Recognition memory for words and pictures: an event-related potential study

Event-related potentials (ERPs) were recorded during the test phase of recognition memory tests for words and pictures of objects. ERPs elicited by recognized items contained a temporo-parietally distributed positive shift (the parietal old/new effect), which was strongly left lateralized regardless of stimulus type. This finding suggests that the lateral distribution of the parietal old/new effect is unrelated to the lateralization of the memory functions supported by the medial temporal lobe memory system. The ERPs to pictures, but not to words, also demonstrated frontally distributed old/new effects, which shifted over time from a left- to a right-sided maximum. These effects may reflect the richer informational content associated with episodic memory for pictures.     

Probability and strategy: an event-related potential study of processing syntactic anomalies

Syntactic ambiguities requiring additional processing usually elicit positive going waveforms with onset latencies between 300 and 600 ms in the event-related potential (ERP). It is still unclear to what extent these components can be viewed either (a) as language specific in nature or (b) as members of the domain-unspecific P300 family of components. The present study investigates this question by means of probability manipulations applied to German sentences with subject-object ambiguities. Non-preferred object-subject (OS) word order requires structural revisions whereas the initially preferred subject-object (SO) word order does not. In the present experiment, the proportions of OS and SO structures were varied across experimental blocks (i.e., .25/.75 vs. .75/.25). The data of 20 participants reveal that ERP components were predominantly influenced when the subjects were explicitly informed about the actual proportions before each single block. In this case an early frontal positive component at about 400 ms and a subsequent posterior positivity were elicited by rare sentence structures irrespective of word order, suggesting that sentence processing was under strategic control. Conversely, participants that were not informed about sentence proportions showed larger positivities to the unpreferred OS sentences. Probability manipulations did not affect this pattern significantly. The data suggest that positivities evoked by syntactic ambiguities respond differently to probability manipulations than the P300 component.     

Effects of age on working memory: an event-related potential study

The effects of age on behavioural performance and event-related potentials recorded during a working memory task using digits presented either acoustically or visually, were studied in 37 healthy subjects with an age range from 19 to 71 years. With increasing age, psychological tests showed a progressive decline in visuo-spatial performance and both auditory and visual reaction times (RT) increased. There were multiple and varying effects of age on both early and late ERP components. For both auditory and visual responses, increasing age was associated with an increased amplitude of early positive waves (auditory P100 and visual P145) and, in the oldest subjects, significant delays of the major late positive waves. Other changes were modality-specific with a progressive shift of amplitude maxima in the early negative waves of the visual ERPs (from an N190 peak maximal at Pz in the young, to an N270 peak maximal at Cz in the older subjects) and an altered amplitude distribution of late potentials (after the P250 wave) in the auditory responses. The age at which ERP changes occurred varied-significant latency prolongations and increases in the amplitude of the major frontal positive waves occurred only in the oldest subjects, whereas a redistribution of late auditory ERPs also occurred in the intermediate age group. There was no interaction between age and increasing memory load, suggesting that there is no specific effect of age on memory scanning in this age range for these levels of task difficulty. Thus, although performance in working memory was apparently unaffected by age, as judged by behavioural parameters (apart from slowing of the reaction times), ERPs revealed significant changes in both early and late electrical brain processes associated with working memory as age increases. These changes which were not symptomatically manifest and only revealed by sensitive tests, may represent subtle dysfunction of working memory (or associated processes) which does not prevent the successful completion of our task, compensatory mechanisms (which are essential to successfully complete the task), or a combination of both age-induced dysfunction and compensatory mechanisms.     

Recognition memory for object form and object location: an event-related potential study

In this study, the processes associated with retrieving object forms and object locations from working memory were examined with the use of simultaneously recorded event-related potential (ERP) activity. Subjects memorized object forms and their spatial locations and made either object-based or location-based recognition judgments. In Experiment 1, recognition performance was higher for object locations than for object forms. Old responses evoked more positive-going ERP activity between 0.3 and 1.8 sec poststimulus than did new responses. The topographic distribution of these old/new effects in the P300 time interval was task specific, with object-based recognition judgments being associated with anteriorly focused effects and location-based judgments with posteriorly focused effects. Late old/new effects were dominant at right frontal recordings. Using an interference paradigm, it was shown in Experiment 2 that visual representations were used to rehearse both object forms and object locations in working memory. The results of Experiment 3 indicated that the observed differential topographic distributions of the old/new effects in the P300 time interval are unlikely to reflect differences between easy and difficult recognition judgments. More specific effects were obtained for a subgroup of subjects for which the processing characteristics during location-based judgments presumably were similar to those in Experiment 1. These data, together with those from Experiment 1, indicate that different brain areas are engaged in retrieving object forms and object locations from working memory. Further analyses support the view that retrieval of object forms relies on conceptual semantic representation, whereas retrieving object locations is based on structural representations of spatial information. The effects in the later time intervals may play a functional role in post-retrieval processing, such as recollecting information from the study episode or other processes operating on the products of the retrieval process, and presumably are mediated by right frontal cortical areas. The results support the view of functionally dissociable object and spatial visual working memory systems.     

Shifting attention between global features and small details: an event-related potential study

In two experiments, large letters H or Z composed of small letters (also H or Z) were presented. Subjects had to make a two-choice motor response (e.g. H--left key, Z--right key). A cue presented 500 ms before the letter indicated which level (global or local) was relevant. In Experiment I, a third letter (T) sometimes appeared either at the cued or the non-cued level; in the former case, subjects had to shift their attention and to respond to stimulus features located at the non-cued level. The interference effect (RT delay in response to incongruent stimuli as compared to congruent ones) was larger when the local, rather than global, level was cued. A slow anterior negativity preceding globally-cued stimuli and shorter N1 and P2 ERP component latencies to these stimuli indicated better preparation for processing of global, as compared to local, stimulus features. The shift from local to global focus yielded a larger increase of RT, error rate, and of the P600 latency than the global-to-local shift. The P600 latency changes were parallel to those of RT. In Experiment II, the attentional shift was provoked by stimulus color red-colored letters meant that the cue was invalid, and thus, subjects had to respond to the non-cued level. Neither the interference nor the attentional shift demonstrated any asymmetry between the global and local levels. ERPs also did not differ substantially after local and global cues. In the condition demanding a shift of focus (invalid cue, incongruent letter), a positive deflection of the lateralized readiness potential indicated the activation of the wrong response channel. The large RT increment in this condition was not accompanied by an increase of the P600 latency. Two possible mechanisms of attentional shift may be proposed, the first related to perceptual processes (e.g. an additional visual search), and the second, to the competition between two response intentions.     

The gradient of spatial auditory attention in free field: an event-related potential study

Young adult subjects attended selectively to brief noise bursts delivered in free field via a horizontal array of seven loudspeakers spaced apart by 9 degrees of angle. Frequent "standard" stimuli (90%) and infrequent "target/deviant" stimuli (10%) of increased bandwidth were delivered at a fast rate in a random sequence equiprobably from each speaker. In separate runs, the subjects' task was to selectively attend to the leftmost, center, or rightmost speaker and to press a button to the infrequent "target" stimuli occurring at the designated spatial location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sound source, thus providing support for gradient models of auditory spatial attention. Furthermore, the ERP data suggested that the spatial focusing of attention was achieved in two distinct stages, with an early more broadly tuned filtering of inputs occurring over the first 80-200 msec after stimulus onset, followed by a more narrowly focused selection of attended-location deviants that began at around 250 msec and closely resembled the behavioral gradient of target detections.     

Response-monitoring dysfunction in schizophrenia: An event-related brain potential study.

Error-monitoring abnormalities may underlie positive symptoms of schizophrenia. Response-synchronized event-related potentials during picture-word matching yielded error- and correct-response-related negativity (ERN, CRN) and positivity (Pe, Pc) and preresponse lateralized readiness potentials (LRP) from 18 schizophrenic patients and 18 controls. Both groups responded faster to matches than nonmatches, although patients were generally slower and made more errors to nonmatches. Compared with controls, patients, particularly with paranoid subtype, had smaller ERNs and larger CRNs, which were indistinguishable. LRPs showed evidence of more response conflict before errors than before correct responses in controls but not patients. Despite ERN/CRN abnormalities, post-error slowing and Pe were normal in patients, suggesting a dissociation of ERN and error awareness. Anterior cingulate and dorsolateral prefrontal cortical dysfunction in schizophrenia are implicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The organization of multidimensional selection on the basis of color and shape: an event-related brain potential study

In this paper, we examine whether color and shape, tied to a single object in space, (1) are identified and selected in series or in parallel, (2) are identified and selected in a dependent, self-terminating manner or in an independent and exhaustive manner, and (3) are conjoined by a feature integration process before or only after an initial stage of separate attribute analyses has finished. We measured response time and the selection negativity (SN) derived from event-related brain potentials when participants responded to a unique conjunction of color and shape in a go/no-go target detection task. The discriminability of the color and the shape of the conjunction was manipulated in three conditions. When color and shape were easy to discriminate, the SNs to color and shape started at the same time. When one attribute was less discriminable the SN to that attribute started later, but not the SN to the complementary attribute. This suggests that color and shape are identified and selected in parallel. In all three discriminability conditions, the SNs to color and shape were initially independent but later interacted. This suggests that color and shape are initially selected independently and exhaustively, after which their conjunction is analyzed. The SN to local shape features started later than that to the conjunction of color and global shape features, which suggests that feature integration can start before the analyses of the separate attributes have finished.     

The many facets of repetition: a cued-recall and event-related potential analysis of repeating words in same versus different sentence contexts

Event-related potential (ERP) and cued-recall performance were used to investigate the influence of (a) context, (b) repeating a word's meaning to word repetition priming, and (c) repetition on the ERP difference related to memory (Dm). Sentences ended with either nonhomographs or homographs. For nonhomographs, either the sentence context, the final word, both, or neither were repeated. Homographs were repeated in their original context or in new sentences that biased the same or an alternative meaning. Large repetition effects were found for all words repeated in their original contexts; in contrast, changing contexts led to no repetition effects whether the meaning of the repeated words was preserved or not. These results favor an episodic contribution to word repetition priming and suggest a common process for Dm and repetition.     

An event-related potential examination of masked and unmasked repetition priming in Alzheimer's disease: Implications for theories of implicit memory.

Fifteen patients diagnosed with Alzheimer's disease (AD) and 26 matched older controls engaged in a lexical-decision task with a list of words and nonwords while event-related brain potentials (ERPs) were recorded. Two repetition conditions were embedded in the list: words repeated at relatively long lags or words repeated shortly after a brief masked presentation. Although older controls displayed behavioral and ERP repetition priming for words repeated at long lags, consistent with previous studies, AD patients displayed neither. In contrast, both controls and AD patients displayed an ERP repetition priming effect for words repeated shortly after a brief masked presentation. ERP priming effects for masked and unmasked repetition differed in older controls, and additionally, the ERP masked priming effect differed between controls and AD patients. Results are discussed in the context of studies that have examined memory performance in brain-damaged populations using an impaired-intact dichotomy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stages of auditory feature conjunction: An event-related brain potential study.

Auditory event-related brain potentials (ERPs) were recorded to tones of different frequencies and locations in a dichotic selective attention task in which Ss responded to occasional deviant tones of a prespecified location and frequency. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no attended features from ERPs to the same tones when they shared target frequency, location, or both cues. The N1/P90 (latency 80–200 msec), originating in a tonotopically organized generator, was enhanced for all tones in the attended ear. Nd waves, beginning at 80 msec and lasting up to 700 ms, were seen to tones with either attended feature. Nd waves to frequency and location features had different scalp distributions consistent with generation in different cortical fields. Conjunction-specific Nds began 30–50 msec after Nds to individual features. The relative timing suggests that feature conjunction began before the analysis of individual features was complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased attention for computer-tailored health communications: An event-related potential study.

The authors tested whether individually tailored health communications receive more attention from the reader than nontailored health communications in a randomized, controlled trial among student volunteers (N = 24). They used objective measures of attention allocation during the message exposure. In a between-subjects design, participants had to read tailored or nontailored nutrition education messages and at the same time had to pay attention to specific odd auditory stimuli in a sequence of frequent auditory stimuli (odd ball paradigm). The amount of attention allocation was measured by recording event-related potentials (ERPs; i.e., N100 and P300 ERPs) and reaction times. For the tailored as opposed to the nontailored group, results revealed larger amplitudes for the N100 effect, smaller amplitudes for the P300 effect, and slower reaction times. Resource allocation theory and these results suggest that those in the tailored group allocated more attention resources to the nutrition message than those in the nontailored group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain systems mediating aversive conditioning: an event-related fMRI study

We have used event-related functional magnetic resonance imaging (fMRI) to characterize neural responses associated with emotional learning. Employing a classical conditioning paradigm in which faces were conditioned by pairing with an aversive tone (US), we compared responses evoked by conditioned (CS+) and nonconditioned (CS-) stimuli. Pairing 50% of the CS+ with the US enabled us to constrain our analysis to responses evoked by a CS+ not followed by a US. Differential evoked responses, related to conditioning, were found in the anterior cingulate and the anterior insula, regions with known involvement in emotional processing. Differential responses of the amygdalae were best characterized by a time by stimulus interaction indicating a rapid adaptation of CS+-specific responses in this region.     

Memory function in aging and Parkinson''s disease--an event-related potential study]

PURPOSE: Though case management has been recommended to improve the outcomes of patients with costly or morbid conditions, it has seldom been studied in controlled trials. We performed a randomized, controlled clinical trial of an intensive, multidisciplinary case management program for patients with chronic renal insufficiency and followed patients for 5 years. PATIENTS AND METHODS: We enrolled 437 primary-care patients (73% of those eligible) with chronic renal insufficiency (estimated creatinine clearance consistently < 50 mL/min with the last serum creatinine level > 1.4 mg/dL) who were attending an urban academic general internal medicine practice. The intensive case management, administered during the first 2 years after enrollment, consisted of mandatory repeated consultations in a nephrology case management clinic staffed by two nephrologists, a renal nurse, a renal dietitian, and a social worker. Control patients received usual care. Primary outcome measurements included serum creatinine level, estimated creatinine clearance, health services use, and mortality in the 5 years after enrollment. Secondary measures included use of renal sparing and potentially nephrotoxic drugs. RESULTS: There were no differences in renal function, health services use, or mortality in the first, second, or third through fifth years after enrollment. There were significantly more outpatient visits among intervention patients, mainly because of the added visits to the nephrology case management clinic. There were also no significant differences in the use of renal sparing or selected potentially nephrotoxic drugs. The annual direct costs of the intervention were $89,355 ($484 per intervention patient). CONCLUSION: This intensive, multidisciplinary case-management intervention had no effect on the outcomes of care among primary-care patients with established chronic renal insufficiency. Such expensive and intrusive interventions, despite representing state-of-the-art care, should be tested prospectively before being widely introduced into practice.     

Improvement predictors in obsessive-compulsive disorder. An event-related potential study

The maturation of HIV-1 virions is accomplished through the proteolytic cleavage of Gag and GagPol precursor polyproteins by the viral-encoded protease (PR). Since virions are assembled from unprocessed polyproteins, the intracellular activation of PR must be limited. An experimental system was established that allows the investigation of the intracellular regulation of PR activity. By expressing Gag in trans with the GagPol precursor, downregulation of the intracellular PR activity associated with GagPol was demonstrated. Inhibition of PR activity was dependent upon the context of PR expression. Sequences capable of mediating this inhibition were localized to capsid. A mechanism through which Gag regulates PR activity is proposed whereby the disproportionate synthesis of Gag inhibits the activation of PR in the cytoplasm. Further elucidation of the mechanism of intracellular inhibition of PR activity may facilitate the development of novel PR inhibitors capable of inhibiting viral replication in vivo.     

An event-related potential study of sensory representations of unfamiliar tonal patterns

The results of the dexamethasone test were compared with the depression depth and pain intensity in patients with low back pain caused by degenerative changes and/or disc prolapse. In the light of these studies no correlation was demonstrated between the positive results of the dexamethasone test and depression symptoms and the intensity and duration of pain.     

Effects of inter- and intramodal selective attention to non-spatial visual stimuli: an event-related potential analysis

Event-related potentials (ERPs) were recorded to trains of rapidly presented auditory and visual stimuli. ERPs in conditions in which subjects attended to different features of visual stimuli were compared with ERPs to the same type of stimuli when subjects attended to different features of auditory stimuli. This design permitted us to study effects of variations in both intramodal and intermodal visual attention on the timing and topography of ERP components in the same experiment. There were no indications that exogenous N110, P140 and N180 components to line gratings of high and low spatial frequencies were modulated by either intra- or intermodal forms of attention. Furthermore, intramodal and intermodal attention effects on ERPs showed similar topographical distributions. These combined findings suggest that the same neural generators in extrastriate occipital areas are involved in both forms of attention. Visual ERPs elicited in the condition in which subjects were engaged in auditory selective attention showed a large positive displacement at the occipital scalp sites relative to ERPs to attended and unattended stimuli in the visual condition. The early onset of this positivity might be associated with a highly confident and early rejection of the irrelevant visual stimuli, when these stimuli are presented among auditory stimuli. In addition, the later onset of selection potentials in the intramodal condition suggests that a more precise stimulus selection is needed when features of visual stimuli are rejected among other features of the same stimulus pattern, than when visual stimuli are rejected among stimuli of another modality.     

An event-related potential study of age-related changes in sensitivity to stimulus deviance

The mismatch negativity (MMN) of the event-related (brain) potential (ERP) has been shown to reflect the storage of information in sensory memory and is thought to reflect the operation of a mechanism that compares frequently occurring standard with infrequently occurring deviant acoustic events. The MMN was recorded from young (mean = 23 years) and elderly (mean = 72 years) adults to small (50 Hz) and large (300 Hz) frequency deviants and to a variety of novel, environmental sounds. At each level of deviance, MMN amplitude was smaller in the ERPs of older relative to younger adults. Young, but not older adults showed robust MMNs at the smallest level of deviance. Moreover, a P3 component was observed in the ERPs of the young to both large tonal and novel deviants, whereas a robust P3 component was evident only to the novel deviants in the ERPs of the old. The data suggest that older adults demonstrate less sensitivity to stimulus deviance and that only highly deviant events are likely to involuntarily capture their attention.