The marmoset as a model for visual neuroscience
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Research Description:
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. This has, in turn, limited our understanding of
devastating disorders of the nervous system that result from miswiring of neural
circuits. 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, such as the marmoset
(Callithrix jacchus), offer many advantages including the potential to develop
transgenic lines (Sasaki et al., 2009). Developing such lines would bring optogenetic tools now
fruitfully being used to tease apart circuits of the mouse brain to bear on
understanding the brains of non-human primates. But a critical question is
whether marmosets can perform behavioral tasks when the head is stabilized,
which both facilitates neuronal recording as well as the measurement and
control of eye movements. The goal of the proposed project is to test this.
This will be a critical step in the development of transgenic primate lines
for neuroscience research. In addition, because the cost and health risks
associated with the marmoset are small, in comparison to the macaque, this
will open new avenues of research to the broader neuroscience community.
Funding provided by the Kavli Institute for Brain and Mind at UCSD.
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Behavioral Demonstrations:
- Demo of Fixation During RF Mapping (MOV File)
- Holding fixation up to 4 seconds (after 20 days training)
- Video demos of an awake marmoset in a fixation task. Each trial begins with a central fixation point (shown in white). A low contrast purple ring is superimposed on the video screen, and indicates the fixation position of the marmoset. After fixation is acquired on the central point, Gabor stimuli are flashed in the periphery for 1-2 seconds. If the marmoset holds fixation through this period then a picture of a marmoset face is shown, a bell tone is rung, and a juice reward is given. If the marmoset breaks from fixation a gunshot sounds is played and no reward given.
- Early training with a delayed saccade task
- Video demo of awake marmoset delaying a saccade to a peripherally cued location for reward. Again, his fixation is indicated by a very low contrast purple ring (you may have to squint). Each trial begins with a white fixation point flashing. Once fixation is acquired the fixation point stops flashing, and then the marmoset must hold fixation at the center while a peripheral target in one of four apertures is flashed. After 600-1000 ms the fixation point turns black, indicating it is allowed to saccade to the peripheral stimulus for reward. This task is a first step towards covert attention tasks. Unlike the fixation demo above, reward is not delivered at fixation but instead is associated with a cued peripheral location. The natural response is to make a saccade to the rewarded location, but this must be inhibited until the central fixation is extinguished.
- Odd-man out orientation discrimination
- Video demo of awake marmoset selecting a vertical oriented grating from distracter stimuli of a similar orientation. Again, fixation is shown by a low contrast purple ring, and his choice indicated by a saccade.
- Orientation tilt from horizontal reference
- Same movie, .MOV format
- Video demo of awake marmoset selecting a tilted grating from a set of horizontal distracter stimuli. Tilts varied in magnitude from trial to trial. Again, fixation is shown by a low contrast purple ring, and his choice indicated by a saccade.
- Scan-paths of natural image (slow speed)
- Video of the scanpaths of viewing the image of the girl shown above. Paths shown in yellow with fixations indicated by red points (in slow motion).
- Video demos of an awake marmoset in a fixation task. Each trial begins with a central fixation point (shown in white). A low contrast purple ring is superimposed on the video screen, and indicates the fixation position of the marmoset. After fixation is acquired on the central point, Gabor stimuli are flashed in the periphery for 1-2 seconds. If the marmoset holds fixation through this period then a picture of a marmoset face is shown, a bell tone is rung, and a juice reward is given. If the marmoset breaks from fixation a gunshot sounds is played and no reward given.
- For further details and project updates, please contact Jude at jude@salk.edu.