Network level characteristics in the emotion recognition network after unilateral temporal lobe surgery.

The human amygdala is considered a key region for successful emotion recognition. We recently reported that temporal lobe surgery (TLS), including resection of the amygdala, does not affect emotion recognition performance (Journal of Neuroscience, 2018, 38, 9263). In the present study, we investigate the neural basis of this preserved function at the network level. We use generalized psychophysiological interaction and graph theory indices to investigate network level characteristics of the emotion recognition network in TLS patients and healthy controls. Based on conflicting emotion processing theories, we anticipated two possible outcomes: a substantial increase of the non-amygdalar connections of the emotion recognition network to compensate functionally for the loss of the amygdala, in line with basic emotion theory versus only minor changes in network level properties as predicted by psychological construction theory. We defined the emotion recognition network in the total sample and investigated group differences on five network level indices (i.e. characteristic path length, global efficiency, clustering coefficient, local efficiency and small-worldness). The results did not reveal a significant increase in the left or right temporal lobectomy group (compared to the control group) in any of the graph measures, indicating that preserved behavioural emotion recognition in TLS is not associated with a massive connectivity increase between non-amygdalar nodes at network level. We conclude that the emotion recognition network is robust and functionally able to compensate for structural damage without substantial global reorganization, in line with a psychological construction theory.

Anterior Temporal Lobectomy Impairs Neural Classification of Body Emotions in Right Superior Temporal Sulcus and Reduces Emotional Enhancement in Distributed Brain Areas without Affecting Behavioral Classification.

Humans with amygdalar lesions show proportional reductions of the emotional response to facial expressions in the fusiform face area as well as deficits in emotion recognition from facial expressions. While processing of bodily expressions shares many similarities with facial expressions, there is no substantial evidence that lesions of the amygdala result in similar behavioral and neural sequelae. We combined behavioral assessment with functional neuroimaging in a group of male and female humans with unilateral anterior temporal lobe (ATL) resections, including the amygdala (right: n = 10; left: n = 10) and 12 matched controls. The objective was to assess whether the amygdala is crucial for the recognition of body expressions and for modulatory effects on distant areas during perception of body expressions. The behavioral results revealed normal performance in both patient groups on emotion categorization of body expressions. The neuroimaging results showed that ATL patients displayed no enhanced activations in right fusiform body area and left extrastriate body area and that left ATL patients additionally displayed no enhanced activations in right posterior superior temporal sulcus and right extrastriate body area, respectively. Multivoxel pattern analysis revealed altered categorization capacity between emotional and neutral stimuli in right posterior superior temporal sulcus in right ATL patients. In addition, we also found emotional enhancement in frontal, parietal, occipital, and cingulate regions in controls. Together, our data show that the amygdala and ATLs are not necessary for recognition of dynamic body expressions, but suggest that amygdala lesions affect body emotion processing in distant brain areas.SIGNIFICANCE STATEMENT For humans, information from emotional expressions of others is crucial to support social interactions. The majority of emotion studies has focused on facial expressions; however, in daily life, we also use information from body postures and body movement. Visual processing of body expressions relies on a brain network, including body-specific visual areas and visuomotor areas. Even though the importance of the amygdala and its modulatory effects on distant brain regions have been documented, it remains unclear whether the amygdala plays a crucial role in emotional body processing. By combining behavioral and neuroimaging data in patients with amygdalar lesions, we provide further evidence for its modulatory effect on distant areas during the perception of body expressions.

Investigating common coding of observed and executed actions in the monkey brain using cross-modal multi-variate fMRI classification.

Mirror neurons are generally described as a neural substrate hosting shared representations of actions, by simulating or 'mirroring' the actions of others onto the observer's own motor system. Since single neuron recordings are rarely feasible in humans, it has been argued that cross-modal multi-variate pattern analysis (MVPA) of non-invasive fMRI data is a suitable technique to investigate common coding of observed and executed actions, allowing researchers to infer the presence of mirror neurons in the human brain. In an effort to close the gap between monkey electrophysiology and human fMRI data with respect to the mirror neuron system, here we tested this proposal for the first time in the monkey. Rhesus monkeys either performed reach-and-grasp or reach-and-touch motor acts with their right hand in the dark or observed videos of human actors performing similar motor acts. Unimodal decoding showed that both executed or observed motor acts could be decoded from numerous brain regions. Specific portions of rostral parietal, premotor and motor cortices, previously shown to house mirror neurons, in addition to somatosensory regions, yielded significant asymmetric action-specific cross-modal decoding. These results validate the use of cross-modal multi-variate fMRI analyses to probe the representations of own and others' actions in the primate brain and support the proposed mapping of others' actions onto the observer's own motor cortices.

Studying emotion theories through connectivity analysis: Evidence from generalized psychophysiological interactions and graph theory.

Psychological construction models of emotion state that emotions are variable concepts constructed by fundamental psychological processes, whereas according to basic emotion theory, emotions cannot be divided into more fundamental units and each basic emotion is represented by a unique and innate neural circuitry. In a previous study, we found evidence for the psychological construction account by showing that several brain regions were commonly activated when perceiving different emotions (i.e. a general emotion network). Moreover, this set of brain regions included areas associated with core affect, conceptualization and executive control, as predicted by psychological construction models. Here we investigate directed functional brain connectivity in the same dataset to address two questions: 1) is there a common pathway within the general emotion network for the perception of different emotions and 2) if so, does this common pathway contain information to distinguish between different emotions? We used generalized psychophysiological interactions and information flow indices to examine the connectivity within the general emotion network. The results revealed a general emotion pathway that connects neural nodes involved in core affect, conceptualization, language and executive control. Perception of different emotions could not be accurately classified based on the connectivity patterns from the nodes of the general emotion pathway. Successful classification was achieved when connections outside the general emotion pathway were included. We propose that the general emotion pathway functions as a common pathway within the general emotion network and is involved in shared basic psychological processes across emotions. However, additional connections within the general emotion network are required to classify different emotions, consistent with a constructionist account.

Seeing biological actions in 3D: An fMRI study.

Precise kinematics or body configuration cannot be recovered from visual input without disparity information. Yet, no imaging study has investigated the role of disparity on action observation. Here, we investigated the interaction between disparity and the main cues of biological motion, kinematics and configuration, in two fMRI experiments. Stimuli were presented as point-light figures, depicting complex action sequences lasting 21 s. We hypothesized that interactions could occur at any of the three levels of the action observation network, comprising occipitotemporal, parietal and premotor cortex, with premotor cortex being the most likely location. The main effects of kinematics and configuration confirmed that the biological motion sequences activated all three levels of the action observation network, validating our approach. The interaction between configuration and disparity activated only premotor cortex, whereas interactions between kinematics and disparity occurred at all levels of the action observation network but were strongest at the premotor level. Control experiments demonstrated that these interactions could not be accounted for by low level motion in depth, task effects, spatial attention, or eye movements, including vergence. These results underscore the role of premotor cortex in action observation, and in imitating others or responding to their actions.

Functional dissociation between anterior temporal lobe and inferior frontal gyrus in the processing of dynamic body expressions: Insights from behavioral variant frontotemporal dementia.

Several brain regions are involved in the processing of emotional stimuli, however, the contribution of specific regions to emotion perception is still under debate. To investigate this issue, we combined behavioral testing, structural and resting state imaging in patients diagnosed with behavioral variant frontotemporal dementia (bvFTD) and age matched controls, with task-based functional imaging in young, healthy volunteers. As expected, bvFTD patients were impaired in emotion detection as well as emotion categorization tasks, testing dynamic emotional body expressions as stimuli. Interestingly, their performance in the two tasks correlated with gray matter volume in two distinct brain regions, the left anterior temporal lobe for emotion detection and the left inferior frontal gyrus (IFG) for emotion categorization. Confirming this observation, multivoxel pattern analysis in healthy volunteers demonstrated that both ROIs contained information for emotion detection, but that emotion categorization was only possible from the pattern in the IFG. Furthermore, functional connectivity analysis showed reduced connectivity between the two regions in bvFTD patients. Our results illustrate that the mentalizing network and the action observation network perform distinct tasks during emotion processing. In bvFTD, communication between the networks is reduced, indicating one possible cause underlying the behavioral symptoms. Hum Brain Mapp 37:4472-4486, 2016. © 2016 Wiley Periodicals, Inc.

Heterogeneous single-unit selectivity in an fMRI-defined body-selective patch.

Although the visual representation of bodies is essential for reproduction, survival, and social communication, little is known about the mechanisms of body recognition at the single neuron level. Imaging studies showed body-category selective regions in the primate occipitotemporal cortex, but it is difficult to infer the stimulus selectivities of the neurons from the population activity measured in these fMRI studies. To overcome this, we recorded single unit activity and local field potentials (LFPs) in the middle superior temporal sulcus body patch, defined by fMRI in the same rhesus monkeys. Both the spiking activity, averaged across single neurons, and LFP gamma power in this body patch was greater for bodies (including monkey bodies, human bodies, mammals, and birds) compared with other objects, which fits the fMRI activation. Single neurons responded to a small proportion of body images. Thus, the category selectivity at the population level resulted from averaging responses of a heterogeneous population of single units. Despite such strong within-category selectivity at the single unit level, two distinct clusters, bodies and nonbodies, were present when analyzing the responses at the population level, and a classifier that was trained using the responses to a subset of images was able to classify novel images of bodies with high accuracy. The body-patch neurons showed strong selectivity for individual body parts at different orientations. Overall, these data suggest that single units in the fMRI-defined body patch are biased to prefer bodies over nonbody objects, including faces, with a strong selectivity for individual body images.

Tolerance of macaque middle STS body patch neurons to shape-preserving stimulus transformations.

Functional imaging studies in human and nonhuman primates have demonstrated regions in the brain that show category selectivity for faces or (headless) bodies. Recent fMRI-guided single unit studies of the macaque face category-selective regions have increased our understanding of the response properties of single neurons in these face patches. However, much less is known about the response properties of neurons in the fMRI-defined body category-selective regions ("body patches"). Recently, we reported that the majority of single neurons in one fMRI-defined body patch, the mid-STS body patch, responded more strongly to bodies compared with other objects. Here we assessed the tolerance of these neurons' responses and stimulus preference for shape-preserving image transformations. After mapping the receptive field of the single neurons, we found that their stimulus preference showed a high degree of tolerance for changes in the position and size of the stimulus. However, their response strongly depended on the in-plane orientation of a body. The selectivity of most neurons was, to a large degree, preserved when silhouettes were presented instead of the original textured and shaded images, suggesting that mainly shape-based features are driving these neurons. In a human psychophysical study, we showed that the information present in silhouettes is largely sufficient for body versus nonbody categorization. These data suggest that mid-STS body patch neurons respond predominantly to oriented shape features that are prevalent in images of bodies. Their responses can inform position- and retinal size-invariant body categorization and discrimination based on shape.

Common neural correlates of emotion perception in humans.

Whether neuroimaging findings support discriminable neural correlates of emotion categories is a longstanding controversy. Two recent meta-analyses arrived at opposite conclusions, with one supporting (Vytal and Hamann []: J Cogn Neurosci 22:2864-2885) and the other opposing this proposition (Lindquist et al. []: Behav Brain Sci 35:121-143). To obtain direct evidence regarding this issue, we compared activations for four emotions within a single fMRI design. Angry, happy, fearful, sad and neutral stimuli were presented as dynamic body expressions. In addition, observers categorized motion morphs between neutral and emotional stimuli in a behavioral experiment to determine their relative sensitivities. Brain-behavior correlations revealed a large brain network that was identical for all four tested emotions. This network consisted predominantly of regions located within the default mode network and the salience network. Despite showing brain-behavior correlations for all emotions, muli-voxel pattern analyses indicated that several nodes of this emotion general network contained information capable of discriminating between individual emotions. However, significant discrimination was not limited to the emotional network, but was also observed in several regions within the action observation network. Taken together, our results favor the position that one common emotional brain network supports the visual processing and discrimination of emotional stimuli.

Fine-grained stimulus representations in body selective areas of human occipito-temporal cortex.

Neurophysiological and functional imaging studies have investigated the representation of animate and inanimate stimulus classes in monkey inferior temporal (IT) and human occipito-temporal cortex (OTC). These studies proposed a distributed representation of stimulus categories across IT and OTC and at the same time highlighted category specific modules for the processing of bodies, faces and objects. Here, we investigated whether the stimulus representation within the extrastriate (EBA) and the fusiform (FBA) body areas differed from the representation across OTC. To address this question, we performed an event-related fMRI experiment, evaluating the pattern of activation elicited by 200 individual stimuli that had already been extensively tested in our earlier monkey imaging and single cell studies (Popivanov et al., 2012, 2014). The set contained achromatic images of headless monkey and human bodies, two sets of man-made objects, monkey and human faces, four-legged mammals, birds, fruits, and sculptures. The fMRI response patterns within EBA and FBA primarily distinguished bodies from non-body stimuli, with subtle differences between the areas. However, despite responding on average stronger to bodies than to other categories, classification performance for preferred and non-preferred categories was comparable. OTC primarily distinguished animate from inanimate stimuli. However, cluster analysis revealed a much more fine-grained representation with several homogeneous clusters consisting entirely of stimuli of individual categories. Overall, our data suggest that category representation varies with location within OTC. Nevertheless, body modules contain information to discriminate also non-preferred stimuli and show an increasing specificity in a posterior to anterior gradient.

Common and segregated processing of observed actions in human SPL.

To clarify the functional organization of parietal cortex involved in action observation, we scanned subjects observing 3 widely different classes of actions: Manipulation with the hands, locomotion, and climbing. An effector-based organization predicts that parietal regions involved in the observation of climbing should not differ from those involved in observing manipulation and locomotion, opposite to the prediction of an organization based upon the action performed. Compared with individual controls, the observation of climbing evoked activity in dorsal superior parietal lobule (SPL), extending into precuneus and posterior cingulate sulcus. Observation of locomotion differentially activated similar regions less strongly. Observation of manipulation activated ventro-rostral SPL, including putative human AIP (phAIP). Using interaction testing and exclusive masking to directly compare the parietal regions involved in observing the 3 action classes, relative to the controls, revealed that the rostral part of dorsal SPL was specifically involved in observing climbing and phAIP in observing manipulation. Parietal regions common to observing all 3 action classes were restricted and likely reflected higher order visual processing of body posture and 3D structure from motion. These results support a functional organization of some parietal regions involved in action observation according to the type of action in the case of climbing and manipulation.

Acting alters visual processing: flexible recruitment of visual areas by one's own actions.

Using functional magnetic resonance imaging, we investigated the effect of motor preparation/execution on the activation of visual cortical areas by action observation. We presented videos of human actors performing several fine manipulative actions (e.g., grasping) with the hand or foot, together with appropriate control stimuli. Subjects either responded in a central fixation task with the hand (A) or foot (B) or viewed the stimuli passively (C). Experimental conditions were arranged according to a 2 × 2 × 3 factorial design with action, effector, and response as factors. Bilateral posterior parietal cortex was more strongly activated for action videos compared with controls during active runs (A or B) contrasted with passive runs (C). Two neighboring regions in the right fusiform gyrus (FG) were activated when the effector employed to respond in the task matched that displayed in the videos (A or B), independently of whether the stimulus was an action or a control. Neighboring regions in the right posterior middle temporal gyrus (MTG) were also activated when the effector observed and that used to respond matched (A or B), but only for action videos, not controls. Our results indicate flexible modulation of visual areas during concurrent action observation and action execution/preparation, which was effector specific in the FG and MTG.

Predictive value of gastrointestinal symptoms and patient risk factors for NSAID-associated gastrointestinal ulcers defined by endoscopy? Insights from a pooled analysis of two naproxen clinical trials.

OBJECTIVE: Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to treat pain and rheumatic conditions. To facilitate patient management, we determined the predictive value of gastrointestinal (GI) symptoms and risk factors for the development of NSAID-associated GI injuries. METHODS: Post-hoc analysis of pooled data from naproxen treatment arms of two identical, randomized, double-blind, controlled phase 3 trials in arthritis patients at risk of GI adverse events. Endoscopic incidence of GI ulcers at baseline, and 1, 3, and 6 months was employed as a surrogate parameter for GI injury. For GI symptom analysis, Severity of Dyspepsia Assessment questionnaire was used. For GI risk factor analysis, the high risk factors: previous GI injury, concomitant selective serotonin reuptake inhibitors or corticosteroids, ulcer history, concomitant low-dose aspirin, and age >65 years were employed. RESULTS: Data of 426 naproxen patients were analyzed. Distribution of GI symptoms between patients with and without ulcer was similar; about one third of patients developing an ulcer reported no GI pain symptoms. GI symptoms experienced under naproxen treatment were thus not indicative of GI injury. The proportion of patients developing an ulcer increased with the number of risk factors present, however, about a quarter of patients without any of the analyzed risk factors still developed an ulcer. CONCLUSION: GI symptoms and the number of risk factors are not reliable predictors of NSAID-induced GI injury to decide which patients need gastroprotection and will lead to a large group of patients with GI injuries. A preventive rather than reactive approach should be taken.

Stimulus representations in body-selective regions of the macaque cortex assessed with event-related fMRI.

Functional imaging studies in humans and monkeys have shown category-selective regions in the temporal cortex, in particular for faces and bodies. Although the body-selective regions have been well studied in humans, little is understood about the functional properties of such regions in macaques. To address this, we first mapped body-selective activations in the visual cortex of four rhesus monkeys in a block design fMRI study and identified two regions in the middle and anterior Superior Temporal Sulcus (STS) that were more strongly activated by monkey bodies compared to well-controlled manmade objects. These two regions partially overlapped with regions that were more activated by faces than manmade objects. Secondly, using an event-related, single image fMRI design we measured the activations to 200 images of 10 stimulus classes (monkey bodies, human bodies, mammals, birds, monkey faces, human faces, body-like sculptures, fruits/vegetables, and two sets of control objects). Multivoxel-pattern analyses showed that both body-selective regions primarily distinguished faces from other inanimate and animate objects, including bodies. Another distinction was present between inanimate objects and bodies in the middle STS body region. The category-based clustering was less pronounced in the anterior compared to the middle STS body-selective regions. In addition, both body-selective regions showed further selectivity for different "subclasses" of the broad body category such as monkeys, human, mammals and birds. Overall, these data indicate strong spatial clustering of animate categories in the macaque STS with a surprisingly marked distinction between faces and bodies within body-selective regions which was stronger than between manmade objects and bodies.

Integration of shape and motion cues in biological motion processing in the monkey STS.

To correctly perceive biological actions, the movement pattern generated in the course of the action has to be linked to the configuration of the actor. Recently, we showed that in humans, motion and configuration cues are processed separately in occipito-temporal cortex, and that both cues are integrated in the extrastriate (EBA) and fusiform (FBA) body areas (Jastorff and Orban, 2009). Using the same factorial design as in our human study, we performed fMRI experiments in awake monkeys to compare biological motion processing in the two species. Point-light displays of monkeys engaged in various actions were presented in a 2×2 factorial design. One factor manipulated the configuration of the stimuli, the other, the kinematics. As in humans, the two factors were anatomically segregated in the superior temporal sulcus (STS) rostral to the MT/V5 complex, with the effect of configuration significant along the lower bank and that of kinematics significant in the fundus and the upper bank of the STS. Moreover, voxels showing a significant interaction between the two factors were mainly confined to body-selective patches within the STS, mimicking our human findings. Importantly, this study reports for the first time differential activation for biological actions presented as point-light displays in the monkey. Moreover, our results suggest that the processing mechanisms of biological actions are remarkably similar in humans and macaque monkeys, and provide the basis for linking existing and future single-cell physiology in the monkey with human functional imaging.

Cortical regions involved in the observation of bimanual actions.

Although we are beginning to understand how observed actions performed by conspecifics with a single hand are processed and how bimanual actions are controlled by the motor system, we know very little about the processing of observed bimanual actions. We used fMRI to compare the observation of bimanual manipulative actions with their unimanual components, relative to visual control conditions equalized for visual motion. Bimanual action observation did not activate any region specialized for processing visual signals related to this more elaborated action. On the contrary, observation of bimanual and unimanual actions activated similar occipito-temporal, parietal and premotor networks. However, whole-brain as well as region of interest (ROI) analyses revealed that this network functions differently under bimanual and unimanual conditions. Indeed, in bimanual conditions, activity in the network was overall more bilateral, especially in parietal cortex. In addition, ROI analyses indicated bilateral parietal activation patterns across hand conditions distinctly different from those at other levels of the action-observation network. These activation patterns suggest that while occipito-temporal and premotor levels are involved with processing the kinematics of the observed actions, the parietal cortex is more involved in the processing of static, postural aspects of the observed action. This study adds bimanual cooperation to the growing list of distinctions between parietal and premotor cortex regarding factors affecting visual processing of observed actions.

Neural mechanisms of understanding rational actions: middle temporal gyrus activation by contextual violation.

Performing goal-directed actions toward an object in accordance with contextual constraints, such as the presence or absence of an obstacle, has been widely used as a paradigm for assessing the capacity of infants or nonhuman primates to evaluate the rationality of others' actions. Here, we have used this paradigm in a functional magnetic resonance imaging experiment to visualize the cortical regions involved in the assessment of action rationality while controlling for visual differences in the displays and directly correlating magnetic resonance activity with rationality ratings. Bilateral middle temporal gyrus (MTG) regions, anterior to extrastriate body area and the human middle temporal complex, were involved in the visual evaluation of action rationality. These MTG regions are embedded in the superior temporal sulcus regions processing the kinematics of observed actions. Our results suggest that rationality is assessed initially by purely visual computations, combining the kinematics of the action with the physical constraints of the environmental context. The MTG region seems to be sensitive to the contingent relationship between a goal-directed biological action and its relevant environmental constraints, showing increased activity when the expected pattern of rational goal attainment is violated.

Human functional magnetic resonance imaging reveals separation and integration of shape and motion cues in biological motion processing.

In a series of human functional magnetic resonance imaging experiments, we systematically manipulated point-light stimuli to identify the contributions of the various areas implicated in biological motion processing (for review, see Giese and Poggio, 2003). The first experiment consisted of a 2 x 2 factorial design with global shape and kinematics as factors. In two additional experiments, we investigated the contributions of local opponent motion, the complexity of the portrayed movement and a one-back task to the activation pattern. Experiment 1 revealed a clear separation between shape and motion processing, resulting in two branches of activation. A ventral region, extending from the lateral occipital sulcus to the posterior inferior temporal gyrus, showed a main effect of shape and its extension into the fusiform gyrus also an interaction. The dorsal region, including the posterior inferior temporal sulcus and the posterior superior temporal sulcus (pSTS), showed a main effect of kinematics together with an interaction. Region of interest analysis identified these interaction sites as the extrastriate and fusiform body areas (EBA and FBA). The local opponent motion cue yielded only little activation, limited to the ventral region (experiment 3). Our results suggest that the EBA and the FBA correspond to the initial stages in visual action analysis, in which the performed action is linked to the body of the actor. Moreover, experiment 2 indicates that the body areas are activated automatically even in the absence of a task, whereas other cortical areas like pSTS or frontal regions depend on the complexity of movements or task instructions for their activation.

Visual learning shapes the processing of complex movement stimuli in the human brain.

Recognition of actions and complex movements is fundamental for social interactions and action understanding. While the relationship between motor expertise and visual recognition of body movements has received a vast amount of interest, the role of visual learning remains largely unexplored. Combining psychophysics and functional magnetic resonance imaging (fMRI) experiments, we investigated neural correlates of visual learning of complex movements. Subjects were trained to visually discriminate between very similar complex movement stimuli generated by motion morphing that were either compatible (experiments 1 and 2) or incompatible (experiment 3) with human movement execution. Employing an fMRI adaptation paradigm as index of discriminability, we scanned human subjects before and after discrimination training. The results of experiment 1 revealed three different effects as a consequence of training: (1) Emerging fMRI-selective adaptation in general motion-related areas (hMT/V5+, KO/V3b) for the differences between human-like movements. (2) Enhanced of fMRI-selective adaptation already present before training in biological motion-related areas (pSTS, FBA). (3) Changes covarying with task difficulty in frontal areas. Moreover, the observed activity changes were specific to the trained movement patterns (experiment 2). The results of experiment 3, testing artificial movement stimuli, were strikingly similar to the results obtained for human movements. General and biological motion-related areas showed movement-specific changes in fMRI-selective adaptation for the differences between the stimuli after training. These results support the existence of a powerful visual machinery for the learning of complex motion patterns that is independent of motor execution. We thus propose a key role of visual learning in action recognition.

Coding observed motor acts: different organizational principles in the parietal and premotor cortex of humans.

Understanding actions of conspecifics is a fundamental social ability depending largely on the activation of a parieto-frontal network. Using functional MRI (fMRI), we studied how goal-directed movements (i.e., motor acts) performed by others are coded within this network. In the first experiment, we presented volunteers with video clips showing four different motor acts (dragging, dropping, grasping, and pushing) performed with different effectors (foot, hand, and mouth). We found that the coding of observed motor acts differed between premotor and parietal cortex. In the premotor cortex, they clustered according to the effector used, and in the inferior parietal lobule (IPL), they clustered according to the type of the observed motor act, regardless of the effector. Two subsequent experiments in which we directly contrasted these four motor acts indicated that, in IPL, the observed motor acts are coded according to the relationship between agent and object: Movements bringing the object toward the agent (grasping and dragging) activate a site corresponding approximately to the ventral part of the putative human AIP (phAIP), whereas movements moving the object away from the agent (pushing and dropping) are clustered dorsally within this area. These data provide indications that the phAIP region plays a role in categorizing motor acts according to their behavioral significance. In addition, our results suggest that in the case of motor acts typically done with the hand, the representations of such acts in phAIP are used as templates for coding motor acts executed with other effectors.