and Cognition

Primer

Memory and Cognition complaints are some of the most common symptoms in psychiatric and neurologic practice.

Terminology

  • Retrograde amnesia: inability to remember things that occured prior to a central nervous system injury
  • Anterograde amnesia: Inability to remember things that occur after a central nervous system injury (i.e. - cannot form new memories)

Cognition

The DSM-5 breaks down cognition into 6 domains:

  1. Social
  2. Language
  3. Executive
  4. Complex attention
  5. Perceptual motor
  6. Learning and memory

Mnemonic

The mnemonic SAMPLE can be used to remember the 6 key domains of cognitive function:
  • S - Social cognition
  • A - Attention (Complex Attention)
  • M - Memory and Learning
  • P - Perceptual-Motor
  • L - Language
  • E - Executive function

Learning and Memory

On history and mental status:

  • Difficulty remembering recent events (conversations, meals)
  • Increased reliance on lists/calendars
  • Repetition
  • Requires frequent reminders
  • Autobiographical and implicit memory relatively preserved until severe stages

On cognitive testing:

  • Difficulty with repeating words and/or digits
  • Difficulty with delayed recall
  • Rey Auditory Verbal Learning Test

Langauge

On history and mental status:

  • Expressive
    • Word-finding difficulty
    • Decreased spontaneity of speech
    • May not recall names of friends or family
    • Paraphasic errors, substitution of specific terms with general
      • “that thing” or “you know what I mean”
  • Comprehension

On cognitive testing:

  • Expressive - Naming, verbal fluency (letter and category), “Boston Naming”
  • Comprehension – verbal commands

Perceptual-Motor

On history and mental status:

  • Increased reliance on others or maps for directions
  • Getting lost
  • Difficulties with previously familiar tasks (carpentry, sewing, driving)
  • Gnosis – inability to recognize familiar objects

On cognitive testing:

  • Drawing a clock
  • Figure copying - cube/intersecting pentagons
  • Demonstrating learned movements, i.e. - testing for apraxia (wave goodbye, show me how you would comb your hair)

Social

On history and mental status:

  • Change in personality
  • ↓ Empathy
  • ↓ Recognition of emotions
  • Apathy
  • Inappropriate social behavior

On cognitive testing:

  • Identification of emotions in images of faces
  • Theory of Mind story cards – elicit information about characters

Executive function

On history and mental status:

  • Difficulty with multitasking
  • Decision making
  • Problems with IADLs

On cognitive testing:

  • Trail making test
  • Clock drawing (+visual-spatial tasks)
  • Working memory: repeating letters/numbers backwards
  • Insults to circuits from dorsolateral prefrontal cortex (frontal) going all the way basal ganglia/thalamus (deep brain structures) can be be responsible for bedside “frontal” findings

Complex Attention

On history and mental status:

  • Routine tasks take longer or more errors
  • ↑ Difficulty in environments with multiple stimuli (TV, radio, conversation)
  • ↑ Difficulty holding new information in mind (e.g. - phone numbers, addresses)

On cognitive testing:

  • Digit span forward
  • Vigilance A test (tapping)
  • Spelling backwards

Memory Systems

Memory Systems

Adapted from Budson, A. E. et al (2007). Memory dysfunction in neurological practice. Practical neurology, 7(1), 42-47.
Memory System Example Awareness Length of storage Anatomy
Episodic memory Remembering a short story, what you had for dinner last night, and what you did on your last birthday Explicit (associated with conscious awareness) and declarative (can be consciously recalled) Minutes to years Medial temporal lobes, anterior thalamic nucleus, mamillary body, fornix, prefrontal cortex
Semantic memory Knowing who was the first President of the US, the colour of a lion, and how a fork and comb are different Explicit Minutes to years Highly localized to the anterior and inferior lateral temporal lobes.[1]
Procedural memory Driving a standard transmission car (explicit), and learning the sequence of numbers on a touch-tone phone without trying (implicit) Explicit/Implicit Minutes to years Basal ganglia, cerebellum, supplementary motor area
Working memory • Phonological: keeping a phone number ‘‘in your head’’ before dialing
• Spatial: mentally following a route, or rotating an object in your mind 		Explicit Seconds to minutes; information actively rehearsed or manipulated • Phonological: prefrontal cortex, Broca’s area, Wernike’s area
• Spatial: prefrontal cortex, visual association areas
Declarative/Explicit = requires conscious awareness to remember, Non-delcarative/Implicit = unconsciously and effortlessly remembered, usually marked by a change in behaviour

References

1) Pobric, G., Jefferies, E., & Ralph, M. A. L. (2007). Anterior temporal lobes mediate semantic representation: mimicking semantic dementia by using rTMS in normal participants. Proceedings of the National Academy of Sciences, 104(50), 20137-20141.