Michela Sarlo

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.

Attentional Resources Measured by Reaction Times Highlight Differences Within Pleasant and Unpleasant, High Arousing Stimuli

Simple reaction times (RTs) to acoustic tones were recorded during picture viewing in order to investigate attentional resource allocation to threat stimuli compared with pleasant (sport/adventure) and neutral (household objects) contents. Stimuli were selected as equally arousing according to standardized subjective ratings. In the late stage of picture processing threat pictures showed shorter RTs compared with neutral and pleasant ones. In a second study, a choice-RT task was employed, and a wider range of both pleasant and unpleasant contents was shown. Results indicated slower RTs when blood/injury and erotic couples were presented, compared with other threat, and with other positive (sport/adventure) scenes. Specifically, erotic couples require a greater amount of attentional resources compared with sport/adventure; the same is true for blood/injury stimuli as compared with threat. Remarkable differences were thus shown in attentional deployment to specific stimulus contents within the same valence category. These differences should be taken into account when using such stimuli to investigate emotional processing.

Sleep onset and cardiovascular activity in primary insomnia

The transition from wakefulness to sleep is characterized typically by a shift from sympathetic to parasympathetic regulation. Physiological functions, depending on the neurovegetative system, decrease overall. Previous studies have shown cardiovascular and electroencephalographic hyperactivity during wakefulness and sleep in insomniacs compared with normal sleepers, but there is very little evidence of this in the process of sleep onset. The purpose of this study was to compare cardiovascular and autonomic responses before and after falling asleep in eight insomniacs (who met DSM‐IV criteria for primary insomnia) and eight normal sleepers. Non‐invasive measures of heart rate (HR), stroke volume (SV), cardiac output (CO) and pre‐ejection period (PEP) were collected by impedance cardiography during a night of polysomnographic recording. Frequency domain measures [low‐frequency (LF), high‐frequency (HF)] of heart rate variability (HRV) were also estimated. Decrements in HR and CO and increases in SV and HF normalized units (n.u.) were found in both groups after sleep onset compared with wakefulness. Conversely, PEP (related inversely to sympathetic β‐adrenergic activity) showed increases after sleep onset in controls, but remained unchanged in insomniacs. PEP was also significantly lower in insomniacs than in normal sleepers in both conditions. These data suggest that, whereas normal sleepers follow the expected progressive autonomic drop, constant sympathetic hyperactivation is detected in insomniacs. These results support the aetiological hypothesis of physiological hyperarousal underlying primary insomnia.

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.

Changes in EEG alpha power to different disgust elicitors: the specificity of mutilations

It is unclear in the literature whether the various disgust elicitors are differentially processed by the brain and/or able to elicit distinct psychophysiological response patterns. On the other hand, disgusting stimuli depicting mutilations have been proved to elicit a distinct autonomic response pattern and to demand greater attentional resources, as compared with other unpleasant visual stimuli. In this EEG study, 34 participants viewed 4 film-clips depicting surgery, cockroach invasion, human attack and neutral landscape during EEG recording, and then rated the clips for valence, arousal and the basic emotions. Independent of location, the highest cortical activation was found during the viewing of the surgery scene. Moreover, the above activation was prominent over the right posterior regions.

Cardiovascular dynamics in blood phobia: Evidence for a key role of sympathetic activity in vulnerability to syncope

This study was aimed at clarifying the mechanism predisposing people with blood phobia to syncope by investigating the complete hemodynamic response pattern and the underlying autonomic control. Blood phobics and controls were shown 3 film-clips: phobia-related, phobia-unrelated, and neutral. Hemodynamic responses were recorded using impedance cardiography and Finapres. Preejection period and respiratory sinus arrhythmia were employed as indices of cardiac sympathetic and parasympathetic activity. Self-ratings of emotion were also collected. Blood phobics displayed global heart rate and cardiac output increases to the phobic film, mediated by augmented cardiac sympathetic activity. Systolic blood pressure and total peripheral resistance markedly declined, with no evidence of diphasic reaction or parasympathetic activation. An impaired vasomotor response under sympathetic control might be the key mechanism underlying the phobic dysfunctional response.

Automatic Temporal Expectancy: A High-Density Event-Related Potential Study

How we compute time is not fully understood. Questions include whether an automatic brain mechanism is engaged in temporally regular environmental structure in order to anticipate events, and whether this can be dissociated from task-related processes, including response preparation, selection and execution. To investigate these issues, a passive temporal oddball task requiring neither time-based motor response nor explicit decision was specifically designed and delivered to participants during high-density, event-related potentials recording. Participants were presented with pairs of audiovisual stimuli (S1 and S2) interspersed with an Inter-Stimulus Interval (ISI) that was manipulated according to an oddball probabilistic distribution. In the standard condition (70% of trials), the ISI lasted 1,500 ms, while in the two alternative, deviant conditions (15% each), it lasted 2,500 and 3,000 ms. The passive over-exposition to the standard ISI drove participants to automatically and progressively create an implicit temporal expectation of S2 onset, reflected by the time course of the Contingent Negative Variation response, which always peaked in correspondence to the point of S2 maximum expectation and afterwards inverted in polarity towards the baseline. Brain source analysis of S1- and ISI-related ERP activity revealed activation of sensorial cortical areas and the supplementary motor area (SMA), respectively. In particular, since the SMA time course synchronised with standard ISI, we suggest that this area is the major cortical generator of the temporal CNV reflecting an automatic, action-independent mechanism underlying temporal expectancy.

The neural correlates of attentional bias in blood phobia as revealed by the N2pc

In the literature, a lack of attentional bias in blood phobia has been reported, using both behavioral and ERP measures. However, in the tasks employed so far, attentional resources to single stimuli, rather than attentional selection, were evaluated. The present study investigated whether in blood phobics disorder-relevant pictures can capture visuo-spatial attention when paired with neutral or non-specific unpleasant pictures (attack), and participants have to focus on a visual detection task. The N2pc component of the ERPs was measured as an index of spatial attentional selection. Results showed that in blood phobics, but not in controls, injuries elicited a larger early N2pc than attack pictures when paired with neutral material. Moreover, only in blood phobics a reliable N2pc to injury-attack pairs was found. The late N2pc reversal to injury pictures suggests that early orienting to phobic cues was followed by cognitive avoidance.

Blood pressure changes highlight gender differences in emotional reactivity to arousing pictures

The current study was aimed at investigating the effects of gender on the magnitude and patterning of blood pressure responses to specific pleasant and unpleasant, arousing visual stimuli. Systolic and diastolic blood pressure (SBP and DBP), as well as heart rate (HR) and skin conductance (SCR) responses were investigated during picture viewing in 21 female and 25 male students. The pattern of SCR and HR reactivity across emotional categories was found to be similar for men and women. Gender was found to be an effective moderator of BP responses specifically to sexual stimulus content, which prompted greater reactivity in men than in women. These findings extend prior research on gender differences in autonomic responding to emotional visual stimuli and suggest that BP changes might reflect sexual peripheral arousal more than other autonomic measures.

Reorienting of spatial attention in gaze cuing is reflected in N2pc

Research has shown that gaze cuing of attention is reflected in the modulation of P1 and N1 components of ERPs time-locked to target onset. Studies focusing on cue-locked analyses have produced mixed results. The present study examined ERP reflections of gaze cuing in further detail by recording electric brain activity from the scalp of participants engaged in a spatial cuing paradigm with noninformative gaze cues embedded in fearful, disgusted, or neutral faces. Unlike previous work, we focused on N2pc, a recent ERP index of attention shifting over space. Behavioral data showed that gaze-driven orienting was not influenced by facial expression. Importantly, electrophysiological data showed a significant amplitude modulation of the N2pc time-locked to target onset as a function of cue–target spatial congruence. This pattern, however, was independent of facial expression. The results are interpreted as evidence that N2pc can be used as a marker of reorienting of attention in spatially incongruent trials due to gaze cuing. The overall findings support the idea that the effects of facial expression on gaze cuing are weak and likely context-dependent.