Stereoscopic motion-in-depth perception: fMRI and neurophysiological studies

描述（由申请人提供）：本R21探索性提案旨在推进高场fMRI与“信息”神经生理学在警觉猕猴中的整合，并将其应用于解决关于立体三维运动的神经处理的长期研究问题。立体和运动通常是分开研究的，猕猴参与双目深度运动感知的皮层区域特征尚不清楚，而独眼（完全基于差异的）立体运动感知的皮层区域尚不清楚。然而，在人类中，最近的研究已经确定了专门参与独眼立体运动处理的大脑区域，包括运动复合体hMT+附近的一个区域，称为独眼立体运动区域。我们已经开发了对警觉、行为端正的猕猴进行高场功能磁共振成像研究的技术。因此，采用与人类相同的视觉刺激，我们将使用功能磁共振成像来识别猕猴的独眼立体运动区域，然后表征一个目标区域内的神经元反应。计划中的研究与健康相关，因为立体运动处理中的视野缺陷与会聚眼运动的缺陷密切相关，而双眼相互作用的相同缺陷似乎是这两种异常行为的基础。对非人类灵长类动物立体运动的神经处理的研究不仅将提供对参与处理这种运动信息和控制眼球运动的皮质区域的深入了解，而且还将潜在地有助于斜视和复视的诊断和治疗。具体地说，我们将使用功能磁共振成像（fMRI）检查被cyclopean激活的皮质区域，动态随机点立体图（DRDS）呈现运动深度刺激。这些刺激将与适当的固定视差DRDS刺激进行对比。我们从猕猴身上获得的初步fMRI数据已经确定了这些刺激的两个定位良好的激活灶：一个在颞上沟（STS），部分与MSTv重合，另一个在顶叶内沟。接下来，由于这是一项有限时间的探索性拨款，我们将把我们的神经生理学研究集中在STS中激活的良好定位焦点上。具体来说，使用mri引导电极放置在这个目标区域，我们将在动物观看cyclopean，运动深度DRDS刺激时寻找响应神经元，运动深度的唯一线索是视差随时间的变化（CD）。接下来，利用这些刺激，我们将确定接受野的大小和位置，以及神经元的速度调整和z轴方向选择性。然后，使用同时具有CD和眼间速度差的深度运动线索的RDS刺激，我们将研究同时存在深度运动的双眼线索时的神经元反应。我们将进一步描述神经元对立体运动刺激的反应，包括平行和斜向运动轨迹，以及眼球运动。双眼准确对准不同距离的目标需要两只眼睛的精确协调运动，称为聚光眼运动；有会聚性眼球运动缺陷的个体通常是斜视和复视（复视）。立体运动加工中的视野缺陷与眼球聚集运动的缺陷密切相关，并且有人认为双目相互作用的相同缺陷是这两种异常行为的基础（Regan et al., 1986）。我们对非人类灵长类动物独眼立体运动的神经加工的研究，不仅将为处理这种运动信息和控制眼球运动的皮层机制提供基本的见解，而且还将潜在地有助于斜视和复视的诊断和治疗。

Description (provided by applicant): This R21 exploratory proposal is designed to advance the integration of high field fMRI in alert macaque monkeys with "informed" neurophysiology, and to apply it in addressing a long-standing research question regarding the neural processing of stereoscopic 3-D motion. Stereo and motion are usually studied separately, and the cortical regions involved in the binocular perception of motion-in-depth in macaque monkeys are poorly characterized, while those for cyclopean (solely disparity-based) stereomotion perception are unknown. However, in humans, recent studies have identified specialized brain regions specifically involved in cyclopean stereomotion processing, including one near the motion complex hMT+, termed the cyclopean stereomotion region. We have developed techniques for performing fMRI studies at high-field in alert, behaving macaques. Therefore, employing the same visual stimuli as used in humans, we will use fMRI to identify cyclopean stereomotion regions in macaques, and to then characterize neuronal responses within one targeted region. The planned studies are relevant to health, since visual field deficits in stereomotion processing are closely correlated with deficits in vergence eye movements, and the same defect in binocular interaction appears to underlie both abnormal behaviors. Studies of the neural processing of stereomotion in non-human primates will not only provide insights into the cortical areas involved in processing this motion information and in controlling vergence eye movements, but will also potentially aid in the diagnosis and treatment of strabismus and diplopia. Specifically, using fMRI we will examine the cortical areas activated by cyclopean, motion-in-depth stimuli presented with dynamic random-dot stereograms (DRDS). These stimuli will be contrasted with appropriate, fixed-disparity DRDS stimuli. Our preliminary fMRI data from macaques have identified two well-localized foci of activation with these stimuli: one in the superior temporal sulcus (STS) in a location that partially coincides with MSTv, and the other is in the intraparietal sulcus. Next, since this is an exploratory grant of limited duration, we will concentrate our neurophysiological studies on the well-localized focus of activation within the STS. Specifically, using MRI-guided electrode placement in this targeted region, we will search for responsive neurons while the animals view cyclopean, motion-in-depth DRDS stimuli with the only cue to motion-in-depth being the change in disparity over time (CD). Next, using these stimuli, we will determine the receptive field size and location, and the speed tuning and z-axis directional selectivity of the neurons. Then, using RDS stimuli that possess both CD and interocular velocity difference motion-in-depth cues, we will examine neuronal response when both binocular cues to motion-in-depth are present. We will further characterize neuronal responses to stereomotion stimuli with frontoparallel and oblique trajectories, and during vergence eye movements. PUBLIC HEALTH RELEVANCE Accurate binocular alignment of the eyes on targets at different distances requires precisely coordinated movements of the two eyes, known as vergence eye movements; individuals with deficits in vergence eye movements are often strabismic and report diplopia (double-vision). Visual field deficits in stereomotion processing are closely correlated with deficits in vergence eye movements, and it has been suggested that the same defect in binocular interaction underlies both abnormal behaviors (Regan et al., 1986). Our studies of the neural processing of cyclopean stereomotion in non-human primates will not only provide fundamental insights into the cortical mechanisms involved in processing this motion information and in controlling vergence eye movements, but will also potentially aid in the diagnosis and treatment of strabismus and diplopia.