Monitoring the Changing Status of Semantic Memory in Alzheimer's Disease: An Evaluation of Several Process Measures

The deficits in generating correct words on verbal fluency tasks exhibited by patients with Alzheimer's disease (AD) are accompanied by fewer switching responses, smaller phonemic and semantic cluster sizes, and greater than normal percentages of errors and category labels. On category fluency tasks, patients generate a greater proportion of words that are prototypical of their semantic class. To determine whether any of these supplementary measures of verbal fluency performance might be useful in revealing processes involved in the decline of semantic memory in AD, we studied 219 patients with AD and 115 elderly control participants longitudinally. Previously reported group differences between patients and controls were replicated, but changes in average cluster size, error rates, and prototypicality were not related to changes in overall severity of dementia and test-retest stability was only modest. The change in the percentage of labels generated on the Supermarket task was related to changes in dementia severity, but test-retest stability on this measure was quite low. All of these process measures appear to reflect only the current status of the patient's attention to the task and access to semantic knowledge, but they do not forecast future performance. The numbers of switching responses on the fluency tasks were sensitive to differences between clinically deteriorated and clinically stable patients and showed fairly high test-retest stability. However, the number of switching responses is so highly correlated with the number of correct words that it contributes little to the understanding of the processes involved in the progressive decline in performance on fluency tasks by patients with AD.     

The consequences of encoding information on the maintenance of internally generated images and thoughts: the role of meaning complexes

Three experiments investigated the hypothesis that internally generated images and thoughts were driven by meaning complexes, a construct which reflects a synthesis of semantic meaning and personal salience (Klinger, 1999). Experiments 1 and 2 contrasted the mutual inhibition between encoding words and non-words on: (i) the frequency that thoughts and images unrelated to the task (task unrelated thought, TUT) were experienced (Experiment 1) and (ii) on the intensity of images generated from long-term memory and maintained under dual task conditions, which whilst familiar were not of particular personal salience (Experiment 2). Experiment 3 examined the physiological arousal associated with the experience of TUT in a semantic encoding task. Evidence suggested that, in general, internally generated images and thoughts, irrespective of the personal salience, were suppressed by the co-ordination of information in working memory. In addition, only the experience of spontaneous images and thoughts of personal salience (TUT, Experiments 1 and 3) interfered reliably with the encoding/retrieval of semantic information from memory. Finally, in Experiment 3, physiological arousal, as indexed by mean heart rate, was associated with a high frequency of TUT. The results of all three experiments support the notion that the maintenance of spontaneously occurring images and thoughts is simultaneously influenced by both the semantic content and the personal salience of the information held in working memory.     

Effects of being observed on learning following success and failure experiences

In two experiments female subjects performed a task either alone or while being observed by a female experimenter, after which they were told that they had performed well or poorly. On a paired-associates (PA) learning task that followed, subjects who performed in the presence of the observing experimenter required more trials to criterion and committed more errors than those who worked alone only if they had supposedly done poorly on the preceding task. Subjects who had done well on the prior task performed better on the PA task when observed than when alone provided that the preliminary task had also measured verbal learning. A measure of skin conductance indicated increased arousal under conditions of observation on the PA task only after a poor performance on the preceding task. The results are discussed in terms of the drive theory of social facilitation and the conditions under which being observed produces evaluation apprehension.     

Type of stimulus mediates the relationship between working-memory performance and type of precocity

The relationship between type of stimulus (numeric and verbal) and type of precocity (mathematical and verbal) was examined in tasks designed to tap three aspects of working memory: encoding, capacity, and manipulation of information. The tasks included semantic categorization, odd-even categorization, recall of five-item lists after semantic categorization, and recall of items in a continuous paired-associates task. Correlations between task performance and the mathematical and verbal portions of the Scholastic Aptitude Test (SAT-M and SAT-V) were computed for gifted youth. There were no sex differences in the performance measures or in the pattern of correlations between performance and SAT scores. The analysis revealed positive relationships between SAT-M scores and numeric categorization latency, recall in the continuous paired-associate task with words and digits, and recall of digit lists. SAT-V scores were related only to word recall in the continuous paired-associate task and recall of word lists. In the working-memory tasks used, mathematical precocity is more strongly related to performance than is verbal precocity. The relationship is especially strong with numeric stimuli, even when the numeric stimuli are simply items to be remembered. The relationship between type of stimulus and type of precocity suggests underlying differences between verbally and mathematically precocious youth in how different types of stimuli are represented in memory.     

Individual Differences in Arousal and Accessibility to Information in Memory

The authors conducted 9 experiments to test the hypothesis (S. Schwartz, 1975) that arousal influences the accessibility of information stored in memory. They investigated the relationship between arousal levels (as indexed by personality types) and the type of stimuli or cues presented during study or test. They predicted that low-arousal individuals (stable extroverted individuals in Experiments 1-3 and 5-9 and high-impulsive individuals in Experiment 4) would be influenced by semantic stimuli, whereas high-arousal individuals (neurotic introverted individuals in Experiments 1-3 and 5-9 and low-impulsive individuals in Experiment 4) would be influenced by physical (i.e., graphic, phonetic, or both) stimuli. They tested the arousal-accessibility hypothesis by using a variety of tasks including verbal discrimination, false recognition, cued recall, and paired associates. With the exception of the finding that stable extroverted participants performed better than neurotic introverted participants on an incidental associative-matching task (Experiment 3), the results from the verbal discrimination studies (1-5) did not support the hypothesis. In Experiment 6, the authors tested the hypothesis by using a false-recognition task. False alarms varied as a function of phonetic and semantic stimuli, but personality types were not differentially sensitive to the manipulation. The same was true for the cued-recall studies (Experiments 7 and 8); personality types were not differentially sensitive to the semantic and phonetic stimuli. Experiment 9 (paired-associate learning) was a replication of Schwartz's study. The authors found some support for the Schwartz hypothesis: Extraverted participants were adversely affected by semantic similarity. Overall, the findings did not provide much support for the arousal-accessability hypothesis.     

The animacy advantage for free-recall performance is not attributable to greater mental arousal

People often demonstrate better memory for animate concepts (e.g., lion and sailor) than for inanimate concepts (e.g., hammer and mountain). Researchers have attributed this effect to an adaptive memory mechanism that favours information relevant for survival, including information about living things. In the present experiment, we examined the hypothesis that people demonstrate better free-recall performance for animate than inanimate words because animate words tend to be associated with greater mental arousal than inanimate words, a factor that was not controlled for in previous experiments on this topic. To this end, we matched animate and inanimate word lists on mental arousal (and several other factors), and compared participants’ free-recall performance for the two word types. We were able to replicate past findings that participants’ free-recall of animate words exceeds their free-recall of inanimate words, but we found no support for the possibility that the effect stems from differences in mental arousal between animate and inanimate concepts, as this effect maintained even when the word lists were matched on mental arousal. The present results therefore indicate that mental arousal cannot explain the effects of animacy on free-recall performance.     

Verbal imagery and connotation as memory-induced mediators of aggressive behavior.

Three studies investigated the effects of an information-processing variable (imagery-concreteness) on susceptibility to aggressive stimulation. Study 1 (n=83) results indicated that subjects' rating of imagery level and aggressive connotation for words can be manipulated independently. In study 2 (n=64), manipulations of verbal connotation and verbal imagery indicated that imagery level but not aggressive connotation significantly influenced the delayed recall of the verbal material. In Study 3 (n=60), males in a 2 X 2 between-subjects factorial design first learned lists of words varying in imagery (high or low) and verbal connotation (aggressive or neutral). Next, subjects were given the opportunity to shock their partners as part of a sham learning task. To induce arousal, all subjects learning high-imagery-aggressive word lists delivered significantly more intense shock to their partners. The results were interpreted as supporting an information-processing (memory) analysis of the effects of exposure to aggressive material.     

Differential effects of personality on access to various long-term memory codes

Arousal, as indexed by personality measures, has been related to memory encoding, organization, and retrieval. In an attempt to investigate one of the component information-processing mechanisms underlying both encoding and retrieval, the effects of introversion-extraversion on performance in a simultaneous matching task was investigated. As predicted from earlier research, personality did not influence performance on a physical identity matching task but extraverts were faster than introverts in making taxonomic category matches (a semantic task). Somewhat unexpectedly, extraverts were also faster at making “homophone” identity matches. Arousal, then, appears to influence access to long-term memory codes of any type—a characteristic that may be reflected in tests of both encoding and retrieval.     

情绪效价和唤醒对熟悉性和回想的不同影响

本研究检验了情绪的效价和唤醒对记忆提取阶段熟悉性过程和回想过程的影响及其心理机制。结果发现,编码阶段无分心任务时,积极图片的高、低自信再认准确率均高于消极图片,而唤醒对于高自信再认准确率的影响只限于消极图片;在编码阶段设置分心任务时,发现积极和消极的高唤醒图片的高自信再认准确率显著高于低唤醒图片。这些结果说明情绪的效价影响了熟悉性和回想两类记忆过程,而唤醒只影响回想过程,效价效应是编码阶段被试调用认知资源对积极图片进行精细加工的结果,而唤醒对回想过程的影响是自动编码高唤醒刺激细节的结果。     

Sustained attention failures are primarily due to sustained cognitive load not task monotony

We conducted two studies using a modified sustained attention to response task (SART) to investigate the developmental process of SART performance and the role of cognitive load on performance when the speed-accuracy trade-off is controlled experimentally. In study 1, 23 participants completed the modified SART (target stimuli location was not predictable) and a subjective thought content questionnaire 4 times over the span of 4 weeks. As predicted, the influence of speed-accuracy trade-off was significantly mitigated on the modified SART by having target stimuli occur in unpredictable locations. In study 2, 21 of the 23 participants completed an abridged version of the modified SART with a verbal free-recall memory task. Participants performed significantly worse when completing the verbal memory task and SART concurrently. Overall, the results support a resource theory perspective with concern to errors being a result of limited mental resources and not simply mindlessness per se.     

Cognitive activity and physiological arousal: Processes that mediate mood-congruent memory

This research proposes that the cognitive activity associated with the experience of an emotional state mediates the occurrence of mood-congruent processing. Two experiments examined the role of cognitive activity in selective processing of words in a mood congruence paradigm. Four induction procedures were used: a depressed-mood induction, a schema induction organized around the theme of writing a paper, an arousal induction, and a control neutral-mood induction. The memory task consisted of recalling a word list composed of negatively associated and thematically organized words. Selective processing was demonstrated in conjunction with the depressed-mood and organizational-schema induction procedures. In contrast, the arousal and neutral induction procedures did not produce selective processing of words from the list. The findings support the thesis that cognitive activity mediates the selective processing typical of mood congruence as distinct from arousal processes per se. The findings are discussed with respect to the resource allocation model and semantic network theory.     

Mind wandering and retrieval from episodic memory: a pilot event-related potential study

The present study investigated the effects of mind wandering (task-unrelated thought) on the subcomponents of episodic memory as reflected by event-related potentials (ERPs). Specifically, individual differences in the pattern of ERP episodic 'old/new' effects (left-parietal, right-frontal and central-negativity effects) were examined across groups of participants experiencing either high or low frequencies of task-unrelated thought during encoding. Twenty participants studied lists of words and line drawings in one of two contexts (red versus green coloured boxes). At test, participants discriminated between target (old words or line drawings presented in one colour) and nontargets (old items from the other colour and new items). On completion of the memory task, participants completed the 'thinking' component of the Dundee Stress State Questionnaire to provide a retrospective measure of task-unrelated thought. Behavioural data indicated that irrespective of the presence of task-unrelated thought, participants were able to complete the memory task equally well. However, an analysis of ERPs across High and Low task-unrelated thought groups revealed differences in retrieval strategy. Those individuals with infrequent episodes of task-unrelated thought at study used a 'pure' recollection strategy (left-parietal effect only). Conversely, those participants experiencing frequent episodes of task-unrelated thought were unable to recollect the stimuli with ease, as indexed by a diminished parietal effect. As a consequence, these participants employed additional strategic processes for task completion, as indexed by an elevated amplitude of central negativity effects. These data are consistent with the decoupling hypothesis of mind wandering which suggests impaired recollection when attention becomes directed away from the task.     

Alexithymia and levels of processing: Evidence for an overall deficit in remembering emotion words

Alexithymia is a multifaceted personality construct that is thought to reflect a deficit in the cognitive processing of emotions. The effects of low vs. high Alexithymia, neutral vs. positive vs. negative words processed, and perceptual vs. semantic processing on memory were investigated in a group of 82 students using the levels of processing paradigm and the Remember/Know procedure. No differences were observed between low and high Alexithymia students when neutral material was considered. However, for both levels of processing, high Alexithymia students recalled fewer emotion words (both positive and negative) when “Remember” responses were considered. “Know” responses were comparable across Alexithymia groups. The deficit in the ability to consciously access emotional material (the “Remember” responses) may help explain the impaired regulation of intense emotional states by high Alexithymia individuals.     

Effects of aging on source monitoring: differences in susceptibility to false fame

Older adults were less likely than young adults to spontaneously recollect the source of familiarity for previously read nonfamous names. Older adults were more likely to call old nonfamous names famous when subsequently encountered in a fame judgment task. Poor source monitoring by the elderly could not be accounted for by inability to recognize earlier read nonfamous names when specifically asked to do so. Both source-monitoring errors and recognition memory performance were based on attributions made about the experience of familiarity. Elderly subjects most prone to making familiarity errors recalled fewer items on a verbal learning task and were less likely to chunk information into semantic categories as it was recalled. This finding suggests that a decline in the tendency to spontaneously organize and integrate information underlies the poor source monitoring observed.     

Facilitation of recall with intralist cues: Time-dependent characteristics of cued recall

List items were given as retrieval cues in a free-recall experiment which factorially combined the presence or absence of cues with the amount of time allowed for use of each cue (10 sec or 30 sec). A categorizable list of 75 randomly presented words was learned, and 48 h later a free-recall test trial was given, followed by a final memory search task. During the final task, cued subjects received words from categories that had not been recalled during the free-recall test. With both time intervals, cued subjects recalled more words than noncued subjects, indicating that random presentation of categorized words does not necessarily preclude the observation of a cueing effect with list items, as has been reported previously. The composition of recall, whether from previously recalled or nonrecalled categories, varied as a function of time for both groups. The results were interpreteod in terms of retrieval strategies employed by cued and noncued subjects and the effect of time on these strategies.     

The moderating effects of stimulus valence and arousal on memory suppression

This study examined the separate and combined effects of stimulus valence and arousal on retrieval inhibition. Participants performed Anderson and Green's (2001) memory suppression task with stimuli varying across dimensions of valence and arousal. Memory was tested through free and cued recall as well as speeded recognition. Results showed that both stimulus valence and arousal influenced the extent to which participants successfully inhibited retrieval, but not in the ways anticipated. Specifically, the strongest inhibition effects were for highly arousing, pleasant words. In addition, unpleasant stimuli that were suppressed were better recalled during both cued and free-recall tasks than pleasant stimuli that were suppressed. Across all tests of memory performance, there were no significant differences between the experimental conditions for highly arousing, unpleasant words. The implications of these findings are discussed.     

语音回路和视空间模板对音位流畅性和语义流畅性的影响

采用双任务范式,通过四种次任务考察了工作记忆两个子系统－语音回路和视空间模板对音位流畅性和语义流畅性的影响。实验1表明,主动产生系列发音和被动聆听声音判断对音位流畅性影响更大,表明音位流畅性更依赖于语音回路。实验2表明,字形匹配和字形旋转判断对语义流畅性影响更大,表明语义流畅性更依赖于视空间模板。研究还表明,被试完成音位流畅性任务的策略更易受语言的特点影响,完成语义流畅性任务的策略更易受概念系统的特性影响     

Sex differences in working memory

In two separate studies, sex differences in modal-specific elements of working memory were investigated by utilizing words and pictures as stimuli. Groups of men and women performed a free-recall task of words or pictures in which 20 items were presented concurrently and the number of correct items recalled was measured. Following stimulus presentation, half of the participants were presented a verbal-based distraction task. On the verbal working-memory task, performance of men and women was not significantly different in the no-distraction condition. However, in the distraction condition, women's recall was significantly lower than their performance in the no-distraction condition and men's performance in the distraction condition. These findings are consistent with previous research and point to sex differences in cognitive ability putatively resulting from functional neuroanatomical dissimilarities. On the visual working-memory task, women showed significantly greater recall than men. These findings are inconsistent with previous research and underscore the need for further research.     

Field articulation and working memory

This experiment assessed the proposal that performance differences associated with field independence/field articulation reflect differential efficiency in the use of a limited capacity information-processing system termed working memory. Extreme scores on a group-administered version of the embedded figures test were used to identify subjects “high” and “low” in degree of field articulation. The task required that a subject retain a series of digits for subsequent report while performing a semantic modification of a target phrase. Concurrent information load on working memory was varied in two ways: by increasing memory load from 3 to 6 digits, and by increasing the complexity of the semantic processing required. In low information load conditions no differences were found between high FA and low FA groups. In high information load conditions low FA subjects made more errors in digit recall and took longer to perform the difficult semantic modification.     

The (lack of) effect of dynamic visual noise on the concreteness effect in short-term memory

It has been suggested that the concreteness effect in short-term memory (STM) is a consequence of concrete words having more distinctive and richer semantic representations. The generation and storage of visual codes in STM could also play a crucial role on the effect because concrete words are more imaginable than abstract words. If this were the case, the introduction of a visual interference task would be expected to disrupt recall of concrete words. A Dynamic Visual Noise (DVN) display, which has been proven to eliminate the concreteness effect on long-term memory (LTM), was presented along encoding of concrete and abstract words in a STM serial recall task. Results showed a main effect of word type, with more item errors in abstract words, a main effect of DVN, which impaired global performance due to more order errors, but no interaction, suggesting that DVN did not have any impact on the concreteness effect. These findings are discussed in terms of LTM participation through redintegration processes and in terms of the language-based models of verbal STM.