Chapter SIX III.docx

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Steve Joordens

Chapter SIX MEMORY - Memory is the ability to store and retrieve information over time. - They are the residues of those events, the enduring changes that experience makes in our brains and leaves behind when it passes. - Three key functions of memory are o Encoding, the process by which we transform what we perceive, think, or feel into an enduring memory; o Storage, the process of maintaining information in memory over time; o Retrieval, the process of bringing to mind information that has been previously encoded and stored. ENCODING: TRANSFORMING PERCEPTIONS INTO MEMORIES - Memories are made by combining information we already have in our brains with new information that comes in through our senses. - Memories are constructed, not recorded, and encoding is the process by which we transform what we perceive, think, or feel into an enduring memory. - The three types of encoding processes are – elaborative encoding, visual imagery encoding, and organizational encoding. ELABORATIVE ENCODING - Memories are a combination of old and new information, so the nature of any particular memory depends as much on the old information already in our memories as it does on the new information coming in through our senses. o How we remember something depends on how we think about it at the time. - In a study, participants were asked to make one of three type of judgements with a series of words: o Semantic judgements required the participants to think about the meaning of the words o Rhyme judgements required the participants to think about the sound of the words o Visual judgements required the participants to think about the appearance of the words - The type of judgement task influenced how participants thought about each word – what old information they combined with the new – and had a powerful impact on their memories. - It was found that those who made semantic judgements had much better memory for the words than those who had thought about how the word looked or sounded. - Long-term retention is greatly enhanced by elaborative encoding, the process of actively relating new information to knowledge that is already in memory - Studies reveal that elaborative encoding is uniquely associated with increases activity in the lower left part of the frontal lobe and the inner part of the left temporal lobe. - The amount of activity in each of these two regions during encoding is DIRECTLY related to whether people later remember an item. o The more activity there is in these areas, the more likely the person will remember the information VISUAL IMAGERY ENCODING - Visual imagery encoding, is the process of storing new information by converting it into mental pictures - We could use Simonides method by simply converting the information we wanted to remember into a visual image and then “store it” in a familiar location. - Experiments have shown that visual imagery encoding can substantially improve memory. - Visual imagery encoding does some of the same things that elaborative encoding does: when we create a visual image, we relate incoming information to knowledge already in memory. - When we use visual imagery to encode words and other verbal information, we end up with two different mental “placeholders” for the items – a visual one and a verbal one – which gives us more ways to remember them than just a verbal placeholder alone. - Visual imagery encoding activates visual processing regions in the occipital lobe, which suggests that people actually enlist the visual system when forming memories based on mental images. ORGANIZATIONAL ENCODING - Organizational encoding is the process of categorizing information according to the relationships among a series of items. - Studies have shown that instructing people to sort items into categories is an effective way to enhance their subsequent recall of those items. - Organizational encoding activates the upper surface of the left frontal lobe. ENCODING OF SURVIVAL RELATED INFORMATION - Recent experiments have addressed ideas by examining encoding of survival related information - The experiments were motivated by an evolutionary perspective based on Darwin’s principle of natural selection: that the features of an organism that help it survive and reproduce are more likely than other features to be passed on to subsequent generations - 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. - Researchers gave participants three different encoding tasks: o In the survival encoding condition, participants were asked to imagine that they were stranded in the grasslands of a foreign land without any survival materials and that over the next few months they would need supplies of food and water and also need to protect themselves from predators. Then showed them randomly chosen words and asked them to rate on a 1-5 scale how relevant each item would be to survival in the hypothetical situation o In the moving encoding condition, a second group of participants were asked to imagine that they were planning to move to a new home in a foreign land, and to rate on a 1-5 scale how useful each item might be in helping them to set up a new home. o In the pleasantness encoding condition, a third group was shown the same words and asked to rate on a 1-5 scale the pleasantness of each word. - The findings showed that participants recalled more words after the survival encoding task than after either the moving or pleasantness tasks. - Researchers later found that survival encoding resulted in higher levels of recall than several other non-survival encoding tasks involving elaborative encoding, imagery encoding, or organizational encoding. - Survival encoding draws on elements of elaborative, imagery, and organizational encoding, which may give it an advantage over any other one. STORAGE: MAINTAINING MEMORIES OVER TIME - Encoding is the process of turning perceptions into memories. - The three major kinds of memory storage are sensory, short-term, and long-term. SENSORY STORAGE - Sensory memory hold sensory information for a few seconds or less - in an experiment, participants were asked to remember 12 letters they have just seen flash before them, but they have recalled few than half. - In which case, either people simply couldn’t encode all the letters in a short time OR - They had encoded the letters but forgotten them while trying to recall everything they had seen - Researchers then had a trick to test these ideas, they had a tone sounded that cued the participants to report the letters in a particular row. o A high tone cued them to report the contents of the top row o A medium tone cued them to report the contents of the middle row o A low tone cued them to report the contents of the bottom row. - As a result, researchers inferred that virtually all the letters had been encoded, because they had no way of knowing which of the three rows would be cued. - Iconic memory is a fast-decaying store of visual information o a similar storage area serves as a temporary warehouse for sounds - Echoic memory is a fast-decaying store of auditory information. - Iconic memories usually decay in about a second or less - Echoic memories usually decay in about five seconds SHORT-TERM STORAGE AND WORKNG MEMORY - Short-term memory hold nonsensory information for more than a few seconds but less than a minute. - The results of the consonant string experiment, suggests that information can be held in the short-term memory store for about 15-20 seconds. - Rehearsal is the process of keeping information in short-term memory by mentally repeating it. - Short-term memory is limited in how long it can hold information, and also limited in how much information it can hold. - Short-term memory can hold about seven meaningful items at one. - 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. - It differs from the traditional view that short-term memory is simply a place to hold information and instead includes the operations and processes we use to work with information in short-term memory. - Working memory includes subsystems that store and manipulate visual images or verbal information, as well as a central executive that coordinates the subsystems. - Working memory includes the visual representation of the positions of the pieces, your mental manipulation of the possible moves, and your awareness of the flow of information into and out of memory, all stored for a limited amount of time. - The working memory acknowledges both the limited nature of this kind of memory storage and the activities that are commonly associated with it. - Brain-imaging studies indicate that the central executive component of working memory depends on regions within the frontal lobe that are important for controlling and manipulating information on a wide range of cognitive tasks LONG-TERM STORAGE - Long-term memory holds information for hours, days, weeks, or years. - Long-term memory has no known capacity limits. THE ROLE OF THE HIPPOCAMPUS AS INDEX - 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 operation. - Psychologists now believe that the hippocampal region acts as a kind of “index” that links together all of these otherwise separate bits and pieces so that we remember them as one memory. - The hippocampal region index is critical when a new memory is first formed, it may become less important as the memory ages. - The notion of the hippocampus as an index explains why people like HM cannot make new memories and why they can remember old ones MEMORY CONSOLIDATION - Consolidation is a process by which memories become stable in the brain. - Shortly after encoding, memories exist in a fragile state in which they can be easily disrupted; once consolidation has occurred, they are more resistant to disruption. - One type of consolidation operates over seconds or minutes. (e.g car crash) - Another type of consolidation occurs over much longer periods of time – days, weeks, months, and years – and likely involves transfer of information from the hippocampus to more permanent storage sites in the cortex. - The operation of this longer-term consolidation process is seen in the retrograde amnesia of patients with hippocampal damage who can recall memories from childhood relatively normally, but are impaired when recalling experiences that occurred just a few days prior to the time they became amnesic. - QUESTION: How does memory become consolidated? - ANSWER: The act of recalling a memory, thinking about it, and talking about it with others probably contributes to consolidation - Sleep plays an important role in memory consolidation - Many researchers have long believed that a fully consolidated memory becomes a permanent fixture in the brain, more difficult to get rid of than a tenured professor. - Experiments have shown that even seemingly consolidated memories can again become vulnerable to disruption when they are recalled, thus requiring them to be consolidated again, this is referred to as reconsolidation. - Evidence for this mainly comes from experiments with rats showing that when animals are cued to retrieve a new memory that was acquired a day earlier, giving the animal a drug that prevents initial consolidation will cause forgetting. - If the animal is not actively retrieving the memory, the same drug has no effect when given a day after initial encoding. - Memories are not given permanent “tenure” - Adding nonfearful information to the reactivated memory a few minutes later – when the memory is vulnerable to reconsolidation – resulted in long-lasting reduction of fear responses to the object, whereas adding nonfearful information to the reactivated memory six hours later – when the memory is no longer vulnerable to reconsolidation – did not have a long-lasting effect. MEMORIES, NEURONS, AND SYNAPSES - Memories are in the spaces between neurones. - A synapse is the small space between the axon of one neuron and the dendrite of another, and neurons communicate by sending neurotransmitters across these synapses. - Sending a neurotransmitter across a synapse actually changes the synapse. - It strengthens the connection between the two neurons, making it easier for them to transmit to each other the next time. - The idea that the connections between neurons are strengthened by their communication, making communication easier the next time, provides the neurological basis for long-term memory, and much of what we know about this comes from the tiny sea slug Aplysia. o If the experimenter shocks the slug over and over, it does develop and enduring “memory” that can last for days or even weeks - Research suggests that this long-term storage involves the growth of new synaptic connections between neurons - So leaning in Aplysia is based on changes involving the synapses for both short-term storage (enhanced neurotransmitter release) and long-term storage (growth of new synapses). - Long-term potentiation (LTP) 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 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. - QUESTIONS: So how does LTP take place? What’s going on in the neurons in the hippocampus to produce these stronger synaptic connections? - ANSWERS: The primary agent is a neural receptor site called the NMDA, known more formally as N-methyl-D- aspartate. - The NMDA receptor influences the flow of information between neurons by controlling the initiation of LTP in most hippocampal pathways. - How it works: o The hippocampus contains an abundance of NMDA receptors. o For these NMDA receptors to become activated, TWO things must happen at roughly the same time.  First, the presynaptic, or “sending”, neuron releases a neurotransmitter called glutamate(a major excitatory neurotransmitter in the brain), which attaches to the NMDA receptor site on the postsynaptic, or “receiving”, neuron.  Second, excitation takes place in the postsynaptic neuron  Together, these two initiate LTP, which then in turn increases synaptic connections by allowing - neurons that fire together to wire together. RETRIEVAL: BRINGING MEMORIES TO MIND - 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 CUES: REINSTATING THE PAST - One of the best ways to retrieve information from inside the head is to encounter information outside the head that is somehow connected to it. - The information outside our head is called a retrieval cue, which is external information that is associated with stored information and helps bring it to mind. - Information is sometimes available in memory even when it is momentarily inaccessible and that retrieval cues help us bring inaccessible information to mind. o Refer to the example about the undergraduates and the list of words (page 233) - The encoding specificity principle states that a retrieval cue can serve as an effective reminder when it helps re- create the specific way in which information was initially encoded. - State-dependent retrieval is the tendency for information to be better recalled when the person is in the same state during encoding and retrieval. - A person’s physiological or psychological state at the time of encoding is associated with the information that is encoded. - If the person’s state at the time of retrieval matches the person’s state at the time of encoding, the state itself serves as a retrieval cue – a bridge that connects the moment at which we experience somethi
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