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Cortical modulations increase in early sessions with brain-machine interface.

Zacksenhouse M, Lebedev MA, Carmena JM, O'Doherty JE, Henriquez C, Nicolelis MA - PLoS ONE (2007)

Bottom Line: We conclude that the enhanced modulations are related to computational tasks that are significant especially in novel motor contexts.Although the function and neuronal mechanism of the enhanced cortical modulations are open for further inquiries, we discuss their potential role in processing execution errors and representing corrective or explorative activity.These representations are expected to contribute to the formation of internal models of the external actuator and their decoding may facilitate BMI improvement.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Mechanical Engineering, Technion, Haifa, Israel. mermz@tx.technion.ac.il

ABSTRACT

Background: During planning and execution of reaching movements, the activity of cortical motor neurons is modulated by a diversity of motor, sensory, and cognitive signals. Brain-machine interfaces (BMIs) extract part of these modulations to directly control artificial actuators. However, cortical modulations that emerge in the novel context of operating the BMI are poorly understood.

Methodology/principal findings: Here we analyzed the changes in neuronal modulations that occurred in different cortical motor areas as monkeys learned to use a BMI to control reaching movements. Using spike-train analysis methods we demonstrate that the modulations of the firing-rates of cortical neurons increased abruptly after the monkeys started operating the BMI. Regression analysis revealed that these enhanced modulations were not correlated with the kinematics of the movement. The initial enhancement in firing rate modulations declined gradually with subsequent training in parallel with the improvement in behavioral performance.

Conclusions/significance: We conclude that the enhanced modulations are related to computational tasks that are significant especially in novel motor contexts. Although the function and neuronal mechanism of the enhanced cortical modulations are open for further inquiries, we discuss their potential role in processing execution errors and representing corrective or explorative activity. These representations are expected to contribute to the formation of internal models of the external actuator and their decoding may facilitate BMI improvement.

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Related in: MedlinePlus

Percent Overall Modulation (POM) in pole control, BCWH and BCWOH for two representative M1 units.
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pone-0000619-g003: Percent Overall Modulation (POM) in pole control, BCWH and BCWOH for two representative M1 units.

Mentions: The percent overall modulation (POM), defined in Equation (1), represents the percentage of the variance of the binned spike-count that is attributed to rate modulations (Figure 1, Methods). The pie-plots in Figure 3 illustrate the distribution of the variance in the spike-counts recorded from two M1 neurons in different control modes, based on the POM computed using Equation (2) (Methods). During pole control (Figure 3, top pies), rate modulations accounted for only 7% for the typical neuron depicted on the right and 36% for a highly modulated neuron depicted on the left. The contribution of rate-modulations to the variance of the neural activity was more significant in brain control with and without hand movements, accounting, respectively, for 13% and 34% of the variance for the typical neuron (Figure 3, right middle and bottom pies) and 37% and 58% for the highly modulated neuron (Figure 3, left middle and bottom pies). These examples indicate that POM was higher in brain control than in pole control.


Cortical modulations increase in early sessions with brain-machine interface.

Zacksenhouse M, Lebedev MA, Carmena JM, O'Doherty JE, Henriquez C, Nicolelis MA - PLoS ONE (2007)

Percent Overall Modulation (POM) in pole control, BCWH and BCWOH for two representative M1 units.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1919433&req=5

pone-0000619-g003: Percent Overall Modulation (POM) in pole control, BCWH and BCWOH for two representative M1 units.
Mentions: The percent overall modulation (POM), defined in Equation (1), represents the percentage of the variance of the binned spike-count that is attributed to rate modulations (Figure 1, Methods). The pie-plots in Figure 3 illustrate the distribution of the variance in the spike-counts recorded from two M1 neurons in different control modes, based on the POM computed using Equation (2) (Methods). During pole control (Figure 3, top pies), rate modulations accounted for only 7% for the typical neuron depicted on the right and 36% for a highly modulated neuron depicted on the left. The contribution of rate-modulations to the variance of the neural activity was more significant in brain control with and without hand movements, accounting, respectively, for 13% and 34% of the variance for the typical neuron (Figure 3, right middle and bottom pies) and 37% and 58% for the highly modulated neuron (Figure 3, left middle and bottom pies). These examples indicate that POM was higher in brain control than in pole control.

Bottom Line: We conclude that the enhanced modulations are related to computational tasks that are significant especially in novel motor contexts.Although the function and neuronal mechanism of the enhanced cortical modulations are open for further inquiries, we discuss their potential role in processing execution errors and representing corrective or explorative activity.These representations are expected to contribute to the formation of internal models of the external actuator and their decoding may facilitate BMI improvement.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Mechanical Engineering, Technion, Haifa, Israel. mermz@tx.technion.ac.il

ABSTRACT

Background: During planning and execution of reaching movements, the activity of cortical motor neurons is modulated by a diversity of motor, sensory, and cognitive signals. Brain-machine interfaces (BMIs) extract part of these modulations to directly control artificial actuators. However, cortical modulations that emerge in the novel context of operating the BMI are poorly understood.

Methodology/principal findings: Here we analyzed the changes in neuronal modulations that occurred in different cortical motor areas as monkeys learned to use a BMI to control reaching movements. Using spike-train analysis methods we demonstrate that the modulations of the firing-rates of cortical neurons increased abruptly after the monkeys started operating the BMI. Regression analysis revealed that these enhanced modulations were not correlated with the kinematics of the movement. The initial enhancement in firing rate modulations declined gradually with subsequent training in parallel with the improvement in behavioral performance.

Conclusions/significance: We conclude that the enhanced modulations are related to computational tasks that are significant especially in novel motor contexts. Although the function and neuronal mechanism of the enhanced cortical modulations are open for further inquiries, we discuss their potential role in processing execution errors and representing corrective or explorative activity. These representations are expected to contribute to the formation of internal models of the external actuator and their decoding may facilitate BMI improvement.

Show MeSH
Related in: MedlinePlus