September 2011
Volume 11, Issue 11
Free
Meeting Abstract  |   September 2011
Deficit of Temporal Dynamics of Detection of a Moving Object During Egomotion in a Stroke Patient: A Psychophysical and MEG Study
Author Affiliations
  • Lucia-Maria Vaina
    Brain and Vision Research Lab., Biomedical Engineering, Boston University
    Department of Neurology, Massachusetts General Hospital, Harvard Medical School
    Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School
  • Kunjan D. Rana
    Brain and Vision Research Lab., Biomedical Engineering, Boston University
  • Ferdinando Buonanno
    Department of Neurology, Massachusetts General Hospital, Harvard Medical School
  • Finnegan Calabro
    Brain and Vision Research Lab., Biomedical Engineering, Boston University
  • Matti Hamalainen
    Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School
Journal of Vision September 2011, Vol.11, 723. doi:10.1167/11.11.723
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      Lucia-Maria Vaina, Kunjan D. Rana, Ferdinando Buonanno, Finnegan Calabro, Matti Hamalainen; Deficit of Temporal Dynamics of Detection of a Moving Object During Egomotion in a Stroke Patient: A Psychophysical and MEG Study. Journal of Vision 2011;11(11):723. doi: 10.1167/11.11.723.

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      © 2015 Association for Research in Vision and Ophthalmology.

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To investigate the temporal dynamics underlying object motion detection during egomotion, we used psychophysics and MEG with a motion discrimination task. The display contained nine spheres moving for 1 second, eight moved consistent with forward observer translation, and one (the target) with independent motion within the scene (approaching or receding). Observers's task was to detect the target. Seven healthy subjects (7HS) and patient PF with an infarct involving the left occipital-temporal cortex participated in both the psychophysical and MEG study. Psychophysical results showed that PF was severely impaired on this task. He was also impaired on the discrimination of radial motion (with even poorer performance on contraction) and 2D direction as well as on detecting motion discontinuity. We used anatomically constrained MEG and dynamic Granger causality to investigate the direction and dynamics of connectivity between the functional areas involved in the object-motion task and compared the results of 7HS and PF. The dynamics of the causal connections among the motion responsive cortical areas (MT, STS, IPS) during the first 200 ms of the stimulus was similar in all subjects. However, in the later part of the stimulus (>200 ms) PF did not show significant causal connections among these areas. Also the 7HS had a strong, probably attention modulatory connection, between MPFC and MT, which was completely absent in PF. In PF and the 7HS, analysis of onset latencies revealed two stages of activations: early after motion onset (200–400 ms) bilateral activations in MT, IPS, and STS, followed (>500 ms) by activity in the postcentral sulcus and middle prefrontal cortex (MPFC). We suggest that the interaction of these early and late onset areas is critical to object motion detection during self-motion, and disrupted connections among late onset areas may have contributed to the perceptual deficits of patient PF.

NIH-RO1 NS064100 to LMV and NIH grant P41 RR14075 to MSH. 
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