A right hemisphere role in cognitive reserve

High levels of education, occupational complexity, and/or premorbid intelligence are associated with lower levels of cognitive impairment than would be expected from a given brain pathology. This has been observed across a range of conditions including Alzheimer's disease (Roe et al., 2010), stroke (Ojala-Oksala et al., 2012), traumatic brain injury (Kesler et al., 2003), and penetrating brain injury (Grafman, 1986). This cluster of factors, which seemingly protect the brain from expressing symptoms of damage, has been termed “cognitive reserve” (Stern, 2012). The current review considers one possible neural network, which may contribute to cognitive reserve. Based on the evidence that the neurotransmitter, noradrenaline mediates cognitive reserve's protective effects (Robertson, 2013) this review identifies the neurocognitive correlates of noradrenergic (NA) activity. These involve a set of inter-related cognitive processes (arousal, sustained attention, response to novelty, and awareness) with a strongly right hemisphere, fronto-parietal localization, along with working memory, which is also strongly modulated by NA. It is proposed that this set of processes is one plausible candidate for partially mediating the protective effects of cognitive reserve. In addition to its biological effects on brain structure and function, NA function may also facilitate networks for arousal, novelty, attention, awareness, and working memory, which collectively provide for a set of additional, cognitive, mechanisms that help the brain adapt to age-related changes and disease. It is hypothesized that to the extent that the lateral surface of the right prefrontal lobe and/or the right inferior parietal lobe maintain structural (white and gray matter) and functional integrity and connectivity, cognitive reserve should benefit and behavioral expression of pathologic damage should thus be mitigated.     

The Symmetry of Emotional and Deliberate Facial Actions

Asymmetries of the smiling facial movement were more frequent in deliberate imitations than spontaneous emotional expressions. When asymmetries did occur they were usually stronger on the left side of the face if the smile was deliberate. Asymmetrical emotional expressions, however, were about equally divided between those stronger on the left side of the face and those stronger on the right. Similar findings were obtained for the actions involved in negative emotions, but a small data base made these results tentative.     

The psychophysiology of disgust: Differentiating negative emotional contexts with facial EMG

The goals of this study were (a) to examine differing views on the relationship between self-report of emotion and physiological expression of emotion, (b) to differentiate between negative emotional contexts during imagery using facial electromyogram (EMG), and (c) to describe the facial muscle patterning and autonomic physiology of situations that involve expelling or avoiding disgusting sensory stimulation. Fifty subjects imagined situations eliciting disgust, anger, pleasure, and joy in 8-s trials using a tone-cued imagery procedure. Heart rate, skin conductance level, and facial EMG at the corrugator, zygomatic, and levator labii superioris/alesque muscle regions were recorded during imagery, and self-reports of emotion were collected after imagery trials. Self-reports of emotion produced results consistent with the affective categorization of the images. Activity at the levator labii region was higher during disgust than during anger imagery. Corrugator region increase characterized the negative as compared with the positive emotional contents, and activity at the zygomatic region was higher during joy imagery than during the other three emotions. Heart rate acceleration was greater during disgust, anger, and joy imagery than during pleasant imagery. Disgust imagery could be discriminated from anger imagery using facial EMG, and the expressive physiology of disgust was occasioned by the action set of active avoidance or rejection of sensory stimulation.     

Event-related desynchronization in the EEG during emotional and cognitive information processing: differential effects of extraversion

The aim of the present study was to analyze the influence of the personality dimension extraversion/introversion (E) on the level and topographical distribution of event-related desynchronization (ERD) in the EEG whilst participants were engaged in emotional face and cognitive information processing. In this context we build up on former studies dealing with the role of E as a possible moderator variable in cortical activation patterns during performance of mental speed, reasoning and working memory tasks (i.e., cognitive information processing). In a sample of 33 introverts and 33 extraverts (31 were male, 35 female) we found extraverted individuals displaying a lower (left-hemispheric) cortical activation than introverts when their task was to judge the identity of two simultaneously presented facial emotions. This effect was only observed in the upper alpha frequency band (9.6–11.6 Hz). In analyzing E differences during cognitive information processing (i.e., performance of a verbal and a figural-spatial task) E effects – which were moderated by participants’ sex – were restricted to lower EEG (alpha) frequency ranges (5.6–9.6 Hz). The results generally suggest that E is differently involved when different kinds of information are processed.     

Laterality, Emotionality, and Heartbeat Perception

Recent research on visceral perception has indicated that hemispheric specialization and emotionality may account for individual differences among subjects. The present study was designed to examine the nature of the relationship between hemispheric specialization and emotionality, and the manner in which these variables influence individual differences in visceral perception (i.e., detection of cardiac activity). Male subjects were given 20 questions used to test lateral eye movements. Following the completion of the State-Trait Anxiety Inventory (STAI), Form X-1 (State Anxiety), cardiac awareness was assessed using the Whitehead heartbeat discrimination procedure. Subjects then completed the STAI, Form X-2 (Trait Anxiety), and the Eysenck Personality Inventory. Results indicated that good heartbeat perceivers made significantly more left lateral eye movements (i.e., right hemisphere preferent) than poor perceivers on any of the emotional indicators. It was found, however, that subjects with high scores on two of the three emotional indicators made significantly more left lateral eye movements than subjects with low scores. Additional analyses indicate that respiration rate and subject obesity may affect the ability to detect feedback of cardiovascular function.     

Controlling the emotional heart: Heart rate biofeedback improves cardiac control during emotional reactions

When regulating negative emotional reactions, one goal is to reduce physiological reactions. However, not all regulation strategies succeed in doing that. We tested whether heart rate biofeedback helped participants reduce physiological reactions in response to negative and neutral pictures. When viewing neutral pictures, participants could regulate their heart rate whether the heart rate feedback was real or not. In contrast, when viewing negative pictures, participants could regulate heart rate only when feedback was real. Ratings of task success paralleled heart rate. Participants' general level of anxiety, emotion awareness, or cognitive emotion regulation strategies did not influence the results. Our findings show that accurate online heart rate biofeedback provides an efficient way to down-regulate autonomic physiological reactions when encountering negative stimuli.     

Lateralized startle probes in the study of emotion

Two experiments are reported in which affective modulation of the startle reflex elicited by monaurally presented acoustic probes was further examined. An earlier study in our laboratory obtained significant modulation by effect for probes presented to the left ear, but no significant effect for probes presented to the right ear Experiment 1 replicated the procedures used in that experiment and obtained the same pattern of effects. Experiment 2 changed the presentation of monaural probes from a blocked to a mixed presentation and again obtained a similar pattern. Modulatory differences in reflex magnitude between pleasant and unpleasant stimuli were consistently large and reliable for reflexes elicited by left ear probes but weak and unreliable for reflexes elicited by right ear probes.     

Emotion processing in three systems: the medium and the message.

In the context of picture viewing, consistent and specific relationships have been found between two emotion dimensions (valence and arousal) and self-report, physiological and overt behavioral responses. Relationships between stimulus content and the emotion-response profile can also be modulated by the formal properties of stimulus presentation such as screen size. The present experiment explored the impact of another presentation attribute, stimulus motion, on the perceived quality of the induced emotion and on its associated physiological response pattern. Using a within-subject design, moving and still versions of emotion-eliciting stimuli were shown to 35 subjects while facial muscle, heart rate, skin conductance, and emotion self-reports were monitored. The impact of motion was dramatic. Self-report and physiological data suggested strongly that motion increased arousal, had little impact on valence, and captured and sustained the subject's attention to the image.     

Watching emotional movies: Affective reactions and gender differences

Previous studies have found that unpleasant film clips depicting mutilated bodies or injuries evoke a sustained heart rate deceleration which has been interpreted as reflecting a stimulus-specific aversive response or as increased orienting and attentional processing that varies with stimulus significance. Few studies, however, have examined cardiac changes during the viewing of high arousal pleasant films. To clarify this issue, the present study assessed evaluative, facial and autonomic reactions in both men and women during the viewing of highly arousing pleasant, as well as unpleasant, films. Results indicated a similar skin conductance increase and heart rate deceleration which were greater than those observed during the viewing of a neutral film. Compared to men, women rated both films as less pleasant and rated the unpleasant film as more arousing. The present findings suggest that sustained exposure to pleasant and unpleasant stimuli elicit similar cardiac orienting when stimuli are equated for subjective report of emotional arousal.     

The Asymmetry of Facial Actions is Inconsistent with Models of Hemispheric Specialization

Several models of hemispheric specialization have been used to explain asymmetries in facial actions. This study measured the asymmetry of several different muscular actions individually, alone and in combination, and under different eliciting conditions. The findings did not fit any of the theoretical models. In the deliberate actions, some of the asymmetries were lateralized with greater intensity on the left side; others, on the right side. Spontaneous actions were more symmetrical than the deliberate, requested actions. We rejected specialization for emotion as a cause of the facial asymmetry observed, and discussed the weaknesses of other models.     

Emotion regulation during threat: Parsing the time course and consequences of safety signal processing

Improved understanding of fear inhibition processes can inform the etiology and treatment of anxiety disorders. Safety signals can reduce fear to threat, but precise mechanisms remain unclear. Safety signals may acquire attentional salience and affective properties (e.g., relief) independent of the threat; alternatively, safety signals may only hold affective value in the presence of simultaneous threat. To clarify such mechanisms, an experimental paradigm assessed independent processing of threat and safety cues. Participants viewed a series of red and green words from two semantic categories. Shocks were administered following red words (cue+). No shocks followed green words (cue‐). Words from one category were defined as safety signals (SS); no shocks were administered on cue+ trials. Words from the other (control) category did not provide information regarding shock administration. Threat (cue+ vs. cue‐) and safety (SS+ vs. SS‐) were fully crossed. Startle response and ERPs were recorded. Startle response was increased during cue+ versus cue‐. Safety signals reduced startle response during cue+, but had no effect on startle response during cue‐. ERP analyses (PD130 and P3) suggested that participants parsed threat and safety signal information in parallel. Motivated attention was not associated with safety signals in the absence of threat. Overall, these results confirm that fear can be reduced by safety signals. Furthermore, safety signals do not appear to hold inherent hedonic salience independent of their effect during threat. Instead, safety signals appear to enable participants to engage in effective top‐down emotion regulatory processes.     

Lateral Differences in the Latency Between Finger Tapping and the Heart Beat

Based upon suggestions that the two cerebral hemispheres may be differentially involved in the perception and regulation of autonomic activity, three studies were designed to explore differences in the relationship between left versus right hand finger tapping and the heartbeat. In each study, right-handed subjects were asked to tap with either their left versus right forefingers regularly at the rate of approximately once per second. When the time from the R-spike immediately preceding their tap to the tap was examined, a significant difference between the two hands was obtained in two of the studies, with the left hand tapping closer to the last R-spike compared with the right. A variety of additional conditions in the experiments suggest that this effect may depend upon tapping rhythmically. The implications of these findings for the differential role of the left and right hemispheres in the perception and regulation of cardiac activity are considered.     

Startle and Emotion: Lateral Acoustic Probes and the Bilateral Blink

The affect-startle effect describes the modulation of the reflexive eyeblink response to a probe startle stimulus as a function of foreground emotional valence. Larger blinks occur during viewing of unpleasant slide foregrounds, relative to positive foregrounds. This effect has been obtained repeatedly using binaural acoustic startle probes. The current study examines this phenomenon for monaural probes administered to the left and right ears in separate blocks. Startle probes were presented during and between exposures to pleasant, neutral, and unpleasant slides, with the ear of presentation counterbalanced across subjects. Left monaural probes produced blink magnitudes that increased linearly from pleasant to unpleasant slide foregrounds, and appeared to be independent of attention or interest. Right monaural probes did not vary with foreground valence. These findings suggest that the startle probe indexes emotional processing that is lateralized in the central nervous system.     

The effect of musical experience on emotional self‐reports and psychophysiological responses to dissonance

To study the influence of musical education on emotional reactions to dissonance, we examined self‐reports and physiological responses to dissonant and consonant musical excerpts in listeners with low (LE: n=15) and high (HE: n=13) musical experience. The results show that dissonance induces more unpleasant feelings and stronger physiological responses in HE than in LE participants, suggesting that musical education reinforces aversion to dissonance. Skin conductance (SCR) and electromyographic (EMG) signals were analyzed according to a defense cascade model, which takes into account two successive time windows corresponding to orienting and defense responses. These analyses suggest that musical experience can influence the defense response to dissonance and demonstrate a powerful role of musical experience not only in autonomic but also in expressive responses to music.     

Music and emotion: electrophysiological correlates of the processing of pleasant and unpleasant music

Human emotion and its electrophysiological correlates are still poorly understood. The present study examined whether the valence of perceived emotions would differentially influence EEG power spectra and heart rate (HR). Pleasant and unpleasant emotions were induced by consonant and dissonant music. Unpleasant (compared to pleasant) music evoked a significant decrease of HR, replicating the pattern of HR responses previously described for the processing of emotional pictures, sounds, and films. In the EEG, pleasant (contrasted to unpleasant) music was associated with an increase of frontal midline (Fm) theta power. This effect is taken to reflect emotional processing in close interaction with attentional functions. These findings show that Fm theta is modulated by emotion more strongly than previously believed.     

Manual asymmetries in the directional coding of reaching: further evidence for hemispatial effects and right hemisphere dominance for movement planning

Directional coding of hand movements is of primary importance in the proactive control of goal-directed aiming. At the same time, manual reaction times are known to be asymmetric when reaching at lateralized targets. Generally, ipsilateral movements and left hand advantages are interpreted using the classical model of interhemispheric transmission for simple visuomotor integration, but the use of this model was recently challenged when applied to reaching movements, arguing that attentional and biomechanical effects could also account for such asymmetries. In this work, we aimed at controlling both visual attention orienting and movement mechanical constraints in order to clarify the origin of manual reaction time asymmetries and hemispatial effects in the directional coding of reaching. Choice reaction time pointing tasks were assessed in two experiments in which identical movements were compared in different conditions of target lateralization and different conditions of head, eye and hand position. Results suggested that biomechanical constraints could account for hemispatial effects for movement execution but not for movement direction coding. These results are discussed in the light of models of interhemispheric cooperation and the right hemisphere dominance for spatial processing. Electronic Publication     

Studying the dynamics of autonomic activity during emotional experience

Recent theories emphasize the dynamic aspects of emotions. However, the physiological measures and the methodological approaches that can capture the dynamics of emotions are underdeveloped. In the current study, we investigated whether moment‐to‐moment changes in autonomic nervous system (ANS) activity are reliably associated with the unfolding of emotional experience. We obtained cardiovascular and electrodermal signals from participants while they viewed emotional movies. We found that the ANS signals were temporally aligned across individuals, indicating a reliable stimulus‐driven response. The degree of response reliability was associated with the emotional time line of the movie. Finally, individual differences in ANS response reliability were strongly correlated with the subjective emotional responses. The current research offers a methodological approach for studying physiological responses during dynamic emotional situations.     

Effects of picture content and intensity on affective physiological response

This study evaluated the effects of affective intensity and thematic content of foreground photographic stimuli on various physiological response systems. This was accomplished by assessing responses to pictures that varied systematically in these parameters. Along with overall effects of picture valence reported in previous work, we found effects of thematic content (i.e., specific nature of objects/events depicted) for all measures except heart rate. In addition, we found that the magnitude of startle blink, skin conductance, and corrugator muscle reactions increased with increasing affective intensity of pictures. Additionally, for these three measures, intensity effects also interacted with effects of picture content. These results indicate that stimulus parameters of intensity and thematic content exert separate-and in some cases interactive-modulatory effects on physiological reactions to emotional pictures.     

Behavioral and physiological responses of guide dogs to a situation of emotional distress

The aim of this study was to analyze the behavioral and physiological reactions of guide dogs in a distressing situation which promotes attachment behaviors towards their blind owners, and to compare such reactions with those of untrained or trainee dogs. The subjects were 57 adult Labrador and Golden retriever dogs (14 males, 43 females) belonging to four different groups: 19 Custody dogs, 13 Apprentice dogs, 10 Guide dogs and 15 Pet dogs. Dogs were tested using the Strange Situation Test, consisting in seven 3-minute episodes in which the dogs were placed in an unfamiliar environment, introduced to an unfamiliar woman and subjected to separation from their human companion. Tests were video-recorded and behaviors were scored using a 5-second point sampling method. Polar Vantage telemetric system was used to record cardiac activity. ANOVAs for repeated measures with groups and breeds as independent variables, showed a more anxious reaction in pet dogs, which revealed a high degree of proximity seeking behavior. Cardiac activity increased during episodes characterized by the exclusive presence of the stranger, but this increase was more conspicuous in guide dogs than in custody and apprentice dogs. Golden retrievers showed more behaviors suggesting distress compared to Labrador retrievers. This study showed that guide dogs, when separated from their blind owner, reveal a controlled behavioral reaction that is however accompanied by a stronger cardiac activation.