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[0] Francis JT, Influence of the inter-reach-interval on motor learning.Exp Brain Res 167:1, 128-31 (2005 Nov)

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ref: Wyler-1980.05 tags: operant control motor learning interspike intervals ISI Wyler Lange Neafsey Robbins date: 01-07-2012 21:46 gmt revision:1 [0] [head]

PMID-6769536[0] Operant control of precentral neurons: Control of modal interspike intervals

  • Question: can monkeys control the ISI of operantly controlled neurons?
    • Answer: Seems they cannot. Operant and overt movement cells have about the same ISI, and this cannot be changed by conditioning.
  • Task requires a change from tonic to phasic firing, hence they call it "Differential reinforcement of Tonic Patterns".
    • That is, the monkey is trained to produce spikes within a certain ISI window.
    • PDP8 control, applesauce feedback.
    • modal ISI, in this case, means mode (vs. mean and median) of the ISI.
  • Interesting: "It was not uncommon for a neuron to display bi- or trimodal ISI distributions when the monkey was engaged in a movement unrelated to a unit's firing"
  • For 80% of the units, the more tightly a neuron's firing was related to a specific movement, the more gaussian its ISI became.
  • As the monkey gained control over reinforced units, the ISI became more gaussian.
  • Figure 2: monkey was not able to significantly change the modal ISI.
    • Monkeys instead seem to succeed at the task by decreasing the dispersion of the ISI distribution and increasing the occurrence of the modal ISI.
  • Monkeys mediate response through proprioceptive feedback:
    • Cervical spinal cord sectioning decreases the fidelity of control.
    • When contralateral C5-7 ventral roots were sectioned, PTN responsive to passive arm movements could not be statistically controlled.
    • Thus, monkeys operantly control precentral neurons through peripheral movements, perhaps even small and isometric contractions.
  • Excellent paper. Insightful conclusions.


[0] Wyler AR, Lange SC, Neafsey EJ, Robbins CA, Operant control of precentral neurons: control of modal interspike intervals.Brain Res 190:1, 29-38 (1980 May 19)

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ref: Francis-2005.11 tags: Joe_Francis motor_learning reaching humans delay intertrial interval date: 04-09-2007 22:48 gmt revision:1 [0] [head]

PMID-16132970[0] The Influence of the Inter-Reach-Interval on Motor Learning.

Previous studies have demonstrated changes in motor memories with the passage of time on the order of hours. We sought to further this work by determining the influence that time on the order of seconds has on motor learning by changing the duration between successive reaches (inter-reach-interval IRI). Human subjects made reaching movements to visual targets while holding onto a robotic manipulandum that presented a viscous curl field. We tested four experimental groups that differed with respect to the IRI (0.5, 5, 10 or 20 sec). The 0.5 sec IRI group performed significantly worse with respect to a learning index than the other groups over the first set of 192 reaches. Each group demonstrated significant learning during the first set. There was no significant difference with respect to the learning index between the 5, 10 or 20 sec IRI groups. During the second and third set of 192 reaches the 0.5 sec IRI group's performance became indistinguishable from the other groups indicating that fatigue did not cause the initial poor performance and that with continued training the initial deficit in performance could be overcome.