Alessandro Angrilli

Visual evoked potentials, heart rate responses and memory to emotional pictorial stimuli

Although the effects of emotional stimuli on event-related cortical potentials, heart rate, and memory have been extensively studied, the association of these variables in a single study has been neglected. The influence of pleasant, unpleasant, and neutral photographic slides on visual evoked potentials (VEPs), heart rate responses, and free recall, was investigated in 20 normal subjects. VEPs were recorded from Cz and Pz locations, and analyses were performed on both amplitudes and latencies of identifiable endogenous peaks (P2, N2 and P3), and mean amplitude in the 100-200-ms, 400-600-ms, and 600-900-ms latency ranges. An emotional effect was present on VEPs starting from about 282 ms on, as revealed by the N2, P3, and late components. Both pleasant and unpleasant slides yielded larger cortical positivity as compared to neutral ones. Peak latencies did not show any emotional effect. Heart rate data showed a deceleratory response that was larger to unpleasant slides. Free recall of the projected slides showed a better performance for emotional slides compared to neutral ones. VEPs and memory data showed the same pattern: both pleasant and unpleasant slides induced larger positivity in the event-related potentials and were better remembered than neutral slides. Positive correlations were found between the late negative VEPs component (600-900 ms), recorded from Cz, and heart rate deceleration (r = 0.62), and between P3 (at Pz location) and the number of remembered slides (r = 0.53).

The influence of affective factors on time perception

Several studies have suggested that both affective valence and arousal affect the perception of time. However, in previous experiments, the two affective dimensions have not been systematically controlled. In this study, standardized photographic slides rated for emotional valence and arousal were projected to two groups of subjects for 2, 4, and 6 sec. One group of subjects estimated the projection duration on an analog scale, whereas the second group of subjects reproduced the intervals by pushing a button. Heart rate and skin conductance responses were also recorded during stimulus presentation as indices of attention and arousal. Time estimation results showed neither a main effect of valence nor a main effect of arousal. A highly significant valence × arousal interaction affected duration judgments. For low-arousal stimuli, the duration of negative slides was judged relatively shorter than the duration of positive slides. For high-arousal stimuli, the duration of negative slides was judged longer than the duration of positive slides. The same interaction pattern was observed across judgment modalities. These results are interpreted in terms of a model of action tendency, in which the level of arousal controls two different motivational mechanisms, one emotional and the other attentional.

Cardiac responses associated with affective processing of unpleasant film stimuli

The autonomic basis of cardiac reactions to unpleasant film stimuli was investigated. Film clips depicting major surgery, threats of violence, and neutral material were presented to 46 subjects. Self-report measures of emotion were obtained, as well as heart rate, respiration rate, respiratory sinus arrhythmia, T-wave amplitude and skin conductance level. Resting vagal tone was estimated in a paced breathing task prior to film viewing. Spontaneous blink rate was also taken as a measure of visual engagement during film viewing. Coherent increases in sympathetic activation accompanied the film containing violent threats, whereas the surgery film yielded greater electrodermal activation, as well as heart rate deceleration and T-wave increase. These data support the hypothesis of differential autonomic response patterns to specifically unpleasant material. As compared with threat and neutral films, greater blink rate inhibition was observed during the surgery film. Individual differences in parasympathetic cardiac control measured at rest were able to discriminate cardiac response patterns during film viewing.

Emotional Information Processing and Visual Evoked Brain Potentials

Visual evoked potentials to emotional slides presented for 2 sec. were investigated in 13 subjects. 73 emotional slides (pleasant, unpleasant, and neutral) were selected from a standardized set of photographic slides, the 1988 International Affective Picture System of Lang, Öhman, and Vaitl. Visual evoked potentials were recorded from three head locations, frontal, central and parietal (Fz, Cz, and Pz). Analyses were performed in the two latency ranges: 300–400 msec. and 400–500 msec. Analyses showed an arousal effect, as indicated by a quadratic trend, indicating that emotional slides (both pleasant and unpleasant) gave higher cortical positivity than neutral ones, for all components. In addition, in the two latency epochs, larger positivities were found at Pz, compared to Fz and Cz, whereas Fz and Cz did not differ from each other.

Differences in the perception and time course of syntactic and semantic violations.

A reading time and an ERP experiment conducted in Italian investigated the parsers responses to a syntactic violation (subject-verb number agreement) and to a semantic violation (subject-verb selectional restriction), examining the time course of comprehension processes until sentence end. The reading-time data showed that the syntactic violation was detected earlier than the semantic one and that the two violations differed in the time-course. The ERP data fully supported the reading time data: Syntactic anomalies elicited a left anterior negativity (LAN) and a P600. Semantic anomalies elicited a N400 centred on the parietal sites which started 90 ms later (latency 430 ms) than the LAN. Furthermore, the N400 evoked by the words that followed the target word continued and increased until sentence end. The results are discussed with respect to the hypotheses that the parser constructs distinct syntactic and semantic analyses of a sentence and that this characteristic holds cross-linguistically. The appropriateness of different methodologies to the study of sentence processing is also evaluated.

Emotional impairment after right orbitofrontal lesion in a patient without cognitive deficits.

The present study describes a patient, M.L., with right orbitofrontal lesion, who showed no impairment on main neuropsychological tests, including those measuring frontal functions. Nevertheless, he had deeply affected emotional responses. In line with Damasios work, the patient had lower skin conductance during the projection of a standardized set of emotional slides. Furthermore, he showed altered facial expressions to unpleasant emotions, displaying low corrugator supercilii electromyographical activity associated with reduced recall of unpleasant stimuli. During a task focusing on imagery of emotional situations, M.L.s heart rate and skin conductance responses were affected during both pleasant and unpleasant conditions. Facial expressions to unpleasant imagery scripts were also impaired. Thus, the orbitofrontal cortex proved to play a critical role in retrieval of psychophysiological emotional patterns, particularly to unpleasant material. These results provide the first evidence that orbitofrontal lesions are associated with emotional impairment at several psychophysiological levels.

Gender differences in emotional responses: a psychophysiological study.

Gender differences in emotional responses have been investigated in two groups of students, 22 males and 21 females. Participants watched a set of sixty emotional standardized slides divided into pleasant, neutral and unpleasant, while Startle reflex, Evoked Potentials, Heart Rate, facial EMG and Skin Conductance were recorded. Startle reflex amplitude, an index modulated by amygdala and orbitofrontal cortex and sensitive to aversive emotional stimuli, was overall larger in women. In addition, startle emotion modulation was greater in women with respect to men. Slow Evoked Potentials (400-800 ms), a measure representing the cognitive component of the emotional response, revealed gender differences in the left prefrontal site, with women showing greater positivity to unpleasant compared with pleasant slides while men had greater positivity to pleasant vs. neutral slides. Women, compared with men, perceived all slides as less pleasant and reported greater arousal to unpleasant condition. Results are in line with known functional brain differences, at level of limbic and paralimbic structures, between men and women, and point to biologically grounded greater sensitivity and vulnerability of women to adverse/stressful events.

Schizophrenia as Failure of Left Hemispheric Dominance for the Phonological Component of Language

Background T. J. Crow suggested that the genetic variance associated with the evolution in Homo sapiens of hemispheric dominance for language carries with it the hazard of the symptoms of schizophrenia. Individuals lacking the typical left hemisphere advantage for language, in particular for phonological components, would be at increased risk of the typical symptoms such as auditory hallucinations and delusions. Methodology/Principal Findings Twelve schizophrenic patients treated with low levels of neuroleptics and twelve matched healthy controls participated in an event-related potential experiment. Subjects matched word-pairs in three tasks: rhyming/phonological, semantic judgment and word recognition. Slow evoked potentials were recorded from 26 scalp electrodes, and a laterality index was computed for anterior and posterior regions during the inter stimulus interval. During phonological processing individuals with schizophrenia failed to achieve the left hemispheric dominance consistently observed in healthy controls. The effect involved anterior (fronto-temporal) brain regions and was specific for the Phonological task; group differences were small or absent when subjects processed the same stimulus material in a Semantic task or during Word Recognition, i.e. during tasks that typically activate more widespread areas in both hemispheres. Conclusions/Significance We show for the first time how the deficit of lateralization in the schizophrenic brain is specific for the phonological component of language. This loss of hemispheric dominance would explain typical symptoms, e.g. when an individuals own thoughts are perceived as an external intruding voice. The change can be interpreted as a consequence of “hemispheric indecision”, a failure to segregate phonological engrams in one hemisphere.

Blood phobia and spider phobia: two specific phobias with different autonomic cardiac modulations

Cardiac reactions to two fear-related and one control film were compared in individuals high in spider or blood/injury fear. Twelve subjects in each phobic group were selected on the basis of their scores in the Spider or Mutilation Questionnaires and a semi-structured interview. Cardiac responses and self-reported affective ratings to the films were investigated. Sympathetic and parasympathetic cardiac influences were indexed by T-wave amplitude and respiratory sinus arrhythmia measured during film viewing. Basal parasympathetic cardiac control was also assessed during a paced breathing task. Results indicate differential autonomic modulation of cardiac responses for blood and spider phobics. Although each group reacted with marked cardiac activation to its feared stimulus, a sympathetic increase followed by withdrawal over time was found in blood phobics. Greater vagal tone at rest was present in blood phobics compared with spider phobics.

Electrophysiological correlates of stimulus-driven multiplication facts retrieval

We investigated ERPs elicited by stimulus-driven retrieval of arithmetic facts related to multiplication. To this purpose, we recorded the electrophysiological activity from the scalp of participants while they were performing a number-matching task. Crucially, arithmetic was task-irrelevant within this paradigm, because participants were simply to physically compare a cue composed of two one- or two-digit numbers and a single probe number. In line with past literature, behavioral data showed that, in non-matching trials, participants were significantly slower and/or less accurate to respond when the probe number was the product of the two numbers in the cue compared to when the probe number was arithmetically unrelated (i.e., neutral) to those numbers (interference effect). Consistent with recent findings on ERPs and task-relevant arithmetic facts retrieval, we showed that the interference effect resulted in a modulation of the amplitude of an N400-like ERP component, with neutral probes generating relatively more negativity than product probes. The observed dissociation between behavioral data and ERP measures is interpreted as evidence of activation spreading in the lexicon of arithmetic facts, because alternative accounts that rely on strategic factors such as expectancy or semantic matching would have predicted the two measures to show a converging trend.