1. Unit 4: Memory
5.2.16

2. Part 4
Storage

3. Working/Short-term Memory
Memory Storage
Storage is at the heart of memory
3 types of memory storage:
Info
Unconscious processing
Sensory Memory
New & important information consciously encodes
Long-term Memory
Working/Short-term Memory
Encoding
Retrieving

4. Sensory Memory R G T F M Q L Z S George Sperling (1960)
Showed participants 3 rows of letters for only 1/20th of a second
People can recall only about half of them (RTMZ)
The exposure time for the stimulus is so small that items cannot be rehearsed.

5. Sensory Memory R G T F M Q L Z S
When given cues to focus only on one row at a time, people can recall all the letters, but only momentarily
Iconic memory: a momentary sensory memory of visual stimuli; a photographic or picture-image memory lasting no more than a few tenths of a second

6. Sensory Memory
Echoic memory: a momentary sensory memory of auditory stimuli; if attention is elsewhere, sounds & words can still be recalled within 3 or 4 seconds
The duration of sensory memory varies for the different senses.
Iconic
0.5 sec. long
Echoic
3-4 sec. long
Hepatic
< 1 sec. long

7. Sensory Memory

8. Working/Short-term Memory
Working memory, the new name for short- term memory, has a limited capacity (7 +/- 2) and a short duration (20 seconds).
Without active processing, memories have a limited life
Recall is slightly better for numbers than letters
Using chunking, but no rehearsal, average person retains only about 4 chunks in short- term memory
Main idea: at any given moment, we can consciously process only a very limited amount of information

9. The Magical Number Seven, Plus or Minus Two
Ready to test it?
M U T G I K T L R S Y P
You should be able to remember 5-9 letters

10. Long-term Memory
Our capacity for storing long-term memories is essentially limitless
Computers have the ability to beat our brain’s capacity to remember literal text, but given the number of brain synapses, “the total memory capacity of all computers in the world is less than that of a single brain”
Rajan Mahadevan

11. Long-term Memory

12. Memory Stores Feature Sensory Memory Working Memory LTM Encoding
Copy: sight/photographic
Phonemic: sound of the words
Semantic: meaning of the words
Capacity
Unlimited
7±2 Chunks
Very Large
Duration
0.25 sec.
20 sec.
Years

13. Storing Memories in the Brain
Memories do not reside in a single spot in our brains
Using rats, Lashley (1950) suggested that even after removing parts of the brain, the animals retain partial memory of the maze.
Forgetting occurs as new experiences interfere with our retrieval

14. Synaptic Changes
Neuroscientists are focusing on synapses to find the physical basis of memory
Memories begin as impulses whizzing through brain circuits; leaving permanent neural traces
Where does the neural change occur? Clues point to the synapses (where nerve cells communicate with one another)
With increased activity, neural interconnections form and strengthen

15. Synaptic Changes
Studies of the sea snail Aplysia showed an increase in releasing the neurotransmitter serotonin after conditioning
Serotonin increases the efficiency of transmitting signals between the affected synapses, which leads to more efficient neural circuits
Long-term potential: an increase in a synapse’s firing after brief, rapid stimulation. Believed to be a neural basis for learning & remembering

16. Synaptic Changes
Electron microscope images show just one receptor site (gray) reaching toward a sending neuron (red) before long-term potential (top) and two receptor sites afterward (bottom). A doubling of receptor sites means that the receiving neuron has increased sensitivity for the neurotransmitter molecules released by the sending neuron

17. Synaptic Changes
After LTP has occurred, passing current through the brain won’t disrupt old memories, but will wipe out recent memories
Electroconvulsive therapy for depressed people can wipe out recent memories
Blow to the head has the same effect

18. Stress Hormones & Memory
Stress hormones produced when excited/stressed make more glucose to fuel the brain, signaling that something important has happened
Amygdala (brain’s emotion processing center) boosts activity in the brain’s memory-forming areas
Stronger emotional experiences = stronger, more reliable memories

19. Implicit & Explicit Memories
Amnesia: the loss of memory
Implicit memory: retention independent of conscious recollection
Explicit memory: memory of facts and experiences that one can consciously know & “declare”
We have two different memory systems going on, implicit and explicit. Some people with brain damage cannot consciously recognize faces, but will have a physiological response to seeing a familiar face, demonstrating an unconscious recognition.
Even Alzheimer’s patients whose explicit memories for people & events are lost display an ability to form new implicit memories.

20. Hippocampus
Hippocampus – a neural center in the limbic system that processes explicit memories
Brain scans capture activity in the hippocampus when brain is forming a memory & when recalling words
Damage to the hippocampus disrupts some types of memory: birds cannot return to places where they have stored food if their hippocampus is removed; damage to the left hippocampus impairs ability to remember verbal info, but not visual designs or locations & vise-versa; loss of hippocampus means a loss of recent memories (within a month) but not older memories

21. Anterograde Amnesia
After losing his hippocampus in surgery, patient Henry M. (HM) remembered everything before the operation but cannot make new memories. We call this anterograde amnesia.
Memory Intact
No New Memories
Surgery

22. Cerebellum
Cerebellum – a neural center in the hindbrain that processes implicit memories.

23. Dual Memory System
Explicit-implicit system explains infantile amnesia: reactions & skills we learn during infancy stay with us, yet as adults we recall nothing (explicitly) of our first 3 years
We index much of our explicit memories with words nonspeaking children have not yet learned
The hippocampus is one of the last brain structures to mature

24. Crash Course Psychology
Episode 13: How We Make Memories