Deep brain chronic recording and the neural mechanisms of spatial-to-temporal transform in oculomoto & Differences in eye-tracking between rhesus monkeys and humans
1 The chapter review the technology of extracellular neural recording. After introduce the history of recording electrodes and recording methods, the author pointed out the importance of chronic recording in research of neuroscience. Currently, the application of chronic recording in small animals and cortex of large animals is very common. But, when refer to the study of deep brain of large animals, the chronic recording is no that well developed. After analyze the difficulty in chronic recording of deep brain nuclei, we developed a new recording method which could solve the problem. During the experiment, a total of neurons in the brainstem of rhesus macaque were recorded. Through out the experiment, all animals were well treated and the infection was limited to lowest degree. The result proved that our recording method is efficient in deep brain study. Spatial-temporal transformation is a very important mechanism of signal processing and transformation. Base on the brain stem control of saccade eye movement, the authors first introduced the important role of SC(superior colliculus) in the initiation of saccadic eye movement. After then the role of PPRF(paramedian pontine reticular formation) and riMLF(rostral interstitial nucleus of medial longitudinal fasciculus) were also introduce. They pointed out that the transformation of signals from SC to PPRF and riMLF is a typical way of spatial-temporal transformation. But how the spatial information in SC transfer to the temporal information in the PPRF or riMLF is still unclear. After reviewed three kinds of hypothesis of spatial-temporal transformation, author propose their opinions on the future study. Base on a new deep brain chronic recording technology and the electronic microstimulation eliminator of our lab, a new phenomenon was discovered after the primary research. The result show that the part of EBNs of riMLF are not innervated by SC saccade related neurons. We conclude that part of the EBNs of riMLF(even PPRF) are innervated by the FEF independent of SC. This discovery may be a break through for the current theory. 2 Studies estimating eye movements have demonstrated that non-human primates have fi xation patterns similar to humans at the first sight of a picture. In the current study, three sets of pictures containing monkeys, humans or both were presented to rhesus monkeys and humans. The eye movements on these pictures by the two species were recorded using a Tobii eye-tracking system. We found that monkeys paid more attention to the head and body in pictures containing monkeys, whereas both monkeys and humans paid more attention to the head in pictures containing humans. The humans always concentrated on the eyes and head in all the pictures, indicating the social role of facial cues in society. Although humans paid more attention to the hands than monkeys, both monkeys and humans were interested in the hands and what was being done with them in the pictures. This may suggest the importance and necessity of hands for survival. Finally, monkeys scored lower in eye-tracking when fi xating on the pictures, as if they were less interested in looking at the screen than humans. The locations of fixation in monkeys may provide insight into the role of eye movements in an evolutionary context.
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