Event-related potentials in the dorsal hippocampus of rats during an auditory discrimination paradigm

The relation of the hippocampal neuronal activity to the rat event-related potential (ERP) generation was examined during an auditory discrimination oddball paradigm. ERPs were recorded using a linearly-arranged series of electrodes chronically implanted at the skull, in the frontoparietal cortex, in the CA1 and CA3 regions of the dorsal hippocampus and in the thalamus. The target tone elicited N40, P100, N200, and P450 at the skull electrode. The non-target tone, on the other hand, prominently evoked only the P100 component. At the intracranial electrodes, the ERP amplitude at the latency of the skull P450 was significantly greater in the CA3 region than that at other recording sites, although a phase reversal was not observed. The results indicate that the P450 of the rat may correspond to the human P3, and that the neuronal activity in the hippocampus is involved in its generation.     

Event-related potentials at different stages of the operation of visual working memory

Trace fixation and comparison with incoming information was studied using event-related potentials (ERPs) recorded from various cortical areas during passive viewing and matching of two consecutive pictures. Visual stimuli differing in the spatial location of elements (4 × 4 square patterns with random positions of 4 black and 12 white squares) and phonological stimuli (differently written letters) were used. Trace fixation was studied by comparing the ERPs generated in response to the first (reference) stimulus in the pair with those generated during passive viewing. Sensory analysis of the reference stimuli was observed in the time interval 128–196 ms. For the patterns presented, it was reflected by an increased amplitude of the N1 component in the caudal areas as compared with passive viewing. The phonological stimuli produced a higher amplitude of a positive wave in the frontotemporal area in the same time interval. Processing of subsequent information to be stored in memory was observed in the interval 232–452 ms. Processing of patterns was reflected by a decreased positivity, most pronounced in the left temporo-parieto-occipital area. Comparison of a trace with incoming information was studied by comparing the ERPs generated in response to the first (reference) and second (test) stimuli. The number of cortical areas involved in the sensory analysis of the test stimuli was larger than the number involved in the analysis of the reference stimuli. Comparison of the new information with the trace was reflected by an increased amplitude of the late positive wave (components P3, Pc, and Pc-Nc) in the frontocentral and caudal cortical areas. The topographic changes in the late positive components depended on the type of stimulus.     

Event-related potentials to Italian spoken words

Forty-four right-handed volunteers were invited to listen to Italian 5-letter words of different kinds, including non-words, digitally recorded. Signals from 16 electrodes were averaged and displayed both as traces and maps. When the same word was monotonously delivered to the subject, a positive component at 340 ms was recorded following the N100–P200 complex. This potential was automatic, phonologically driven, independent of habituation, specific for verbal material and lateralized to the left side. By contrast, semantic tasks evoked bilateral N400, by using the oddball paradigm with different kinds of target stimuli, including non-words. The N400 duration was related to the task complexity. The late positive component was locked-in-time with the end of the words. Therefore, N400 reached its peak before the word completion. At that time the probability of recognition was 60%, progressively reaching 100% at the time of the late positive component. Intra- and interindividual variance was low. The findings indicates two different language processings: one is confined to the perisylvian regions of the left hemisphere in right-handed subjects and appears earlier, reflecting phonological processing, whereas the other one is bilateral and takes places when semantic judgments are going on. Event-related potentials during language processing appear to be a very useful tool, especially when EEG maps are displayed, giving us the information on both temporal and spatial events.     

Event-related auditory evoked potentials and multiple sclerosis

Long latency event-related auditory evoked potentials, particularly the P300 wave, constitute an objective electrophysiological index of cognitive function. For this reason, these potentials have been studied in a series of 101 patients with multiple sclerosis (MS), classified according to McAlpine's criteria into definite, probable and possible cases. The patients were also classified as depressed or non-depressed according to the DSM-III and Research Diagnostic Criteria. They were also subjected to a battery of psychometric tests.In the patient population the N200 and P300 latencies were increased, as were the P200 latencies, when compared with a control population. This electrophysiological pattern had previously been observed in other conditions characterised by subcortical lesions. Partial correlations (at constant disease duration) between the disability score and the cognitive deficit were found to be significant. Patients with an increased P300 latency had a greater disability and the P300 latency was significantly correlated with the duration of the illness.The N200 and P300 latencies were increased in depressed MS subjects, but this increase did not reach the level of significance. Depression was more frequent in the more severely handicapped patients. This suggests that the origin of the depression seen in multiple sclerosis is only partly organic, and that it is one of the factors contributing to the subcortical cognitive deficit in multiple sclerosis.Progressive forms of the disease exhibited the most profound cognitive deficit, and the most marked increase in P300 latency.     

Event-related potentials of human brain in spatial hearing

The review presents the data concerning auditory event-related potentials and their "mismatch negativity" component under conditions of stationary and moving sound source localization. Both free-field and dichotic experimental conditions are considered. The interhemispheric asymmetry of the brain responses elicited by the sound sources of various spatial properties is also discussed.     

Event-related potentials in schizotypal personality disorder and schizophrenia

The article analyzes event-related potentials in the Go/NoGo test of patients with schizophrenia and schizotypal personality disorder in relation to healthy subjects. Differences identified in the group of patients with schizophrenia are consistent with previous studies and indicate disruption in processes associated with different stages of visual information processing and executive functions. Specific features of brain activity in patients with schizotypal personality disorder were significantly less pronounced and presumably pointed to changes in the processes of attention redistribution and action monitoring. The results agree well with the clinical symptoms of schizophrenia and schizotypal personality disorder, so that this technique can be considered a possible additional diagnostic criterion for these disorders.     

Motor potentials evoked by paired cortical stimuli

We recorded the motor evoked potentials (MEPs) from the abductor pollicis brevis muscle, after supramaximal electrical transcranial stimulation, and studied the effect of paired transcranial shocks with varying interstimulus time intervals, in 10 normal subjects, 4 patients with median nerve neuropathy and 2 patients with motoneurone disease.In relaxed muscles the amplitude of the MEP evoked by a single shock averaged 30% of the M wave. With intervals from 1 to 2.5 msec 2 shocks evoked one MEP far larger in size than the control MEP (70% of the M wave). With intervals of 10 msec and longer, the 2 shocks evoked 2 independent MEPs; the size of the MEP following the second shock (test) was inversely correlated with the size of the control MEP: the more the control MEP approached the size of the M wave, the smaller the test MEP. Single motor unit records showed that, in the normal subjects and patients with peripheral neuropathy, the same motor unit was activated either by the first or the second shock, whereas in the patients with motoneurone disease it fired twice. In active muscles, the control MEP averaged 70% of the M wave. With intervals of 10 msec and longer the test MEP was markedly suppressed; with 100 msec intervals it fully recovered. In relaxed muscles, by delivering a double shock at a 1.5 msec interval, thus evoking a large MEP, followed by a second double-shock, the test MEP was completely suppressed for a period of 20 msec; it began to recover at 50 msec intervals and fully recovered after 150 msec.These results indicate that: (1) high-threshold spinal motoneurones can profit from temporal summation if double-shocks are delivered at short time intervals; (2) the synchronous excitation of the motoneuronal pool produced by transcranial stimulation is followed by a 20 msec period of absolute inhibition, possibly through a massive activation of the Renshaw system; (3) during voluntary contraction, only a portion of the motoneuronal pool remains refractory, possibly because of the enhanced spinal excitability.     

Auditory event-related potentials from a single-stimulus paradigm during rapid eye movement sleep

Sleep and Biological Rhythms - Auditory evoked potentials to a 2000-Hz pure tone were recorded in wakefulness and in rapid eye movement (REM) sleep. A late positive wave with a maximal amplitude...     

Event-related potentials elicited by social commerce and electronic-commerce reviews

There is an increasing interest regarding the use of electroencephalography (EEG) in social commerce and electronic commerce (e-commerce) research. There are several reviews in the field of social commerce or e-commerce; these have great potential value and mining them is fundamental and significant. To our knowledge, EEG is rarely applied to study these. In this study, we examined the neural correlates of social commerce reviews (SCRs) and e-commerce reviews (ECRs) by using them as stimuli to evoke event-related potentials. All SCRs were from friends through a social media platform, whereas ECRs were from strangers through an e-commerce platform. The experimental design was similar to that of a priming paradigm, and included 40 pairs of stimuli consisting of product information (prime stimulus) and reviews (target stimulus). The results showed that the P300 component was successfully evoked by SCR and ECR stimuli. Moreover, the P300 components elicited by SCRs had higher amplitudes than those elicited by ECRs. These findings indicate that participants paid more attention to SCRs than to ECRs. In addition, the associations between neural responses and reviews in social commerce have the potential to assist companies in studying consumer behaviors, thus permitting them to enhance their social commerce strategies.     

Event-related potentials study on cross-modal discrimination of Chinese characters

Event-related potentials (ERPs) were measured in 15 normal young subjects (18—22 years old) using the "cross-modal and delayed response" paradigm, which is able to improve inattention purity. The stimuli consisted of written and spoken single Chinese characters. The presentation probability of standard stimuli was 82.5% and that of deviant stimuli was 17.5%. The attention components were obtained by subtracting the ERPs of inattention condition from those of attention condition. The results of the N1 scalp distribution demonstrated a cross-modal difference. This result is in contrast to studies with non-verbal as well as with English verbal stimuli. This probably reflected the brain mechanism feature of Chinese language processing. The processing location of attention was varied along with verbal/non-verbal stimuli, auditory/visual modalities and standard/deviant stimuli, and thus it has plasticity. The early attention effects occurred before the exogenous components, and thus provided evidence support     

Event-related brain potentials during semantic categorization in normal aging and senile dementia of the Alzheimer's type

To assess the effects of normal aging and senile dementia of the Alzheimer's type (SDAT) on semantic analysis of words, we examined the N400 component of the event-related potential (ERP) elicited during the processing of highly constrained (opposites) and less constrained materials (category-category exemplars) in 12 young control subjects, 12 elderly control subjects and 12 patients with SDAT. We employed a priming paradigm in which a context phrase was spoken and a target word (congruent or incongruent) was presented visually. The N400 effect was reduced in amplitude and delayed in the elderly control group relative to that of the younger subjects, and was further attenuated in amplitude, delayed in latency and somewhat flatter in its distribution across the scalp in the SDAT patients. These findings are consistent with less efficient processing and integration of lexical items with semantic context in normal aging, which is further exacerbated by SDAT. Differences in the N400 range associated with the opposite and category conditions were observed only in the young subjects, suggesting less use of controlled attentional resources or perhaps weaker associative links with age.     

Event-related potentials in an auditory oddball situation in the rat

Evoked potentials were recorded from the auditory cortex of both freely moving and anesthetized rats when deviant sounds were presented in a homogenous series of standard sounds (oddball condition). A component of the evoked response to deviant sounds, the mismatch negativity (MMN), may underlie the ability to discriminate acoustic differences, a fundamental aspect of auditory perception. Whereas most MMN studies in animals have been done using simple sounds, this study involved a more complex set of sounds (synthesized vowels). The freely moving rats had previously undergone behavioral training in which they learned to respond differentially to these sounds. Although we found little evidence in this preparation for the typical, epidurally recorded, MMN response, a significant difference between deviant and standard evoked potentials was noted for the freely moving animals in the 100-200 ms range following stimulus onset. No such difference was found in the anesthetized animals.     

Event-related desynchronization (ERD) patterns during memory processes: effects of aging and task difficulty

Event-related desynchronization (ERD) was studied in 10 young (mean age = 19.1) and 10 older (mean age = 62.8) subjects during two recognition tasks: verbal and visuo-spatial. The difficulty of these tasks varied according to the difficulty to distinguish between targets and distractors. EEGs recorded from 29 electrodes were used to compute ERDs from 14 source derivations in 125 msec intervals. Thereafter, they were displayed as spatio-temporal maps. The results show that desynchronization was more widespread in the visuo-spatial compared to the verbal task. This was observed in the two age groups, although it was more pronounced in the young subjects. The effect of task complexity was also influenced by the kind of material to be remembered: more differences between the two levels of difficulty were observed during the verbal task.The results revealed significant influences of the task and time variables on the ERD patterns. A distinct time course of the desynchronization phenomenon was observed to be related to the kind of recognition task. Age and task complexity interacted with the other variables.     

Evoked potentials of the auditory cortex on paired stimuli

Changes in the responsiveness of the auditory cortex to an acoustic click and to direct stimulation of the medial geniculate body were studied by the method of evoked potentials in an extended experiment on cats with implanted electrodes. It is shown that the minimum interval between two stimuli for which a second click produces an EP in the auditory cortex is from 30 to 50 msec. The relative refractory period consists of two parts. The first (50–100 msec) is characterized by a rapid recovery, and the second (about 500 msec) by a slow recovery. In contrast with a click, direct stimulation of the geniculate body does not produce a refractory condition but one of facilitation. The effects of Nembutal and chloralose anesthesia and the state of alertness on the recovery of auditory cortex responsiveness were investigated. The reason for the absence and the reduction of an EP from the auditory cortex to a testing click during absolute and relative refractory periods is not a passive decrease of excitability of the usual refractory kind, but an active interplay of excitatory and inhibitory processes in the cerebral cortex, geniculate bodies, and reticular formation of the brain stem.A. A. Bogomolets' Institute of Physiology, Academy of Sciences, Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 54–64, July–August, 1969.     

Event-related potentials associated with a shift in the strategy of visual perception during recognition of a hierarchical stimulus

Recording of event-related potentials (ERPs) was used to study the brain mechanisms of shifting the strategy of recognition of the global and local levels of a hierarchical image by adult subjects. A shift in the strategy of visual recognition results in substantial changes in ERP parameters in the caudal and frontocentral cortical areas. The activation effect of the switchover from one recognition strategy to another is associated with an increase in the amplitude of early ERP components (C1, P100, and N150) of the caudal cortical areas. Changes in the late ERP components associated with processing of significant information features during the shift in the recognition strategy are observed in the frontal areas within the interval 388–579 ms, with the amplitude of components N300 and N400 increasing.     

Event-related potentials to faces: the effects of priming and recognition

Short-term visual memory, as in both implicit priming and explicit recognition tasks, can be demonstrated by decreased reaction times, the ability to preferentially select previously presented objects from lists and the ability to more readily complete previously exposed words from fragmented letters. The visual processing of faces occurs separately from the visual processing of non-face stimuli, within discrete areas of bilateral posterior inferotemporal cortices. While visual recognition and memory of faces are independent of those for non-faces, their processing appears to be similar. We have demonstrated an electrophysiologic correlate of short-term visual memory in a face-matching paradigm. We have observed a series of evoked potential components consisting predominantly of a C140, C180 and C240 with a posterior, bitemporal distribution. The priming effect is reflected by a diminution of C240 amplitude in the response to repeated pictures of faces compared to novel pictures of faces. These data reflect a previously unreported set of neurophysiological observations on short-term visual memory for faces.     

Event-related potentials to visually presented verbal stimuli in the examination stress condition

The work is aimed at the study of ERPs to visually presented verbal stimuli in the examination stress condition. EEG was recorded while participants made a decision whether or not visually presented words were related to a given category. Three types of stimuli were presented: familiar words related and unrelated to the given category, and unfamiliar words. Components N170, P170 and N400 of the ERP to familiar words unrelated to the given category and unfamiliar words were higher in the stress condition than in a usual experimental situation. Component P600 was higher in the stress condition for all types of stimuli. It was suggested that enhanced N170/P170 and N400 components reflect changes in the cognitive functions ofword processing, whereas the increase in P600 is related to nonspecific arousal in the stress condition.     

Operative memory and evoked visual potentials

Changes in human EEG and event-related potentials to the complex color stimulus were studied during performance of three cognitive tasks: passive viewing, visual searching, and memorizing and storing of the stimulus in the operative memory. It was shown that involvement of memory mechanisms resulted in the alpha rhythm suppression in both occipital and frontal brain areas. It was also accompanied by a generation of the slow positive component in the evoked potential recorded in the frontal areas (in the occipital areas this wave was manifested as negative).