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Visual perception of actions is supported by a network of brain regions in the occipito-temporal, parietal, and premotor cortex in the primate brain, known as the Action Observation Network (AON). Although there is a growing body of research that characterizes the functional properties of each node of this network, the communication and direction of information flow between the nodes is unclear. According to the predictive coding account of action perception (Kilner, Friston, & Frith, 2007a; 2007b), this network is not a purely feedforward system but has backward connections through which prediction error signals are communicated between the regions of the AON. In the present study, we investigated the effective connectivity of the AON in an experimental setting where the human subjects' predictions about the observed agent were violated, using fMRI and Dynamical Causal Modeling (DCM). We specifically examined the influence of the lowest and highest nodes in the AON hierarchy, pSTS and ventral premotor cortex, respectively, on the middle node, inferior parietal cortex during prediction violation. Our DCM results suggest that the influence on the inferior parietal node is through a feedback connection from ventral premotor cortex during perception of actions that violate people's predictions.

Brief use of a tool recalibrates multisensory representations of the user’s body, a phenomenon called tool embodiment. Despite two decades of research, little is known about its boundary conditions. It has been widely argued that embodiment requires active tool use, suggesting a critical role for somatosensory and motor feedback. The present study used a visual illusion to cast doubt on this view. We used a mirror-based setup to induce a visual experience of tool use with an arm that was in fact stationary. Following illusory tool use, tactile perception was recalibrated on this stationary arm, and with equal magnitude as physical use. Recalibration was not found following illusory passive tool holding, and could not be accounted for by sensory conflict or general interhemispheric plasticity. These results suggest visual tool-use signals play a critical role in driving tool embodiment.

Contains fulltext : 215844.pdf (Publisher’s version ) (Closed access) Tool use leads to plastic changes in sensorimotor body representations underlying tactile perception. The neural correlates of this tool-induced plasticity in humans have not been adequately characterized. This study used ERPs to investigate the stage of sensory processing modulated by tool use. Somatosensory evoked potentials, elicited by median nerve stimulation, were recorded before and after two forms of object interaction: tool use and hand use. Compared with baseline, tool use - but not use of the hand alone - modulated the amplitude of the P100. The P100 is a mid-latency component that indexes the construction of multisensory models of the body and has generators in secondary somatosensory and posterior parietal cortices. These results mark one of the first demonstrations of the neural correlates of tool-induced plasticity in humans and suggest that tool use modulates relatively late stages of somatosensory processing outside primary somatosensory cortex. This finding is consistent with what has been observed in tool-trained monkeys and suggests that the mechanisms underlying tool-induced plasticity have been preserved across primate evolution. 14 p.

Mental body representations underlying tactile perception do not accurately reflect the body's true morphology. For example, perceived tactile distance is dependent on both the body part being touched and the stimulus orientation, a phenomenon called Weber's illusion. These findings suggest the presence of size and shape distortions, respectively. However, whereas each morphological feature is typically measured in isolation, a complete morphological characterization requires the concurrent measurement of both size and shape. We did so in three experiments, manipulating both the stimulated body parts (hand; forearm) and stimulus orientation while requiring participants to make tactile distance judgments. We found that the forearm was significantly more distorted than the hand lengthwise but not widthwise. Effects of stimulus orientation are thought to reflect receptive field anisotropies in primary somatosensory cortex. The results of the present study therefore suggest that mental body representations retain homuncular shape distortions that characterize early stages of somatosensory processing.

Visual processing of actions is supported by a network consisting of occipito-temporal, parietal, and premotor regions in the human brain, known as the Action Observation Network (AON). In the present study, we investigate what aspects of visually perceived actions are represented in this network using fMRI and computational modeling. Human subjects performed an action perception task during scanning. We characterized the different aspects of the stimuli starting from purely visual properties such as form and motion to higher-aspects such as intention using computer vision and categorical modeling. We then linked the models of the stimuli to the three nodes of the AON with representational similarity analysis. Our results show that different nodes of the network represent different aspects of actions. While occipito-temporal cortex performs visual analysis of actions by means of integrating form and motion information, parietal cortex builds on these visual representations and transforms them into more abstract and semantic representations coding target of the action, action type and intention. Taken together, these results shed light on the neuro-computational mechanisms that support visual perception of actions and provide support that AON is a hierarchical system in which increasing levels of the cortex code increasingly complex features. NSF (CAREER) DARPA Kavli Institute for Brain and Mind Qualcomm Institute (Calit2)

Two decades of research have demonstrated that using a tool modulates spatial representations of the body. Whether this embodiment is specific to representations of the tool-using limb or extends to representations of other body parts has received little attention. Several studiesof other perceptual phenomena have found that modulations to the primary somatosensory representation of the hand transfers to the face, due in part to their close proximity in primary somatosensory cortex. In the present study, we investigated whether tool-induced recalibration of tactile perception on the hand transfers to the cheek. Participants verbally estimated the distance between two tactile points applied to either their hand or face, before and after using a hand-shaped tool. Tool use recalibrated tactile distance perception on the hand-in line with previous findings-but left perception on the cheek unchanged. This finding provides support for the idea that embodiment is body-part specific. Furthermore, it suggests that tool-induced perceptual recalibration occurs at a level of somatosensory processing, where representations of the hand and face have become functionally disentangled.

Uncanny valley refers to humans' negative reaction to almost-but-not-quite-human agents. Theoretical work proposes prediction violation as an explanation for uncanny valley but no empirical work has directly tested it. Here, we provide evidence that supports this theory using event-related brain potential recordings from the human scalp. Human subjects were presented images and videos of three agents as EEG was recorded: a real human, a mechanical robot, and a realistic robot in between. The real human and the mechanical robot had congruent appearance and motion whereas the realistic robot had incongruent appearance and motion. We hypothesize that the appearance of the agent would provide a context to predict her movement, and accordingly the perception of the realistic robot would elicit an N400 effect indicating the violation of predictions, whereas the human and the mechanical robot would not. Our data confirmed this hypothesis suggesting that uncanny valley could be explained by violation of one's predictions about human norms when encountered with realistic but artificial human forms. Importantly, our results implicate that the mechanisms underlying perception of other individuals in our environment are predictive in nature.

A fundamental and seemingly unbridgeable psychological boundary divides humans and nonhumans. Essentialism theories suggest that mixing these categories violates "natural kinds." Perceptual theories propose that such mixing creates incompatible cues. Most theories suggest that mixed agents, with both human and nonhuman features, obligatorily elicit discomfort. In contrast, we demonstrate top-down, cognitive control of these effects-such that the discomfort with mixed agents is partially driven by disfluent categorization of ambiguous features that are pertinent to the agent. Three experiments tested this idea. Participants classified 3 different agents (humans, androids, and robots) either on the human-likeness or control dimension and then evaluated them. Classifying on the human-likeness dimensions made the mixed agent (android) more disfluent, and in turn, more disliked. Disfluency also mediated the negative affective reaction. Critically, devaluation only resulted from disfluency on human-likeness-and not from an equally disfluent color dimension. We argue that negative consequences on evaluations of mixed agents arise from integral disfluency (on features that are relevant to the judgment at-hand, like ambiguous human-likeness). In contrast, no negative effects stem from incidental disfluency (on features that do not bear on the current judgment, like ambiguous color backgrounds). Overall, these findings support a top-down account of why, when, and how mixed agents elicit conflict and discomfort. (PsycINFO Database Record

Biological motion detection is both commonplace and important, but there is great inter-individual variability in this ability, the neural basis of which is currently unknown. Here we examined whether the behavioral variability in biological motion detection is reflected in brain anatomy. Perceptual thresholds for detection of biological motion and control conditions (non-biological object motion detection and motion coherence) were determined in a group of healthy human adults (n=31) together with structural magnetic resonance images of the brain. Voxel based morphometry analyzes revealed that gray matter volumes of left posterior superior temporal sulcus (pSTS) and left ventral premotor cortex (vPMC) significantly predicted individual differences in biological motion detection, but showed no significant relationship with performance on the control tasks. Our study reveals a neural basis associated with the inter-individual variability in biological motion detection, reliably linking the neuroanatomical structure of left pSTS and vPMC with biological motion detection performance., Highlights ► We examined neuroanatomical correlates of biological motion detection ability. ► Left pSTS and vPMC's neural structure predicted biological motion detection ability. ► These region's neural structure did not predict performance on the control tasks.

Visual processing of actions is supported by a network of brain regions in occipito-temporal, parietal, and premotor cortex in the primate brain, known as the Action Observation Network (AON). What remain unclear are the representational properties of each node of this network. In this study, we investigated the representational content of brain areas in AON using fMRI, representational similarity analysis (RSA), and modeling. Subjects were shown video clips of three agents performing eight different actions during fMRI scanning. We then computed the representational dissimilarity matrices (RDMs) for each brain region, and compared them with that of two sets of model representations that were constructed based on computer vision and semantic attributes. Our findings reveal that different nodes of the AON have different representational properties. PSTS as the visual area of the AON represents high level visual features such as movement kinematics. As one goes higher in the AON hierarchy, representations become more abstract and semantic as our results revealed that parietal cortex represents several aspects of actions such as action category, intention of the action, and target of the action. These results suggest that during visual processing of actions, pSTS pools information from visual cortex to compute movement kinematics, and passes that information to higher levels of AON coding semantics of actions such as action category, intention of action, and target of action, consistent with computational models of visual action recognition.

How are environmental sounds relevant to the neurobiology of language? As studied in the 20th century, the purported structure of language and its processing—a human-specific “faculty” characterized by an abstract system of rules governing the hierarchical recombination of symbols encoded by arbitrary sound units—is seemingly unrelated to the recognition and comprehension of environmental sounds. Environmental sounds have often been used as a means of defining what is “language-specific” in the brain. However, as research in both language and environmental sounds has matured, useful parallels between the two domains have emerged, as well as some illustrative differences. In this chapter, we first discuss what environmental sounds are (and are not), and then move through different aspects of environmental sounds research that parallel fields of study in language. We consider, in detail, the behavioral and neuroimaging evidence for how environmental sounds are processed, highlighting the range of perceptual, cross-modal, semantic, and contextual processes involved, and finish by considering how studying environmental sounds informs our understanding of language processing.

We used a novel stimulus set of human and robot actions to explore the role of humanlike appearance and motion in action prediction. Participants viewed videos of familiar actions performed by three agents: human, android and robot, the former two sharing human appearance, the latter two nonhuman motion. In each trial, the video was occluded for 400 ms. Participants were asked to determine whether the action continued coherently (in-time) after occlusion. The timing at which the action continued was early, late, or in-time (100, 700 or 400 ms after the start of occlusion). Task performance interacted with the observed agent. For early continuations, accuracy was highest for human, lowest for robot actions. For late continuations, the pattern was reversed. Both android and human conditions differed significantly from the robot condition. Given the robot and android conditions had the same kinematics, the visual form of the actor appears to affect action prediction. We suggest that the selection of the internal sensorimotor model used for action prediction is influenced by the observed agent's appearance.

International audience; Using functional magnetic resonance imaging (fMRI) repetition suppression, we explored the selectivity of the human action perception system (APS), which consists of temporal, parietal and frontal areas, for the appearance and/or motion of the perceived agent. Participants watched body movements of a human (biological appearance and movement), a robot (mechanical appearance and movement) or an android (biological appearance, mechanical movement). With the exception of extrastriate body area, which showed more suppression for human like appearance, the APS was not selective for appearance or motion per se. Instead, distinctive responses were found to the mismatch between appearance and motion: whereas suppression effects for the human and robot were similar to each other, they were stronger for the android, notably in bilateral anterior intraparietal sulcus, a key node in the APS. These results could reflect increased prediction error as the brain negotiates an agent that appears human, but does not move biologically, and help explain the uncanny valley phenomenon.

We provide a corpus-based computational approach to analyzing acquisition data on Turkish, a richly inflected language. We describe the process by which transcripts from the CHILDES database for 16 children aged 2;0 to 3;0 were morphologically tagged and parsed. We computed a number of imitation, overlap, and repetition measures on the transcripts using CLAN and CHIP programs. These measures tended to decrease as a function of mean length of utterance, which was broadly consistent with previously published work on English-speaking children. The data also revealed additional usage patterns, where the adult utterances provided children with rich morphosyntax in the input, while at the same time helping them to maintain discourse. Children on the other hand, tended to omit optional constituents and repeat morphemes from the previous utterance. The Turkish data and previously published English data showed cross-linguistic differences in repetition patterns that were congruent with the typological differences between the two languages. More generally, the data were consistent with a usage-based model for the acquisition of Turkish as a first language. The corpora and methods provided here can be extended to future applications.

We report the case of patient M, who suffered unilateral left posterior temporal and parietal damage, brain regions typically associated with language processing. Language function largely recovered since the infarct, with no measurable speech comprehension impairments. However, the patient exhibited a severe impairment in nonverbal auditory comprehension. We carried out extensive audiological and behavioral testing in order to characterize M’s unusual neuropsychological profile. We also examined the patient’s and controls’ neural responses to verbal and nonverbal auditory stimuli using functional magnetic resonance imaging (fMRI). We verified that the patient exhibited persistent and severe auditory agnosia for nonverbal sounds in the absence of verbal comprehension deficits or peripheral hearing problems. Acoustical analyses suggested that his residual processing of a minority of environmental sounds might rely on his speech processing abilities. In the patient’s brain, contralateral (right) temporal cortex as well as perilesional (left) anterior temporal cortex were strongly responsive to verbal, but not to nonverbal sounds, a pattern that stands in marked contrast to the controls’ data. This substantial reorganization of auditory processing likely supported the recovery of M’s speech processing.

Understanding others' actions is essential for functioning in the physical and social world. In the past two decades research has shown that action perception involves the motor system, supporting theories that we understand others' behavior via embodied motor simulation. Recently, empirical approach to action perception has been facilitated by using well-controlled artificial stimuli, such as robots. One broad question this approach can address is what aspects of similarity between the observer and the observed agent facilitate motor simulation. Since humans have evolved among other humans and animals, using artificial stimuli such as robots allows us to probe whether our social perceptual systems are specifically tuned to process other biological entities. In this study, we used humanoid robots with different degrees of human-likeness in appearance and motion along with electromyography (EMG) to measure muscle activity in participants' arms while they either observed or imitated videos of three agents produce actions with their right arm. The agents were a Human (biological appearance and motion), a Robot (mechanical appearance and motion), and an Android (biological appearance and mechanical motion). Right arm muscle activity increased when participants imitated all agents. Increased muscle activation was found also in the stationary arm both during imitation and observation. Furthermore, muscle activity was sensitive to motion dynamics: activity was significantly stronger for imitation of the human than both mechanical agents. There was also a relationship between the dynamics of the muscle activity and motion dynamics in stimuli. Overall our data indicate that motor simulation is not limited to observation and imitation of agents with a biological appearance, but is also found for robots. However we also found sensitivity to human motion in the EMG responses. Combining data from multiple methods allows us to obtain a more complete picture of action understanding and the underlying neural computations.

Identifying the movements of those around us is fundamental for many daily activities, such as recognizing actions, detecting predators, and interacting with others socially. A key question concerns the neurobiological substrates underlying biological motion perception. Although the ventral "form" visual cortex is standardly activated by biologically moving stimuli, whether these activations are functionally critical for biological motion perception or are epiphenomenal remains unknown. To address this question, we examined whether focal damage to regions of the ventral visual cortex, resulting in significant deficits in form perception, adversely affects biological motion perception. Six patients with damage to the ventral cortex were tested with sensitive point-light display paradigms. All patients were able to recognize unmasked point-light displays and their perceptual thresholds were not significantly different from those of three different control groups, one of which comprised brain-damaged patients with spared ventral cortex (n > 50). Importantly, these six patients performed significantly better than patients with damage to regions critical for biological motion perception. To assess the necessary contribution of different regions in the ventral pathway to biological motion perception, we complement the behavioral findings with a fine-grained comparison between the lesion location and extent, and the cortical regions standardly implicated in biological motion processing. This analysis revealed that the ventral aspects of the form pathway (e.g., fusiform regions, ventral extrastriate body area) are not critical for biological motion perception. We hypothesize that the role of these ventral regions is to provide enhanced multiview/posture representations of the moving person rather than to represent biological motion perception per se.

Contrasting linguistic and nonlinguistic processing has been of interest to many researchers with different scientific, theoretical, or clinical questions. However, previous work on this type of comparative analysis and experimentation has been limited. In particular, little is known about the differences and similarities between the perceptual, cognitive, and neural processing of nonverbal environmental sounds and that of speech sounds. With the aim of contrasting verbal and nonverbal processing in the auditory modality, we developed a new on-line measure that can be administered to subjects from different clinical, neurological, or sociocultural groups. This is an on-line task of sound to picture matching, in which the sounds are either environmental sounds or their linguistic equivalents and which is controlled for potential task and item confounds across the two sound types. Here, we describe the design and development of our measure and report norming data for healthy subjects from two different adult age groups: younger adults (18-24 years of age) and older adults (54-78 years of age). We also outline other populations to which the test has been or is being administered. In addition to the results reported here, the test can be useful to other researchers who are interested in systematically contrasting verbal and nonverbal auditory processing in other populations.

We examined the abilities of aphasic patients to make grammaticality judgments on English sentences instantiating a variety of syntactic structures. Previous studies employing this metalinguistic task have suggested that aphasic patients typically perform better on grammaticality judgment tasks than they do on sentence comprehension tasks, a finding that has informed the current view that grammatical knowledge is relatively preserved in agrammatic aphasia. However, not all syntactic structures are judged equally accurately, and several researchers have attempted to provide explanatory principles to predict which structures will pose problems to agrammatic patients. One such proposal is Grodzinsky and Finkel's (1998) claim that agrammatic aphasics are selectively impaired in their ability to process structures involving traces of maximal projections. In this study, we tested this claim by presenting patients with sentences with or without such traces, but also varying the level of difficulty of both kinds of structures, assessed with reference to the performance of age-matched and young controls. We found no evidence that agrammatic aphasics, or any other subgroup, are selectively impaired on structures involving traces: Some judgments involving traces were made quite accurately, whereas other judgments not involving traces were made very poorly. Subgroup analyses revealed that patient groups and agematched controls had remarkably similar profiles of performance across sentence types, regardless of whether the patients were grouped based on Western Aphasia Battery classification, an independent screening test for agrammatic comprehension, or lesion site. This implies that the pattern of performance across sentence types does not result from any particular component of the grammar, or any particular brain region, being selectively compromised. Lesion analysis revealed that posterior temporal areas were more reliably implicated in poor grammaticality judgment performance than anterior areas, but poor performance was also observed with some anterior lesions, suggesting that areas important for syntactic processing are distributed throughout the left peri-sylvian region.

Summary Although aphasia is often characterized as a selective impairment in language function, left hemisphere lesions may cause impairments in semantic processing of auditory information, not only in verbal but also in nonverbal domains. We assessed the ‘online’ relationship between verbal and nonverbal auditory processing by examining the ability of 30 left hemisphere-damaged aphasic patients to match environmental sounds and linguistic phrases to corresponding pictures. The verbal and nonverbal task components were matched carefully through a norming study; 21 age-matched controls and five right hemisphere-damaged patients were also tested to provide further reference points. We found that, while the aphasic groups were impaired relative to normal controls, they were impaired to the same extent in both domains, with accuracy and reaction time for verbal and nonverbal trials revealing unusually high correlations (r = 0.74 for accuracy, r = 0.95 for reaction time). Severely aphasic patients tended to perform worse in both domains, but lesion size did not correlate with performance. Lesion overlay analysis indicated that damage to posterior regions in the left middle and superior temporal gyri and to the inferior parietal lobe was a predictor of deficits in processing for both speech and environmental sounds. The lesion mapping and further statistical assessments reliably revealed a posterior superior temporal region (Wernicke’s area, traditionally considered a language-specific region) as being differentially more important for processing nonverbal sounds compared with verbal sounds. These results suggest that, in most cases, processing of meaningful verbal and nonverbal auditory information break down together in stroke and that subsequent recovery of function applies to both domains. This suggests that language shares neural resources with those used for processing information in other domains.

What factors constrain whether tool use modulates the user’s body representations? To date, studies on representational plasticity following tool use have primarily focused on the act of using the tool. Here, we investigated whether the tool’s morphology also serves to constrain plasticity. In two experiments, we varied whether the tool was morphologically similar to a target body part (Experiment 1: hand; Experiment 2: arm). Participants judged the tactile distance between pairs of points applied to their tool-using target body surface and forehead (control surface), before and after tool use. We applied touch in two orientations, allowing us to quantify how tool use modulates the representation’s shape. Significant representational plasticity in hand shape (increase in width, decrease in length) was found when the tool was morphologically similar to a hand (Experiment 1A), but not when the tool was arm-shaped (Experiment 1B). Conversely, significant representational plasticity was found on the arm when the tool was arm-shaped (Experiment 2B), but not when hand-shaped (Experiment 2A). Taken together, our results indicate that morphological similarity between the tool and the effector constrains tool-induced representational plasticity. The embodiment of tools may thus depend on a match-to-template process between tool morphology and representation of the body.

© 2014 Troyer, Curley, Miller, Saygin and Bergen. Language comprehension requires rapid and flexible access to information stored in long-term memory, likely influenced by activation of rich world knowledge and by brain systems that support the processing of sensorimotor content. We hypothesized that while literal language about biological motion might rely on neurocognitive representations of biological motion specific to the details of the actions described, metaphors rely on more generic representations of motion. In a priming and self-paced reading paradigm, participants saw video clips or images of (a) an intact point-light walker or (b) a scrambled control and read sentences containing literal or metaphoric uses of biological motion verbs either closely or distantly related to the depicted action (walking). We predicted that reading times for literal and metaphorical sentences would show differential sensitivity to the match between the verb and the visual prime. In Experiment 1, we observed interactions between the prime type (walker or scrambled video) and the verb type (close or distant match) for both literal and metaphorical sentences, but with strikingly different patterns. We found no difference in the verb region of literal sentences for Close-Match verbs after walker or scrambled motion primes, but Distant-Match verbs were read more quickly following walker primes. For metaphorical sentences, the results were roughly reversed, with Distant-Match verbs being read more slowly following a walker compared to scrambled motion. In Experiment 2, we observed a similar pattern following still image primes, though critical interactions emerged later in the sentence. We interpret these findings as evidence for shared recruitment of cognitive and neural mechanisms for processing visual and verbal biological motion information. Metaphoric language using biological motion verbs may recruit neurocognitive mechanisms similar to those used in processing literal language but be represented in a less-specific way.

The Turing Test is one of the most disputed topics in artificial intelligence, philosophy of mind, and cognitive science. This paper is a review of the past 50 years of the Turing Test. Philosophical debates, practical developments and repercussions in related disciplines are all covered. We discuss Turing's ideas in detail and present the important comments that have been made on them. Within this context, behaviorism, consciousness, the `other minds' problem, and similar topics in philosophy of mind are discussed. We also cover the sociological and psychological aspects of the Turing Test. Finally, we look at the current situation and analyze programs that have been developed with the aim of passing the Turing Test. We conclude that the Turing Test has been, and will continue to be, an influential and controversial topic.

Visual motion perception is fundamental to many aspects of visual perception. Visual motion perception has long been associated with the dorsal (parietal) pathway and the involvement of the ventral ‘form’ (temporal) visual pathway has not been considered critical for normal motion perception. Here, we evaluated this view by examining whether circumscribed damage to ventral visual cortex impaired motion perception. The perception of motion in basic, non-form tasks (motion coherence and motion detection) and complex structure-from-motion, for a wide range of motion speeds, all centrally displayed, was assessed in five patients with a circumscribed lesion to either the right or left ventral visual pathway. Patients with a right, but not with a left, ventral visual lesion displayed widespread impairments in central motion perception even for non-form motion, for both slow and for fast speeds, and this held true independent of the integrity of areas MT/V5, V3A or parietal regions. In contrast with the traditional view in which only the dorsal visual stream is critical for motion perception, these novel findings implicate a more distributed circuit in which the integrity of the right ventral visual pathway is also necessary even for the perception of non-form motion.

Perception of others’ actions supports important social skills, such as communication, intention understanding, and empathy. Are mechanisms of action processing in human brain specifically tuned to process biological agents? Humanoid robots can perform recognizable actions, but can look and move differently from humans so they can be used as stimuli to address such questions. Here, we recorded EEG during the observation of human and robot actions. Sensorimotor mu (8-13 Hz) rhythm has been linked to the motor simulation aspect of action processing (and to human mirror neuron system, MNS) and frontal theta (4-8 Hz) rhythm to semantic and memory-related aspects. We explored whether these measures exhibit selectivity for biological entities: for whether the motion and/or the visual appearance of the observed agent is biological. Participants watched videos of three agents performing the same actions. The first was a Human, and had biological motion and appearance. The other two were a state-of-the-art robot in two different appearances: Android, which had biological appearance but mechanical motion, and Robot, which had mechanical motion and appearance. Observation of all agents induced significant attenuation in the power of mu oscillations that was equivalent for all agents. Thus, mu suppression, considered an index of the activity of the MNS, did not appear to be selective for biological agents. Observation of the Robot resulted in greater frontal theta activity compared to the Android and the Human, whereas the latter two did not differ from each other. Frontal theta activity thus appears to be sensitive to visual appearance, suggesting artificial agents that are not sufficiently biological in appearance may result in greater memory processing demands for the observer. Studies combining robotics and neuroscience thus can allow us to explore functional properties of action processing on the one hand, and help inform the design of social robots on the other.

For more than a century, lesion–symptom mapping studies have yielded valuable insights into the relationships between brain and behavior, but newer imaging techniques have surpassed lesion analysis in examining functional networks. Here we used a new method—voxel-based lesion–symptom mapping (VLSM)—to analyze the relationship between tissue damage and behavior on a voxel-by-voxel basis, as in functional neuroimaging. We applied VLSM to measures of speech fluency and language comprehension in 101 left-hemisphere-damaged aphasic patients: the VLSM maps for these measures confirm the anticipated contrast between anterior and posterior areas, and they also indicate that interacting regions facilitate fluency and auditory comprehension, in agreement with findings from modern brain imaging.

This chapter summarizes recent research on biological motion perception using structural brain imaging and lesion-mapping techniques in brain-lesioned patients. It also explores how these findings complement research using functional neuroimaging in the healthy human brain and neurophysiological studies on nonhuman primates. Such converging methods have allowed for the identification of a network of brain areas that are involved in the perception of biological motion and areas that are causally linked to deficits in biological motion perception.

Biological motion perception is often claimed to support social cognition, and to rely upon embodied representations and motor imagery. Are people with higher levels of social traits or more vivid motor imagery better at biological motion perception? We administered four experiments measuring sensitivity in using (global) form and (local) motion cues in biological motion, plus well-established measures of social cognition (e.g., empathy) and motor imagery (e.g., kinesthetic motor imagery). This first systematic investigation of individual variability in biological motion processing demonstrated significant relationships between these domains, along with a dissociation. Sensitivity for using form cues in biological motion processing was correlated with social (and not the imagery) measures; sensitivity for using motion cues was correlated with motor imagery (and not the social) measures. These results could not be explained by performance on non-biological control stimuli. We thus show that although both social cognition and motor imagery predict sensitivity to biological motion, these skills likely tap into different aspects of perception.

Using MRI-guided off-line TMS, we targeted two areas implicated in biological motion processing: ventral premotor cortex (PMC) and posterior STS (pSTS), plus a control site (vertex). Participants performed a detection task on noise-masked point-light displays of human animations and scrambled versions of the same stimuli. Perceptual thresholds were determined individually. Performance was measured before and after 20 sec of continuous theta burst stimulation of PMC, pSTS, and control (each tested on different days). A matched nonbiological object motion task (detecting point-light displays of translating polygons) served as a further control. Data were analyzed within the signal detection framework. Sensitivity (d′) significantly decreased after TMS of PMC. There was a marginally significant decline in d′ after TMS of pSTS but not of control site. Criterion (response bias) was also significantly affected by TMS over PMC. Specifically, subjects made significantly more false alarms post-TMS of PMC. These effects were specific to biological motion and not found for the nonbiological control task. To summarize, we report that TMS over PMC reduces sensitivity to biological motion perception. Furthermore, pSTS and PMC may have distinct roles in biological motion processing as behavioral performance differs following TMS in each area. Only TMS over PMC led to a significant increase in false alarms, which was not found for other brain areas or for the control task. TMS of PMC may have interfered with refining judgments about biological motion perception, possibly because access to the perceiver's own motor representations was compromised.

Previous research indicates that motion-sensitive brain regions are engaged when comprehending motion semantics expressed by words or sentences. Using fMRI, we investigated whether such neural modulation can occur when the linguistic signal itself is visually dynamic and motion semantics is expressed by movements of the hands. Deaf and hearing users of American Sign Language (ASL) were presented with signed sentences that conveyed motion semantics (“The deer walked along the hillside.”) or were static, conveying little or no motion (“The deer slept along the hillside.”); sentences were matched for the amount of visual motion. Motion-sensitive visual areas (MT +) were localized individually in each participant. As a control, the Fusiform Face Area (FFA) was also localized for the deaf participants. The whole-brain analysis revealed static (locative) sentences engaged regions in left parietal cortex more than motion sentences, replicating previous results implicating these regions in comprehending spatial language for sign languages. Greater activation was observed in the functionally defined MT + ROI for motion than static sentences for both deaf and hearing signers. No modulation of neural activity by sentence type was observed in the FFA. Deafness did not affect modulation of MT + by motion semantics, but hearing signers exhibited stronger neural activity in MT + for both sentence types, perhaps due to differences in exposure and/or use of ASL. We conclude that top down modulation of motion-sensitive cortex by linguistic semantics is not disrupted by the visual motion that is present in sign language sentences.