Perception of Biological Motion in Schizophrenia and Healthy Individuals: A Behavioral and fMRI Study

Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea.
PLoS ONE (Impact Factor: 3.23). 05/2011; 6(5):e19971. DOI: 10.1371/journal.pone.0019971
Source: PubMed


Anomalous visual perception is a common feature of schizophrenia plausibly associated with impaired social cognition that, in turn, could affect social behavior. Past research suggests impairment in biological motion perception in schizophrenia. Behavioral and functional magnetic resonance imaging (fMRI) experiments were conducted to verify the existence of this impairment, to clarify its perceptual basis, and to identify accompanying neural concomitants of those deficits.
In Experiment 1, we measured ability to detect biological motion portrayed by point-light animations embedded within masking noise. Experiment 2 measured discrimination accuracy for pairs of point-light biological motion sequences differing in the degree of perturbation of the kinematics portrayed in those sequences. Experiment 3 measured BOLD signals using event-related fMRI during a biological motion categorization task. Compared to healthy individuals, schizophrenia patients performed significantly worse on both the detection (Experiment 1) and discrimination (Experiment 2) tasks. Consistent with the behavioral results, the fMRI study revealed that healthy individuals exhibited strong activation to biological motion, but not to scrambled motion in the posterior portion of the superior temporal sulcus (STSp). Interestingly, strong STSp activation was also observed for scrambled or partially scrambled motion when the healthy participants perceived it as normal biological motion. On the other hand, STSp activation in schizophrenia patients was not selective to biological or scrambled motion.
Schizophrenia is accompanied by difficulties discriminating biological from non-biological motion, and associated with those difficulties are altered patterns of neural responses within brain area STSp. The perceptual deficits exhibited by schizophrenia patients may be an exaggerated manifestation of neural events within STSp associated with perceptual errors made by healthy observers on these same tasks. The present findings fit within the context of theories of delusion involving perceptual and cognitive processes.

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    • "This technique is useful for measuring acuity for discriminating small perturbations in normal PL sequences, but it is not designed to destroy perception of biological motion. Readers interested in this technique and the kinds of results obtained using it are referred to Kim et al. (2011). Another technique for degrading BM sequences is to shuffle the starting locations of all dots in the initial frame of the animation, meaning that each dot will begin its unique motion at a start location within the dot array normally occupied by another dot. "
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    ABSTRACT: Studies of biological motion perception often use stimuli depicting human actions portrayed via point-light (PL) displays. Typically, counterpart, or control, stimuli for PL biological motion are created by spatially scrambling motion trajectories of individual PL dots. Depending on the purpose of the study, however, this procedure may be inappropriate as a foil for genuine PL animations, because spatial scrambling not only disrupts coherent motion activity but also eliminates pair-wise motion relationships among dots and, unless corrected, alters the spatial spread of PL dot motions. We introduce a new technique for producing perturbed PL animations, called pair-wise shuffled motion, that preserves the elementary features of biological motion in spatial and motion energy domains and only disrupts the specific sense of global, coherent perception of biological motion. First we describe the procedure for creating pair-wise shuffled motion sequences. Next we compare unperturbed PL animations to pair-wise shuffled motion, to spatially scrambled motion, and to spatially constrained scrambled motion in terms of spatial distributions of the dots, spatiotemporal amplitude spectra derived from Fourier analysis of those sequences, and space-time motion energy associated with those perturbed animations. We then show that the results from those analyses generalize to a large family of PL animations, including the widely used PL walker. Finally we present results from a two-interval forced-choice biological-motion discrimination experiment comparing the robustness of scrambled and pair-wise shuffled motions as foil stimuli. Results from these comparisons suggest that pair-wise shuffled motion offers advantages as a foil stimulus compared to foils using the conventional scrambling technique. Pair-wise shuffled motion provides an additional, effective control display for evaluating PL biological motion perception in future psychophysical, computational, and imaging studies that focus on mechanisms of processing spatiotemporal information signifying biological motion within PL displays.
    Full-text · Article · Aug 2015 · Journal of Vision
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    • "ms of physiological arousal , there was a curi - ous interaction between group and sociality on the mean GSR rate . The GSR rates of the two groups do not differ for the social neutral images but for non - social images , it was elevated for SZ compared to CO . One possibility is that the social and non - social boundary may be blurred in SZ ( see Kim et al . , 2011 ) ."
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    ABSTRACT: Adaptive emotional responses are important in interpersonal relationships. We investigated self-reported emotional experience, physiological reactivity, and micro-facial expressivity in relation to the social nature of stimuli in individuals with schizophrenia (SZ). Galvanic skin response (GSR) and facial electromyography (fEMG) were recorded in medicated outpatients with SZ and demographically matched healthy controls (CO) while they viewed social and non-social images from the International Affective Pictures System. Participants rated the valence and arousal, and selected a label for experienced emotions. Symptom severity in the SZ and psychometric schizotypy in CO were assessed. The two groups did not differ in their labeling of the emotions evoked by the stimuli, but individuals with SZ were more positive in their valence ratings. Although self-reported arousal was similar in both groups, mean GSR was greater in SZ, suggesting differential awareness, or calibration of internal states. Both groups reported social images to be more arousing than non-social images but their physiological responses to non-social vs. social images were different. Self-reported arousal to neutral social images was correlated with positive symptoms in SZ. Negative symptoms in SZ and disorganized schizotypy in CO were associated with reduced mean fEMG. Greater corrugator mean fEMG activity for positive images in SZ indicates valence-incongruent facial expressions. The patterns of emotional responses differed between the two groups. While both groups were in broad agreement in self-reported arousal and emotion labels, their mean GSR, and fEMG correlates of emotion diverged in relation to the social nature of the stimuli and clinical measures. Importantly, these results suggest disrupted self awareness of internal states in SZ and underscore the complexities of emotion processing in health and disease.
    Full-text · Article · Apr 2015 · Frontiers in Psychology
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    • "Schizophrenia individuals, however, seem to be processing all stimuli the same. Interestingly, a similar pattern of results using fMRI has been observed in schizophrenia individuals in the STSp (Kim et al. 2011), a brain region known to be involved in the perception of biological motion and registration of socially relevant sensory information (Grossman et al. 2000). These subjects had a strong, undifferentiated STSp activation to both biological and scrambled motion. "
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    ABSTRACT: IntroductionThe ability to recognize human biological motion is a fundamental aspect of social cognition that is impaired in people with schizophrenia. However, little is known about the neural substrates of impaired biological motion perception in schizophrenia. In the current study, we assessed event-related potentials (ERPs) to human and nonhuman movement in schizophrenia.Methods Twenty-four subjects with schizophrenia and 18 healthy controls completed a biological motion task while their electroencephalography (EEG) was simultaneously recorded. Subjects watched clips of point-light animations containing 100%, 85%, or 70% biological motion, and were asked to decide whether the clip resembled human or nonhuman movement. Three ERPs were examined: P1, N1, and the late positive potential (LPP).ResultsBehaviorally, schizophrenia subjects identified significantly fewer stimuli as human movement compared to healthy controls in the 100% and 85% conditions. At the neural level, P1 was reduced in the schizophrenia group but did not differ among conditions in either group. There were no group differences in N1 but both groups had the largest N1 in the 70% condition. There was a condition × group interaction for the LPP: Healthy controls had a larger LPP to 100% versus 85% and 70% biological motion; there was no difference among conditions in schizophrenia subjects.Conclusions Consistent with previous findings, schizophrenia subjects were impaired in their ability to recognize biological motion. The EEG results showed that biological motion did not influence the earliest stage of visual processing (P1). Although schizophrenia subjects showed the same pattern of N1 results relative to healthy controls, they were impaired at a later stage (LPP), reflecting a dysfunction in the identification of human form in biological versus nonbiological motion stimuli.
    Full-text · Article · Dec 2014 · Brain and Behavior
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