所長招聘セミナー

Our understanding of the neural mechanisms underlying perception and cognition has been limited by the lack of tools to modulate the activity of specific neural circuits in the awake animal. Recent advances in optogenetic techniques have begun to make this level of control possible in the mouse. However, mice are difficult to train, and the mouse brain differs substantially from the primate brain. While the rhesus macaque has traditionally been the model system of choice for studying perception and cognition, smaller New World primates, the common marmoset (Callithrix jacchus), offer many advantages including the potential to develop transgenic lines (Sasaki et al, 2009). Studies in the anaesthetized marmoset have detailed the anatomy and physiology of their visual system (Rosa et al, 2009) while studies of auditory processing have established their utility for awake neurophysiological investigations (Lu, Liang, and Wang 2001). However, a critical unknown is whether marmosets can perform visual tasks under head restraint. This has been essential for studies in the macaque, enabling both accurate eye tracking and head stabilization for neurophysiology. In one set of experiments we compared the free viewing behavior of head-fixed marmosets to that of macaques, and found that their saccadic behavior is comparable across a number of saccade metrics and that saccades target similar regions of interest including faces. In a second set of experiments we applied behavioral conditioning techniques to determine if the marmoset could control fixation for liquid reward. Two marmosets could fixate a central point and ignore peripheral flashing stimuli, as needed for receptive field mapping. One highly trained marmoset also performed an orientation discrimination task, exhibiting a saturating psychometric function with reliable performance and shorter reaction times for easier discriminations. The marmoset is a viable model for studies of active vision and its underlying neural mechanisms.