Human but not robotic gaze facilitates action prediction.

Do people ascribe intentions to humanoid robots as they would to humans or non-human-like animated objects? In six experiments, we compared people's ability to extract non-mentalistic (i.e., where an agent is looking) and mentalistic (i.e., what an agent is looking at; what an agent is going to do) information from gaze and directional cues performed by humans, human-like robots, and a non-human-like object. People were faster to infer the mental content of human agents compared to robotic agents. Furthermore, although the absence of differences in control conditions rules out the use of non-mentalizing strategies, the human-like appearance of non-human agents may engage mentalizing processes to solve the task. Overall, results suggest that human-like robotic actions may be processed differently from humans' and objects' behavior. These findings inform our understanding of the relevance of an object's physical features in triggering mentalizing abilities and its relevance for human-robot interaction.

Left Amygdala and Putamen Activation Modulate Emotion Driven Decisions in the Iterated Prisoner's Dilemma Game.

Although economic decision-making is commonly characterized as a purely rational phenomenon, it is clear that real-world decision-making is influenced by emotions. Yet, relatively little is known about the neural correlates of this process. To explore this issue, 20 participants underwent fMRI scanning while engaged in the Prisoner's Dilemma game under partner-directed sympathy, anger and neutral emotion conditions. Participants were most and least likely to cooperate after sympathy and anger induction, respectively, with the neutral condition eliciting intermediate cooperation rates. Moreover, the sympathy condition elicited quicker responses for cooperation than defection choices, whereas this pattern was reversed in the anger and neutral conditions. Left amygdala activation showed a positive correlation with cooperation rates and self-reports of partner directed sympathy in the sympathy condition. In the anger condition, left putamen activation was positively correlated with cooperation rates and negatively correlated with self-reports of partner directed anger strength. These findings indicate that while the left amygdala activation may be indicative of emotion enhancement and increase of cooperative behavior, the left putamen may help to suppress an emotion to overcome anger and engage in cooperation.

Transcranial magnetic stimulation over contralateral primary somatosensory cortex disrupts perception of itch intensity.

Itch, a complex unpleasant sensation causing the desire to scratch, results from the activity of a network of brain regions. However, the specific functional contributions of individual regions within this network remain poorly understood. We investigated whether contralateral primary and secondary somatosensory cortices (S1, S2) and ipsilateral inferior frontal gyrus (IFG) are critically involved in the cortical processing of acute itch. Continuous theta burst transcranial magnetic stimulation (cTBS) was applied to either S1, S2 or IFG, followed by itch induction using a histamine prick. Results indicate a significant reduction in itch intensity when cTBS was applied to S1. Stimulation of S2 or the IFG was not associated with a significant reduction in itch intensity. The novel finding of an antipruritic effect elicited by disruption of activity in contralateral S1 suggests a causal role of S1 in encoding the sensory-discriminative aspect of itch and might be important in future studies on brain interventions for the treatment of itch.

Differential roles of polar orbital prefrontal cortex and parietal lobes in logical reasoning with neutral and negative emotional content.

To answer the question of how brain pathology affects reasoning about negative emotional content, we administered a disjunctive logical reasoning task involving arguments with neutral content (e.g. Either there are tigers or women in NYC, but not both; There are no tigers in NYC; There are women in NYC) and emotionally laden content (e.g. Either there are pedophiles or politicians in Texas, but not both; There are politicians in Texas; There are no pedophiles in Texas) to 92 neurological patients with focal lesions to various parts of the brain. A Voxel Lesion Symptom Mapping (VLSM) analysis identified 16 patients, all with lesions to the orbital polar prefrontal cortex (BA 10 & 11), as being selectively impaired in the emotional reasoning condition. Another 17 patients, all with lesions to the parietal cortex, were identified as being impaired in the neutral content condition. The reasoning scores of these two patient groups, along with 23 matched normal controls, underwent additional analysis to explore the effect of belief bias. This analysis revealed that the differences identified above were largely driven by trials where there was an incongruency between the believability of the conclusion and the validity of the argument (i.e. valid argument/false conclusion or invalid argument/true conclusion). Patients with lesions to polar orbital prefrontal cortex underperformed in incongruent emotional content trials and over performed in incongruent neutral content trials (compared to both normal controls and patients with parietal lobe lesions). Patients with lesions to parietal lobes underperformed normal controls (at a trend level) in neutral trials where there was a congruency between the believability of the conclusion and the validity of the argument (i.e. valid argument/true conclusion or invalid argument/false conclusion). We conclude that lesions to the polar orbital prefrontal cortex (i) prevent these patients from enjoying any emotionally induced cognitive boost, and (ii) block the belief bias processing route in the neutral condition. Lesions to parietal lobes result in a generalized impairment in logical reasoning with neutral content.

Transcranial Magnetic Stimulation over Left Inferior Frontal and Posterior Temporal Cortex Disrupts Gesture-Speech Integration.

Language and action naturally occur together in the form of cospeech gestures, and there is now convincing evidence that listeners display a strong tendency to integrate semantic information from both domains during comprehension. A contentious question, however, has been which brain areas are causally involved in this integration process. In previous neuroimaging studies, left inferior frontal gyrus (IFG) and posterior middle temporal gyrus (pMTG) have emerged as candidate areas; however, it is currently not clear whether these areas are causally or merely epiphenomenally involved in gesture-speech integration. In the present series of experiments, we directly tested for a potential critical role of IFG and pMTG by observing the effect of disrupting activity in these areas using transcranial magnetic stimulation in a mixed gender sample of healthy human volunteers. The outcome measure was performance on a Stroop-like gesture task (Kelly et al., 2010a), which provides a behavioral index of gesture-speech integration. Our results provide clear evidence that disrupting activity in IFG and pMTG selectively impairs gesture-speech integration, suggesting that both areas are causally involved in the process. These findings are consistent with the idea that these areas play a joint role in gesture-speech integration, with IFG regulating strategic semantic access via top-down signals acting upon temporal storage areas.SIGNIFICANCE STATEMENT Previous neuroimaging studies suggest an involvement of inferior frontal gyrus and posterior middle temporal gyrus in gesture-speech integration, but findings have been mixed and due to methodological constraints did not allow inferences of causality. By adopting a virtual lesion approach involving transcranial magnetic stimulation, the present study provides clear evidence that both areas are causally involved in combining semantic information arising from gesture and speech. These findings support the view that, rather than being separate entities, gesture and speech are part of an integrated multimodal language system, with inferior frontal gyrus and posterior middle temporal gyrus serving as critical nodes of the cortical network underpinning this system.

Subliminal galvanic-vestibular stimulation influences ego- and object-centred components of visual neglect.

Neglect patients show contralesional deficits in egocentric and object-centred visuospatial tasks. The extent to which these different phenomena are modulated by sensory stimulation remains to be clarified. Subliminal galvanic vestibular stimulation (GVS) induces imperceptible, polarity-specific changes in the cortical vestibular systems without the unpleasant side effects (nystagmus, vertigo) induced by caloric vestibular stimulation. While previous studies showed vestibular stimulation effects on egocentric spatial neglect phenomena, such effects were rarely demonstrated in object-centred neglect. Here, we applied bipolar subsensory GVS over the mastoids (mean intensity: 0.7mA) to investigate its influence on egocentric (digit cancellation, text copying), object-centred (copy of symmetrical figures), or both (line bisection) components of visual neglect in 24 patients with unilateral right hemisphere stroke. Patients were assigned to two patient groups (impaired vs. normal in the respective task) on the basis of cut-off scores derived from the literature or from normal controls. Both groups performed all tasks under three experimental conditions carried out on three separate days: (a) sham/baseline GVS where no electric current was applied, (b) left cathodal/right anodal (CL/AR) GVS and (c) left anodal/right cathodal (AL/CR) GVS, for a period of 20min per session. CL/AR GVS significantly improved line bisection and text copying whereas AL/CR GVS significantly ameliorated figure copying and digit cancellation. These GVS effects were selectively observed in the impaired- but not in the unimpaired patient group. In conclusion, subliminal GVS modulates ego- and object-centred components of visual neglect rapidly. Implications for neurorehabilitation are discussed.

The effect of partner-directed emotion in social exchange decision-making.

Despite the prevalence of studies examining economic decision-making as a purely rational phenomenon, common sense suggests that emotions affect our decision-making particularly in a social context. To explore the influence of emotions on economic decision-making, we manipulated opponent-directed emotions prior to engaging participants in two social exchange decision-making games (the Trust Game and the Prisoner's Dilemma). Participants played both games with three different (fictional) partners and their tendency to defect was measured. Prior to playing each game, participants exchanged handwritten "essays" with their partners, and subsequently exchanged evaluations of each essay. The essays and evaluations, read by the participant, were designed to induce either anger, sympathy, or a neutral emotional response toward the confederate with whom they would then play the social exchange games. Galvanic skin conductance level (SCL) showed enhanced physiological arousal during anger induction compared to both the neutral and sympathy conditions. In both social exchange games, participants were most likely to defect against their partner after anger induction and least likely to defect after sympathy induction, with the neutral condition eliciting intermediate defection rates. This pattern was found to be strongest in participants exhibiting low cognitive control (as measured by a Go/no-Go task). The findings indicate that emotions felt toward another individual alter how one chooses to interact with them, and that this influence depends both on the specific emotion induced and the cognitive control of the individual.

Task- and response related dissociations between neglect in near and far space: a morphometric case study.

INTRODUCTION: Patients with unilateral neglect may show line bisection errors selectively in either near (within hand reaching) or far (beyond hand reaching) space which suggests that these two spatial areas are coded differently by the brain. This exploratory study investigated, whether any difference in performance between these spatial domains might be task-independent or modulated by the requirement for a motor response. METHODS: A 31-year-old right brain damaged patient (MF) and a group of age matched healthy controls were assessed with two serial visual search tasks and a Landmark paradigm. Both types of task required either a directional (pointing) or non-directional (button press) motor response. Participants were assessed with both task types and response modes in near (57 cm) and far space (114 cm). RESULTS: MF showed left neglect during visual search only in far space for the perceptual condition and in near space for the motor condition. MF showed no neglect in both versions of the Landmark task irrespective of spatial distance. A voxel-based morphometric assessment of MF's brain lesion showed marked damage in the right ventro-temporal cortex, superior temporal gyrus, insula, inferior frontal gyrus, angular gyrus and bilaterally in the posterior cingulate cortex. CONCLUSIONS: Our preliminary findings suggest that processing of far space during visual search is associated with ventral stream damage but only when space is coded through visual information. Neglect involving directional motor activity in near space seems to be associated with damage of structures sharing close connections with the dorsal stream.

Near and far space neglect: task sensitivity and anatomical substrates.

Most group studies which have investigated neglect for near and far space have found an increased severity of symptoms in far space compared to near space. However, the majority of these studies used relatively small samples and based their findings almost exclusively on line bisection performance. The aim of the present study was, therefore, to explore the occurrence of neglect for near and far space in a larger group of unselected right brain damaged patients and to evaluate whether neglect specific to near and far space is a task-related deficit or generalises across distance irrespective of task. In addition, a lesion overlap analysis was carried out to identify critical lesion sites associated with distance specific neglect deficits. Thirty-eight right hemisphere damaged patients carried out a line bisection and a cancellation task by using a pen in near space (40 cm) and a laser pointer in far space (320 cm). The results showed that both the number of left-sided omissions and rightward bisection errors were significantly increased in near compared to far space. Distance specific dissociations, albeit less common, were more frequently observed for cancellation than line bisection. These results suggest that space representation in neglect is more severely impaired in near than in far space. In addition, distance related dissociations in neglect may depend on task demands. Although the anatomical findings were broadly consistent with a dorsal and ventral stream dichotomy for near and far space processing, they also suggest the involvement of intermediate structures in distance related neglect phenomena.

Optokinetic stimulation affects word omissions but not stimulus-centered reading errors in paragraph reading in neglect dyslexia.

Patients with right hemisphere lesions often omit or misread words on the left side of a text or the initial letters of single words, a phenomenon termed neglect dyslexia (ND). Omissions of words on the contralesional side of the page are considered as egocentric or space-based errors, whereas misread words can be viewed as a type of stimulus-centered error where the left part of a single perceptual entity (the word) is neglected. Previous patient studies have shown that optokinetic stimulation (OKS) significantly modulates many facets of the neglect syndrome, including the subjective body midline, line bisection and size distortions. An open question is whether OKS can also influence omissions and stimulus-centered errors in paragraph reading in ND. The current study compared the influence of OKS on both types of reading errors using controlled indented paragraph reading tests in a group of 9 right-hemisphere lesioned patients with ND, 7 patients without ND and 9 matched healthy controls. Leftward OKS significantly reduced omissions on the left side of the text in ND. In contrast, the pattern of stimulus-centered reading errors remained unchanged. In conclusion egocentric manipulations like OKS only appear to influence space-based attentional processes evident as omissions in paragraph reading but have no impact on stimulus-centered attentional processes evident as word-based errors during paragraph reading in ND.

Delay abolishes the obstacle avoidance deficit in unilateral optic ataxia.

Optic ataxic patients have deficits in the visual control of manual reaching and grasping. It has been established previously that these deficits in target-directed behaviour improve following a delay in response. Recently it has been demonstrated that optic ataxic patients also have deficits in taking potential obstacles into account during reaching. The present study was therefore designed to test whether delay would bring an improvement in this behaviour as well. We present experimental data from a patient with unilateral optic ataxia (M.H.). First we document M.H.'s pointing errors, which show a reliable pattern of impairment when pointing to targets in his right visual field, particularly when using his right hand. We then show that a similar pattern of deficits is observable in his ability to negotiate between non-targets: that is, M.H. selectively fails to take account of obstacles in his right visual field, but only while reaching with his right hand. Finally we demonstrate that this obstacle avoidance deficit disappears following a 5s delay in response: under these conditions M.H. now takes account of both non-target objects with either hand. The results are interpreted within the 'two visual streams' model of cortical visual processing.

Intact automatic avoidance of obstacles in patients with visual form agnosia.

In everyday life our reaching behaviour has to be guided not only by the location and properties of the target object, but also by the presence of potential obstacles in the workspace. Recent evidence from neglect and optic ataxia patients has suggested that this automatic obstacle avoidance is mediated by the dorsal, rather than the ventral, stream of visual processing. We tested this idea in two studies involving patients with visual form agnosia resulting from bilateral ventral-stream damage. In the first study, we asked patient DF to reach out and pick up a target object in the presence of obstacles placed at varying distances to the left or right of the target. We found that both DF and controls shifted their trajectories away from the potential obstacles and adjusted their grip aperture in such a way as to minimize risk of collision. In a second study, we asked DF and a second patient, SB, to either reach between, or to bisect the space between, two cylinders presented at varying locations. We found that both patients adjusted their reach trajectories to account for shifts in cylinder location in the reaching task, despite showing significantly worse performance than control subjects when asked to make a bisection judgement. Taken together, these data indicate that automatic obstacle avoidance behaviour is spared in our patients with visual form agnosia. We attribute their ability to the functional intactness of the dorsal stream of visual processing, and argue that the ventral stream plays no important role in automatic obstacle avoidance.

A common basis for visual and tactile exploration deficits in spatial neglect?

One of the fundamental characteristics of spatial neglect is an imbalanced visual search behaviour favouring stimuli on the right side of space while largely ignoring those on the left side. Opinions differ as to whether this reflects a general orientational bias caused by impaired supramodal body-centred reference systems, or a modality-specific search disorder. A prediction of the former model would be that exploratory activity is similarly impaired both in vision and in the absence of visual control. We addressed this hypothesis by comparing patients' visual and tactile search in the same workspace. Our results show that the centre of exploration activity in both modalities was substantially shifted towards the ipsilesional right side in the neglect group as compared to healthy and patient controls. This bias was more accentuated for visual search. We found a clear linear relationship between the visual and tactile search biases in the patient group with spatial neglect. Our finding suggests that the critical component guiding search behaviour in neglect, whether visually or tactually, is a general rightward orientation bias. In addition, we observed an increased repetition rate in both modalities which affected the whole workspace. This implies that the apparent spatial working memory deficit dissociates from the mechanisms inducing the orientation bias.

Rotation or translation of auditory space in neglect? A case study of chronic right-sided neglect.

Egocentric models of neglect explain the lateralised omission of stimuli in neglect patients by an ipsilesional shift of a subjective reference frame. However, they differ in the direction of shift (rotation around the midsagittal plane versus translation in front/back space). We tested this hypothesis in a patient (AJ) with persistent right-sided neglect following a left temporo-parieto-occipital and hypoxic lesion and in six age-matched healthy subjects. AJ showed visual neglect in line bisection, size matching, reading and visual search. Auditory localization was tested by using two different psychophysical techniques based on binaurally simulated stimuli for the horizontal plane in front and back space. Eye position was continuously monitored during stimulus presentation in all subjects. AJ revealed a significant ipsilesional, leftward shift of his auditory subjective median plane (ASMP) in front space (mean: -22.6 degrees), and a rightward shift of the ASMP in back space (+14.5 degrees). This pattern of results was replicated with a different psychophysical technique in a retest 10 months later. The rotational shift of AJ's ASMP contrasted with normal performance in the healthy subjects. Monaural hearing deficits can not account for these differential findings as all subjects (including AJ) performed normally. In conclusion, a rotation of the egocentric spatial reference frame may occur in the auditory modality for right-sided neglect.

The fusiform face area is not sufficient for face recognition: evidence from a patient with dense prosopagnosia and no occipital face area.

We tested functional activation for faces in patient D.F., who following acquired brain damage has a profound deficit in object recognition based on form (visual form agnosia) and also prosopagnosia that is undocumented to date. Functional imaging demonstrated that like our control observers, D.F. shows significantly more activation when passively viewing face compared to scene images in an area that is consistent with the fusiform face area (FFA) (p < 0.01). Control observers also show occipital face area (OFA) activation; however, whereas D.F.'s lesions appear to overlap the OFA bilaterally. We asked, given that D.F. shows FFA activation for faces, to what extent is she able to recognize faces? D.F. demonstrated a severe impairment in higher level face processing--she could not recognize face identity, gender or emotional expression. In contrast, she performed relatively normally on many face categorization tasks. D.F. can differentiate faces from non-faces given sufficient texture information and processing time, and she can do this is independent of color and illumination information. D.F. can use configural information for categorizing faces when they are presented in an upright but not a sideways orientation and given that she also cannot discriminate half-faces she may rely on a spatially symmetric feature arrangement. Faces appear to be a unique category, which she can classify even when she has no advance knowledge that she will be shown face images. Together, these imaging and behavioral data support the importance of the integrity of a complex network of regions for face identification, including more than just the FFA--in particular the OFA, a region believed to be associated with low-level processing.

Weights and measures: a new look at bisection behaviour in neglect.

Horizontal line bisection is a ubiquitous task in the investigation of visual neglect. Patients with left neglect typically make rightward errors that increase with line length and for lines at more leftward positions. For short lines, or for lines presented in right space, these errors may 'cross over' to become leftward. We have taken a new approach to these phenomena by employing a different set of dependent and independent variables for their description. Rather than recording bisection error, we record the lateral position of the response within the workspace. We have studied how this varies when the locations of the left and right endpoints are manipulated independently. Across 30 patients with left neglect, we have observed a characteristic asymmetry between the 'weightings' accorded to the two endpoints, such that responses are less affected by changes in the location of the left endpoint than by changes in the location of the right. We show that a simple endpoint weightings analysis accounts readily for the effects of line length and spatial position, including cross-over effects, and leads to an index of neglect that is more sensitive than the standard measure. We argue that this novel approach is more parsimonious than the standard model and yields fresh insights into the nature of neglect impairment.

The use of visual feedback is independent of visual awareness: evidence from visual extinction.

Milner and Goodale (The visual brain in action, Oxford Press, 1995) made a distinction between vision for perception and vision for action. In contrast to perception, many action tasks have strict temporal constraints, which can only be met if the visual information is relayed directly to the motor system without first passing through a conscious decision making process. Milner and Goodale therefore predict that visual stimuli do not have to reach visual awareness in order to guide rapid motor responses. Online visual feedback provides a good example of visual information that is used under tight temporal constraints to guide rapid motor responses. Online visual feedback provides information about the position of the moving limb. This information can be used to improve the accuracy of our movements. If vision for action operates independently of visual awareness, visual feedback should be beneficial even if the subject is unaware of this information. We tested this prediction in a patient (V.E.) with left-sided visual extinction, a condition in which a visual stimulus typically fails to reach awareness if a second stimulus is presented simultaneously at a more rightward location. V.E. was asked to point towards a central target with his left hand. In some trials a light-emitting diode (LED) provided brief visual feedback from the moving hand. However, in the majority of trials, V.E. was unaware of this LED, due to his extinction. His performance was nevertheless significantly better when visual feedback was present, regardless of whether or not the information was available for verbal report. We conclude that visual awareness is not essential for the effective use of online visual feedback.

An exploration of the role of the superior temporal gyrus in visual search and spatial perception using TMS.

This study sought to investigate the recent claim by H.-O. Karnath and his colleagues that the crucial locus of neurological damage in neglect patients lies in the right superior temporal gyrus (STG), and not in the right posterior parietal cortex (PPC) as conventionally thought. Using transcranial magnetic stimulation (TMS), we first tested the involvement of the right STG in a task commonly used in the diagnosis of neglect, the landmark task. No evidence was found for a critical involvement of the right STG in the processing of this task, though evidence was found for the involvement of the right PPC. In contrast, however, when we examined the effects of TMS on exploratory search, a double dissociation between right STG and right PPC was found. When the processing of conjunction items was required, involvement of the right PPC (and not STG) was found in accordance with our previous research. When a difficult exploratory search through feature items was required, however, the right STG (not PPC) was found to be involved. A hitherto unknown role for right STG in visual search tasks was thus uncovered. These data suggest that conclusions about the area of brain damage resulting in neglect-like symptoms are highly dependent on the task used to diagnose them, with lesions in right PPC leading to deficits on the landmark task and conjunction visual search, and lesions in right STG resulting in deficits in feature based serial exploratory search tasks.

Automatic avoidance of obstacles is a dorsal stream function: evidence from optic ataxia.

When we reach out to pick something up, our arm is directed to the target by visuomotor networks in the cortical dorsal stream. However, our reach trajectories are influenced also by nontarget objects, which might be construed as potential obstacles. We tested two patients with bilateral dorsal-stream (parietal lesions, both of whom were impaired at pointing to visual stimuli (optic ataxia). We asked them to reach between two cylinders, which varied in location from trial to trial. We found that the patients' reaches remained invariant with changes in obstacle location. In a control task when they were asked to point midway between the two objects, however, their responses shifted in an orderly fashion. We conclude that the dorsal stream provides the visual guidance we automatically build into our movements to avoid potential obstacles, as well as that required to ensure arrival at the target.