Human memory Flashcards
(45 cards)
What are the two most basic types of memory? what are these based on?
Short-term and long-term
- based on the length of the period of time the information is retained for
Describe short-term memory
- information decays very rapidly (unless rehersed) - scale is seconds
- has limited capacity
What can short-term memory be shown by?
Tests such as:
- Digit span test → measure verbal short-term memory (normally about 7 items can be retained)
- Cori block test → measures visuospatial short-term memory. by requiring the subject to remember locations tapped in correct sequence (normally about 7 items retained as well)
What is memory?
the creation of an internal representation of a percept/idea based on past experience which then later affects experience and behaviour
Shiffrin and Atkinson model
1968
environmental input → sensory memory → short-term memory → long-term memory (through rehearsal)
What are double dissociations?
When two related mental processes are shown to function independently of each other → brain structures that control a function work independently
Discuss double-dissociations within memory
Patients studies reveal double dissociation between verbal and visuospatial memory (different anatomical locations):
• Patient KF (Shallice and Warrington, 1970) with a left parietal lesion had a digit span of 2 (impaired STM), but normal visuospatial and long-term memory;
• By contrast, patient ELD (Hanley et al, 1991) with a right hemisphere lesion had an impaired visuospatial span, but normal digit span and long-term memory.
• This evidence from patients with lesions is supported by PET studies in healthy humans.
Therefore, it is though that verbal short-term memory is localized to the left parietal lobe, while visuospatial short-term memory is localized to the right parietal lobe. It is now thought that early sensory areas in the cortex may also play a role in short-term memory storage.
Discuss how these different types of memory change with age
Short-term memory improves with development (Gathercole et al, 2004) and declines with age (Reuter-Lorenz and Park, 2009). But with age, semantic (type of LTM) knowledge remains intact.
Peterson & Peterson
1960
Asked individuals to remember a series of number and repeat it back
They observed a curve in decay
Illustrates STM decay
What is working memory?
Working memory refers not just to storage, but to manipulation of short-term memory contents.
What is working memory thought to consist of?
- Executive control (PFC) = mechanisms that manipulate contents of short-term memory, for example to allow performance of a reverse digit span test where people are asked to recall a sequence of numbers in reverse;
- Storage systems (parietal lobes + early sensory areas?), which can be further subdivided into the
- Visuospatial sketchpad;
- Episodic buffer;
- Phonological loop.
Draw a diagram of working memory. Who came up with this?
See Eva’s notes
Fig 2. The Working Memory Model Components (Baddeley and Hitch, 1974)
What is the visuospatial sketchpad?
A component of the working memory model which stores and processes information in the visual or spatial form
What is the phonological loop?
Component of the working memory model that deals with spoken or written material
What is the episodic buffer?
A ‘backup’ store which communicates with both LTM and the components of the working memory
In the Baddeley model, what does ‘working memory’ replace?
STM
What does the phonological loop consist of?
Two parts:
- short term phonological store containing autotory memory traces subject to rapid decay
- articulatory rehearsal component that can revive the memory traces
What is an area of the brain that is crucial for working memory?
Frontoparietal netwroks (note similarity to attention networks)
Discuss views about how fronto-parietal networks contribute to working memory?
Parietal cortex - maintenance/ storage
Prefrontal cortex - manipulation and monitoring info in STM
BUT now clear that even early sensory areas play some roles in STM storage
Gathercole et al
2004
demonstrated that short term memory capacity improves with age up to a point (20) after which we know there is a decline in short term memory (along with long term memory and other cognitive functions such as processing speed)
Essentially tested individuals in a variety of recall tasks, ranging from simple verbal storage to complex working memory functions and visuo-spatial memory functions, and found that in each test the score trend was correlated with increased age
Whilst STM and LTM decline after this point (20-80), sementic knowledge remains the same
With maturation of frontoparietal networks???
Jaeggi et al
CLINICAL IMPLICATIONS OF THIS STUDY?
2008
Short-term memory capacity and working memory are highly related to intelligence. However, whether training short-term memory can improve intelligence is highly controversial. A 2008 paper by Jaeggi et al showed that training on a working memory task may improve fluid intelligence - the ability to reason and to solve new problems independently of previously acquired knowledge. They trained the working memory of participants with a very demanding tasks where they saw to series of synchronously presented stimuli - single letters and spatial locations marked on a screen. The task was to decide for each string whether the current stimulus matched the one that was presented n items back in the series, with n changing to adaptively to maintain the task’s demands. During the study, all participants improved greatly on the task, with the improvement correlating positively with the length of training of participants in sub-groups. All participants also improved on the fluid intelligence tests, but the improvement in trained subjects was significantly greater than in controls who didn’t receive training, and also showed dose-dependency: more training was associated with greater improvement
Clinical implications → we can train working memory to ward off degenerative dementia
What can LTM be divided into?
subdivided into explicit or declarative, which involves conscious recall, and implicit or non-declarative, which doesn’t require it.
What is LTM?
any memory that persists for longer than a few tens of seconds
Discuss anatomicial segregation of STM and LTM
Long-term memory and short-term memory are clearly anatomically segregated. We’ve already seen examples of lesions that affect short-term, but not long-term memory. Likewise, there are lesions that affect long-term, but not short-term memory, a prime example being bilateral hippocampal resection performed in patient H.M. in 1953, which very severely affected his long-term memory.
