Memory

231 quotes found

"The purpose of this review is to evaluate the effects of chronic stress on hippocampal-dependent function, based primarily upon studies using young, adult male rodents and spatial navigation tasks. Despite this restriction, variability amongst the findings was evident and how or even whether chronic stress influenced spatial ability depended upon the type of task, the dependent variable measured and how the task was implemented, the type and duration of the stressors, housing conditions of the animals that include accessibility to food and cage mates, and duration from the end of the stress to the start of behavioral assessment. Nonetheless, patterns emerged as follows: For spatial memory, chronic stress impairs spatial reference memory and has transient effects on spatial working memory. For spatial learning, however, chronic stress effects appear to be task-specific: chronic stress impairs spatial learning on appetitively motivated tasks, such as the radial arm maze or holeboard, tasks that evoke relatively mild to low arousal components from fear. But under testing conditions that evoke moderate to strong arousal components from fear, such as during radial arm water maze testing, chronic stress appears to have minimal impairing effects or may even facilitate spatial learning. Chronic stress clearly impacts nearly every brain region and thus, how chronic stress alters hippocampal spatial ability likely depends upon the engagement of other brain structures during behavioral training and testing."

- Memory

0 likesMental processes
"The ability to apprehend a small number of items at one time in the conscious mind can be distinguished from the need to attend to items individually when a larger number of such items are presented. This point is one of the earliest to be noted in psychological commentaries on the limitations in capacity. Hamilton (1859) treated this topic at length and noted (vol. 1, p. 254) that two philosophers decided that six items could be apprehended at once, whereas at least one other (Abraham Tucker) decided that four items could be apprehended. He went on to comment: “The opinion [of six] appears to me correct. You can easily make the experiment for yourselves, but you must be aware of grouping the objects into classes. If you throw a handful of marbles on the floor, you will find it difficult to view at once more than six, or seven at most, without confusion; but if you group them into twos, or threes, or fives, you can comprehend as many groups as you can units; because the mind considers these groups only as units, – it views them as wholes, and throws their parts out of consideration. You may perform the experiment also by an act of imagination.” When the experiment actually was conducted, however, it showed that Hamilton’s estimate was a bit high. Many studies have shown that the time needed to count a cluster of dots or other such small items rises very slowly as the number of items increases from one to four, and rises at a much more rapid rate after that. Jevons (1871) was probably the first actual study, noting that Hamilton’s conjecture was “one of the very few points in psychology which can, as far as we yet see, be submitted to experiment.” He picked up handfuls of beans and threw them into a box, glancing at them briefly and estimating their number, which was then counted for comparison. After over a thousand trials, he found that numbers up to four could be estimated perfectly, and up to five with very few errors"

- Memory

0 likesMental processes
"Other theorists (Hummel & Holyoak 1997; Shastri & Ajjanagadde 1993) have applied this neural synchronization principle in a way that is more abstract. It can serve as an alternative compatible with Halford et al.’s (1998) basic notion of a limit on the complexity of relations between concepts, though Halford et al. instead worked with a more symbolically based model in which “the amount of information that can be represented by a single vector is not significantly limited, but the number of vectors that can be bound in one representation of a relation is limited” (p. 821). Shastri and Ajjanagadde (1993) formulated a physiological theory of working memory very similar to Lisman and Idiart (1995), except that the theory was meant to explain “a limited-capacity dynamic working memory that temporarily holds information during an episode of reflexive reasoning” (p. 442), meaning reasoning that can be carried out “rapidly, spontaneously, and without conscious effort” (p. 418). The information was said to be held as concepts or predicates that were in the form of complex chunks; thus, it was cautioned, “note that the activation of an entity together with all its active superconcepts counts as only one entity” (p. 443). It was remarked that the bound on the number of entities in working memory, derived from facts of neural oscillation, falls in the 7 6 2 range; but the argument was not precise enough to distinguish that from the lower estimate offered in the present paper. Hummel and Holyoak (1997) brought up similar concepts in their theory of thinking with analogies. They defined “dynamic binding” (a term that Shastri & Ajjanagadde also relied upon to describe how entities came about) as a situation in which “units representing case roles are temporarily bound to units representing the fillers of those roles” (p. 433). They estimated the limit of dynamic binding links as “between four and six” (p. 434). In both the approaches of Shastri and Ajjanagadde (1993) and Hummel and Holyoak (1997), these small limits were supplemented with data structures in long term memory or “static bindings” that appear to operate in the same manner as the long-term working memory of Ericsson and Kintsch (1995), presumably providing the “active superconcepts” that Shastri and Ajjanagadde mentioned."

- Memory

0 likesMental processes
"Working memory is a fundamental aspect of executive cognition that is thought to encompass three primary mental processes: 1) the access of information, 2) “on-line” operation(s) on this information, and 3) the production of a motor output response based on these operations (Goldman-Rakic, 1987). At present, several distinct theoretical conceptualizations of working memory exist within the cognitive science literature (reviewed in Kimberg, D’Esposito, & Farah, 1998). This lack of consensus may be due, in part, to the functional complexity of working memory, which includes aspects of rehearsal, maintenance, short term storage, attention, and executive control (Kimberg, et al., 1998). Working memory is widely accepted as being dependent on the lateral frontal cortex (Fuster, 1997; Goldman-Rakic, 1987; Owen, et al., 1998; 1999; Owen, 2000), and plays an important role in the temporal coordination of guided behavior via the perception-action cycle (Fuster, 2000). Immediate serial recall and memory span tasks are two common tools used to assess working memory in humans (Baddeley, 1996). In such tasks, the participant is presented with a series of stimuli, and required to recall this stimulus string in sequential order (Baddeley, 1996). In these tasks, the likelihood of correct recall is directly related to the length of the stimulus string, and by manipulating the length of this string, the participant’s working memory capacity (memory span) can be assessed (Baddeley, 1996)."

- Memory

0 likesMental processes
"In the practical use of our intellect, forgetting is as important a function as recollecting. ... If we remembered everything, we should on most occasions be as ill off as if we remembered nothing. It would take as long for us to recall a space of time as it took the original time to elapse, and we should never get ahead with our thinking. All recollected times undergo, accordingly, what M. Ribot calls foreshortening; and this foreshortening is due to the omission of an enormous number of the facts which filled them. ... A thing forgotten on one day will be remembered on the next. Something we have made the most strenuous efforts to recall, but all in vain, will, soon after... saunter into the mind... [T]he sphere of possible recollection may be wider than we think, and... apparent oblivion is no proof against possible recall under other conditions. ... [M]ost of what happens actually is forgotten. ... When memory begins to decay, proper names are what go first ...[[wikt:common#Adjective|[C]ommon]] qualities and names have contracted an infinitely greater number of associations ...than the names of most of the persons ...Their memory is better organized. ...'Organization' means numerous associations; and the more numerous the associations, the greater the number of paths of recall. For the same reason... words... which form the grammatical framework of all our speech, are the very last to decay. ... We have ...as M. Ribot says, not memory so much as memories. The visual... tactile... muscular... auditory memory may all vary independently... and different individuals may have them developed in different degrees. As a rule, a man’s memory is good in the departments in which his interest is strong; but those departments are apt to be those in which his discriminative sensibility is high. ...[D]ifferences in men’s imagining power... the machinery of memory must be largely determined thereby. ... Mr. Galton ...in his English Men of Science, has given ...cases showing individual variations in the type of memory... Some have it verbal. Others... for facts and figures, others for form. Most say... [it] must first be rationally conceived and assimilated. ... Setting the mind to remember... involves a continual minimal irradiation of excitement into paths which lead thereto... the continued presence of the thing in the 'fringe' of our consciousness. Letting the thing go involves withdrawal of the irradiation, unconsciousness of the thing, and... obliteration of the paths. ... [T]hings are impressed better by active than by passive repetition. ...[I]t pays better to wait and recollect by an effort from within, than to look at the book again."

- Memory

0 likesMental processes
"What happens when people witness an event, say, a crime or accident, and are later exposed to new information about the event? Two decades of research have been devoted to the influence of new information on the recollections of such witnesses. An all-too-common finding is that after receipt of new information that is misleading in some way, people make errors when they report what they saw. New, post-event information often becomes incorporated into a recollection, supplementing or altering it, sometimes in dramatic ways. New information invades us, like a Trojan horse, precisely because we do not detect its influence. Understanding how we become tricked by revised data about a witnessed event is a central goal of this research. Current research showing how memory can become skewed when people assimilate new data utilizes a simple paradigm. Participants first witness a complex event, such as a simulated violent crime or automobile accident. Subsequently, half the participants receive new, misleading information about the event. The other half do not get any misinformation. Finally, all participants attempt to recall the original event. In a typical example of a study using this paradigm, participants saw a simulated traffic accident. They then received written information about the accident, but some people were misled about what they saw. A stop sign, for instance, was referred to as a yield sign. When asked whether they originally saw a stop or a yield sign, participants given the phony information tended to adopt it as their memory; they said they saw a yield sign. In these and many other experiments, people who had not received the phony information had much more accurate memories. In some experiments, the deficits in memory performance following receipt of misinformation have been dramatic, with performance differences as large as 30% or 40%."

- Memory

0 likesMental processes