Do older adults forget as much as they think, or is it rather that they ‘misremember’?
A small study adds to evidence that gist memory plays an important role in false memories at any age, but older adults are more susceptible to misremembering because of their greater use of gist memory.
A small study has tested the eminent Donald Hebb’s hypothesis that visual imagery results from the reactivation of neural activity associated with viewing images, and that the re-enactment of eye-movement patterns helps both imagery and neural reactivation.
A study involving 60 undergraduate students confirms the value of even a single instance of retrieval practice in an everyday setting, and also confirms the value of cues for peripheral details, which are forgotten more readily.
An imaging study has revealed that it is retrieval cues that trigger activity in the hippocampus, rather than, as often argued, the strength of the memory. The study involved participants learning unrelated word pairs (a process which included making up sentences with the words), then being asked whether various familiar words had been previously seen or not — the words being shown first on their own, and then with their paired cue word. Brain activity for words judged familiar on their own was compared with activity for the same items when shown with context cues. Increased hippocampal activity occurred only with cued recall. Moreover, the amount of activity was not associated with familiarity strength, and recollected items were associated with greater activity relative to highly familiar items.
Cohn, M., Moscovitch, M., Lahat, A., & McAndrews, M. P. (2009). Recollection versus strength as the primary determinant of hippocampal engagement at retrieval. Proceedings of the National Academy of Sciences, 106(52), 22451-22455.
http://www.eurekalert.org/pub_releases/2009-12/uot-dik120709.php
An imaging study in which participants were shown a previously studied scene along with three previously studied faces and asked to identify the face that had been paired with that scene earlier has found that hippocampal activity was closely tied to participants' tendency to view the associated face, even when they failed to identify it. Activity in the lateral prefrontal cortex, an area required for decision making, was sensitive to whether or not participants had responded correctly and communication between the prefrontal cortex and the hippocampus was increased during correct, but not incorrect, trials. The findings suggest that conscious memory may depend on interactions between the hippocampus and the prefrontal cortex.
Hannula, D.E. & Ranganath, C. 2009. The Eyes Have It: Hippocampal Activity Predicts Expression of Memory in Eye Movements. Neuron, 63 (5), 592-599.
http://www.eurekalert.org/pub_releases/2009-09/cp-ycb090309.php
http://sciencenow.sciencemag.org/cgi/content/full/2009/910/4?etoc
Brain scans of students listening to their favorite music CDs has revealed plenty of neural activity during the silence between songs — activity that is absent in those listening to music they had never heard in sequence before. Such anticipatory activity probably occurs whenever we expect any particular action to happen. In this case, the activity took the form of excitatory signals passing from the prefrontal cortex (where planning takes place) to the nearby premotor cortex (which is involved in preparing the body to act).
Leaver, A.M. et al. 2009. Brain Activation during Anticipation of Sound Sequences. Journal of Neuroscience, 29, 2477-2485.
http://www.eurekalert.org/pub_releases/2009-02/gumc-rcw022509.php
Analysis of the changes in brain activity that occurred when volunteers heard or read critical sentences as part of a longer text or placed in some other type of context, has revealed how anticipatory and contextual our comprehension is. The brain relates unfolding sentences to earlier ones astonishingly quickly (brain effects usually occur before a word is even finished being spoken), and findings indicate that it does this by trying to predict upcoming information. In addition to the words themselves, the person speaking them is a crucial component in understanding what is being said. The study found brain effects occurring very rapidly when the content of a statement being spoken did not match with the voice of the speaker (e.g. "I have a large tattoo on my back" in an upper-class accent or "I like olives" in a young child's voice). It also appears that grammar is less important than various heuristics that help you arrive at the earliest possible interpretation. Speed is more important than accuracy. “Language comprehension is opportunistic, proactive, and, above all, immediately context-dependent.”
Berkum, J.J.A. 2008. Understanding Sentences in Context: What Brain Waves Can Tell Us. Current Directions in Psychological Science, 17 (6), 376-380.
http://www.physorg.com/news154349880.html
Recently, there has been increased interest in the power of implicit, or unconscious, memory. In the latest study, participants were briefly shown a series of colorful kaleidoscope images and asked to memorise them. Half the time, they simultaneously heard a spoken single-digit number, which they had to keep in mind until the next trial, when they indicated whether it was odd or even. On every trial they had to listen to a new number and press a button to complete the number task. They were tested a short time after the learning period by having to recognize the images they had seen earlier, from pairs of similar kaleidoscope images. It was found that people were more accurate in selecting the old image when they had been distracted than when they had paid full attention, and were also more accurate when they claimed to be guessing than when they thought an image was familiar. During implicit recognition took place, a different pattern of brain activity was observed than that seen with conscious memory experiences, specifically, frontal-occipital negative brain potentials 200–400 ms after participants saw the old image.
Voss, J.L. & Paller, K.A 2009. An electrophysiological signature of unconscious recognition memory. Nature Neuroscience, 12, 349–355.
http://www.eurekalert.org/pub_releases/2009-02/nu-tgf020509.php
A study of search modes in both spatial and abstract settings has found evidence that how we look for things, such as our car keys or umbrella, could be related to how we search for more abstract needs, such as words in memory or solutions to problems. The studies compared two search modes: exploitation, where seekers stay with a place or task until they have gotten appreciable benefit from it, and exploration, where seekers move quickly from one place or one task to another, looking for a new set of resources to exploit. In the study, participants "foraged" in a computerized world, moving around until they stumbled upon a hidden supply of resources, then deciding if and when to move on, and in which direction. The scientists tracked their movements. Two different worlds ("clumpy", with fewer but richer resources, and "diffuse", with many more, but much smaller, supplies) encouraged one mode or other. The idea was to "prime" the optimal foraging strategy for each world. The volunteers then participated in a more abstract, intellectual search task -- a computerized game akin to Scrabble. It was found that although the human brain appears capable of using exploration or exploitation search modes depending on the demands of the task, it also has a tendency through "priming" to continue searching in the same way even if in a different domain, such as when switching from a spatial to an abstract task. Moreover, people who have a tendency to use one mode more in one task have a similar tendency to use that mode more in other tasks. The findings also support the view that goal-directed cognition is an evolutionary descendant of spatial-foraging behavior.
Hills, T.T., Todd, P.M. & Goldstone, R.L. 2008. Search in External and Internal Spaces: Evidence for Generalized Cognitive Search Processes. Psychological Science, 19 (8), 802-808.
http://www.eurekalert.org/pub_releases/2008-09/iu-sis090908.php
A new technique has confirmed the idea that when we retrieve memories we try to reinstate our original mindset, when we formed the memory. As you search for memories of a particular event, your brain state progressively comes to resemble the state it was in when you initially experienced the event, as one memory triggers another. They also found patterns of brain activity for specific categories, such as faces, started to emerge approximately five seconds before subjects recalled items from that category — suggesting that participants were bringing to mind the general properties of the images in order to cue for specific details. The technique also enabled researchers to predict with reasonable accuracy what items participants would successfully recall.
Polyn, S.M., Natu, V.S., Cohen, J.D. & Norman, K.A. 2005. Category-Specific Cortical Activity Precedes Retrieval During Memory Search. Science, 310 (5756), 1963–1966.
http://www.eurekalert.org/pub_releases/2005-12/pu-rdn122205.php
http://www.eurekalert.org/pub_releases/2005-12/uop-rkw121905.php
The role of the hippocampus in the formation of new memories has been well-documented, and we know that the hippocampus is involved in transferring immediate or short-term memories into long-term memories. However, its specific contribution to the representation of very well-learned information is not well understood. Now a study has recorded the activity of individual hippocampal neurons as monkeys retrieved information from memory, demonstrating significantly different response when the stimuli were well-learned, compared to novel stimuli. This differentiated response in the hippocampus provides strong evidence for a memory signal specific for well-learned information, and suggests a way for well-learned information to be incorporated into everyday memories.
Yanike, M., Wirth, S. & Suzuki, W.A. 2004. Representation of Well-Learned Information in the Monkey Hippocampus. Neuron, 42 (3), 477-487.
http://www.eurekalert.org/pub_releases/2004-05/nyu-ssh051204.php
We know that recent memories are stored in the hippocampus, but these memories do not remain there forever. It has been less clear how we retrieve much older memories. Now studies of mice genetically altered to be unable to recall old memories have demonstrated that a part of the cortex called the anterior cingulate is critical for this process. It is suggested that, rather than this structure being the storage site for old memories, the anterior cingulate assembles signals of an old memory from different sites in the brain. Dementia may result from a malfunction in this assembling process, leaving the memory too fragmented to make proper sense. Both ageing and certain aspects of Alzheimer's disease and other dementias are all accompanied by reduced activity in the anterior cingulate.
Frankland, P.W., Bontempi, B., Talton, L.E., Kaczmarek, L. & Silva, A.J. 2004. The Involvement of the Anterior Cingulate Cortex in Remote Contextual Fear Memory. Science, 304, 881-883.
http://news.bbc.co.uk/2/hi/health/3689335.stm
In the first description of a molecule implicated in recalling memories as opposed to laying down new memories, researchers have found that the neurotransmitter norepinephrine is essential in retrieving certain types of memories. The studies involved mutant mice lacking norepinephrine and rats treated with drugs that block some norepinephrine receptors (beta blockers). The results run counter to currently held hypotheses that suggest that stress hormones like norepinephrine are responsible for the formation of long-term consolidation of emotional memories, instead finding that norepinephrine was critical for retrieving intermediate-term contextual and spatial memories. The research may help us better understand post-traumatic stress disorder (PTSD) and depression, both of which involve alterations in memory retrieval in different ways.
Murchison, C.F., Zhang, X-Y., Zhang, W-P., Ouyang, M., Lee, A. & Thomas, S.A. 2004. A Distinct Role for Norepinephrine in Memory Retrieval. Cell, 117 (1), 131-143.
http://www.eurekalert.org/pub_releases/2004-04/uopm-nii033104.php
Data from two longitudinal studies of older adults (a nationally representative sample of older adults, and the Alzheimer’s Disease Neuroimaging Initiative) has found that a brief cognitive test can distinguish memory decline associated with healthy aging from more serious memory disorders, years before obvious symptoms show up.
Moreover, the data challenge the idea that memory continues to decline through old age: after excluding the cognitively impaired, there was no evidence of further memory declines after the age of 69.
Evidence is accumulating that age-related cognitive decline is rooted in three related factors: processing speed slows down (because of myelin degradation); the ability to inhibit distractions becomes impaired; working memory capacity is reduced.
A new study adds to this evidence by looking at one particular aspect of age-related cognitive decline: memory search.
We know that people with depression tend to focus on, and remember, negative memories rather than positive. Interestingly, it’s not simply an emotion effect. People with depression, and even those at risk of depression (including those who have had depression), tend to have trouble remembering specific autobiographical memories. That is, memories of events that happened to them at a specific place and time (as opposed to those generalized event memories we construct from similar events, such as the ‘going to the dentist’ memory).
Our life-experiences contain a wealth of new and old information. The relative proportions of these change, of course, as we age. But how do we know whether we should be encoding new information or retrieving old information? It’s easy if the information is readily accessible, but what if it’s not? Bear in mind that (especially as we get older) most information / experiences we meet share some similarity to information we already have.
Here’s an intriguing study for those interested in how language affects how we think. It’s also of interest to those who speak more than one language or are interested in learning another language, because it deals with the long-debated question as to whether bilinguals working in their non-native language automatically access the native-language representations in long-term memory, or whether they can ‘switch off’ their native language and use only the target language memory codes.
A study involving 75 perimenopausal women aged 40 to 60 has found that those with memory complaints tended to show impairments in working memory and attention. Complaints were not, however, associated with verbal learning or memory.
Complaints were also associated with depression, anxiety, somatic complaints, and sleep disturbance. But they weren’t linked to hormone levels (although estrogen is an important hormone for learning and memory).