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[0] Ojakangas CL, Shaikhouni A, Friehs GM, Caplan AH, Serruya MD, Saleh M, Morris DS, Donoghue JP, Decoding movement intent from human premotor cortex neurons for neural prosthetic applications.J Clin Neurophysiol 23:6, 577-84 (2006 Dec)

[0] Lavin A, Nogueira L, Lapish CC, Wightman RM, Phillips PE, Seamans JK, Mesocortical dopamine neurons operate in distinct temporal domains using multimodal signaling.J Neurosci 25:20, 5013-23 (2005 May 18)[1] Pirot S, Godbout R, Mantz J, Tassin JP, Glowinski J, Thierry AM, Inhibitory effects of ventral tegmental area stimulation on the activity of prefrontal cortical neurons: evidence for the involvement of both dopaminergic and GABAergic components.Neuroscience 49:4, 857-65 (1992 Aug)

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ref: OReilly-2006.02 tags: computational model prefrontal_cortex basal_ganglia date: 12-07-2011 04:11 gmt revision:1 [0] [head]

PMID-16378516[0] Making Working Memory Work: A Computational Model of Learning in the Prefrontal Cortex and Basal Ganglia

found via: http://www.citeulike.org/tag/basal-ganglia

____References____

[0] O'Reilly RC, Frank MJ, Making working memory work: a computational model of learning in the prefrontal cortex and basal ganglia.Neural Comput 18:2, 283-328 (2006 Feb)

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ref: Vasilaki-2009.02 tags: associative learning prefrontal cortex model hebbian date: 02-17-2009 03:37 gmt revision:2 [1] [0] [head]

PMID-19153762 Learning flexible sensori-motor mappings in a complex network.

  • Were looking at a task, presented to monkeys over 10 years ago, where two images were presented to the monkeys, and they had to associate left and rightward saccades with both.
  • The associations between saccade direction and image was periodically reversed. Unlike humans, who probably could very quickly change the association, the monkeys required on the order of 30 trials to learn the new association.
  • Interestingly, whenever the monkeys made a mistake, they effectively forgot previous pairings. That is, after an error, the monkeys were as likely to make another error as they were to choose correctly, independent of the number of correct trials preceding the error. Strange!
  • They implement and test reward-modulated hebbian learning (RAH), where:
    • The synaptic weights are changed based on the presynaptic activity, the postsynaptic activity minus the probability of both presynaptic and postsynaptic activity. This 'minus' effect seems similar to that of TD learning?
    • The synaptic weights are soft-bounded,
    • There is a stop-learning criteria, where the weights are not positively updated if the total neuron activity is strongly positive or strongly negative. This allows the network to ultimately obtain perfection (at some point the weights are no longer changed upon reward), and explains some of the asymmetry of the reward / punishment.
  • Their model perhaps does not scale well for large / very complicated tasks... given the presence of only a single reward signal. And the lack of attention / recall? Still, it fits the experimental data quite well.
  • They also note that for all the problems they study, adding more layers to the network does not significantly affect learning - neither the rate nor the eventual performance.

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ref: bookmark-0 tags: murder cerebrum PET scan Adrian Raine violence prefrontal corpus callosum amygdala activation brain scan date: 08-29-2008 14:32 gmt revision:0 [head]

http://www.dana.org/news/cerebrum/detail.aspx?id=3066 -- great article, with a well thought out, delicate treatment of the ethical/moral/ legal issues created by the interaction between the biological roots of violence (or knowlege thereof) and legal / social systems. He posits that there must be a continuum between ratinoal free will and irrational, impulsive violent behavior, with people biased to both by genetics, development, traumatic head injury, and substance abuse (among others).

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ref: Ojakangas-2006.12 tags: BMI Donoghue prosthetic DBS prefrontal cortex planning date: 04-09-2007 22:32 gmt revision:3 [2] [1] [0] [head]

PMID-17143147[0] Decoding movement intent from human premotor cortex neurons for neural prosthetic applications

  • they suggest using additional frontal areas beyond M1 to provide signal sources for human neuromotor prosthesis.
    • did recording in prefrontal cortex during DBS surgeries.
    • these neurons were able to provide information about movement planning production, and decision-making.
  • unusual for BMI studies, their significance levels are near 0.02 - they show distros of % correct based on a ML decoding scheme.

____References____

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ref: Dum-2003.01 tags: cerebellum dentate_nucleus projections cerebrum prefrontal posterior_pareital M1 PM thalamus somatotopic date: 03-11-2007 04:42 gmt revision:2 [1] [0] [head]

PMID-12522208 An unfolded map of the cerebellar dentate nucleus and its projections to the cerebral cortex

  • the dentate nucleus of the cerebellum projects to (at least four sections of if not all) of the cerebral cortex in a spatially-organized way.
    • dentate nucleus projects via the ventral anterior (VA) nucleus of the thalamus
    • dentate nucleus receives projections from the lateral hemispheres of the cerebellum (neocerebellum), which receives extensive collaterals from the pyramidal tract.

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ref: Lavin-2005.05 tags: dopamine PFC VTA prefrontal_cortex ventral_tegmentum 2005 date: 02-05-2007 20:37 gmt revision:1 [0] [head]

PMID-15901782[0]Mesocortical Dopamine Neurons Operate in Distinct Temporal Domains Using Multimodal Signaling

  • good paper, decent review of relevant infos in the introduction.
  • they suggest that the mesocortical system transmits fast signals about reward/salience via corelease of glutamate, whereas dopamine provides a more long-term modulator of cortical processing dynamics.
  • the ventral tegmental area provides dopamine to the prefrontal cortex.
  • DA levels in the PFC can increase ~10x above baseline for 10's of minutes.
    • these responses occur to both to unexpectedly rewarding stimuli as well as to aversive stimuli.
  • brief VTA stimulation invokes a short, transient (~200ms) inhibition of PFC in vivo, and this inhibition is typically blocked by DA antagonists. from: PMID-1436485[1]
    • transient inhibition begins ~20ms after VTA stimulation, which is barely enough time for activation of ionotropic receptors, let alone metabotropic DA receptors.
  • MFB stimulation evoked increased DA levels and an elevation in firing of nearby striatal neurons that outlasted the period of stimulation by > 300s.
  • strangely, the excitatory glutamergic response in the PFC to VTA stimulation is blocked by lesion of the MFB.
  • in suppport of co-release, TH-positive neurons in rats and primates are co-reactive for glutamate.
    • DA neurons can form glutamate synapses in vitro.
  • check it out:
    • midbrain DA neurons respond by firing a ~200ms burst of spikes to primary rewards, conditioned, or secondary rewards, rewards that are not predicted, and novel or unexpected stimuli.
    • DA neurons are activated by rewarding events that are better than predicted, remain unaffected by events that are as good as predicted, and are depressed by events that are worse than predicted (yet they do not cite any refs for this... there are a bunch of refs in the prev sentence. ) see:
    • stress can also increase PFC DA

____References____

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ref: Lewis-2000.12 tags: UP_DOWN VTA dopamine D1 prefrontal cortex PFC date: 0-0-2007 0:0 revision:0 [head]

PMID-11073866 Ventral Tegmental Area Afferents to the Prefrontal Cortex Maintain Membrane Potential ‘Up’ States in Pyramidal Neurons via D1 Dopamine Receptors

  • need i say more?