ERP Modules Research Articles

Correlates of implicit memory for words and faces in event-related brain potentials

Prior research has suggested an ERP correlate of implicit memory for words consisting of a centro-parietal positivity around 400 ms. We attempted (1) to replicate this ERP modulation in a different task, involving only trials with correct responses, and (2) to compare the findings to the domain of faces. Two experiments were conducted with a modified Sternberg task, in which both targets and nontargets were presented repeatedly. In Experiment 1, positive ERP differences between repeated and new nontargets were observed, which were domain-specific in topography and, for words, replicated the previously reported findings. In Experiment 2, the amplitude of the modulation for words, but not for faces, was unaffected by a variation of the level of processing during encoding, supporting the implicitness of the processes underlying the ERP modulation to nontarget words.

Crossmodal links in spatial attention are mediated by supramodal control processes: Evidence from event‐related potentials

Crossmodal links in spatial attention were studied in an experiment where participants had to detect peripheral tactile or visual targets on the attended side, while ignoring all stimuli on the unattended side and in the currently irrelevant modality. Both relevant locations and relevant modalities were specified on a trial‐by‐trial basis by auditory precues. Spatial orienting in the cue–target interval was reflected in anterior negativities and occipital positivities contralateral to the cued side, either when vision or touch was cued as relevant. These effects resembled previously reported ERP modulations during shifts of visual attention, implicating supramodal mechanisms in the control of spatial attention and demonstrating their independence of cue modality. Early effects of spatial attention on somatosensory and visual ERPs were of equivalent size for currently relevant and irrelevant modalities. Results support the idea that crossmodal links in spatial attention are mediated by supramodal control mechanisms.

Theoretical and methodological implications of variability in infant brain response during a recognition memory paradigm

Previously published reports have sought to elucidate the development of visual recognition memory in the human infant by investigating the modulation of infant ERPs by a familiar and novel face (e.g., de Haan & Nelson, 1997, 1999). Variability in infants’ brain responses elicited under the same mnemonic condition, however, has not been previously examined. The present report undertook two separate analyses in order to examine two kinds of variability: variability in the brain’s response to a stimulus over time as a function of stimulus repetition, and variability in the brain’s response between subjects as a function of the total number of trials completed in an ERP session. There were three major findings: (a) the mid-latency negative component (Nc) and long-latency slow wave (SW) were found to dissociate cognitive processes associated with familiarity from processes associated with stimulus repetition, (b) individual differences in the number of trials an infant completes in an ERP session were observed to be associated with differences in the amplitude and latency of the Nc, and (c) individual differences in the number of trials an infant completes appear to reflect differences in the extent to which the familiar and novel faces are encoded. The implications of these results are discussed with respect to models of habituation and preferential looking, infant ERP methodology, and developmental processes.

Application Service Providers: Will They Succeed?

This article examines the likelihood of success for application service providers (ASP) drawing from the outsourcing literature, interviews with ASPs in the USA, and the experience of Bennett who has held leadership roles in ASP and ERP in South East Asia. This article proposes that application service providers (ASP) rent packaged software, predominantly over the Internet. It shows why organizations might employ the ASP model to manage their enterprise resource planning systems. Using a framework adapted from Lacity and Hirschheim, it demonstrates that the financial, business, technical and political reasons why organizations evaluate outsourcing can be applied to ASP model. While ASPs generally target the mid-market, large enterprises are also using ASPs to introduce new ERP modules. Potential users of ASP should regard the risks of outsourcing prior to entering into business arrangements. This examination concludes that there are strong financial and technical reasons for adopting the ASP model and therefore it has potential to succeed.

The Effect of Cholinergic Receptor Blockade by Scopolamine on Memory Performance and the Auditory P3

Abstract Previous research has suggested a possible link between the effects of scopolamine-induced muscarinic cholinergic receptor blockade on memory and its effect on auditory P3 amplitude and latency. A potential problem with this hypothesis is that, although scopolamine has been reported to increase P3 latency in both visual and auditory modalities, amplitude reductions have been reported only in the case of auditory P3 at Cz. In the present study, subjects were injected intravenously with 5.7 μg/kg of scopolamine or saline in a double blind design. A significant reduction in verbal recognition memory performance was observed. This memory impairment was shown to be largely specific to the encoding of verbal material. The drug effect was of equal magnitude when words of either high or low word frequency were used. Auditory P3 was recorded from frontal central and parietal sites along the midline and over left and right hemispheres. In contrast to a number of earlier reports using a similar drug dose, only limited evidence was found of either latency increase or amplitude reduction of the auditory P3. Importantly, two potentially confounding drug-related ERP modulations were observed prior to and during the latency range of the P3. The first was a widespread increase in N2 amplitude and latency preceding the P3. The second was that ERPs became relatively more negative at frontal and central sites in the 200-450 ms latency range in both target and non-target conditions. Whether this effect is the result of an increase in negativity or a reduction in P3a amplitude remains to be determined. Interestingly, ERPs to target stimuli became significantly less positive at frontal sites in the drug condition in the latency range 400-900 ms. This is consistent with recent reports highlighting the importance of frontal regions in normal memory function. Previously hypothesized links between cholinergic receptor block ade, effects on P3 latency and amplitude, and drug-induced memory impairments are discussed in the light of these findings.

176 ERPS in locked-in patients

Prior research has suggested an ERP correlate of implicit memory for words consisting of a centro-parietal positivity around 400 ms. We attempted (1) to replicate this ERP modulation in a different task, involving only trials with correct responses, and (2) to compare the findings to the domain of faces. Two experiments were conducted with a modified Sternberg task, in which both targets and nontargets were presented repeatedly. In Experiment 1, positive ERP differences between repeated and new nontargets were observed, which were domain-specific in topography and, for words, replicated the previously reported findings. In Experiment 2, the amplitude of the modulation for words, but not for faces, was unaffected by a variation of the level of processing during encoding, supporting the implicitness of the processes underlying the ERP modulation to nontarget words.

Modulation of EEG Rhythmic Activities and ERPs Related to the Alternation of Binocular Rivalry and Binocular Fusion

Modulation of EEG Rhythmic Activities and ERPs Related to the Alternation of Binocular Rivalry and Binocular Fusion

Language-Related ERPs: Scalp Distributions and Modulation by Word Type and Semantic Priming

Abstract Event-related potentials (ERPs) were recorded from the scalp to investigate the processing of word stimuli. Three tasks were used: (1) a task comparing words that provided an anomalous or normal sentence ending, (2) a word-list task in which different word types were examined, and (3) a word-list task in which semantic priming was examined. ERPs were recorded from a 50-channel montage in an attempt to dissociate overlapping ERP features by their scalp distributions. The focus of these studies was the N400, an ERP previously associated with language processing (Kutas & Hillyard, 1980). The temporal interval typically associated with N400 (250-500 msec) was found to contain overlapping ERP features. Two of these features were common to both sentence and word-list tasks-but one appeared different. Anomalous sentence endings and words with semantic content in lists both showed coincident negative left frontotemporal and midline-anterior ERP foci, peaking at 332 msec for sentences and 316 msec for word lists. The most negative voltage obtained in the sentence task peaked at 386 msec and had a midline-posterior focus. A right frontotemporal focus developed after the midline-posterior focus and outlasted its duration. The most negative voltage for content words in lists was reached at 364 msec. The distribution of this ERP was extensive over the midline and appeared to differ from that observed in the sentence task. Modulation of language-related ERPs by word type and semantic priming was investigated using the word-list tasks, which required category-detection responses. Two novel findings were obtained: (1) The ERP distributions for words serving grammatical function and content words differed substantially in word lists. Even when devoid of any sentence context, function words presented significantly attenuated measures of N400 compared to content words. These findings support hypotheses that suggest a differential processing of content and function words. (2) Semantic priming functionally dissociated two ERP features in the 250-500 msec range. The later and most negative midline ERP feature (peaking at 364 msec) was attenuated by semantic priming. However, the earlier left frontotemporal feature (peaking at 316 msec) was enhanced by semantic priming. The isolation of this novel language-related ERF' that is sensitive to semantic manipulations has important consequences for temporal and mechanistic aspects of theories of language processing.

Event-related potential investigations of cognitive development and aging.

Comparison of the results of the studies of cognitive development and normal aging suggests a large degree of commonality in both behavioral and ERP effects across a wide age range. Whether measured in young children, adolescents, young, middle-aged or elderly adults, the size of the ERP repetition effect did not differ among the various age groups. This was true whether memory was tested directly during continuous recognition or indirectly during variants of semantic categorization tasks. Similarly, in the studies of adult aging, the degree of RT facilitation during the semantic task did not differ with age and, in both the studies of cognitive development and aging, the degree of RT prolongation during the explicit tasks did not appear to differ as a function of age. Moreover, in the studies of adult aging, the effects of three versus two exposures of a word assessed in the PM session (TABLE 1), modulated RT similarly in all three age groups. These data argue for continuity of information processing across a very wide age range during both direct and indirect memory tasks, when retention is assessed during the recognition (for explicit testing) and repetition (for implicit testing) phases of the task. Since ERP and RT modulation do not appear to differ with age during the retrieval phases of these experiments, how can the performance differential seen in young children and older adults be explained? Some evidence comes from the ERP data recorded during the study phases of our explicit tasks. During continuous recognition, both young children and elderly adults did not show the typical subsequent "memory effect." In the case of the children, the subsequently unrecognized ERP was larger than the subsequently recognized ERP, whereas for the older adults, there was no difference between these two ERPs. Moreover, during these same tasks, the young children did show the "crossover" (new greater than old) pattern for slow wave activity, whereas the older adults did not. Since these ERP findings were obtained during the acquisition phase (i.e., to new items that had to be encoded for subsequent retrieval), the data argue for encoding difficulties as one means of explaining the performance differences seen at the two ends of the age spectrum. However, since the older adults displayed a different new/old pattern for slow wave activity, the two age groups may differ qualitatively in the strategies employed to encode items for subsequent retrieval.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of early auditory processing during selective listening to rapidly presented tones

Two dichotic listening experiments were performed in which stimulus and task conditions were optimized for the early selection of inputs. Subjects listened selectively to sequences of rapidly presented tone pips in one ear while ignoring tone pips of a different pitch in the opposite ear. In both experiments, an enhanced positivity between 20 and 50 msec (the ‘P20–50’) was observed over central and frontal sites in the ERPs to the attended-channel tone pips. At longer latencies, the effects of attention appeared to include an amplitude modulation of several exogenous ERPs, including subcomponents of the central N1 (60–150 msec) and P2 (170–230 msec) waves and the temporal T complex (80–150 msec). In contrast, the attention effect prefrontally consisted of a broad negativity that appeared to be largely endogenous. A signal processing technique (Adjar) was employed to correct for distortion of mutually overlapping ERPs elicited by successive stimuli presented at short interstimulus intervals (ISIs). It was confirmed that the P20–50 attention effect was not the result of differential overlap from previous ERPs. In addition, this technique allowed an analysis to be made of the effects of the preceding stimulus type and ISI on the attention-sensitive ERPs, which provided further support for the view that highly focused selective attention can directly modulate exogenous components of the auditory ERP. Moreover, these sequence-dependent ERP modulations were paralleled by variations in target discrimination performance. Taken together, these results provide strong support for the early selection hypothesis that attention can serve to selectively bias or gate stimulus processing before full perceptual analysis has occurred.