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Perceived intensity of somatosensory cortical electrical stimulation.

Fridman GY, Blair HT, Blaisdell AP, Judy JW - Exp Brain Res (2010)

Bottom Line: Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood.We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex.We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Engineering Department, UCLA, Los Angeles, CA 90095, USA. gfridma1@jhmi.edu

ABSTRACT
Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood. Based on prior work in cortical stimulation, we hypothesized that perceived intensity of electrical stimulation may be explained by the population response of the neurons affected by the stimulus train. To explore this hypothesis, we modeled perceived intensity of a stimulation pulse train with a leaky neural integrator. We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex. We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train.

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Results of the experiment comparing the frequency discrimination performance when the pulse trains’ inter pulse intervals are randomized when compared to the performance in response to test pulse trains which consist of periodically timed pulses for animal 1. Circles show performance for pulse trains with regular intervals (CV = 0), and squares to indicate performance in response to pulse trains with randomized inter pulse intervals (CV = 1). Both plots are similar, indicating that the performance did not depend on the coefficient of variation of the pulse train. Model predictions were established for these experiments using the model parameters obtained for animal 1 from the frequency discrimination experiment. The solid line represents the model prediction for the performance on the frequency discrimination of the periodic pulse trains (CV = 0), and the dashed line represents the model prediction for the performance on the frequency discrimination of the pulse trains with randomized inter-pulse intervals (CV = 1). The similar predictions for the two cases suggest that the behavior of the model, as well as the animal does not rely on periodicity, but rather on the pulse rate, in agreement with previously published results (Romo et al. 1998; Hernandez et al. 2000; Salinas and Romo 2000; Luna et al. 2005)
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Fig7: Results of the experiment comparing the frequency discrimination performance when the pulse trains’ inter pulse intervals are randomized when compared to the performance in response to test pulse trains which consist of periodically timed pulses for animal 1. Circles show performance for pulse trains with regular intervals (CV = 0), and squares to indicate performance in response to pulse trains with randomized inter pulse intervals (CV = 1). Both plots are similar, indicating that the performance did not depend on the coefficient of variation of the pulse train. Model predictions were established for these experiments using the model parameters obtained for animal 1 from the frequency discrimination experiment. The solid line represents the model prediction for the performance on the frequency discrimination of the periodic pulse trains (CV = 0), and the dashed line represents the model prediction for the performance on the frequency discrimination of the pulse trains with randomized inter-pulse intervals (CV = 1). The similar predictions for the two cases suggest that the behavior of the model, as well as the animal does not rely on periodicity, but rather on the pulse rate, in agreement with previously published results (Romo et al. 1998; Hernandez et al. 2000; Salinas and Romo 2000; Luna et al. 2005)

Mentions: We conducted a further experiment, in which we varied the coefficient of variance (CV) for the frequency discrimination test pulse trains for animal 1. In agreement with the model predictions, the results indicate that the performance of the subject did not depend on the coefficient of variation of the pulse train (Fig. 7). These results agree with prior findings (Romo et al. 1998) on the ability of the monkey to discriminate frequencies of cortical stimulation. Additionally, the results are consistent with the prior findings which suggest that firing rate rather than periodicity account for the ability to differentiate frequency of stimulation (Romo et al. 1998; Hernandez et al. 2000; Salinas et al. 2000; Luna et al. 2005).Fig. 7


Perceived intensity of somatosensory cortical electrical stimulation.

Fridman GY, Blair HT, Blaisdell AP, Judy JW - Exp Brain Res (2010)

Results of the experiment comparing the frequency discrimination performance when the pulse trains’ inter pulse intervals are randomized when compared to the performance in response to test pulse trains which consist of periodically timed pulses for animal 1. Circles show performance for pulse trains with regular intervals (CV = 0), and squares to indicate performance in response to pulse trains with randomized inter pulse intervals (CV = 1). Both plots are similar, indicating that the performance did not depend on the coefficient of variation of the pulse train. Model predictions were established for these experiments using the model parameters obtained for animal 1 from the frequency discrimination experiment. The solid line represents the model prediction for the performance on the frequency discrimination of the periodic pulse trains (CV = 0), and the dashed line represents the model prediction for the performance on the frequency discrimination of the pulse trains with randomized inter-pulse intervals (CV = 1). The similar predictions for the two cases suggest that the behavior of the model, as well as the animal does not rely on periodicity, but rather on the pulse rate, in agreement with previously published results (Romo et al. 1998; Hernandez et al. 2000; Salinas and Romo 2000; Luna et al. 2005)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2875471&req=5

Fig7: Results of the experiment comparing the frequency discrimination performance when the pulse trains’ inter pulse intervals are randomized when compared to the performance in response to test pulse trains which consist of periodically timed pulses for animal 1. Circles show performance for pulse trains with regular intervals (CV = 0), and squares to indicate performance in response to pulse trains with randomized inter pulse intervals (CV = 1). Both plots are similar, indicating that the performance did not depend on the coefficient of variation of the pulse train. Model predictions were established for these experiments using the model parameters obtained for animal 1 from the frequency discrimination experiment. The solid line represents the model prediction for the performance on the frequency discrimination of the periodic pulse trains (CV = 0), and the dashed line represents the model prediction for the performance on the frequency discrimination of the pulse trains with randomized inter-pulse intervals (CV = 1). The similar predictions for the two cases suggest that the behavior of the model, as well as the animal does not rely on periodicity, but rather on the pulse rate, in agreement with previously published results (Romo et al. 1998; Hernandez et al. 2000; Salinas and Romo 2000; Luna et al. 2005)
Mentions: We conducted a further experiment, in which we varied the coefficient of variance (CV) for the frequency discrimination test pulse trains for animal 1. In agreement with the model predictions, the results indicate that the performance of the subject did not depend on the coefficient of variation of the pulse train (Fig. 7). These results agree with prior findings (Romo et al. 1998) on the ability of the monkey to discriminate frequencies of cortical stimulation. Additionally, the results are consistent with the prior findings which suggest that firing rate rather than periodicity account for the ability to differentiate frequency of stimulation (Romo et al. 1998; Hernandez et al. 2000; Salinas et al. 2000; Luna et al. 2005).Fig. 7

Bottom Line: Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood.We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex.We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Engineering Department, UCLA, Los Angeles, CA 90095, USA. gfridma1@jhmi.edu

ABSTRACT
Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood. Based on prior work in cortical stimulation, we hypothesized that perceived intensity of electrical stimulation may be explained by the population response of the neurons affected by the stimulus train. To explore this hypothesis, we modeled perceived intensity of a stimulation pulse train with a leaky neural integrator. We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex. We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train.

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