Phenomenologies as research methodologies for nursing: from philosophy to researching practice

The effects of synthetic tetrahydrocannabinol (THC) on event-related brain potentials (ERPs) were assessed in 19 healthy male volunteers while they performed a visual continuous word recognition task. The study used a double-blind cross-over design. Specifically, word lists were manipulated to contain an equal number of emotionally neutral, negative, and positive words. Most words were repeated after several intervening items with the subject's task to classify each word as old (previously seen) or new. Behaviorally, a decrease in recognition rate was observed under THC but no influence of the emotional charge of a word on recognition rate was seen. The ERPs showed a typical difference between old and new words taking the form of an enhanced positivity for old words beginning 250 ms poststimulus. The effects of THC were confined to the positive words, for which an enhancement of the positivity to the old words was seen. This effect was interpreted in terms of a congruity of the drug-induced mood state and the material to be recognized. The dissociation between ERPs and behavioral indices suggested that the former primarily reflect implicit memory processes.     

Recognition memory for new associations: electrophysiological evidence for the role of recollection

The electrophysiological correlates of recognition memory for new associations were investigated in two experiments. In both experiments subjects first studied unrelated word pairs. At test, they were presented with old words in the same pairing as at study (same pairs), old words in a different pairing from study (rearranged pairs), and pairs of new words. In Experiment 1 the test requirement was to discriminate between old and new pairs and, for any pair judged old, to then judge whether the pair was the same or rearranged. In Experiment 2 the requirement was merely to discriminate between old and new pairs. Event-related potentials (ERPs) were recorded for correctly classified same, rearranged and new pairs. The ERPs elicited by same pairs exhibited a similar pattern of effects in both experiments. Relative to the ERPs to new pairs, these effects took the form of sustained positive shifts with two distinct scalp maxima, over the left temporo-parietal and right frontal scalp respectively. ERPs to rearranged pairs showed effects which were similar in scalp topography, but markedly smaller in magnitude. This pattern of ERP effects closely resembles that found previously for test items defined as recollected on the basis of their attracting a successful source judgement. The findings therefore suggest that associative recognition memory shares some of the recollective processes that are engaged by the requirement to retrieve contextual information about a study episode. The findings from Experiment 2 indicate that the processes associated with the recollection of associated pairs are engaged regardless of whether the retrieval of associative information is an explicit task requirement.     

A spatio-temporal analysis of recognition-related event-related brain potentials

Words correctly recognized as previously studied (i.e. old) elicit greater amounts of positive event-related brain potential (ERP) activity over posterior scalp between 400 and 800 ms than do previously unstudied (i.e. new) words. While investigators have reported that this old/new effect consists of more than one subcomponent, the spatio-temporal parameters of these possible subcomponents, as well as any other patterns of brain activity associated with recognition, remain incompletely specified. Thus, ERPs were recorded from 32 scalp sites while 13 subjects performed four repetitions of a study-test recognition paradigm. The subjects' task was to decide whether each word was old or new and press the appropriate button as quickly as possible. The timing and topography of the ERPs elicited by old and new words was assessed with topographic profile comparisons on the areas with a variety of temporal windows, and visualized with potential and CSD maps. The results revealed that seven patterns of ERP activity, dissociable on the basis of their topography, timing and response to experimental variables, were elicited between 300 and 2000 ms. Three of these appeared as subcomponents of the old/new effect (maximal over left medial frontal, left parietal-occipital and right central-frontal scalp), another was related to decision confidence and/or memory trace strength (maximal over left central scalp) and three others appeared to be related to more general aspects of recognition (maximal over the frontal poles, midline frontal scalp and right frontal scalp). Taken together, the seven distinct patterns of neural generator activity described here support the hypothesis that retrieval of information from episodic memory depends on a collection of different processes that occur in a temporally and spatially distributed neural circuit.     

Memory with and without awareness: Performance and electrophysiological evidence of savings.

ERPs recorded on the scalp were shown to be sensitive indicators of the strength of a memory trace on both implicit and explicit tests of memory. In explicit recognition tests, the amplitude of a positive potential identified as P300 was larger for "old" than for "new" words regardless of whether the S categorized the items correctly. This effect, however, was statistically reliable only when the recognition memory (d′) was relatively high. In contrast to ERPs, the reaction times (RTs) in explicit recognition were sensitive to accuracy but not to repetition. In implicit tests, lexical decisions to repeated words were faster than to newly presented words. The magnitude of the repetition effect varied neither with elapsed time since the last repetition nor with the number of previous repetitions. In contrast, the P300 elicited by the same words were sensitive to both lag and recency of repetition, suggesting that they were influenced by the episodic memory strength of the items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meaning and modality: Influences of context, semantic memory organization, and perceptual predictability on picture processing.

Using event-related potentials (ERPs), the authors investigated the influences of sentence context, semantic memory organization, and perceptual predictability on picture processing. Participants read pairs of highly or weakly constraining sentences that ended with (a) the expected item, (b) an unexpected item from the expected semantic category, or (c) an unexpected item from an unexpected category. Pictures were unfamiliar in Exp 1 but preexposed in Exp 2. ERPs to pictures reflected both contextual fit and memory organization, as do ERPs to words in the same contexts (K. D. Federmeier and M. Kutas, see record 1999-15076-002). However, different response patterns were observed to pictures than to words. Some of these arose from perceptual predictability differences, whereas others seem to reflect true modality-based differences in semantic feature activation. Although words and pictures may share semantic memory, the authors' results show that semantic processing is not amodal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Who said what? An event-related potential investigation of source and item memory.

Event-related potentials (ERPs) were recorded during recognition tasks for spoken words alone (items) or for both words and the voice of the speaker (sources). Neither performance nor ERP measures suggested that voice information was retrieved automatically during the item-recognition task. In both tasks, correctly recognized old words elicited more positive ERPs than new words, beginning around 400 ms poststimulus onset. In the source task only, old words also elicited a focal prefrontal positivity beginning about 700 ms. The prefrontal task effect did not distinguish trials with accurate and inaccurate voice judgments and is interpreted as reflecting the search for voice information in memory. More posterior recording sites were sensitive to the successful recovery of voice or source information. The results indicate that word and voice information were retrieved hierarchically and distinguish retrieval attempt from retrieval success. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

True memory, false memory, and subjective recollection deficits after focal parietal lobe lesions.

Objective: There is mounting evidence that the posterior parietal cortex (PPC) plays an important role in episodic memory. We previously found that patients with PPC damage exhibit retrieval-related episodic memory deficits. Here we assess whether parietal lobe damage affects episodic memory on a different task: the Deese–Roediger–McDermott (DRM) false-memory paradigm. Methods: Two patients with bilateral PPC damage and a group of matched controls were tested. In Experiment 1, the task was to remember words; in Experiment 2 the task was to remember pictures of common objects. Prior studies have shown that normal participants have high levels of false memory to words, low levels to pictures. Results: The patients exhibited significantly lower levels of false memory to words. One patient showed significantly elevated levels of false memory to pictures. The patients' false memories were accompanied by reduced levels of recollection, as tested by a Remember/Know procedure. Conclusions: PPC damage causes decreased levels of false memories and an abnormal Remember/Know profile. Their false memory rate is similar to the rate exhibited by patients with medial temporal lobe damage. These results support the view that portions of the PPC play a critical role in objective and subjective aspects of recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysical evidence reveals affective evaluation deficits early in stimulus processing in patients with panic disorder.

Cognitive and neurobiological accounts of clinical anxiety and depression were examined via event-related brain potentials (ERPs) recorded from patients with panic disorder and healthy controls as they performed an old/new recognition memory task with emotionally negative and neutral words. The emotive connotation of words systematically influenced control subjects'--but not patients'--ERP effects at prefrontal sites in a latency range (–300-500 ms) generally assumed to reflect greater contribution of automatic than controlled memory processes. This provides evidence for dysfunctional inhibitory modulation of affective information processing in panic disorder. The ERP effects after 700 ms, however, suggest that some patients may adopt conscious strategies to minimize the impact of these early processing abnormalities on overt behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in storage-retrieval processes: A stages-of-learning analysis of developmental interactions in concreteness effects.

In standard list-learning experiments, Age × Treatment interactions have been regarded as an important source of information regarding the locus (storage/retrieval) of age-related memory deficits in adulthood. Unfortunately, these interactions may be spurious byproducts of the use of fixed-trials designs in which age and completeness of learning are confounded. In this paper, we report two experiments in which these problems were explored in the context of item concreteness effects in young and old adults' free recall. In each experiment, eighty 20-year-olds and forty-two 70-year-olds memorized a 16-item list to a stringent acquisition criterion. The manipulations were pictures versus words (Exp. 1) and concrete versus abstract nouns (Exp. 2). The data were analyzed using a recently developed two-stage model that delivers numerical estimates of the impact of these manipulations on the storage and retrieval components of recall. For Experiment 1, the results showed that: (a) for young adults, pictures were easier to store and retrieve than words; (b) for old adults, there was a pictorial superiority effect at storage but a marked pictorial inferiority effect at retrieval; and (c) although younger adults were better than older adults at storing pictures and words and at retrieving pictures, older adults were better than younger adults at retrieving words. For Experiment 2, the results showed that: (a) on average, concrete words were easier to store and retrieve than abstract words at both age levels; and (b) on average, although younger adults were better than older adults at storing concrete and abstract words and at retrieving abstract words, older adults were better than younger adults at retrieving concrete words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials of verbal encoding into episodic memory: dissociation between the effects of subsequent memory performance and distinctiveness

Episodic memory encoding and distinctiveness detection were examined using event-related potentials (ERP) in a single-trial word list learning paradigm with free recall following distraction. To manipulate distinctiveness, encoding of high- and very low-frequency words was contrasted. Amplitudes of the N400 and late positive component (LPC) were larger for low- than for high-frequency words, and ERPs were more positive for subsequently recalled than not recalled words. This subsequent memory effect was dissociated from the correlates of distinctiveness by polarity for the N400 and by time course for the LPC and dissociable into two effects. The data suggest that the first subsequent memory effect, which occurred for both word categories, is more directly related to episodic memory formation, whereas the second effect, which occurred for high-frequency words only, is related to processes influencing episodic encoding success indirectly.     

Long-lasting effects of briefly flashed words and pseudowords in ultrarapid serial visual presentation.

Our ability to identify even complex scenes in rapid serial visual presentation (RSVP) is astounding, but memory for such items seems lacking. Rather than pictures, we used streams of more than 200 verbal stimuli, rushing by on the screen at a rate of more than 12 items per second while participants had to detect infrequent names (Experiments 1 and 2) or words written in capitals (Experiment 3). By direct and indirect tests, we investigated what is remembered of these masses of task-irrelevant distractor words and pseudowords embedded in an RSVP stream. Lexical decision, the indirect test applied either immediately after each stimulus train or with a delay, revealed strong long-term priming effects. Relative to stimuli not shown before, lexical decisions were faster and more accurate to words but slower to pseudowords. The size of these effects mirrored how often words and pseudowords had occurred in a stream, suggesting that memory traces are strengthened with successive presentations and survive for several minutes at least. Moreover, in a direct test (old–new categorization), words as well as pseudowords benefited from prior occurrence in an RSVP stream if they had occurred more than once. These findings parallel recent physiological and behavioral evidence for memory consolidation of distractor pictures in RSVP and highlight that, despite huge numbers of interfering stimuli, distractor words and pseudowords exhibit long-lasting memory effects. Consolidation seems to progress at higher cognitive levels at the same time that subsequent stimuli are perceptually processed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A high biotin diet improves the impaired glucose tolerance of long-term spontaneously hyperglycemic rats with non-insulin-dependent diabetes mellitus

Event-related potentials (ERPs) were recorded in a continuous memory recognition task. Readable non-words and abstract geometric figures were presented in an alternating manner with an inter-stimulus interval of 2.1 s. Probability of item repetition was 0.25, a lag of one item lay between initial presentation and repetition. OLD/NEW distinction was indicated by the subject's motor response. Using linked-mastoid electrodes for reference, material-specific hemispheric asymmetries of ERPs started 150 ms after stimulus onset in temporo-lateral and parietal recordings with ERPs elicited by non-words being lateralized to the left and those by figures to the right. Clear OLD/NEW ERP effects were found with non-words: Starting about 200-250 ms after stimulus presentation, ERPs of formerly presented (OLD) items were more positive-going in recordings over the midline than ERPs of items that were new and to be repeated (NEW). In contrast, no local OLD/NEW ERP-difference was found with figures. In some brain regions, OLD/NEW ERP-differences were larger over the left hemisphere compared to the right. This finding, however, did not differ between non-words and figures.     

Location of the epileptic zone and its physiopathological effects on memory-related activity of the temporal lobe structures: a study with intracranial event-related potentials

PURPOSE: Neuropsychological research with epileptic patients has suggested that the location of seizure focus may be an important variable determining the nature and severity of memory impairments. According to this assumption, this study was designed to investigate the effects of the location of the epileptic zone on the memory-related activity recorded directly from different temporal lobe structures. METHODS: Intracranial event-related potentials (ERPs) were recorded during a continuous recognition memory task, which is known to elicit the modulation of N400 and P600 components (i.e., the ERP old/new effect). The patients were separated into three groups according to the location of their epileptic zone: unilateral temporal (UTE), temporal plus extratemporal (TEE), and bitemporal (BTE). Recordings were obtained from three temporal lobe structures: hippocampus, amygdala, and lateral temporal cortex. RESULTS: The results showed that in the hippocampus, the ERP old/new effect was abolished in the TEE group only. In the amygdala, although largely unaffected, the ERP modulation appeared to be more impaired in UTE patients. Contrasting with these data is the observation that the magnitude and reliability of the ERP old/new effect recorded at the neocortical level increases as the epileptic zone extends to the temporal lobes (i.e., BTE>TEE>UTE). CONCLUSIONS: It is concluded that the memory-related activity modulation of memory ERPs recorded from different temporal lobe structures is affected differently by the presence of an epileptic zone as a function of its location. The possible clinical implications of these findings in surgery planning are also discussed.     

Electrophysiologic dissociations in memory encoding of abstract and concrete words

This study examined memory encoding of auditorily presented abstract and concrete nouns. 22 subjects performed various blocks of a free recall memory task in which lists of 22 either abstract or concrete words had to be memorized. Consistent with a large variety of memory studies, recall performance was better for concrete than for abstract words. When the event-related potentials (ERPs) recorded during study were selectively averaged for those words that were subsequently recalled and those subsequently not recalled, the ERPs were more positive going for words that were subsequently recalled. These Dm effects (Difference due to memory) started around 500 ms post-stimulus and differed in timing and scalp topography for both types of words: For abstract words, they were present in an early (i.e., 600 to 1100 ms) time interval at parieto-occipital electrodes only. In contrast, for concrete words, Dm effects were obtained with a broad topographic distribution in the 600 to 1000 ms time range and were also present in a late time interval (1100 to 1600 ms) at fronto-central recording sites. The topographical dissociations of the Dm effects in the early time interval are taken to reflect the larger distinctiveness of concrete words during encoding, whereas the late effects presumably play a functional role in elaborative processing of concrete words. The results do not agree with models of word concreteness that propose separate processing systems for the two types of words, and rather support those models that propose quantitative differences in the processing of abstract and concrete words.     

Aging and strategic retrieval processes: Reducing false memories with a distinctiveness heuristic.

The authors show that a strategic retrieval process--the distinctiveness heuristic--is a powerful mechanism for reducing false memories in the elderly. Individuals studied words, pictures, or both types of items and then completed a recognition test on which the studied items appeared once, whereas the new words appeared twice. After studying either pictures only or a mixture of pictures and words, both younger and older adults falsely recognized fewer repeated new words than did participants who studied words. Studying pictures provided a basis for using a distinctiveness heuristic during the recognition test: Individuals inferred that the absence of memory for picture information indicates that an item is "new." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the development of declarative memory.

In the visual paired-comparison task, which has been used to demonstrate memory abilities in human infants, Ss view pairs of pictures and then view new pictures paired with old ones. Memory is demonstrated when Ss spend more time looking at new pictures than at old ones. In a series of studies involving amnesic patients and normal Ss, the authors evaluated what kind of memory is exhibited in this task. The results suggest that performance ordinarily depends on the brain structures essential for declarative memory. These and other findings suggest that the visual paired-comparison test also depends on declarative memory when the task is given to human infants. Thus, successful performance on this task by infants probably reflects an early capacity for declarative memory. The relevance of these findings to the phenomenon of infantile amnesia is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of the episodic encoding of pictures and words

A striking characteristic of human memory is that pictures are remembered better than words. We examined the neural correlates of memory for pictures and words in the context of episodic memory encoding to determine material-specific differences in brain activity patterns. To do this, we used positron emission tomography to map the brain regions active during encoding of words and pictures of objects. Encoding was carried out by using three different strategies to explore possible interactions between material specificity and types of processing. Encoding of pictures resulted in greater activity of bilateral visual and medial temporal cortices, compared with encoding words, whereas encoding of words was associated with increased activity in prefrontal and temporoparietal regions related to language function. Each encoding strategy was characterized by a distinctive activity pattern, but these patterns were largely the same for pictures and words. Thus, superior overall memory for pictures may be mediated by more effective and automatic engagement of areas important for visual memory, including medial temporal cortex, whereas the mechanisms underlying specific encoding strategies appear to operate similarly on pictures and words.     

Event-related potentials differentiate the effects of aging on word and nonword repetition in explicit and implicit memory tasks.

Explicit memory declines with age while implicit memory remains largely intact. These experiments extended behavioral findings by recording event-related potentials (ERPs) in young and elderly adults during repetition priming and recognition memory paradigms. Words and pronounceable nonwords repeated after 1 of 3 delays. Stimuli were categorized as either word-nonword or old-new. Repeated items elicited more positive-going potentials in both tasks. Hemispheric asymmetries for word and nonword processing were observed during lexical decision: Repetition effects were larger over the left hemisphere for words and over the right hemisphere for nonwords. For the young, ERP repetition effects were larger during recognition memory. For old adults, conversely, repetition produced more positive-going waveforms during lexical decision. The elderly had ERP and behavioral deficits at long recognition delays. ERP repetition effects in the elderly, like behavioral performance, were preserved in an implicit task but impaired in an explicit memory task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of environmental context on recognition memory and claims of remembering.

Recognition memory for words was tested in same or different contexts using the remember/know response procedure. Context was manipulated by presenting words in different screen colors and locations and by presenting words against real-world photographs. Overall hit and false-alarm rates were higher for tests presented in an old context compared to a new context. This concordant effect was seen in both remember responses and estimates of familiarity. Similar results were found for rearranged pairings of old study contexts and targets, for study contexts that were unique or were repeated with different words, and for new picture contexts that were physically similar to old contexts. Similar results were also found when subjects focused attention on the study words, but a different pattern of results was obtained when subjects explicitly associated the study words with their picture context. The results show that subjective feelings of recollection play a role in the effects of environmental context but are likely based more on a sense of familiarity that is evoked by the context than on explicit associations between targets and their study context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct comparison of two implicit memory tests: Word fragment and word stem completion.

In 3 experiments, the implicit memory tests of word fragment and word stem completion showed comparable effects over several variables: Study of words produced more priming than did study of pictures; no levels-of-processing effect occurred for words; more priming was obtained from pictures when Ss imaged the pictures' names than when they rated them for pleasantness; and forgetting rates were generally similar for the tests. A different pattern of results for the first 3 variables occurred under explicit test conditions with the same word fragments or word stems as cues. It is concluded that the 2 implicit tests are measuring a similar form of perceptual memory. Furthermore, it is argued that both tests are truly implicit because they meet the D. L. Schacter et al (1989) retrieval intentionality criterion: Levels of processing of words have a powerful effect on explicit versions of the tests but no effect on implicit versions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)