To keep a stable internal representation of the environment as we move, extraretinal sensory or motor cues are critical for updating neural maps of visual space. Using a memory-saccade task, we studied whether visuospatial updating uses vestibular information. Specifically, we tested whether trained rhesus monkeys maintain the ability to update the conjugate and vergence components of memory-guided eye movements in response to passive translational or rotational head and body movements after bilateral labyrinthine lesion. We found that lesioned animals were acutely compromised in generating the appropriate horizontal versional responses necessary to update the directional goal of memory-guided eye movements after leftward or rightward rotation/translation. This compromised function recovered in the long term, likely using extravestibular (e.g., somatosensory) signals, such that nearly normal performance was observed 4 mo after the lesion. Animals also lost their ability to adjust memory vergence to account for relative distance changes after motion in depth. Not only were these depth deficits larger than the respective effects on version, but they also showed little recovery. We conclude that intact labyrinthine signals are functionally useful for proper visuospatial memory updating during passive head and body movements.
"For translation, however, the transformation required to predict the updated visual position of objects is considerably more involved. This is because each object in the scene moves differently relative to the observer depending on its distance and direction  . "
[Show abstract][Hide abstract] ABSTRACT: Chuck Oman has been a guide and mentor for research in human perception and performance during space exploration for over 25 years. His research has provided a solid foundation for our understanding of how humans cope with the challenges and ambiguities of sensation and perception in space. In many of the environments associated with work in space the human visual system must operate with unusual combinations of visual and other perceptual cues. On Earth physical acceleration cues are normally available to assist the visual system in interpreting static and dynamic visual features. Here we consider two cases where the visual system is not assisted by such cues. Our first experiment examines perceptual stability when the normally available physical cues to linear acceleration are absent. Our second experiment examines perceived orientation when there is no assistance from the physically sensed direction of gravity. In both cases the effectiveness of vision is paradoxically reduced in the absence of physical acceleration cues. The reluctance to rely heavily on vision represents an important human factors challenge to efficient performance in the space environment.
Journal of Vestibular Research 01/2010; 20(1):25-30. DOI:10.3233/VES-2010-0352 · 1.19 Impact Factor
"Notably, trained animals loose their ability to properly adjust memory vergence angle after destruction of the vestibular labyrinths (Li and Angelaki, 2005). Such deficits are also observed for lateral translation and yaw rotation, however, while yaw rotation updating deficits recover over time, updating capacity after forward and backward movements remain compromised even several months following a lesion (Wei et al., 2006). These uncompensated deficits are reminiscent of the permanent loss observed for fine direction discrimination after labyrinthine lesions (Gu et al., 2007) and suggest a dominant role of otolith signals for the processing of both self-motion information and spatial updating in depth. "
[Show abstract][Hide abstract] ABSTRACT: The vestibular system helps maintain equilibrium and clear vision through reflexes, but it also contributes to spatial perception. In recent years, research in the vestibular field has expanded to higher-level processing involving the cortex. Vestibular contributions to spatial cognition have been difficult to study because the circuits involved are inherently multisensory. Computational methods and the application of Bayes theorem are used to form hypotheses about how information from different sensory modalities is combined together with expectations based on past experience in order to obtain optimal estimates of cognitive variables like current spatial orientation. To test these hypotheses, neuronal populations are being recorded during active tasks in which subjects make decisions based on vestibular and visual or somatosensory information. This review highlights what is currently known about the role of vestibular information in these processes, the computations necessary to obtain the appropriate signals, and the benefits that have emerged thus far.
"Immediately after the lesion, the animals' updating abilities were significantly compromised for both rotations and translations (figure 7). However, while updating ability slowly improved over time to near normal levels for yaw rotations and lateral translations, there was no improvement for fore-aft motion, even after four months (Wei et al., 2006). Thus, vestibular signals may play a more important role for updating movements that require a vergence response (i.e., fore-aft motion) than for those that require a version response. "
[Show abstract][Hide abstract] ABSTRACT: Spatial updating is the means by which we keep track of the locations of objects in space even as we move. Four decades of research have shown that humans and non-human primates can take the amplitude and direction of intervening movements into account, including saccades (both head-fixed and head-free), pursuit, whole-body rotations and translations. At the neuronal level, spatial updating is thought to be maintained by receptive field locations that shift with changes in gaze, and evidence for such shifts has been shown in several cortical areas. These regions receive information about the intervening movement from several sources including motor efference copies when a voluntary movement is made and vestibular/somatosensory signals when the body is in motion. Many of these updating signals arise from brainstem regions that monitor our ongoing movements and subsequently transmit this information to the cortex via pathways that likely include the thalamus. Several issues of debate include (1) the relative contribution of extra-retinal sensory and efference copy signals to spatial updating, (2) the source of an updating signal for real life, three-dimensional motion that cannot arise from brain areas encoding only two-dimensional commands, and (3) the reference frames used by the brain to integrate updating signals from various sources. This review highlights the relevant spatial updating studies and provides a summary of the field today. We find that spatial constancy is maintained by a highly evolved neural mechanism that keeps track of our movements, transmits this information to relevant brain regions, and then uses this information to change the way in which single neurons respond. In this way, we are able to keep track of relevant objects in the outside world and interact with them in meaningful ways.
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