Jill Price was capable of remembering everything that happened last year and several years ago.
Memory is the ability to store and retrieve information over time. Memories are the residue of those events, the
enduring changes that experience makes in our brains and leaves behind when it passes.
The three main functions of the memory: 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 made by combining information we already have in our brains with new information that come in through
our senses. Memory is influenced by the type of encoding we perform regardless of whether we consciously intend to
remember an event or a fact. Three types of encoding processes are:
1) Elaborative encoding - the process of actively relating new information to knowledge that is already in memory.
Elaborative encoding enhances subsequent retention. Thinking about a word’s meaning (semantic judgment)
results in deeper processing-and better memory for the word later-than merely attending to its sound (rhyme
judgment) or shape (visual judgment). This helps remembering things in the long run
fMRI studies reveal that different parts of the brain are active during different types of judgments: (a) During
semantic judgments, the lower left frontal lobe is active; (b) during organizational judgments, the upper left
frontal lobe is active; and (c) during visual judgments, the occipital lobe is active.
2) Visual Imagery Encoding - the process of storing new information by converting it into mental pictures. Visual
imagery encoding can substantially improve memory. Why does visual imagery encoding work so well? First,
visual imagery encoding relates incoming information to knowledge already in memory. Second, when you use
visual imagery to encode words and other verbal information, you end up with two different mental
“placeholders” for the items—a visual one and a verbal one—which gives you more ways to remember them
than just a verbal placeholder alone. This encoding activates visual processing regions in the occipital lobe.
3) Organizational Encoding - the process of categorizing information according to the relationships among a series
of items. Waitresses use this type of encoding when they take orders instead of writing them down. In their
head, they begin to group the orders into a sequence that matches the layout of the kitchen. Organizational
encoding activates the upper surface of the left frontal lobe.
Memory mechanisms that help us to survive and reproduce should be preserved by natural selection, and our memory
systems should be built in a way that allows us to remember especially well encoded information that is relevant to our
survival. Three different encoding tasks were used to test the idea: (1) Survival encoding – when you have rank certain
words that will help you to survive; (2) Moving encoding – when you have to move to a different place and rank the
words that will be most useful to you; (3) Pleasantness encoding – when you have the rank the words based on their
pleasantness. Survival encoding helps you to remember more words because it draws on elements of elaborative,
imagery, and organizational encoding and we also tend to remember things that are linked to our survival.
There are three major kinds of storage:
1) Sensory memory - holds sensory information for a few seconds or less. Because we have more than one sense,
we have more than one kind of sensory memory. Iconic memory is a fast-decaying store of visual information
(decay in about a second). Echoic memory is a fast-decaying store of auditory information (decay in about 5
seconds). The hallmark of both the iconic and echoic memory stores is that they hold information for a very
short time. 2) Short term memory - holds non-sensory information for more than a few seconds but less than a minute.
Information can be held in this storage for about 15-20 secs. Rehearsal is the process of keeping information in
short-term memory by mentally repeating it. This memory is limited in how long and how much it can hold
information. This memory can hold about seven meaningful items at once. One way to increase storage is to
group several letters into a single meaningful item. Chunking involves combining small pieces of information
into larger clusters or chunks.
Working memory refers to active maintenance of information in short-term storage. Working memory includes
subsystems that store and manipulate visual images or verbal information, as well as a central executive that
coordinates the subsystems. This memory helps to remember the arrangement of pieces on a chessboard.
Damage to the working memory will make it hard for people to remember a few letters/words and affect
learning language. Working memory depends on regions within the frontal lobe.
3) Long term memory - holds information for hours, days, weeks, or years. In contrast to both sensory and short-
term memory, long-term memory has no known capacity limits. The hippocampal region of the brain is critical
for putting new information into the long-term store. When this region is damaged, patients suffer from a
condition known as anterograde amnesia, which is the inability to transfer new information from the short-term
store into the long-term store. Some amnesic patients also suffer from retrograde amnesia, which is the
inability to retrieve information that was acquired before a particular date, usually the date of an injury or
The idea that the hippocampus becomes less important over time for maintaining memories is related to the
concept of consolidation, a process by which memories become stable in the brain. One type of consolidation
operates over seconds or minutes. Eg: when someone meets an accident and cannot recall what happened right
before the accident. The head injury probably prevented consolidation of short-term memory into long-term
memory. Another type of consolidation occurs over much longer periods of time. These people can recall
information from when they were kids but not of recent years.
How does a memory become consolidated? The act of recalling a memory, thinking about it, and talking about it
with others probably contributes to consolidation. Sleep contributes to memory consolidation by (1) increasing
hippocampal involvement in recall a couple of days later and (2) facilitating interaction of the hippocampus with
the frontal lobe, such that the hippocampus is later less centrally involved in recall. Reconsolidation is when
memories can again become vulnerable to interference when they are recalled, thus requiring them to be
consolidated again. Memories are not given permanent “occupancy”.
Memories, Neurons & Synapses
Memories are stored in the synapse - the small space between the axon of one neuron and the dendrite of
another, and neurons communicate by sending neurotransmitters across these synapses. Sending
neurotransmitters across a synapse strengthens the connection between the neurons.
The story of Aplysia and memory is closely linked with the work of neuroscientist Eric Kandel. Aplysia has a
simple nervous system with 20,000 neurons.
Memory storage depends on changes in synapses, and LTP increases synaptic connections.
Long-term potentiation, more commonly known as LTP, which is a process whereby communication across the
synapse between neurons strengthens the connection, making further communication easier. Long-term
potentiation has a number of properties that indicate to researchers that it plays an important role in long-term
memory storage: It occurs in several pathways within the hippocampus; it can be induced rapidly; and it can last
for a long time. How does LTP take place? The NMDA receptor influences the flow of information between neurons by
controlling the initiation of LTP in most hippocampal pathways. The presynaptic neuron releases the
neurotransmitter glutamate into the synapse. Glutamate then binds to the NMDA receptor sites on the post-
synaptic neuron. At about the same time, excitation in the postsynaptic neuron takes place. The combined
effect of these two processes initiates long-term potentiation and the formation of long-term memories. (see
img pg 232)
The information outside your head is called a retrieval cue, which is external information that is associated with
stored information and helps bring it to mind. Hints is an example of a retrieval cue like when you said you know