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

描述(申请人提供)：这份R21探索性建议旨在推动警觉猕猴的高场fMRI与“知情的”神经生理学的整合，并将其应用于解决关于立体3-D运动的神经处理的长期研究问题。立体视觉和运动通常是分开研究的，猕猴双眼深度运动知觉所涉及的大脑皮层区域特征较差，而环视(仅基于视差)立体运动知觉所涉及的大脑皮层区域尚不清楚。然而，在人类中，最近的研究已经确定了专门参与环视立体运动处理的特定大脑区域，包括靠近运动复合体HMT+的一个区域，称为环视立体运动区域。我们已经开发出了在警觉、行为正常的猕猴高场下进行功能磁共振研究的技术。因此，使用与人类相同的视觉刺激，我们将使用fMRI来识别猕猴的环状立体运动区，然后描述一个靶区内的神经元反应。计划中的研究与健康有关，因为立体运动处理中的视野缺陷与眼球运动的集中缺陷密切相关，而双眼交互中的同样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神经过程的研究不仅将为处理这种运动信息和控制集中眼球运动的皮质区域提供深入的见解，而且还可能有助于斜视和复视的诊断和治疗。具体地说，使用功能磁共振成像，我们将检查由动态随机点立体图(DRDS)呈现的环状深度运动刺激激活的皮质区域。这些刺激将与适当的固定视差DRDS刺激进行对比。我们对猕猴的初步fMRI数据已经确定了这些刺激下两个定位良好的激活灶：一个在颞上沟(STS)，位置与MSTv部分重合，另一个在顶内沟。下一步，由于这是一个有限时间的探索性授权，我们将集中我们的神经生理学研究，在STS内很好地定位激活焦点。具体地说，使用MRI引导的电极放置在这个目标区域，我们将搜索响应性神经元，而动物观看循环的深度运动DRDS刺激时，唯一的线索是视差随时间的变化(CD)。接下来，利用这些刺激，我们将确定神经元的感受野大小和位置，以及速度调节和z轴方向选择性。然后，使用同时具有CD和眼间速度差深度运动线索的RDS刺激，我们将检查当两个双眼深度运动线索都存在时的神经元反应。我们将进一步描述神经元对立体运动刺激的反应，包括前额平行和斜向轨迹，以及眼球会聚运动。公共卫生相关性眼睛在不同距离的目标上准确的双眼对齐需要两只眼睛精确地协调运动，称为会聚眼球运动；散光眼球运动有缺陷的人通常是斜视和复视(复视)。立体运动加工中的视野缺陷与集中眼球运动的缺陷密切相关，有人认为双眼相互作用的相同缺陷是两种异常行为的基础(Regan等人，1986)。我们对非人类灵长类动物圆形立体运动的神经加工的研究不仅将为处理这一运动信息和控制会聚眼球运动的皮质机制提供基本的见解，而且还可能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.