Memory is the ability to store and retrieve information over time. It has 3 key functions:
encoding (the process by which we transform what we perceive, think, or feel into an enduring
memory), storage (the process of maintaining information in memory over time), and retrieval
(the process of bringing to mind information that has been previously encoded and stored).
Memories are constructed, not recorded (combining new with old info), and encoding is the
process by which we transform what we perceive, think, or feel into an enduring memory.
3 types of encoding processes – elaborative, visual imagery, and organizational
How we remember something depends on how we think of it at the time.
Semantic judgments require us to think of the meaning of the words, rhyme judgments require
us to think of the sound of the words, and visual judgments require us to think about the
appearance of the words. The type of judgment impacts our memories of the words. Semantic
had greatest effect. This suggests that long-term retention is greatly enhanced by elaborative
encoding (the process of actively relating new info to knowledge already stored in memory).
Elaborative encoding is associated w/ increased activity in the lower left part of the frontal lobe
and the inner part of the left temporal lobe.
Visual imagery encoding – the process of storing new info by converting it into mental pictures.
This process can greatly improve memory – you relate new info to old knowledge, and have
both a visual and a verbal placeholder. This process activates visual processing regions in the
Organizational encoding: the process of categorizing info according to the relationships among a
series of items i.e. grouping. It activates the upper surface of the left frontal lobe.
Encoding new info is critical to everyday life. There are survival encoding, moving encoding, and
pleasantness encoding conditions. Survival encoding is most effective, and is better than non-
survival encoding tasks involving either elaborative, imagery, or organizational encoding.
Encoding is the process by which we transform into a lasting memory the info our senses take
in. Memory is influenced by encoding type regardless of whether we intend to remember.
Elaborative, visual imagery, and organizational encoding all increase memory, but use different
parts of the brain
Encoding info w/ respect to its survival value is extremely effective for later recall
Storage is the process of maintaining information in memory over time. 3 major kinds of
memory storage – sensory, short-term, and long-term. Difference b/w them is the time period.
Sensory memory holds sensory information for a few seconds or less. We have more than one
kind of sensory memory b/c we have multiple senses. Iconic memory is a fast-decaying (<=1s)
store of visual info. Echoic memory is a fast-decaying (~5s) store of auditory info. Both hold info
for a very short time.
A 2 kind of memory storage is short-term memory, which holds nonsensory info for more than
few seconds but less than a minute (~15 to 20 s). Rehearsal is the process of keeping info in
short-term memory by mentally repeating it (re-entering info). Short-term memory is limited in how long it can hold info, and also how much it can hold (~7
different meaningful items at once). One way to increase storage is chunking. Chunking involves
combining small pieces of info into larger clusters or chunks.
Working memory refers to active maintenance of info in short-term storage. It differs from
traditional view that short-term memory is simply a place to hold info (includes processes).
Working memory includes subsystems that store and manipulate visual images or verbal info, as
well as a central executive that coordinates the subsystems e.g. keeping arrangement of pieces
in mind as you contemplate your next move.
Central executive component of working memory depends on frontal lobe regions that are
important for controlling and manipulating info on a wide range of cognitive tasks – bad grades
Long-term memory holds info for hours, days, weeks, or years, and has no capacity limits,
contrasted w/ sensory, short-term memory. People can recall even w/o thinking for years.
Hippocampal region is critical for storing new info for long-term. When this region is damaged,
patients suffer from anterograde amnesia (inability to transfer new info from short-term store
to long-term store).
Retrograde amnesia – inability to retrieve info that was acquired b4 a particular date (usually
the date of an injury or operation).
Hippocampal region links together separate pieces of info as 1 memory (doesn’t hold the bits)
i.e. it acts as an index. Over time, this index may become less necessary.
Consolidation – process by which memories become stable in the brain. Shortly after encoding,
memories exist in fragile state (easily disrupted). Consolidated – more disruption resistant.
1 type of consolidation occurs over s or min e.g. person cannot recall what happened few s b4
crash. 2 type of consolidation occurs over longer periods (days, weeks, months, years) and
likely involves transfer of info from hippocampus to more permanent storage sites in the cortex
e.g. patients w/ retrograde amnesia can recall childhood memories, not few years b4 amnesia.
Memories get consolidated through recalling, thinking + talking about it w/ others, and sleep.
Experiments: ever seemingly consolidated memories can become vulnerable to disruption when
they are recalled, thus requiring them to be consolidated again (process called reconsolidation).
Evidence comes from experiment w/ rats being shocked, drugged and forgetting recent
memory. It appears each time memories are retrieved, they become vulnerable to disruption.
Memories are stored in the spaces b/w neurons. The act of sending changes the synapse – it
strengthens connection b/w the 2 neurons, easing info transmission next time. This provides the
basis for long-term memory (sea slug Aplysia). Research – long-term storage for Aplysia is the
growth of new synaptic connections b/w neurons.
Long-term potentiation (LTP): process whereby communication across the synapse b/w neurons
strengthens the connection, making further communication easier. LTP occurs in several
pathways in hippocampus, can be induced rapidly, and can last for a long time.
N-methyl-D-aspartate (NMDA): the NMDA receptor influences flow of info b/w neurons by
controlling LTP initiation in most hippocampal pathways.
The hippocampus contains many NMDA receptors. But for these NMDA receptors to become
activated, two things must happen at roughly the same time. 1 , the presynaptic neuron releases a neurotransmitter called glutamate, which attaches to the NMDA receptor site on the
postsynaptic neuron. 2 , excitation takes place in the postsynaptic neuron. Together, these two
events initiate LTP, which in turn increases synaptic connections by allowing neurons that fire
together to wire together. More research on NMDA may lead to cure for Alzheimer’s.
Summary: long-term memory stores info for anywhere from min to years or decades.
Retrieval is the process of bringing to mind information that has been previously encoded and
stored, and it is perhaps the most important of all memory processes
Retrieval cue: external info associated w/ stored info and helps recall it (1 of best ways)
Results suggest info is sometimes available yet inaccessible in memory – use retrieval cues
Encoding specificity principle: a retrieval cue can serve as an effective reminder when it helps re-
create the specific way in which info was initially encoded. External contexts are often powerful
retrieval cues e.g. learning new words on land or underwater.
Retrieval cues can also be inner states. State-dependent retrieval is the tendency for
information to be better recalled when person is in same state during encoding and retrieval
e.g. when happy or sad, it is easier to recall happy or sad memories –hard to be +ve when –ve.
The person’s physiological or psychological state at the time of encoding is associated w/
information that is encoded. Retrieval cues can be thoughts – 1 thought leads to another.
Transfer-appropriate processing: principle stating that memory is likely to transfer from one
situation to another when the encoding context of the situations matches. E.g. Ask you and your
friend to recall word “brain”. We ask you to remember by rhyming and your friend by meaning.
Next day we ask “What was the word that rhymed w/ train?” and you will answer better than
friend, even though semantic judgments almost always yield better memory than rhyme judg.
Human memory differs from computer memory in that retrieval changes memory system state
Retrieval can improve subsequent memory. It is often better than re-studying material.
Retrieval-induced forgetting is a process by which retrieving an item from long-term memory
impairs subsequent recall of related items. Retrieving similar target items caused subsequent
forgetting of the related but suppressed items, even if retrieval is unsuccessful.
Trying to recall and successful recall occur in 2 different regions of brain and are different
processes. Trying – left frontal lobe, success – hippocampal region. Also, successful recall
activates parts of brain that play a role in processing the sensory features of an experience.
Patients behaving as if they were remembering things while claiming to remember nothing at
all, suggests there are several kinds of memory, some are accessible to conscious recall, others
are not (explicit and implicit)
Explicit memory: occurs when