Browsing by Subject "Substantia Nigra"

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    Activity of neurons in monkey globus pallidus during oculomotor behavior compared with that in substantia nigra pars reticulata.
    (J Neurophysiol, 2010-04) Shin, SooYoon; Sommer, Marc A
    The basal ganglia are a subcortical assembly of nuclei involved in many aspects of behavior. Three of the nuclei have high firing rates and inhibitory influences: the substantia nigra pars reticulata (SNr), globus pallidus interna (GPi), and globus pallidus externa (GPe). The SNr contains a wide range of visual, cognitive, and motor signals that have been shown to contribute to saccadic eye movements. Our hypothesis was that GPe and GPi neurons carry similarly diverse signals during saccadic behavior. We recorded from GPe, GPi, and SNr neurons in monkeys that made memory-guided saccades and found that neurons in all three structures had increases or decreases in activity synchronized with saccade generation, visual stimulation, or reward. Comparing GPe neurons with GPi neurons, we found relatively more visual-related activity in GPe and more reward-related activity in GPi. Comparing both pallidal samples with the SNr, we found a greater resemblance between GPe and SNr neurons than that between GPi and SNr neurons. As expected from a known inhibitory projection from GPe to SNr, there was a general reversal of sign in activity modulations between the structures: bursts of activity were relatively more common in GPe and pauses more common in SNr. We analyzed the response fields of neurons in all three structures and found relatively narrow and lateralized fields early in trials (during visual and saccadic events) followed by a broadening later in trials (during reward). Our data reinforce an emerging, new consensus that the GPe and GPi, in addition to the SNr, contribute to oculomotor behavior.
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    Exploring the role of the substantia nigra pars reticulata in eye movements.
    (Neuroscience, 2011-12-15) Basso, MA; Sommer, MA
    Experiments that demonstrated a role for the substantia nigra in eye movements have played an important role in our understanding of the function of the basal ganglia in behavior more broadly. In this review we explore more recent experiments that extend the role of the substantia nigra pars reticulata from a simple gate for eye movements to include a role in cognitive processes for eye movements. We review recent evidence suggesting that basal ganglia nuclei beyond the substantia nigra may also play a role in eye movements and the cognitive events leading up to the production of eye movements. We close by pointing out some unresolved questions in our understanding of the relationship of basal ganglia nuclei and eye movements.