Purpose: Recently devised tests have implemented forms of interocular suppression (e.g. binocular rivalry) to assess eye dominance. In an effort to combine the strengths of these tests, we introduce a new technique for quantifying the magnitude of interocular suppression using an easily administered psychophysical test. Methods: Eighty-eight observers participated in the interocular suppression test, which involved dichoptic presentation of dynamic noise to one eye and a target stimulus to the other. Observers made a form discrimination judgment once the target emerged from suppression. We reasoned that the dominant eye is less susceptible to interocular suppression and as a result, perception and thus, form discrimination would be faster when the target is presented to the dominant eye as opposed to the non-dominant eye. Observers' sighting dominance, acuity, contrast sensitivity, and test-retest reliability were also assessed. Results: There were significant interocular differences in mean reaction times within and across observers. 68% and 32% of observers were categorized as right eye dominant and left eye dominant, respectively, according to our test. Moreover, 38% of observers showed strong eye dominance. Observers' discrimination accuracy (98%) and test-retest reliability (r=0.52-0.67) were high. Consistent with previous studies, statistical relationships were weak between the sighting dominance test, acuity scores, contrast sensitivity measures, and our interocular suppression test. Conclusion: This interocular suppression technique offers an efficient, reliable, quantitative method of evaluating eye dominance and may be useful in making decisions about differential refractive correction of the two eyes.

Converging lines of evidence point to a strong link between action and perception. In this study, we show that this linkage plays a role in controlling the dynamics of binocular rivalry, in which two stimuli compete for perceptual awareness. Observers dichoptically viewed two dynamic rival stimuli while moving a computer mouse with one hand. When the motion of one rival stimulus was consistent with observers' own hand movements, dominance durations of that stimulus were extended and, remarkably, suppression durations of that stimulus were abbreviated. Additional measurements revealed that this change in rivalry dynamics was not attributable to observers' knowledge about the condition under test. Thus, self-generated actions can influence the resolution of perceptual conflict, even when the object being controlled falls outside of visual awareness.

Assessment of the functions of the orbitofrontal cortex and ventromedial prefrontal cortex has proven to be a unique challenge for neuropsychologists. Orbitomedial damage occurs in a range of disorders including traumatic brain injury, ruptured aneurysms, surgical resection, and frontotemporal dementia. We review the effects of orbitomedial damage on a range of neuropsychological tasks, including tasks measuring object alternation and reversal learning, decision-making (gambling), facial emotion recognition, theory of mind, olfactory recognition, autobiographical memory and behavioral rating measures. At present, there is no singular gold standard measure of orbitomedial dysfunction, and assessment requires an integrative approach that reflects the heterogeneity of the region. The heterogeneous neuropsychological deficits arising from orbitomedial damage are difficult to ascribe to a unitary function or process, but appear to reflect a set of processes necessary for monitoring and adapting to changing reinforcement contingencies.

Experience-driven neuronal plasticity allows the brain to adapt its functional connectivity to recent sensory input. Here we use binocular rivalry [1], an experimental paradigm in which conflicting images are presented to the individual eyes, to demonstrate plasticity in the neuronal mechanisms that convert visual information from two separated retinas into single perceptual experiences. Perception during binocular rivalry tended to initially consist of alternations between exclusive representations of monocularly defined images, but upon prolonged exposure, mixture percepts became more prevalent. The completeness of suppression, reflected in the incidence of mixture percepts, plausibly reflects the strength of inhibition that likely plays a role in binocular rivalry [2]. Recovery of exclusivity was possible but required highly specific binocular stimulation. Documenting the prerequisites for these observed changes in perceptual exclusivity, our experiments suggest experience-driven plasticity at interocular inhibitory synapses, driven by the correlated activity (and also the lack thereof) of neurons representing the conflicting stimuli. This form of plasticity is consistent with a previously proposed but largely untested anti-Hebbian learning mechanism for inhibitory synapses in vision [3, 4]. Our results implicate experience-driven plasticity as one governing principle in the neuronal organization of binocular vision.

Dopamine (DA) has long been implicated in impulsivity, but the precise mechanisms linking human variability in DA signaling to differences in impulsive traits remain largely unknown. By using a dual-scan positron emission tomography approach in healthy human volunteers with amphetamine and the D2/D3 ligand [(18)F]fallypride, we found that higher levels of trait impulsivity were predicted by diminished midbrain D2/D3 autoreceptor binding and greater amphetamine-induced DA release in the striatum, which was in turn associated with stimulant craving. Path analysis confirmed that the impact of decreased midbrain D2/D3 autoreceptor availability on trait impulsivity is mediated in part through its effect on stimulated striatal DA release.

Previous theories have proposed that the amygdala is hyper-responsive to novel stimuli in persons with an inhibited temperament-a biologically based predisposition to respond to novelty with wariness or avoidance behavior. In the current study, we used functional magnetic resonance imaging (fMRI) to assess amygdala blood oxygenation level-dependent (BOLD) response when viewing novel or recently familiarized faces in persons with an extreme inhibited or uninhibited temperament. In persons with an inhibited temperament, the amygdala showed increased BOLD response when viewing both novel and recently familiarized faces. In contrast, in persons with an uninhibited temperament, BOLD response in the amygdala was increased only when viewing novel faces. These findings suggest that inhibited temperament is characterized not by a simple exaggerated response to novel faces, but rather by a sustained increase in amygdala response to faces even after the faces have become familiarized. In individuals with an inhibited temperament, this sustained response may be related to the wariness of social situations that persists beyond initial exposure.

Characterizing the temporal limits of the human visual system has long been a central goal of vision research. Spanning three centuries of research, temporal order judgments have been used to estimate the temporal precision of visual processing, with nearly all the research focusing on onset asynchrony discriminations. Recent neurophysiological work, however, demonstrated that neural latencies for stimulus offsets are shorter and less variable than those following event onsets, suggesting that event offsets might provide more reliable timing cues to the visual system than event onsets. Here, we tested this hypothesis by measuring psychophysical thresholds for discriminating onset and offset asynchronies for both stationary and moving stimuli. In three experiments, we showed that offset asynchrony thresholds were indeed consistently lower and were less affected by stimulus variations than onset asynchrony thresholds. These findings are consistent with neurophysiology and suggest a possible role of offset signals as reliable timing references for visual events.

Previous research has indicated that the amygdala is a critical neural substrate of the emotional modulation of attention. However, a recent case-study suggests that the amygdala may not be essential for all types of emotion-attention interactions. In order to test this hypothesis, we assessed the visual-search performance of patients with unilateral amygdala lesions, matched controls, and medication-matched epilepsy patients with intact amygdalae. All participants completed a visual-search task consisting of trials in which (1) an emotional target was embedded amongst neutral distractors,(2) a neutral target was embedded amongst emotional distractors, or (3) a neutral target was embedded amongst neutral distractors. All participant groups, including those with amygdala lesions, detected emotional targets more efficiently than neutral targets. These data indicate that the amygdala is not necessary for emotion-guided visual search and suggest that other mechanisms beyond the amygdala help guide attention toward threatening stimuli.

Anhedonia is a core symptom of major depressive disorder (MDD), the neurobiological mechanisms of which remain poorly understood. Despite decades of speculation regarding the role of dopamine (DA) in anhedonic symptoms, empirical evidence has remained elusive, with frequent reports of contradictory findings. In the present review, we argue that this has resulted from an underspecified definition of anhedonia, which has failed to dissociate between consummatory and motivational aspects of reward behavior. Given substantial preclinical evidence that DA is involved primarily in motivational aspects of reward, we suggest that a refined definition of anhedonia that distinguishes between deficits in pleasure and motivation is essential for the purposes of identifying its neurobiological substrates. Moreover, bridging the gap between preclinical and clinical models of anhedonia may require moving away from the conceptualization of anhedonia as a steady-state, mood-like phenomena. Consequently, we introduce the term "decisional anhedonia" to address the influence of anhedonia on reward decision-making. These proposed modifications to the theoretical definition of anhedonia have implications for research, assessment and treatment of MDD.

When viewing a different stimulus with each eye, we experience the remarkable phenomenon of binocular rivalry: alternations in consciousness between the stimuli [1, 2]. According to a popular theory first proposed in 1901, neurons encoding the two stimuli engage in reciprocal inhibition [3-8] so that those processing one stimulus inhibit those processing the other, yielding consciousness of one dominant stimulus at any moment and suppressing the other. Also according to the theory, neurons encoding the dominant stimulus adapt, weakening their activity and the inhibition they can exert, whereas neurons encoding the suppressed stimulus recover from adaptation until the balance of activity reverses, triggering an alternation in consciousness. Despite its popularity, this theory has one glaring inconsistency with data: during an episode of suppression, visual sensitivity to brief probe stimuli in the dominant eye should decrease over time and should increase in the suppressed eye, yet sensitivity appears to be constant [9, 10]. Using more appropriate probe stimuli (experiment 1) in conjunction with a new method (experiment 2), we found that sensitivities in dominance and suppression do show the predicted complementary changes.

Previous research has shown implicit semantic processing of faces or pictures, but whether symbolic carriers such as words can be processed this way remains controversial. Here we examine this issue by adopting the continuous flash suppression paradigm to ensure that the processing undergone is indeed unconscious without the involvement of partial awareness. Negative or neutral words projected into one eye were made invisible due to strong suppression induced by dynamic-noise patterns shown in the other eye through binocular rivalry. Inverted and scrambled words were used as controls to provide baselines at orthographic and feature levels, respectively. Compared to neutral words, emotion-described and emotion-induced negative words required longer time to release from suppression, but only for upright words. These results suggest that words can be processed unconsciously up to semantic level since under interocular suppression completely invisible words can lead to different processing speed due to the emotion information they carry.

OBJECTIVE: Erythropoietin (Epo) has neuroprotective and neurotrophic effects, and may be a novel therapeutic agent in the treatment of psychiatric disorders. We have demonstrated antidepressant-like effects of Epo on the neural and cognitive processing of facial expressions in healthy volunteers. The current study investigates the effects of Epo on the neural and cognitive response to emotional facial expressions in depressed patients. METHOD: Nineteen acutely depressed patients were randomized to receive Epo (40,000 IU) or saline intravenously in a double-blind, parallel-group design. On day 3, we assessed neuronal responses to fearful and happy faces using functional magnetic resonance imaging and measured facial expression recognition after the scan. RESULTS: Epo reduced neural response to fearful vs. happy faces in the amygdala and hippocampus, and to fearful faces vs. baseline in superior temporal and occipitoparietal regions 3 days after administration in acutely depressed patients. This was accompanied by a specific reduction in the recognition of fear in Epo-treated patients after the scan similar to the effects on face recognition seen with antidepressant drug treatment. CONCLUSIONS: The present findings are similar to the effects of conventional antidepressants in acutely depressed patients and opposite to hypervigilance to negative facial expressions in depression. This highlights a potential antidepressant mechanism and warrants further investigation of Epo as a new candidate compound for treatment of depression.

Impairment in recognizing facial emotions is a prominent feature of schizophrenia patients, but the underlying mechanism of this impairment remains unclear. This study investigated the specific aspects of visual information that are critical for schizophrenia patients to recognize emotional expression. Using the Bubbles technique, we probed the use of visual information during a facial emotion discrimination task (fear vs. happy) in 21 schizophrenia patients and 17 healthy controls. Visual information was sampled through randomly located Gaussian apertures (or "bubbles") at 5 spatial frequency scales. Online calibration of the amount of face exposed through bubbles was used to ensure 75% overall accuracy for each subject. Least-square multiple linear regression analyses between sampled information and accuracy were performed to identify critical visual information that was used to identify emotional expression. To accurately identify emotional expression, schizophrenia patients required more exposure of facial areas (i.e., more bubbles) compared with healthy controls. To identify fearful faces, schizophrenia patients relied less on bilateral eye regions at high-spatial frequency compared with healthy controls. For identification of happy faces, schizophrenia patients relied on the mouth and eye regions; healthy controls did not utilize eyes and used the mouth much less than patients did. Schizophrenia patients needed more facial information to recognize emotional expression of faces. In addition, patients differed from controls in their use of high-spatial frequency information from eye regions to identify fearful faces. This study provides direct evidence that schizophrenia patients employ an atypical strategy of using visual information to recognize emotional faces.

The present study examines the extent to which attentional biases in contamination fear commonly observed in obsessive-compulsive disorder (OCD) are specific to disgust or fear cues, as well as the components of attention involved. Eye tracking was used to provide greater sensitivity and specificity than afforded by traditional reaction time measures of attention. Participants high (HCF; n = 23) and low (LCF; n = 25) in contamination fear were presented with disgusted, fearful, or happy faces paired with neutral faces for 3 s trials. Evidence of both vigilance and maintenance-based biases for threat was found. The high group oriented attention to fearful faces but not disgusted faces compared to the low group. However, the high group maintained attention on both disgusted and fearful expressions compared to the low group, a pattern consistent across the 3 s trials. The implications of these findings for conceptualizing emotional factors that moderate attentional biases in contamination-based OCD are discussed.

Event-related potentials were recorded from adults and 4-month-old infants while they watched pictures of faces that varied in emotional expression (happy and fearful) and in gaze direction (direct or averted). Results indicate that emotional expression is temporally independent of gaze direction processing at early stages of processing, and only become integrated at later latencies. Facial expressions affected the face-sensitive ERP components in both adults (N170) and infants (N290 and P400), while gaze direction and the interaction between facial expression and gaze affected the posterior channels in adults and the frontocentral channels in infants. Specifically, in adults, this interaction reflected a greater responsiveness to fearful expressions with averted gaze (avoidance-oriented emotion), and to happy faces with direct gaze (approach-oriented emotions). In infants, a larger activation to a happy expression at the frontocentral negative component (Nc) was found, and planned comparisons showed that it was due to the direct gaze condition. Taken together, these results support the shared signal hypothesis in adults, but only to a lesser extent in infants, suggesting that experience could play an important role.

Studies of explicit processing of facial expressions by individuals with autism spectrum disorder (ASD) have found a variety of deficits and preserved abilities compared to their typically developing (TD) peers. However, little attention has been paid to their implicit processing abilities for emotional facial expressions. The question has also been raised whether preferential attention to the mouth region of a speaker's face by ASD individuals has resulted in a relative lipreading expertise. We present data on implicit processing of pseudo-dynamic facial emotions and visual speech in adolescents with autism. We compared 25 ASD and 25 TD participants on their ability to recreate the sequences of four dynamic emotional facial expressions (happy, sad, disgust, fear) as well as four spoken words (with, bath, thumb, watch) using six still images taken from a video sequence. Typical adolescents were significantly better at recreating the dynamic properties of emotional expressions than those of facial speech, while the autism group showed the reverse accuracy pattern. For Experiment 2 we obscured the eye region of the stimuli and found no significant difference between the 22 adolescents with ASD and 22 TD controls. Fearful faces achieved the highest accuracy results among the emotions in both groups.

Individuals with pervasive developmental disorder (PDD) have difficulty with social communication via emotional facial expressions, but behavioral studies involving static images have reported inconsistent findings about emotion recognition. We investigated whether dynamic presentation of facial expression would enhance subjective perception of expressed emotion in 13 individuals with PDD and 13 typically developing controls. We presented dynamic and static emotional (fearful and happy) expressions. Participants were asked to match a changeable emotional face display with the last presented image. The results showed that both groups perceived the last image of dynamic facial expression to be more emotionally exaggerated than the static facial expression. This finding suggests that individuals with PDD have an intact perceptual mechanism for processing dynamic information in another individual's face.

Unconscious processing of stimuli with emotional content can bias affective judgments. Is this subliminal affective priming merely a transient phenomenon manifested in fleeting perceptual changes, or are long-lasting effects also induced? To address this question, we investigated memory for surprise faces 24h after they had been shown with 30-ms fearful, happy, or neutral faces. Surprise faces subliminally primed by happy faces were initially rated as more positive, and were later remembered better, than those primed by fearful or neutral faces. Participants likely to have processed primes supraliminally did not respond differentially as a function of expression. These results converge with findings showing memory advantages with happy expressions, though here the expressions were displayed on the face of a different person, perceived subliminally, and not present at test. We conclude that behavioral biases induced by masked emotional expressions are not ephemeral, but rather can last at least 24h.

Previous studies have shown differential event-related potentials (ERPs) to intensities of fearful facial expressions. There are indications that the eyes may be particularly relevant for the recognition of fearful expressions, even the amount of white sclera exposed above and on sides of the dark pupil could activate the amygdala response. To investigate whether the ERP differences between intensities of fearful expressions are driven by the differential salience of the eyes in the fearful faces, ERPs were measured within a backward masking paradigm, where observers were asked to do a gender decision task with male and female neutral faces. The emotional stimuli used were low-intensity (50%), prototypical (100%), and caricatured (150%) fearful eye whites that were derived from corresponding intensities of fearful faces respectively. Three groups of white squares that have the same pixels as the eye whites were created as control conditions. Analysis of the ERP data showed a linear increase in amplitudes of the parietal-occipital P120 by three intensities of fearful eye whites. These ERP effects were proved sensitive to intensities of negative emotions but not to the simple physical features as the same patterns of differences were not observed on white squares. Larger parietal-occipital P250 amplitudes were observed for caricatured 150% than low-intensity 50% fearful eye-white. It might reflect the subcortical pathway of emotion-specific, fearful processing. The results demonstrate that the human brain is sensitive to intensities of fear, even if just shown intensities of fearful eye-white in the absence of awareness.

Empirical evidence shows an effect of gaze direction on cueing spatial attention, regardless of the emotional expression shown by a face, whereas a combined effect of gaze direction and facial expression has been observed on individuals' evaluative judgments. In 2 experiments, the authors investigated whether gaze direction and facial expression affect spatial attention depending upon the presence of an evaluative goal. Disgusted, fearful, happy, or neutral faces gazing left or right were followed by positive or negative target words presented either at the spatial location looked at by the face or at the opposite spatial location. Participants responded to target words based on affective valence (i.e., positive/negative) in Experiment 1 and on letter case (lowercase/uppercase) in Experiment 2. Results showed that participants responded much faster to targets presented at the spatial location looked at by disgusted or fearful faces but only in Experiment 1, when an evaluative task was used. The present findings clearly show that negative facial expressions enhance the attentional shifts due to eye-gaze direction, provided that there was an explicit evaluative goal present.(PsycINFO Database Record (c) 2008 APA, all rights reserved).