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Memory. Memory is the capacity to retain information over time (in both living organisms and computers). It enables us to learn from experience (e.g., trial-and-error). There is no single memory system in our brain but several, functionally distinct systems. They differ in
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Memory is the capacity to retain information over time (in both living organisms and computers). • It enables us to learn from experience (e.g., trial-and-error). • There is no single memory system in our brain but several, functionally distinct systems. • They differ in • the type of information that they store, • the duration for which it is stored, and • the maximum amount of information that can be stored (capacity). Memory
Sensory memory is a “short-term storage facility” for incoming sensory information. • Holds information only long enough for higher-level cognitive processes to operate on it, e.g., object recognition. • There is one separate form of sensory memory for each of the five senses, for example: • Iconic memory: visual sensory memory holding a “snapshot” of recent (200-300 ms) visual input. • Echoic memory: auditory sensory memory “echoing” recent (several seconds) auditory input. Sensory Memory
Sperling (1963): • 43 array of randomly chosen English letters • Whole-report condition: • After brief presentation, letters disappear • Subjects have to report which letters were shown • Partial-report condition: • After brief presentation, letters disappear • The pitch of a played tone indicates whether to report the letters in the first, second, or third row. Iconic Memory Experiment
Whole-Report Condition • Your task: Memorize as many letters as possible in the following display and report them after the display has disappeared. Iconic Memory Experiment
H B X V • M F Z T • P G W Q Iconic Memory Experiment
Iconic Memory Experiment • How many letters did you remember? • Typically, people can report only 4 or 5 of them correctly.
Partial-Report Condition • Your task: Memorize as many letters as possible in the following display. • Right after the display has disappeared, an arrow will point to one of the previously shown rows. • Report as many letters as possible that were shown in that row. Iconic Memory Experiment
E Y H N • G X K F • M Q Z T Iconic Memory Experiment
Iconic Memory Experiment • How many letters did you remember this time? • Often, people can report all four letters.
Iconic Memory Experiment • Partial-Report Condition • Let us do the partial-report condition one more time, in case you were not prepared the first time.
K C R Q • P V Z G • L H X S Iconic Memory Experiment
You did not know where the arrow was going to appear; therefore, you must have memorized all 12 letters in order to get all four relevant letters right. • The Sperling experiment thus shows that iconic memory can hold at least 12 letters. • Other research shows that in fact iconic memory can hold much more information – a quite detailed “snapshot” of the visual scene. • However, this information fades very quickly (fast decay). Iconic Memory Experiment
Working memory is also known as short-term memory. • It can hold information for longer durations than sensory memory. • However, its capacity is severely limited. • Working memory can hold multimodal information, i.e., acoustic and visual information. • It is like a workbench holding all items that we (certain cognitive processes) need to complete a specific task. • Example: Dialing a phone number that somebody has just told us. Working Memory
Do you remember our memory task example when we discussed experimental design? • If subjects memorize numerical data and report them after a certain time interval, there is hardly any decay even for long intervals. • However, if they have to an interfering task (e.g., counting backwards) during the interval, there is increasing decay with longer intervals. • Some studies found that in such situations the amount of stored information has a half-life of about 3 to 5 seconds. Working Memory
In a famous (infamous?) paper, Miller (1956) studied the capacity of working memory. • He found that people can hold about seven plus/minus two items in working memory. • The problem is: How do you define “item?” • For example, expert chess players can store entire game configurations in working memory. • Chess novices can memorize the positions of at most a few pieces. • What is the reason for this? Differences in working memory? Working Memory
No, the reason is chunking, i.e., the grouping of items into meaningful units. • For example, the expert chess players recognize entire common constellations of several pieces as units. • These units then constitute their memorized “items.” • A similar example is the memorization of letters. • You can memorize a much longer sequence of letters if they form an English sentence than when they are randomly chosen. Working Memory
You can still remember events that happened a long time ago, for example, when you were a child. • Long-term memory is able to store large amounts of information over very long durations. • There are several distinct types of long-term memory: • Procedural memory • Declarative memory: • Semantic memory • Episodic memory Long-Term Memory
Also called implicit memory • Memory for skill • Demonstrated only by doing • Arises without conscious recall • Examples: Riding a bike, playing tennis, playing the piano. Procedural Memory
Also called explicit memory • Memory for facts and events • Demonstrated by speaking • Arises with conscious recall • Semantic memory: • Knowledge of facts • For example, things that you learn in this course • Episodic memory: • Contains personally experienced events • E.g., what you did on your birthday last year. Declarative Memory
The Hippocampus • Memory • Learning • Navigation
THE HIPPOCAMPUS = Dentate Gyrus, CA1-CA3, & Subiculum Marjor input from Entorhinal Cortex which is other brain areas such as the Prefrontal Cortex Information Flow: Entorhinal Cortex Dentate Gyrus CA3CA1 Subiculum
Neurogenesis: birth of new neurons Highly active throughout development Also adult hippocampal neurogenesis (dentate gyrus)! What might this mean for learning and memory?
Hippocampal Damage • Retrograde Amnesia: loss of memories before damage to the hippocampus • Anterograde Amnesia: inability to form new memories • Some causes: aging, Alzheimer’s disease, stress, temporal lobe epilepsy
Patient H.M. After Surgery for Temporal Lobe Epilepsy Anterograde Amnesia: Intact working and procedural memory Could not commit to long-term SOME Retrograde Amnesia: Couldn’t remember 3–4 -day prior to surgery, + some events up > 11 years prior Able to commit new motor skills to long-term memory without actually remembering learning them Patient H.M. http://images.google.com/imgres?imgurl=http://dspace.mit.edu/bitstream/handle/1721.1/45580/9-10Spring-2004/NR/rdonlyres/Brain-and-Cognitive-Sciences/9-10Spring-2004/8AFEA93F-9C52-42E5-B967-211CCD2AA287/0/chp_9_10_hip_enc.jpg&imgrefurl=http://dspace.mit.edu/bitstream/handle/1721.1/45580/9-10Spring-2004/OcwWeb/Brain-and-Cognitive-Sciences/9-10Spring-2004/CourseHome/index.htm&usg=__baapQ1i44dpgT7ZDQuuBuOVnwnw=&h=307&w=350&sz=26&hl=en&start=2&um=1&tbnid=n5pajUYXebb7tM:&tbnh=105&tbnw=120&prev=/images%3Fq%3Dcoronal%2Bhippocampal%2Bhuman%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DG%26um%3D1
