Alternative outcomes create biased expectations regarding the received outcome: Evidence from event-related potentials.

After choosing between uncertain options, one might get feedback on both the outcome of the chosen option and the outcome of the unchosen option (the alternative). Behavioral research has shown that in such cases people engage in outcome comparison, and that the alternative outcome influences the way one evaluates his own received outcome. Moreover, this influence differs whether one was responsible or not for the choice made. In two studies, we looked for the electrophysiological correlates of outcome comparison. Subjects chose one of two boxes shown on the screen, each box contained a gain or a loss. The alternative outcome was always revealed first, followed by the received outcome. In half of the trials the software picked one box instead of subjects. We tested whether the feedback-related negativity (FRN) and the P3 elicited by the received reflect outcome comparison. As expected, we found that the FRN and P3 were more positive when the received outcome was a gain (vs. a loss). The FRN and P3 were also sensitive to the value of the alternative outcome, but contrary to our predictions, they were more positive when the alternative outcome was a gain (vs. a loss). As the FRN and P3 are sensitive to expectations, we hypothesized that our findings might result from subjects' biased expectations: subjects might have wrongly believed that a good (bad) alternative outcome signaled a bad (good) received outcome. This hypothesis, coined as the Alternative Omen Effect, was confirmed in parallel in a series of behavioral experiments: people see an illusory negative correlation between the uncorrelated outcomes of choice options (reported in Marciano-Romm et al. (2016)). A challenge for future research will be to disentangle the effects of expectation from those of outcome comparison.

Dysfunction of the Human Mirror Neuron System in Ideomotor Apraxia: Evidence from Mu Suppression.

Stroke patients with ideomotor apraxia (IMA) have difficulties controlling voluntary motor actions, as clearly seen when asked to imitate simple gestures performed by the examiner. Despite extensive research, the neurophysiological mechanisms underlying failure to imitate gestures in IMA remain controversial. The aim of the current study was to explore the relationship between imitation failure in IMA and mirror neuron system (MNS) functioning. Mirror neurons were found to play a crucial role in movement imitation and in imitation-based motor learning. Their recruitment during movement observation and execution is signaled in EEG recordings by suppression of the lower (8-10 Hz) mu range. We examined the modulation of EEG in this range in stroke patients with left (n = 21) and right (n = 15) hemisphere damage during observation of video clips showing different manual movements. IMA severity was assessed by the DeRenzi standardized diagnostic test. Results showed that failure to imitate observed manual movements correlated with diminished mu suppression in patients with damage to the right inferior parietal lobule and in patients with damage to the right inferior frontal gyrus pars opercularis-areas where major components of the human MNS are assumed to reside. Voxel-based lesion symptom mapping revealed a significant impact on imitation capacity for the left inferior and superior parietal lobules and the left post central gyrus. Both left and right hemisphere damages were associated with imitation failure typical of IMA, yet a clear demonstration of relationship to the MNS was obtained only in the right hemisphere damage group. Suppression of the 8-10 Hz range was stronger in central compared with occipital sites, pointing to a dominant implication of mu rather than alpha rhythms. However, the suppression correlated with De Renzi's apraxia test scores not only in central but also in occipital sites, suggesting a multifactorial mechanism for IMA, with a possible impact for deranged visual attention (alpha suppression) beyond the effect of MNS damage (mu suppression).

Rehearsing biological motion in working memory: an EEG study.

Holding biological motion (BM), the movements of animate entities, in working memory (WM) is important to our daily social life. However, how BM is maintained in WM remains unknown. The current study investigated this issue and hypothesized that, analogous to BM perception, the human mirror neuron system (MNS) is involved in rehearsing BM in WM. To examine the MNS hypothesis of BM rehearsal, we used an EEG index of mu suppression (8-12 Hz), which has been linked to the MNS. Using a change detection task, we manipulated the BM memory load in three experiments. We predicted that mu suppression in the maintenance phase of WM would be modulated by the BM memory load; moreover, a negative correlation between the number of BM stimuli in WM and the degree of mu suppression may emerge. The results of Experiment 1 were in line with our predictions and revealed that mu suppression increased as the memory load increased from two to four BM stimuli; however, mu suppression then plateaued, as WM could only hold, at most, four BM stimuli. Moreover, the predicted negative correlation was observed. Corroborating the findings of Experiment 1, Experiment 2 further demonstrated that once participants used verbal codes to process the motion information, the mu suppression or modulation by memory load vanished. Finally, Experiment 3 demonstrated that the findings in Experiment 1 were not limited to one specific type of stimuli. Together, these results provide evidence that the MNS underlies the process of rehearsing BM in WM.

Training-induced recovery of low-level vision followed by mid-level perceptual improvements in developmental object and face agnosia.

Long-term deprivation of normal visual inputs can cause perceptual impairments at various levels of visual function, from basic visual acuity deficits, through mid-level deficits such as contour integration and motion coherence, to high-level face and object agnosia. Yet it is unclear whether training during adulthood, at a post-developmental stage of the adult visual system, can overcome such developmental impairments. Here, we visually trained LG, a developmental object and face agnosic individual. Prior to training, at the age of 20, LG's basic and mid-level visual functions such as visual acuity, crowding effects, and contour integration were underdeveloped relative to normal adult vision, corresponding to or poorer than those of 5-6 year olds (Gilaie-Dotan, Perry, Bonneh, Malach & Bentin, 2009). Intensive visual training, based on lateral interactions, was applied for a period of 9 months. LG's directly trained but also untrained visual functions such as visual acuity, crowding, binocular stereopsis and also mid-level contour integration improved significantly and reached near-age-level performance, with long-term (over 4 years) persistence. Moreover, mid-level functions that were tested post-training were found to be normal in LG. Some possible subtle improvement was observed in LG's higher-order visual functions such as object recognition and part integration, while LG's face perception skills have not improved thus far. These results suggest that corrective training at a post-developmental stage, even in the adult visual system, can prove effective, and its enduring effects are the basis for a revival of a developmental cascade that can lead to reduced perceptual impairments.

Integrating the automatic and the controlled: strategies in semantic priming in an attractor network with latching dynamics.

Semantic priming has long been recognized to reflect, along with automatic semantic mechanisms, the contribution of controlled strategies. However, previous theories of controlled priming were mostly qualitative, lacking common grounds with modern mathematical models of automatic priming based on neural networks. Recently, we introduced a novel attractor network model of automatic semantic priming with latching dynamics. Here, we extend this work to show how the same model can also account for important findings regarding controlled processes. Assuming the rate of semantic transitions in the network can be adapted using simple reinforcement learning, we show how basic findings attributed to controlled processes in priming can be achieved, including their dependency on stimulus onset asynchrony and relatedness proportion and their unique effect on associative, category-exemplar, mediated and backward prime-target relations. We discuss how our mechanism relates to the classic expectancy theory and how it can be further extended in future developments of the model.

Association and dissociation between detection and discrimination of objects of expertise: Evidence from visual search.

Expertise in face recognition is characterized by high proficiency in distinguishing between individual faces. However, faces also enjoy an advantage at the early stage of basic-level detection, as demonstrated by efficient visual search for faces among nonface objects. In the present study, we asked (1) whether the face advantage in detection is a unique signature of face expertise, or whether it generalizes to other objects of expertise, and (2) whether expertise in face detection is intrinsically linked to expertise in face individuation. We compared how groups with varying degrees of object and face expertise (typical adults, developmental prosopagnosics [DP], and car experts) search for objects within and outside their domains of expertise (faces, cars, airplanes, and butterflies) among a variable set of object distractors. Across all three groups, search efficiency (indexed by reaction time slopes) was higher for faces and airplanes than for cars and butterflies. Notably, the search slope for car targets was considerably shallower in the car experts than in nonexperts. Although the mean face slope was slightly steeper among the DPs than in the other two groups, most of the DPs' search slopes were well within the normative range. This pattern of results suggests that expertise in object detection is indeed associated with expertise at the subordinate level, that it is not specific to faces, and that the two types of expertise are distinct facilities. We discuss the potential role of experience in bridging between low-level discriminative features and high-level naturalistic categories.

Mirror-neuron system recruitment by action observation: effects of focal brain damage on mu suppression.

Mu suppression is the attenuation of EEG power in the alpha frequency range (8-12 Hz), recorded over the sensorimotor cortex during execution and observation of motor actions. Based on this dual characteristic mu suppression is thought to signalize activation of a human analogue of the mirror neuron system (MNS) found in macaque monkeys. However, much uncertainty remains concerning its specificity and full significance. To further explore the hypothesized relationship between mu suppression and MNS activation, we investigated how it is affected by damage to cortical regions, including areas where the MNS is thought to reside. EEG was recorded in 33 first-event stroke patients during observation of video clips showing reaching and grasping hand movements. We examined the modulation of EEG oscillations at central and occipital sites, and analyzed separately the lower (8-10 Hz) and higher (10-12 Hz) segments of the alpha/mu range. Suppression was determined relative to observation of a non-biological movement. Normalized lesion data were used to investigate how damage to regions of the fronto-parietal cortex affects the pattern of suppression. The magnitude of mu suppression during action observation was significantly reduced in the affected hemisphere compared to the unaffected hemisphere. Differences between the hemispheres were significant at central (sensorimotor) sites but not at occipital (visual) sites. Total hemispheric volume loss did not correlate with mu suppression. Suppression in the lower mu range in the unaffected hemisphere (C3) correlated with lesion extent within the right inferior parietal cortex. Our lesion study supports the role of mu suppression as a marker of MNS activation, confirming previous studies in normal subjects.

Mapping the time course of other-race face classification advantage: a cross-race ERP study.

The current study investigated the time course of the other-race advantage (ORA) in the subordinate classification of faces by race. A significant ORA was found on RTs for both races. The ERP data showed that the categorization processes follow basic level classification of physiognomic stimuli, which is not influenced by the stimulus race. The most conspicuous difference between own-race and other-race faces was found in the modulation of the amplitude of the P3. Since the amplitude of the P3 is sensitive primarily to the perceptual demands of a task, these data suggest that the delay of the own-race classification is caused by an own-race specific process that precedes or interferes with the subordinate classification.

Are all types of expertise created equal? Car experts use different spatial frequency scales for subordinate categorization of cars and faces.

A much-debated question in object recognition is whether expertise for faces and expertise for non-face objects utilize common perceptual information. We investigated this issue by assessing the diagnostic information required for different types of expertise. Specifically, we asked whether face categorization and expert car categorization at the subordinate level relies on the same spatial frequency (SF) scales. Fifteen car experts and fifteen novices performed a category verification task with spatially filtered images of faces, cars, and airplanes. Images were categorized based on their basic (e.g. "car") and subordinate level (e.g. "Japanese car") identity. The effect of expertise was not evident when objects were categorized at the basic level. However, when the car experts categorized faces and cars at the subordinate level, the two types of expertise required different kinds of SF information. Subordinate categorization of faces relied on low SFs more than on high SFs, whereas subordinate expert car categorization relied on high SFs more than on low SFs. These findings suggest that expertise in the recognition of objects and faces do not utilize the same type of information. Rather, different types of expertise require different types of diagnostic visual information.

Visual search for faces by race: a cross-race study.

Using a single averaged face of each race previous study indicated that the detection of one other-race face among own-race faces background was faster than vice versa (Levin, 1996, 2000). However, employing a variable mapping of face pictures one recent report found preferential detection of own-race faces vs. other-race faces (Lipp et al., 2009). Using the well-controlled design and a heterogeneous set of real face images, in the present study we explored the visual search for own and other race faces in Chinese and Caucasian participants. Across both groups, the search for a face of one race among other-race faces was serial and self-terminating. In Chinese participants, the search consistently faster for other-race than own-race faces, irrespective of upright or upside-down condition; however, this search asymmetry was not evident in Caucasian participants. These characteristics suggested that the race of a face is not a visual basic feature, and in Chinese participants the faster search for other-race than own-race faces also reflects perceptual factors. The possible mechanism underlying other-race search effects was discussed.

Dynamics of the EEG power in the frequency and spatial domains during observation and execution of manual movements.

Mu suppression is the attenuation of EEG power in the alpha frequency range (8-12 Hz) while executing or observing a motor action. Whereas typically observed at central scalp sites, there are diverging reports about the extent of the attenuation over the cortical mantle, its exact frequency range and the specificity of this phenomenon. We investigated the modulation of EEG oscillations in frequency-bands between 4 to 12 Hz at frontal, central, parietal and occipital sites during the execution of manual movements and during observation of similar actions from allocentric (i.e., facing the actor) and egocentric (i.e., seeing the actor from behind) viewpoints. Suppression was determined relative to observation of a non-biological movement. Action observation elicited greater suppression in the lower (8-10 Hz) compared to the higher mu range (10-12 Hz), and greater suppression in the entire range (4-12 Hz) at frontal and central sites compared to parietal and occipital sites. In addition, suppression tended to be greater during observation of a motor action from allocentric compared to egocentric viewpoints. During execution of movement, suppression of the EEG occurred primarily in the higher alpha range and was absent at occipital sites. In the theta range (4-8 Hz), the EEG amplitude was suppressed during action observation and execution. The results suggest a functional distinction between modulation of mu and alpha rhythms, and between the higher and lower ranges of the mu rhythms. The activity of the presumed human mirror-neuron system seems primarily evident in the lower mu range and in the theta range.

MEG premotor abnormalities in children with Asperger's syndrome: determinants of social behavior?

Children with Asperger's syndrome show deficits in social functioning while their intellectual and language development is intact suggesting a specific dysfunction in mechanisms mediating social cognition. An action observation/execution matching system might be one such mechanism. Recent studies indeed showed that electrophysiological modulation of the "Mu-rhythm" in the 10-12Hz range is weaker when individuals with Asperger's syndrome observe actions performed by others compared to controls. However, electrophysiological studies typically fall short in revealing the neural generators of this activity. To fill this gap we assessed magnetoencephalographic Mu-modulations in Asperger's and typically developed children, while observing grasping movements. Mu-power increased at frontal and central sensors during movement observation. This modulation was stronger in typical than in Asperger children. Source localization revealed stronger sources in premotor cortex, the intraparietal lobule (IPL) and the mid-occipito-temporal gyrus (MOTG) and weaker sources in prefrontal cortex in typical participants compared to Asperger. Activity in premotor regions, IPL and MOTG correlated positively with social competence, whereas prefrontal Mu-sources correlated negatively with social competence. No correlation with intellectual ability was found at any of these sites. These findings localize abnormal Mu-activity in the brain of Asperger children providing evidence which associates motor-system abnormalities with social-function deficits.

Resting state functional connectivity reflects abnormal task-activated patterns in a developmental object agnosic.

Even in the absence of stimulation or task, the cerebral cortex shows an incessant pattern of ultra slow fluctuations which are coherent across brain regions. In the healthy brain these coherent patterns (also termed resting state functional connectivity) often exhibit spatial similarity to the large scale organization of task-induced functional networks. However, it is not clear to what extent the resting state patterns can also reflect task-induced abnormalities in cortical activations which are often detected in various brain pathologies. Here we examined whether an abnormal visual activation pattern is recapitulated in the resting state functional connectivity. We examined LG, a sighted young adult with developmental object agnosia and no apparent cortical structural abnormality. We have previously reported that upon visual stimulation, LG's intermediate visual areas (V2, V3) are paradoxically deactivated. Here, examining LG's resting state functional connectivity revealed the same pattern of functional abnormality - including a strong atypical decorrelation between areas V2-V3 and the rest of the visual system. Thus, our results suggest that resting-state functional connectivity could provide a powerful tool which could complement task-specific paradigms in detecting task-related abnormalities in cortical activity without resorting to task performance.

A magnetoencephalographic study of face processing: M170, gamma-band oscillations and source localization.

EEG studies suggested that the N170 ERP and Gamma-band responses to faces reflect early and later stages of a multiple-level face-perception mechanism, respectively. However, these conclusions should be considered cautiously because EEG-recorded Gamma may be contaminated by noncephalic activity such as microsaccades. Moreover, EEG studies of Gamma cannot easily reveal its intracranial sources. Here we recorded MEG rather than EEG, assessed the sources of the M170 and Gamma oscillations using beamformer, and explored the sensitivity of these neural manifestations to global, featural and configural information in faces. The M170 was larger in response to faces and face components than in response to watches. Scrambling the configuration of the inner components of the face even if presented without the face contour reduced and delayed the M170. The amplitude of MEG Gamma oscillations (30-70 Hz) was higher than baseline during an epoch between 230-570 ms from stimulus onset and was particularly sensitive to the configuration of the stimuli, regardless of their category. However, in the lower part of this frequency range (30-40 Hz) only physiognomic stimuli elevated the MEG above baseline. Both the M170 and Gamma were generated in a posterior-ventral network including the fusiform, inferior-occipital and lingual gyri, all in the right hemisphere. The generation of Gamma involved additional sources in the visual system, bilaterally. We suggest that the evoked M170 manifests a face-perception mechanism based on the global characteristics of face, whereas the induced Gamma oscillations are associated with the integration of visual input into a pre-existent coherent perceptual representation.

Spreading activation in an attractor network with latching dynamics: automatic semantic priming revisited.

Localist models of spreading activation (SA) and models assuming distributed representations offer very different takes on semantic priming, a widely investigated paradigm in word recognition and semantic memory research. In this study, we implemented SA in an attractor neural network model with distributed representations and created a unified framework for the two approaches. Our models assume a synaptic depression mechanism leading to autonomous transitions between encoded memory patterns (latching dynamics), which account for the major characteristics of automatic semantic priming in humans. Using computer simulations, we demonstrated how findings that challenged attractor-based networks in the past, such as mediated and asymmetric priming, are a natural consequence of our present model's dynamics. Puzzling results regarding backward priming were also given a straightforward explanation. In addition, the current model addresses some of the differences between semantic and associative relatedness and explains how these differences interact with stimulus onset asynchrony in priming experiments.

Preserved local but disrupted contextual figure-ground influences in an individual with abnormal function of intermediate visual areas.

Visual perception depends not only on local stimulus features but also on their relationship to the surrounding stimulus context, as evident in both local and contextual influences on figure-ground segmentation. Intermediate visual areas may play a role in such contextual influences, as we tested here by examining LG, a rare case of developmental visual agnosia. LG has no evident abnormality of brain structure and functional neuroimaging showed relatively normal V1 function, but his intermediate visual areas (V2/V3) function abnormally. We found that contextual influences on figure-ground organization were selectively disrupted in LG, while local sources of figure-ground influences were preserved. Effects of object knowledge and familiarity on figure-ground organization were also significantly diminished. Our results suggest that the mechanisms mediating contextual and familiarity influences on figure-ground organization are dissociable from those mediating local influences on figure-ground assignment. The disruption of contextual processing in intermediate visual areas may play a role in the substantial object recognition difficulties experienced by LG.

Excessive attractor instability accounts for semantic priming in schizophrenia.

One of the most pervasive findings in studies of schizophrenics with thought disorders is their peculiar pattern of semantic priming, which presumably reflects abnormal associative processes in the semantic system of these patients. Semantic priming is manifested by faster and more accurate recognition of a word-target when preceded by a semantically related prime, relative to an unrelated prime condition. Compared to control, semantic priming in schizophrenics is characterized by reduced priming effects at long prime-target Stimulus Onset Asynchrony (SOA) and, sometimes, augmented priming at short SOA. In addition, unlike controls, schizophrenics consistently show indirect (mediated) priming (such as from the prime 'wedding' to the target 'finger', mediated by 'ring'). In a previous study, we developed a novel attractor neural network model with synaptic adaptation mechanisms that could account for semantic priming patterns in healthy individuals. Here, we examine the consequences of introducing attractor instability to this network, which is hypothesized to arise from dysfunctional synaptic transmission known to occur in schizophrenia. In two simulated experiments, we demonstrate how such instability speeds up the network's dynamics and, consequently, produces the full spectrum of priming effects previously reported in patients. The model also explains the inconsistency of augmented priming results at short SOAs using directly related pairs relative to the consistency of indirect priming. Further, we discuss how the same mechanism could account for other symptoms of the disease, such as derailment ('loose associations') or the commonly seen difficulty of patients in utilizing context. Finally, we show how the model can statistically implement the overly-broad wave of spreading activation previously presumed to characterize thought-disorders in schizophrenia.

Neuroanatomical correlates of visual car expertise.

Expertise in non-visual domains such as musical performance is associated with differences in gray matter volume of particular regions of the human brain. Whether this is also the case for expertise in visual object recognition is unknown. Here we tested whether individual variability in the ability to recognize car models, from novice performance to high level of expertise, is associated with specific structural changes in gray matter volume. We found that inter-individual variability in expertise with cars was significantly and selectively correlated with gray matter volume in prefrontal cortex. Inter-individual differences in the recognition of airplanes, that none of the participants had expertise with, were correlated with structural variability of regions bordering the visual cortex. These results highlight the role of prefrontal regions outside the visual cortex in accessing and processing visual knowledge about objects from the domain of expertise and suggest that expertise in visual object recognition may entail structural changes in regions associated with semantic knowledge.

Crowd perception in prosopagnosia.

Prosopagnosics, individuals who are impaired at recognizing single faces, often report increased difficulty when confronted with crowds. However, the discrimination of crowds has never been fully tested in the prosopagnosic population. Here we investigate whether developmental prosopagnosics can extract ensemble characteristics from groups of faces. DP and control participants viewed sets of faces varying in either identity or emotion, and were asked to estimate the average identity or emotion of each set. Face sets were displayed in two orientations (upright and inverted) to control for low-level visual features during ensemble encoding. Control participants made more accurate estimates of the mean identity and emotion when faces were upright than inverted. In all conditions, DPs performed equivalently to controls. This finding demonstrates that integration across different faces in a crowd is possible in the prosopagnosic population and appears to be intact despite their face recognition deficits. Results also demonstrate that ensemble representations are derived differently for upright and inverted faces, and the effects are not due to low-level visual information.

The right place at the right time: priming facial expressions with emotional face components in developmental visual agnosia.

The current study examined the nature of deficits in emotion recognition from facial expressions in case LG, an individual with a rare form of developmental visual agnosia (DVA). LG presents with profoundly impaired recognition of facial expressions, yet the underlying nature of his deficit remains unknown. During typical face processing, normal sighted individuals extract information about expressed emotions from face regions with activity diagnostic for specific emotion categories. Given LG's impairment, we sought to shed light on his emotion perception by examining if priming facial expressions with diagnostic emotional face components would facilitate his recognition of the emotion expressed by the face. LG and control participants matched isolated face components with components appearing in a subsequently presented full-face and then categorized the face's emotion. Critically, the matched components were from regions which were diagnostic or non-diagnostic of the emotion portrayed by the full face. In experiment 1, when the full faces were briefly presented (150 ms), LG's performance was strongly influenced by the diagnosticity of the components: his emotion recognition was boosted within normal limits when diagnostic components were used and was obliterated when non-diagnostic components were used. By contrast, in experiment 2, when the face-exposure duration was extended (2000 ms), the beneficial effect of the diagnostic matching was diminished as was the detrimental effect of the non-diagnostic matching. These data highlight the impact of diagnostic facial features in normal expression recognition and suggest that impaired emotion recognition in DVA results from deficient visual integration across diagnostic face components.