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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

Firing rate statistics for Nn = 183 units recorded in one session.Mean-variance relationship computed based on 100-ms bins (top panels); and scatter plots of Fano factor in brain versus pole control (bottom panels). BCWH–Brain control with hand movements, BCWOH–Brain control without hand movements.
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pone-0000619-g002: Firing rate statistics for Nn = 183 units recorded in one session.Mean-variance relationship computed based on 100-ms bins (top panels); and scatter plots of Fano factor in brain versus pole control (bottom panels). BCWH–Brain control with hand movements, BCWOH–Brain control without hand movements.

Mentions: The neural activity of most of the cortical neurons was more variable during brain control than during pole control. Generally, rate variability was higher than would be predicted by a homogeneous Poisson process, as indicated by variance that exceeded the mean (Figure 2, top panels). The variance of the binned spike-count (in 100-ms bins) exceeded the mean spike-count for most of the Nn = 183 neurons recorded in this session, (83%, 88% and 92% during pole control, BCWH and BCWOH, respectively). This excess variability was also evident in the ratio of the variance to the mean (the Fano factor), which was found to be mostly above 1.0 (Figure 2, bottom panels). Most importantly, the transition to brain control resulted in even higher excess variability and larger Fano factor for most of the neurons (78% and 87% of the recorded cortical neurons during BCWH and BCWOH, respectively) as evident from the scatter plots of Figure 2.


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)

Firing rate statistics for Nn = 183 units recorded in one session.Mean-variance relationship computed based on 100-ms bins (top panels); and scatter plots of Fano factor in brain versus pole control (bottom panels). BCWH–Brain control with hand movements, BCWOH–Brain control without hand movements.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0000619-g002: Firing rate statistics for Nn = 183 units recorded in one session.Mean-variance relationship computed based on 100-ms bins (top panels); and scatter plots of Fano factor in brain versus pole control (bottom panels). BCWH–Brain control with hand movements, BCWOH–Brain control without hand movements.
Mentions: The neural activity of most of the cortical neurons was more variable during brain control than during pole control. Generally, rate variability was higher than would be predicted by a homogeneous Poisson process, as indicated by variance that exceeded the mean (Figure 2, top panels). The variance of the binned spike-count (in 100-ms bins) exceeded the mean spike-count for most of the Nn = 183 neurons recorded in this session, (83%, 88% and 92% during pole control, BCWH and BCWOH, respectively). This excess variability was also evident in the ratio of the variance to the mean (the Fano factor), which was found to be mostly above 1.0 (Figure 2, bottom panels). Most importantly, the transition to brain control resulted in even higher excess variability and larger Fano factor for most of the neurons (78% and 87% of the recorded cortical neurons during BCWH and BCWOH, respectively) as evident from the scatter plots of Figure 2.

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