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As a major output station of the basal ganglia, the globus pallidus internal segment (GPi) projects to the thalamus and brainstem nuclei thereby controlling motor behavior. A less well known fact is that the GPi also projects to the lateral habenula (LHb) which is often associated with the limbic system. Using the monkey performing a saccade task with(More)
Lateral habenula (LHb) neurons signal negative "reward-prediction errors" and inhibit midbrain dopamine (DA) neurons. Yet LHb neurons are largely glutamatergic, indicating that this inhibition may occur through an intermediate structure. Recent studies in rats have suggested a candidate for this role, the GABAergic rostromedial tegmental nucleus (RMTg), but(More)
This study develops a neuromorphic model of human lightness perception that is inspired by how the mammalian visual system is designed for this function. It is known that biological visual representations can adapt to a billion-fold change in luminance. How such a system determines absolute lightness under varying illumination conditions to generate a(More)
Reward information is represented by many subcortical areas and neuron types, which constitute a complex network. Its output is usually mediated by the basal ganglia where behaviors leading to rewards are disinhibited and behaviors leading to no reward are suppressed. Midbrain dopamine neurons modulate these basal ganglia neurons differentially using(More)
A neural model is proposed of how the visual system processes natural images under variable illumination conditions to generate surface lightness percepts. Previous models clarify how the brain can compute relative contrast. The anchored Filling-In Lightness Model (aFILM) clarifies how the brain 'anchors' lightness percepts to determine an absolute(More)
A new mesopontine structure exerting a strong influence on dopamine systems has recently been defined: the tail of the ventral tegmental area/rostromedial tegmental nucleus (tVTA/RMTg). This review presents a neuroanatomical, physiological, and behavioral overview of some of the recent and ongoing research on this brain region and its relationship with(More)
The reward value of a stimulus can be learned through two distinct mechanisms: reinforcement learning through repeated stimulus-reward pairings and abstract inference based on knowledge of the task at hand. The reinforcement mechanism is often identified with midbrain dopamine neurons. Here we show that a neural pathway controlling the dopamine system does(More)
The inferior olivary nuclei clearly play a role in creating oculopalatal tremor, but the exact mechanism is unknown. Oculopalatal tremor develops some time after a lesion in the brain that interrupts inhibition of the inferior olive by the deep cerebellar nuclei. Over time the inferior olive gradually becomes hypertrophic and its neurons enlarge developing(More)
A new model of cerebellar learning explains how the cerebellum can generate arbitrary output waveforms to adjust output timing in the classical delay conditioning. This model can also reproduce the low frequency ocular oscillations seen in oculopalatal tremor (OPT). A novel circuit in the cerebellum uses both interneurons (INs) and Purkinje cells (PC) to(More)
The basal ganglia are thought to play a crucial role in reinforcement learning. Central to the learning mechanism are dopamine (DA) D1 and D2 receptors located in the cortico-striatal synapses. However, it is still unclear how this DA-mediated synaptic plasticity is deployed and coordinated during reward-contingent behavioral changes. Here we propose a(More)