A left hemispace bias for visualizing emotional situations

Forty-three college-aged subjects posed a series of emotional facial expressions and described their strategies for creating such expressions. The majority of subjects (86%) reported visualizing an image or situation. When asked for the location of the image, the majority (62%) indicated the left hemispace, and only 5% indicated the right.     

Braille reading and left and right hemispace

Twelve blind adults were timed in locating phonologically and semantically defined targets in Braille lists. The “reading” hand was placed either out from or across the body, i.e. in ipsilateral or contralateral hemispace. Despite strong and consistent, if idiosyncratic, hand superiorities for all types of list, contrary to two previous reports there was no evidence of either a general left-hand preference or an overall left-hand superiority. Moreover neither the magnitude nor the direction of hand superiorities changed when hands were tested in contralateral hemispace. At least in this complex continuous task, hemisphere-hand connections appear more important than hemisphere-hemispace relationships. Left-hand (or left-hemispace) superiorities in tactual tasks of a verbal nature may only occur with novel, unfamiliar or perceptually degraded materials.     

Emotionally negative stimuli can overcome attentional deficits in patients with visuo-spatial hemineglect

Left unilateral spatial neglect resulting from right brain damage is characterized by loss of awareness for stimuli in the contralesional side of space, despite intact visual pathways. We examined using fMRI whether patients with neglect are more likely to consciously detect in the neglected hemifield, emotionally negative complex scenes rather than visually similar neutral pictures and if so, what neural mechanisms mediate this effect. Photographs of emotional and neutral scenes taken from the IAPS were presented in a divided visual field paradigm. As expected, the detection rate for emotional stimuli presented in the neglected field was higher than for neutral ones. Successful detection of emotional scenes as opposed to neutral stimuli in the left visual field (LVF) produced activations in the parahippocampal and anterior cingulate areas in the right hemisphere. Detection of emotional stimuli presented in the intact right visual field (RVF) activated a distributed network of structures in the left hemisphere, including anterior and posterior cingulate cortex, insula, as well as visual striate and extrastriate areas. LVF-RVF contrasts for emotional stimuli revealed activations in right and left attention related prefrontal areas whereas RVF-LVF comparison showed activations in the posterior cingulate and extrastriate visual cortex in the left hemisphere. An additional analysis contrasting detected vs. undetected emotional LVF stimuli showed involvement of left anterior cingulate, right frontal and extrastriate areas. We hypothesize that beneficial role of emotion in overcoming neglect is achieved by activation of frontal and limbic lobe networks, which provide a privileged access of emotional stimuli to attention by top-down modulation of processing in the higher-order extrastriate visual areas. Our results point to the importance of top-down regulatory role of the frontal attentional systems, which might enhance visual activations and lead to greater salience of emotional stimuli for perceptual awareness.     

Avoidance of emotionally arousing stimuli predicts social-perceptual impairment in Asperger's syndrome

We combined eye-tracking technology with a test of facial affect recognition and a measure of self-reported social anxiety in order to explore the aetiology of social-perceptual deficits in Asperger's syndrome (AS). Compared to controls matched for age, IQ and visual-perceptual ability, we found a group of AS adults was impaired in their recognition of fearful and sad expressions and spent significantly less time fixating the eye region of all faces. For AS subjects, but not controls, the extent of the failure to fixate the eyes predicted the degree of impairment at recognising fearful expressions. In addition, poor fear recognition and reduced fixation of the eyes were independently associated with greater levels of social anxiety in AS individuals. These findings support the hypothesis that avoidance of emotionally arousing stimuli, such as eyes, contributes to social-perceptual impairment in AS. Furthermore, our findings are consistent with theories implicating amygdala-mediated over-arousal and anxiety in the development of these social-perceptual deficits.     

Effect of stimuli in right hemispace on left-sided neglect in a line cancellation task.

Twenty-seven patients with right cerebral infarcts resulting in left-sided neglect in a line cancellation task were also tested for line cancellation when the lines were confined to the left half of sheets. All but one patient (whose neglect in the former condition was minimal) were still impaired in the latter condition, a finding that indicates that hyperattraction to test stimuli in the unneglected (right) hemispace was not the crucial factor preventing them from completing the standard version of the cancellation task, although it may have played some role. The results are consistent with the conclusion that hyperattention to stimuli in the unneglected hemifield, and possibly to stimuli in the unneglected hemispace, together with other factors, could account for the patients' impairment in line cancellation.     

Neural mechanisms underlying reaching for remembered targets cued kinesthetically or visually in left or right hemispace

Reaching for a target involves integrative coordinate transformation processes between the representation of the target location, the sensorimotor information of limb of reach, and body space. Although right hemisphere dominance for visuospatial information processing is well established, corresponding right hemisphere dominance for kinesthetic spatial information processing remains to be demonstrated. We explored neural mechanisms of encoding target locations using 15O-butanol positron emission tomography (PET) in normal volunteers in a factorial experiment, where modality (visual/kinesthetic) and hemispace of target presentation (left/right of midsagittal plane) were varied systematically. After target presentation, subjects reached to the encoded target location. PET data analysis using SPM99 showed increased neural activity (P < 0.05, corrected) associated with left hemispace target presentation in right hemisphere areas (sensorimotor, anterior cingulate, insular, and temporo-occipital cortex) only. By contrast, right hemispace target presentation activated bilateral temporo-occipital cortex, which extended into the right temporo-parietal cortex and left sensorimotor cortex. A significant interaction of hemispace and modality of target presentation observed in right temporo-parietal cortex resulted from an increase in neural activity with kinesthetic target presentation in right hemispace. The data support an important role for the right temporo-parietal area in visuospatial processing and suggest a specific role of the right hemisphere in kinesthetic spatial processing.     

Right-nostril use during sniffing at arousing stimuli produces higher cardiac activity in jumper horses

Lateralization in horses, Equus caballus, has been reported at both motor and sensory levels. Here we investigated left- and right-nostril use in 12 jumper horses freely sniffing different emotive stimuli. Results revealed that during sniffing at adrenaline and oestrus mare urine stimuli, horses showed a clear right-nostril bias while just a tendency in the use of the right nostril was observed during sniffing of other odours (food, cotton swab and repellent). Sniffing at adrenaline and urine odours was also accompanied by increasing cardiac activity and behavioural reactivity strengthening the role of the right hemisphere in the analysis of intense emotion and sexual behaviour.     

Association of the serotonin transporter promoter region polymorphism with biased attention for negative word stimuli

Background: Biased attention for emotional stimuli reflects vulnerability or resilience to emotional disorders. The current study examines whether the 5‐HTTLPR polymorphism is associated with attentional biases for negative word stimuli. Methods: Unmedicated, young adults with low current depression and anxiety symptoms (N=106) were genotyped for the 5‐HTTLPR, including the single nucleotide polymorphism (SNP) rs25531 in the long allele of the 5‐HTTLPR. Participants then completed a standard dot‐probe task that measured attentional bias toward anxiety, dysphoric, and self‐esteem words. Results: The L_AL_A allele group demonstrated an attentional bias away from negative word stimuli. This attentional bias was absent among the S/L_G carriers. Conclusions: These findings replicate previous work and suggest that 5‐HTTLPR L_A homozygotes possess a protective attentional bias that may decrease susceptibility to depression and anxiety. Depression and Anxiety, 2010. © 2010 Wiley‐Liss, Inc.     

Early attention modulates perceptual interpretation of multisensory stimuli

Perceptual interpretation of the same multisensory stimuli may rely upon influence of attention on multisensory integration. We tested this hypothesis by recording the brain activity using magnetoencephalography in a passing-bouncing illusion with sound. Early activation of the attention-related brain areas and subsequent involvement of the multisensory areas were associated with the bouncing percept. Early activation of the unimodal sensory areas and later involvement of the attention-related areas were associated with the passing percept. Thus, the bouncing percept occurs when early attentional deployment facilitates multisensory integration modulating visual perception. The passing percept results from hierarchical sequence of the perceptual processes: early activation of the unimodal areas and late attentional deployment. Alternation of the perceptual interpretations may depend on spontaneous fluctuation of attention.     

Automatic attention to emotional stimuli: neural correlates

We investigated the capability of emotional and nonemotional visual stimulation to capture automatic attention, an aspect of the interaction between cognitive and emotional processes that has received scant attention from researchers. Event-related potentials were recorded from 37 subjects using a 60-electrode array, and were submitted to temporal and spatial principal component analyses to detect and quantify the main components, and to source localization software (LORETA) to determine their spatial origin. Stimuli capturing automatic attention were of three types: emotionally positive, emotionally negative, and nonemotional pictures. Results suggest that initially (P1: 105 msec after stimulus), automatic attention is captured by negative pictures, and not by positive or nonemotional ones. Later (P2: 180 msec), automatic attention remains captured by negative pictures, but also by positive ones. Finally (N2: 240 msec), attention is captured only by positive and nonemotional stimuli. Anatomically, this sequence is characterized by decreasing activation of the visual association cortex (VAC) and by the growing involvement, from dorsal to ventral areas, of the anterior cingulate cortex (ACC). Analyses suggest that the ACC and not the VAC is responsible for experimental effects described above. Intensity, latency, and location of neural activity related to automatic attention thus depend clearly on the stimulus emotional content and on its associated biological importance.     

Posture oculaire et attention selective a des stimuli cutanes

Les sujets fixent une cible visuelle à droite ou à gauche et reçoivent des stimulations cutanées sur la cheville ipsi- ou contralatérale. Aucune tâche proprement visuelle n'est demandée; les sujets doivent détecter et compter des stimulations liminaires ou bien répondre par un temps de réaction manuel simple à des chocs supraliminaires. Dans les deux cas, la performance est meilleure quand les yeux sont tournés vers le côté stimulé.     

Exogenous attention to facial vs non-facial emotional visual stimuli

The capacity of the two types of non-symbolic emotional stimuli most widely used in research on affective processes, faces and (non-facial) emotional scenes, to capture exogenous attention, was compared. Negative, positive and neutral faces and affective scenes were presented as distracters to 34 participants while they carried out a demanding digit categorization task. Behavioral (reaction times and number of errors) and electrophysiological (event-related potentials—ERPs) indices of exogenous attention were analyzed. Globally, facial expressions and emotional scenes showed similar capabilities to attract exogenous attention. Electrophysiologically, attentional capture was reflected in the P2a component of ERPs at the scalp level, and in left precentral areas at the source level. Negatively charged faces and scenes elicited maximal P2a/precentral gyrus activity. In the case of scenes, this negativity bias was also evident at the behavioral level. Additionally, a specific effect of facial distracters was observed in N170 at the scalp level, and in the fusiform gyrus and inferior parietal lobule at the source level. This effect revealed maximal attention to positive expressions. This facial positivity offset was also observed at the behavioral level. Taken together, the present results indicate that faces and non-facial scenes elicit partially different and, to some extent, complementary exogenous attention mechanisms.     

Spatio-motor cueing in unilateral left neglect: the role of hemispace, hand and motor activation.

Reported beneficial effects of left arm activation on neglect are experimentally examined. The present study of a subject with left visual neglect compared left hand finger movement with an instruction to visually anchor perception on the left arm during letter cancellation. Only the finger movements significantly reduced neglect. Another comparison was between "out of sight" finger movements of the left hand in left and right hemispace, respectively. Only left hemispace "blind" finger movements significantly reduced neglect compared to the standard condition. Thirdly, blind left finger movements in left hemispace were compared with passive visual cueing (reading a changing number) and again it was found that only the finger movements reduced neglect. Finally, right finger movements in left hemispace were compared with left finger movements in left hemispace: only the latter reduced neglect. The implications of these findings for theory and therapy of neglect are discussed.     

Looking left with left neglect: The role of spatial attention when active vision selects local image features for fixation

When we actively explore the visual environment, our gaze preferentially selects regions characterized by high contrast and high density of edges, suggesting that the guidance of eye movements during visual exploration is driven to a significant degree by perceptual characteristics of a scene. Converging findings suggest that the selection of the visual target for the upcoming saccade critically depends on a covert shift of spatial attention. However, it is unclear whether attention selects the location of the next fixation uniquely on the basis of global scene structure or additionally on local perceptual information. To investigate the role of spatial attention in scene processing, we examined eye fixation patterns of patients with spatial neglect during unconstrained exploration of natural images and compared these to healthy and brain-injured control participants. We computed luminance, colour, contrast, and edge information contained in image patches surrounding each fixation and evaluated whether they differed from randomly selected image patches. At the global level, neglect patients showed the characteristic ipsilesional shift of the distribution of their fixations. At the local level, patients with neglect and control participants fixated image regions in ipsilesional space that were closely similar with respect to their local feature content. In contrast, when directing their gaze to contralesional (impaired) space neglect patients fixated regions of significantly higher local luminance and lower edge content than controls. These results suggest that intact spatial attention is necessary for the active sampling of local feature content during scene perception.     

Attentional shift towards the rightmost stimuli in patients with left visual neglect

In a search task where four letters were displayed to the right of a central fixation point, right brain-damaged patients with visual neglect showed the fastest response when the target was at the rightmost position and progressively slower responses as it moved towards the center of the display. This finding confirms Kinsbourne's claim that in visual neglect an important role is played by the magnetic attraction that the extreme end of the right structured space exerts on the patient's attention.     

Feature-specific attention allocation overrules the orienting response to emotional stimuli

Emotional stimuli are generally thought to be processed in an unconditional fashion. Recent behavioral studies suggest, however, that emotional stimulus processing is critically dependent on attention toward emotional stimulus features. We set out to test this hypothesis using EEG measurements and a modified oddball paradigm. Unexpected emotional stimuli evoked amplitude variations of the P3a (an ERP marker of attention orienting) when attention was directed to emotional stimulus properties but not when non-emotional stimulus properties were attended to. We conclude that emotional stimulus processing is not unconditional, but dependent on top-down attentional control.     

Temporal and spatio-temporal attention to tactile stimuli in extinction patients

The temporal deployment of attention to tactile stimuli delivered to the same or to a symmetrical position of the body was assessed in 6 Right-Brain Damaged (RBD) patients with left tactile extinction and 6 healthy controls. Two different tasks called Temporal (T) and Spatio-Temporal (ST) extinction were used. In the T task single or double electro tactile stimuli were delivered to the same point to the left or, in separate blocks, to the right index finger. Double stimuli were separated by different Stimulus Onset Asynchronies (SOAs). In the ST task, stimuli could be single (left or right) or double (left and right). Double stimuli were delivered to the index finger of both hands simultaneously or sequentially. In both tasks subjects were asked to report the number of the stimuli they perceived. In the ST task, subjects were also requested to report the stimuli location. Results show that in both tasks RBD patients' detection of left sided stimuli was significantly lower than of right sided stimuli detection, mainly at shortest SOAs. Moreover, detection of left sided stimuli was higher when two stimuli were delivered in sequence and in symmetrical body areas and in different sides of the space than when stimuli were delivered in sequence in the same body area. Results suggest that the interaction between spatial and temporal variables enhances the ability of tactile extinction patients to detect left sided stimuli.     

Orienting of attention in left unilateral neglect

After right posterior brain damage, patients may ignore events occurring on their left, a condition known as unilateral neglect. Although deficits at different levels of impairment may be at work in different patients, the frequency and severity of attentional problems in neglect patients have been repeatedly underlined. Recent advances in the knowledge of the mechanisms of spatial attention in normals may help characterizing these deficits. The present review focuses on studies exploring several aspect of attentional processing in unilateral neglect, with particular reference to the dichotomy between 'exogenous', or stimulus-related, and 'endogenous', or strategy-driven, orienting of attention. A large amount of neuropsychological evidence suggests that a basic mechanism leading to left neglect behavior is an impaired exogenous orienting toward left-sided targets. In contrast, endogenous processes seem to be relatively preserved, if slowed, in left unilateral neglect. Other component deficits, such as a general slowing of the operations of spatial attention, might contribute to neglect behavior. These results are presented and discussed, and their implications for hemispheric specialization in attentional orienting and for the mechanisms of visual consciousness are explored.     

Neural mechanisms mediating contingent capture of attention by affective stimuli

Attention is attracted exogenously by physically salient stimuli, but this effect can be dampened by endogenous attention settings, a phenomenon called "contingent capture." Emotionally salient stimuli are also thought to exert a strong exogenous influence on attention, especially in anxious individuals, but whether and how top-down attention can ameliorate bottom-up capture by affective stimuli is currently unknown. Here, we paired a novel spatial cueing task with fMRI to investigate contingent capture as a function of the affective salience of bottom-up cues (face stimuli) and individual differences in trait anxiety. In the absence of top-down cues, exogenous stimuli validly cueing targets facilitated attention in low-anxious participants, regardless of affective salience. However, although high-anxious participants exhibited similar facilitation following neutral exogenous cues, this facilitation was completely absent following affectively negative exogenous cues. Critically, these effects were contingent on endogenous attentional settings, such that explicit top-down cues presented before the appearance of exogenous stimuli removed anxious individuals' sensitivity to affectively salient stimuli. fMRI analyses revealed a network of brain regions underlying this variability in affective contingent capture across individuals, including the fusiform face area (FFA), posterior ventrolateral frontal cortex, and SMA. Importantly, activation in the posterior ventrolateral frontal cortex and the SMA fully mediated the effects observed in FFA, demonstrating a critical role for these frontal regions in mediating attentional orienting and interference resolution processes when engaged by affectively salient stimuli.