Bio

Professional Education


  • Doctor of Philosophy, University of Southern California (2013)
  • Bachelor of Science, University of California Berkeley (2005)

Stanford Advisors


Research & Scholarship

Current Research and Scholarly Interests


Functional neuroimaging of emotion processing networks in Veterans with TBI and PTSD.

Publications

Journal Articles


  • Both novelty and expertise increase action observation network activity FRONTIERS IN HUMAN NEUROSCIENCE Liew, S., Sheng, T., Margetis, J. L., Aziz-Zadeh, L. 2013; 7

    Abstract

    Our experiences with others affect how we perceive their actions. In particular, activity in bilateral premotor and parietal cortices during action observation, collectively known as the action observation network (AON), is modulated by one's expertise with the observed actions or individuals. However, conflicting reports suggest that AON activity is greatest both for familiar and unfamiliar actions. The current study examines the effects of different types and amounts of experience (e.g., visual, interpersonal, personal) on AON activation. fMRI was used to scan 16 healthy participants without prior experience with individuals with amputations (novices), 11 experienced occupational therapists (OTs) who had varying amounts of experience with individuals with amputations, and one individual born with below-elbow residual limbs (participant CJ), as they viewed video clips of goal-matched actions performed by an individual with residual limbs and by an individual with hands. Participants were given increased visual exposure to actions performed by both effectors midway through the scanning procedure. Novices demonstrated a large AON response to the initial viewing of an individual with residual limbs compared to one with hands, but this signal was attenuated after they received visual exposure to both effectors. In contrast, OTs, who had moderate familiarity with residual limbs, demonstrated a lower AON response upon initial viewing-similar to novices after they received visual exposure. At the other extreme, CJ, who has extreme familiarity with residual limbs both visually and motorically, shows a largely increased left-lateralized AON response, exceeding that of novices and experienced OTs, when viewing the residual limb compared to hand actions. These results suggest that a nuanced model of AON engagement is needed to explain how cases of both extreme experience (CJ) and extreme novelty (novices) can result in the greatest AON activity.

    View details for DOI 10.3389/fnhum.2013.00541

    View details for Web of Science ID 000324288100001

    View details for PubMedID 24062656

  • Experience with an amputee modulates one's own sensorimotor response during action observation NEUROIMAGE Liew, S., Sheng, T., Aziz-Zadeh, L. 2013; 69: 138-145

    Abstract

    Observing actions performed by others engages one's own sensorimotor regions, typically with greater activity for actions within one's own motor abilities or for which one has prior experience. However, it is unclear how experience modulates the neural response during the observation of impossible actions, beyond one's own abilities. Using fMRI, we scanned typically-developed participants as they observed actions performed by a novel biological effector (the residual limb of a woman born without arms) and a familiar biological effector (a hand). Participants initially demonstrated greater activity in the bilateral inferior and superior parietal cortices when observing actions made by the residual limb compared to the hand, with more empathic participants activating the right inferior parietal lobule, corresponding to the posterior component of the action observation network, more strongly. Activity in the parietal regions may indicate matching the kinematics of a novel effector to one's own existing sensorimotor system, a process that may be more active in more empathic individuals. Participants then received extended visual exposure to each effector, after which they showed little difference between activation in response to residual limb compared to hand actions, only in the right superior parietal lobule. This suggests that visual experience may attenuate the difference between how residual limb and hand actions are represented using one's own body representations, allowing us to flexibly map physically different others onto our own body representations.

    View details for DOI 10.1016/j.neuroimage.2012.12.028

    View details for Web of Science ID 000314627800015

    View details for PubMedID 23268784

  • Understanding Otherness: The Neural Bases of Action Comprehension and Pain Empathy in a Congenital Amputee CEREBRAL CORTEX Aziz-Zadeh, L., Sheng, T., Liew, S., Damasio, H. 2012; 22 (4): 811-819

    Abstract

    How do we understand and empathize with individuals whose bodies are drastically different from our own? We investigated the neural processes by which an individual with a radically different body, a congenital amputee who is born without limbs, engages her own sensory-motor representations as a means to understand other people's body actions or emotional states. Our results support the prediction that when the goal of the action is possible for the observer, one's own motor regions are involved in processing action observation, just as when individuals viewed those similar to themselves. However, when the observed actions are not possible, mentalizing mechanisms, relying on a different set of neural structures, are additionally recruited to process the actions. Furthermore, our results indicate that when individuals view others experiencing pain in body parts that they have, the insula and somatosensory cortices are activated, consistent with previous reports. However, when an individual views others experiencing pain in body parts that she does not have, the insula and secondary somatosensory cortices are still active, but the primary somatosensory cortices are not. These results provide a novel understanding for how we understand and empathize with individuals who drastically differ from the self.

    View details for DOI 10.1093/cercor/bhr139

    View details for Web of Science ID 000302004600008

    View details for PubMedID 21734252

  • Default Network Deactivations Are Correlated with Psychopathic Personality Traits PLOS ONE Sheng, T., Gheytanchi, A., Aziz-Zadeh, L. 2010; 5 (9)

    Abstract

    The posteromedial cortex (PMC) and medial prefrontal cortex (mPFC) are part of a network of brain regions that has been found to exhibit decreased activity during goal-oriented tasks. This network is thought to support a baseline of brain activity, and is commonly referred to as the "default network". Although recent reports suggest that the PMC and mPFC are associated with affective, social, and self-referential processes, the relationship between these default network components and personality traits, especially those pertaining to social context, is poorly understood.In the current investigation, we assessed the relationship between PMC and mPFC deactivations and psychopathic personality traits using fMRI and a self-report measure. We found that PMC deactivations predicted traits related to egocentricity and mPFC deactivations predicted traits related to decision-making.These results suggest that the PMC and mPFC are associated with processes involving self-relevancy and affective decision-making, consistent with previous reports. More generally, these findings suggest a link between default network activity and personality traits.

    View details for DOI 10.1371/journal.pone.0012611

    View details for Web of Science ID 000281631300032

    View details for PubMedID 20830290

  • Common Premotor Regions for the Perception and Production of Prosody and Correlations with Empathy and Prosodic Ability PLOS ONE Aziz-Zadeh, L., Sheng, T., Gheytanchi, A. 2010; 5 (1)

    Abstract

    Prosody, the melody and intonation of speech, involves the rhythm, rate, pitch and voice quality to relay linguistic and emotional information from one individual to another. A significant component of human social communication depends upon interpreting and responding to another person's prosodic tone as well as one's own ability to produce prosodic speech. However there has been little work on whether the perception and production of prosody share common neural processes, and if so, how these might correlate with individual differences in social ability.The aim of the present study was to determine the degree to which perception and production of prosody rely on shared neural systems. Using fMRI, neural activity during perception and production of a meaningless phrase in different prosodic intonations was measured. Regions of overlap for production and perception of prosody were found in premotor regions, in particular the left inferior frontal gyrus (IFG). Activity in these regions was further found to correlate with how high an individual scored on two different measures of affective empathy as well as a measure on prosodic production ability.These data indicate, for the first time, that areas that are important for prosody production may also be utilized for prosody perception, as well as other aspects of social communication and social understanding, such as aspects of empathy and prosodic ability.

    View details for DOI 10.1371/journal.pone.0008759

    View details for Web of Science ID 000273779000008

    View details for PubMedID 20098696

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