Tonic pain grabs attention, but leaves the processing of facial expressions intact-evidence from event-related brain potentials

Emotion and attention are key players in the modulation of pain perception. However, much less is known about the reverse influence of pain on attentional and especially emotional processes. To this end, we employed painful vs. non-painful pressure stimulation to examine effects on the processing of simultaneously presented facial expressions (fearful, neutral, happy). Continuous EEG was recorded and participants had to rate each facial expression with regard to valence and arousal. Painful stimulation attenuated visual processing in general, as reduced P100 and late positive potential (LPP) amplitudes revealed, but did not interfere with structural encoding of faces (N170). In addition, early perceptual discrimination and sustained preferential processing of emotional facial expressions as well as affective ratings were not influenced by pain. Thus, tonic pain demonstrates strong attention-demanding properties, but this does not interfere with concurrently ongoing emotion discrimination processes. These effects point at partially independent effects of pain on emotion and attention, respectively.     

Visual evoked potentials in humans during recognition of emotional facial expressions

Visual evoked potentials were recorded from the occipital, parietal, central, frontal, and posterior temporal areas of the cortex during recognition of emotionally positive, negative and neutral facial expressions and during passive observation in 22 right-handed healthy subjects. These studies showed that in the posterior temporal areas, the latencies of the N90, P150, and N180 waves of potentials evoked by faces with emotionally negative expressions were significantly shorter than those evoked by other types of facial stimuli. Differences were seen both on recognition and during passive observation. Correct recognition involved both hemispheres and was characterized by high levels of interhemisphere temporal correlation of the processes occurring during the development of the P150 wave in the posterior temporal and the N180 wave in the frontal parts of the cortex. The possible relationship of these data to primary subthreshold recognition of facial expressions in the posterior temporal fields of the cortex is discussed, as is the role of the frontal cortex in completing this process and in taking the correct decision about the nature of the image. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 48, No. 5, pp. 797–806, September–October, 1998.     

Impact of cerebellar lesion on syntactic processing evidenced by event-related potentials

In concern to the uncertain neural signature of the cerebellum in syntax processing, we investigated the Syntactic Positive Shift (SPS) for sentences with syntax violations in patients with cerebellar damage. In opposite to controls, patients showed no SPS around 300-650ms for syntax violations. Interestingly, Minimum-Norm analysis of SPS revealed increased activity in supramarginal and homologous Broca area for syntax violations in patients with cerebellar infarction. Overall, our findings support the still growing knowledge of the involvement of the cerebellum in cerebral networks in syntactic processing as evidenced by a sensitive ERP component.     

Topography of event-related potentials elicited by visual emotional stimuli

This experiment was intended to explore the effects of the emotional connotation of stimuli on the hemispheric lateralization. Ten right-handed male subjects (Ss) were presented a set of slides of faces expressing a positive emotion, a negative emotion or emotional neutrality. The ERPs elicited by the face stimuli were recorded from 16 leads and topographic maps of P3 amplitude were created. The results show that when Ss had to discriminate between emotional (target) and neutral (non-target) faces, the main differences were seen predominantly over the right centroparietal area. On the contrary, when Ss had to detect a face particularity not related to the emotional content, the differences betweem target and non-target faces were bilaterally distributed. The present results support the hypothesis that the perception of emotional expressions is processed mainly by the right hemisphere.     

Attention modulates auditory pattern memory as indexed by event-related brain potentials

The role of selective attention on auditory pattern processing was investigated using the mismatch negativity, an event-related brain potential component associated with sensory memory. Participants responded to changes in an alternating tone pattern in a designated ear while a similar auditory pattern was presented in the opposite ear. Participants were also presented with the same sequences while reading a book (no response required). In all conditions, changes in the pattern elicited a mismatch negativity (MMN) that peaked at 160–220 ms poststimulus. MMN amplitude varied with attention: the amplitude was higher in response to deviant stimuli presented in the attended ear than to the deviant stimuli presented in the unattended ear or during reading. The results show that selective attention modulates auditory pattern memory.     

Hemispheric perception of emotional valence from facial expressions.

The authors previously reported that normal subjects are better at discriminating happy from neutral faces when the happy face is located to the viewer's right of the neutral face; conversely, discrimination of sad from neutral faces is better when the sad face is shown to the left, supporting a role for the left hemisphere in processing positive valence and for the right hemisphere in processing negative valence. Here, the authors extend this same task to subjects with unilateral cerebral damage (31 right, 28 left). Subjects with right damage performed worse when discriminating sad faces shown on the left, consistent with the prior findings. However, subjects with either left or right damage actually performed superior to normal controls when discriminating happy faces shown on the left. The authors suggest that perception of negative valence relies preferentially on the right hemisphere, whereas perception of positive valence relies on both left and right hemispheres.     

Schizophrenic patients show facial reactions to emotional facial expressions

Facial reactions in schizophrenic patients were assessed via electromyography (EMG) in response to pictures of facial expressions. Male patients and nonpatient controls viewed photographs of positive and negative facial expressions while EMG activity from the corrugator and zygomatic muscle regions was recorded. Both schizophrenic patients and controls exhibited greater zygomatic reactivity in response to positive pictures than in response to negative pictures and greater corrugator reactivity in response to negative pictures than in response to positive pictures. Schizophrenic patients exhibited greater corrugator reactivity than did nonpatient controls. Implications for understanding emotion expression and perception in schizophrenic patients are discussed.     

Sex differences in brain maturation as measured using event-related potentials

Little is known about how sex influences functional brain maturation. The current study investigated sex differences in the maturation of event-related potential (ERP) amplitudes during an auditory oddball task (N = 170; age = 6-17 years). Performance improved with age. N200 amplitude declined with age: parietal sites showed earlier development than temporal and frontal locations. Girls showed greater bilateral frontal P300 amplitude development, approaching the higher values observed in boys during childhood. After controlling for age, right frontal P300 amplitude was associated with reaction time in girls. The findings demonstrate sex differences in ERP maturation in line with behavioral and neuroimaging studies.     

Early semantic context integration and lexical access as revealed by event-related brain potentials

A late neurophysiological response, the N400, is well known to reflect word processing and semantic context integration. Nevertheless, behavioural and neurophysiological data have demonstrated that word features and semantic sentence context influence linguistic processes already within the first 200 ms following the onset of the critical word stimulus. The lack of early word-related ERP effects in some studies might be due to large stimulus variance on relevant linguistic parameters, for example the length of written words or their frequency of usage. Here we investigated the effect of the length of words, their standardized lexical frequency and probability to occur in a given semantic context, by orthogonally varying these factors in a sentence-reading task. We found word frequency and probability to be reflected neurophysiologically already at 120 and 180 ms after written word onset. However, at these early stages frequency and probability effects were modulated by word length, as documented by significant interactions, whereas at later stages, around 300-500 ms, additive effects of these variables were found. These results indicate that semantic context integration may take place at a surprisingly early stage and near-simultaneously with the processing of information about the form of a word and its lexical properties, therefore challenging serial models of psycholinguistic information access. A methodological implication of this study is that, in order to obtain early psycholinguistic ERP effects, stimulus variance must be kept to a minimum.     

Sentence verification and event-related brain potentials

The purpose of this study was to examine whether the decision process affected scalp recorded event-related brain potentials (ERPs). ERPs were recorded while 10 subjects evaluated the veracity of four types of Japanese sentences; true-affirmative (TA), true-negative (TN), false-affirmative (FA), and false-negative (FN). Each sentence was presented visually, one word at a time in the following order: Subject (S); object (O); and verb (V). This order of words, which is normal in Japanese grammar, allowed the ERP waveforms associated with semantic mismatch between the S and O occurring in the middle of the sentence to be separated from those elicited by the decision concerning the sentence's truth or falsity occurring at the end of the sentence. Semantic mismatch was associated with a negative component (N310) following the O-word. In addition, P3s were elicited by sentence final words. Affirmative sentences elicited larger P3s than did negative sentences, and true sentences elicited earlier P3s than did false sentences. P3s were smaller in amplitude when they followed a mismatch between the S and O words. The result suggested that by using Japanese sentences, it may be possible to examine sentence-level rather than word-level processes.     

Innovations in neuropsychological assessment using event-related brain potentials.

Historically, clinicians have utilized evoked potentials for evaluating sensory functions and neuropsychological tests for evaluating cognitive functions. However, the clinical implementation of event-related brain potentials (ERPs), an on-line index of cognitive processing, remains to be developed fully. We describe a new method for assessing language functions using neuropsychological tests that are formatted for computer presentation with simultaneous ERP recordings. From its inception, there have been two major objectives of this ERP language assessment research. Practically, we have sought to develop assessment techniques that would enable clinicians to evaluate the language functions of individuals with limited behavioral and communicative abilities. Conceptually, we have endeavored to increase the precision of neuropsychological testing through the development of measures that are sensitive to readily identifiable and objective neural responses. This article summarizes the issues central to the development of ERP assessment techniques, reviews recent normative studies with healthy individuals, and suggests some future avenues of research in this area.     

Recognition of affective prosody: continuous wavelet measures of event-related brain potentials to emotional exclamations

The affective state of a speaker can be identified from the prosody of his or her speech. Voice quality is the most important prosodic cue for emotion recognition from short verbal utterances and nonverbal exclamations, the latter conveying pure emotion, void of all semantic meaning. We adopted two context violation paradigms-oddball and priming-to study the event-related brain potentials (ERP) reflecting this recognition process. We found a negative wave, the N300, in the ERPs to contextually incongruous exclamations, and interpreted this component as analogous to the well-known N400 response to semantically inappropriate words. The N300 appears to be a real-time psychophysiological measure of spontaneous emotion recognition from vocal cues, which could prove a useful tool for the examination of affective-prosody comprehension. In addition, we developed a new ERP component detection and estimation method that is based on the continuous wavelet transform (CWT), does not rely on visual inspection of the waveforms, and yields larger statistical difference effects than classical methods.     

Memory and event-related potentials for rapidly presented emotional pictures

Dense array event-related potentials (ERPs) and memory performance were assessed following rapid serial visual presentation (RSVP) of emotional and neutral pictures. Despite the extremely brief presentation, emotionally arousing pictures prompted an enhanced negative voltage over occipital sensors, compared to neutral pictures, replicating previous encoding effects. Emotionally arousing pictures were also remembered better in a subsequent recognition test, with higher hit rates and better discrimination performance. ERPs measured during the recognition test showed both an early (250–350 ms) frontally distributed difference between hits and correct rejections, and a later (400–500 ms), more centrally distributed difference, consistent with effects of recognition on ERPs typically found using slower presentation rates. The data are consistent with the hypothesis that features of affective pictures pop out during rapid serial visual presentation, prompting better memory performance.     

Visual emotional context modulates brain potentials elicited by unattended tones.

To examine whether brain electrical responses to environmental stimuli were influenced by emotional contexts, event-related potentials (ERPs) elicited by nonstartle probe tones were recorded from 13 student volunteers while they were viewing emotionally positive, neutral, and negative slides of the International Affective Picture System. The auditory stimuli consisted of high-deviant (2000 Hz, p=.08), low-deviant (1050 Hz, p=.08), and standard (1000 Hz, p=.84) tones with a mean onset-to-onset interval of 600 ms. Participants were told to ignore the tones. High-deviant tones elicited a larger N1 (peaking around 100 ms) when participants were viewing negative slides than when viewing positive slides. The amplitude of the P2 elicited by standard tones (peaking around 170 ms) was smaller when participants were viewing positive slides than when viewing negative and neutral slides. The amplitude of the mismatch negativity (150-200 ms) tended to reduce during positive slide presentation, but this difference appeared to be due to reduction of the P2 elicited by standard tones. These findings suggest that visually induced emotional states have a sequential effect on auditory information processing, in that the influence of negative emotion appears at an earlier stage than that of positive emotion.     

Monitoring retrieval from long-term memory by slow event-related brain potentials

Slow event-related brain potentials of nine subjects were recorded in an experimentally controlled long-term memory retrieval task (the Fan paradigm) from electrode sites F3, Fz, F4, Cz, P3, Pz, and P4. In all retrieval conditions, a very pronounced DC-like negative potential appeared over the left frontal cortex. This negativity was switched on with the presentation of the probe stimuli and prevailed in some conditions throughout the total recording epoch of 14 s. Particular retrieval conditions became manifest in distinct slow wave effects. The amplitude of a bilaterally distributed frontal negative slow wave increased when a more diversified associative structure had to be searched. The amplitude of another negative slow wave, which peaked bilaterally over parietal areas, was affected by the type of concepts that had to be retrieved. The amplitude was larger with general concepts (category labels) and smaller with specific concepts (category exemplars). These results suggest that distinct strategies are invoked when subjects are required to draw conclusions about different contents stored permanently in an associative network.     

Perceptual interactions between visual processing of facial familiarity and emotional expression: An event-related potentials study during task-switching

Models of face processing suggest that facial familiarity and expression processes involve independent visual systems. But under some conditions, the two processes interact, as when selective attention is solicited, and/or when a link is established between consecutive stimuli. To assess these assumptions during perceptual face processing, event-related potentials (ERPs) were used while subjects discriminated either familiarity or expression in a task-switching paradigm. Switched trials were designed with competitor priming, the unattended dimension being previously attended. The results indicate interactions appearing in the right hemisphere during the perceptual encoding stage (N170) when subjects processed either familiarity or expression during switched trials. These interactions gain both hemispheres during memory retrieval (P2) and in terms of accuracy. Altogether, these results confirm the critical role of the right hemisphere in perceiving faces and their expressions. Moreover, they suggest that familiarity and expression can interact in both directions.     

Time effects on event-related brain potentials and vigilance performance.

A review of the literature showed that in vigilance or oddball tasks, changes over time in event-related potentials (ERPs) and performance measures often seem to be unrelated, but a number of studies had some shortcomings. In the present study a visual vigilance experiment was carried out, in which single-trial ERPs and performance data of 40 males were obtained. A relationship between time trends in behavioral and ERP measures was found: an early P3 amplitude and response latency (RT) showed an inversely varying relation over time. Analysis of covariance showed that the two linear trends tap the same aspect of processing: both trends became insignificant when adjusted for common variance. A negative correlation between mean values of P3 amplitude and RT rather than for change scores has been observed in previous studies, but has been ignored in the literature. However, correlations with RT have also been reported for other ERP deflections. Although there were several correlations between mean scores, most time-induced changes in ERP parameters appeared to be unrelated to worsening performance, for which several explanations are advanced. The ERP results do not support the hypothesis that a decrement in performance is caused by increasing difficulty discriminating targets from nontargets. A gradual decline in effort or resources allocated to the task might be an alternative explanation of performance deterioration. However, an effort-hypothesis cannot easily be tested. Effort is often invoked post hoc, and has previously been associated with many ERP components. The relationship between ERPs and the signal detection measures "sensitivity" d' and "response bias" beta is discussed.     

Phonological priming and auditory event-related brain potentials

Phonological priming effects on auditory event-related brain potentials were compared across different numbers of syllables shared between target words and preceding prime words or pseudowords. All items of words and pseudowords consisted of 3 syllables, and the subject's task was to make a judgment whether the item belonged to a designated category. A large negative wave (N400), commencing at about 250 ms poststimulus and lasting for about 700 ms, was observed irrespective of primes and targets. When targets were preceded by word-primes that shared the first one or two syllables, the onset of N400 at the frontal site was earlier and the initial negative-going phase was steeper than in other conditions. In contrast, the magnitude of N400 to targets was reduced, when the primes were pseudowords that shared the first two syllables. These two types of early and later phonological priming effects were interpreted to reflect facilitations during spoken word recognition at the pre-lexical (phonological) and post-lexical (semantic or contextual integration) levels, respectively.     

Modulation of cognitive processing by emotional valence studied through event-related potentials in humans

This experiment investigated whether the emotional content of a stimulus could modulate its cognitive processing. Particularly, we focused on the influence of the valence dimension on the cognitive processing triggered by a non emotional oddball task. To this end, event-related potentials (ERPs) were recorded from 25 sites during a visual oddball paradigm. Three sets of pictures (unpleasant, neutral and pleasant) with low arousal values served as rare target items. Subjects were simply asked to realize a standard/target categorization task, irrespective of the picture valence. A temporal principal component analysis allowed us to identify several evoked components (i.e. P1, P2, N2, P3a and P3b). Emotional effects observed on P1, P2 and P3b showed that the valence content of the stimulus modulates the cognitive processes at several points in the information processing stream.     

Habituation of the orienting response as reflected by the skin conductance response and by endogenous event-related brain potentials.

The paper is concerned with the question of whether endogenous components of the auditory event-related brain potential (ERP) qualify for showing habituation of the orienting response (OR). Although response decrements have been found in nearly every ERP component, this question is still of current concern because a true selective response inhibition proving habituation of the OR is still lacking. The question has been tackled using single-trial ERP measurements in classical variants of the repetition/change paradigm commonly used in the traditional OR research on autonomous responses such as the skin conductance response (SCR). Results on 120 adults indicate that at least two endogenous components of the ERP, an anterior slow negative wave and a posterior slow positive wave, meet essential requirements of habituation: like the exemplary OR component, the SCR, both slow waves declined systematically with repeated stimulations and, more than that, recovered in response to fundamental changes. In the same way, an anterior positivity resembling the novelty P3 levelled off systematically with the stimulations, but without showing recovery. Thus, in so far as habituation of the OR is conceptualised as a selective inhibitory central nervous system process which can be assumed to have taken place only if a systematic (usually exponential) response decrement is followed by a recovery, the generalised decrement of the P3 cannot be equated with habituation, whereas the selective response diminution of both slow waves would have to be regarded as typical of habituation.