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1.  Brain mechanisms for switching from automatic to controlled eye movements 
Progress in brain research  2008;171:375-382.
Human behaviour is mostly composed of habitual actions that require little conscious control. Such actions may become invalid if the environment changes, at which point we need to switch behaviour by overcoming habitual actions that are otherwise triggered automatically. It is unclear how the brain controls this type of behavioural switching. Here we show that the presupplementary motor area (pre-SMA) in the medial frontal cortex has a function in switching from automatic to volitionally controlled action. This was demonstrated using colour-matching saccade tasks performed by rhesus monkeys. We found that a group of pre-SMA neurons was selectively activated when subjects successfully switched from a habitual saccade to a controlled alternative saccade. Electrical stimulation in the pre-SMA replaced automatic incorrect saccades with slower correct saccades. A further test suggested that the pre-SMA enabled switching by first suppressing an automatic unwanted saccade and then boosting a controlled desired saccade. Our data suggest that the pre-SMA resolves response conflict so that the desired action can be selected. Possible neuronal circuits through which the pre-SMA might exert its switching functions will be discussed.
PMCID: PMC2747307  PMID: 18718329
presupplementary motor area; medial frontal cortex; subthalamic nucleus; substantia nigra pars reticulata; basal ganglia; monkeys; saccadic eye movement; habitual action; conscious control; decision-making
2.  Negative motivational control of saccadic eye movement by the lateral habenula 
Progress in brain research  2008;171:399-402.
Reward is crucial for survival of animals and influences animal behaviors. For example, an approaching behavior to reward is more frequently and quickly elicited when big reward is expected than when small reward is expected. Midbrain dopamine neurons are thought to be crucial for such reward-based control of motor behavior. Indeed, dopamine neurons are excited by cues predicting reward and inhibited by cues predicting no-reward. These excitatory and inhibitory signals would then be used for enhancing and depressing sensorimotor processing, respectively, in the brain areas targeted by dopamine neurons (e.g., striatum). However, it was unknown which parts of the brain provide dopamine neurons with reward-related signals necessary for their responses. We recently showed evidence that the lateral habenula transmits reward-related signals to dopamine neurons, especially to inhibit dopamine neurons. This recent study suggested that the lateral habenula suppresses less rewarding saccadic eye movements by inhibiting dopamine neurons. In the present review, we first summarize anatomical and functional aspects of the lateral habenula. We will then describe our own study. Finally, we will discuss how the lateral habenula, as well as dopamine neurons, contributes to the reward-based control of saccadic eye movements.
PMCID: PMC2735791  PMID: 18718332
reward; lateral habenula; dopamine neuron; saccade; monkey

Results 1-2 (2)