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Pharmacological Mechanisms of Cortical Enhancement Induced by the Repetitive Pairing of Visual/Cholinergic Stimulation.

Kang JI, Huppé-Gourgues F, Vaucher E - PLoS ONE (2015)

Bottom Line: The post-training VEP amplitude was significantly increased compared to the pre-training values for the trained spatial frequency and to adjacent spatial frequencies up to 0.3 CPD, suggesting a long-term increase of V1 sensitivity.However, the M1 mAChR antagonist blocked the increase of the VEP amplitude only for the high spatial frequency (0.3 CPD), suggesting that M1 role was limited to the spread of the enhancement effect to a higher spatial frequency.These findings demonstrate that visual training coupled with cholinergic stimulation improved perceptual sensitivity by enhancing cortical responsiveness in V1.

View Article: PubMed Central - PubMed

Affiliation: École d'optométrie, Université de Montréal, CP 6128 succursale centre-ville, Montréal, Qc, H3C 3J7, Canada; Département de Neuroscience, Université de Montréal, CP 6128 succursale centre-ville, Montréal, Qc, H3C 3J7, Canada.

ABSTRACT
Repetitive visual training paired with electrical activation of cholinergic projections to the primary visual cortex (V1) induces long-term enhancement of cortical processing in response to the visual training stimulus. To better determine the receptor subtypes mediating this effect the selective pharmacological blockade of V1 nicotinic (nAChR), M1 and M2 muscarinic (mAChR) or GABAergic A (GABAAR) receptors was performed during the training session and visual evoked potentials (VEPs) were recorded before and after training. The training session consisted of the exposure of awake, adult rats to an orientation-specific 0.12 CPD grating paired with an electrical stimulation of the basal forebrain for a duration of 1 week for 10 minutes per day. Pharmacological agents were infused intracortically during this period. The post-training VEP amplitude was significantly increased compared to the pre-training values for the trained spatial frequency and to adjacent spatial frequencies up to 0.3 CPD, suggesting a long-term increase of V1 sensitivity. This increase was totally blocked by the nAChR antagonist as well as by an M2 mAChR subtype and GABAAR antagonist. Moreover, administration of the M2 mAChR antagonist also significantly decreased the amplitude of the control VEPs, suggesting a suppressive effect on cortical responsiveness. However, the M1 mAChR antagonist blocked the increase of the VEP amplitude only for the high spatial frequency (0.3 CPD), suggesting that M1 role was limited to the spread of the enhancement effect to a higher spatial frequency. More generally, all the drugs used did block the VEP increase at 0.3 CPD. Further, use of each of the aforementioned receptor antagonists blocked training-induced changes in gamma and beta band oscillations. These findings demonstrate that visual training coupled with cholinergic stimulation improved perceptual sensitivity by enhancing cortical responsiveness in V1. This enhancement is mainly mediated by nAChRs, M2 mAChRs and GABAARs. The M1 mAChR subtype appears to be involved in spreading the enhancement of V1 cortical responsiveness to adjacent neurons.

No MeSH data available.


Related in: MedlinePlus

Effects of repetitive Visual/cholinergic stimulation (VS/HDB) on VEP amplitudes.A) Basal VEPs in response to 30°, 45° and 60° stimuli orientation recorded prior to any experimental procedure. There were no differences in VEP amplitudes between the orientations, which were subsequently pooled into the X° and X+90° groups. B) VEP amplitudes from the sham (grey screen/no HDB stimulation) animals in response to different orientations and spatial frequencies. There were no significant differences between the pre- and post-training values. C) VEP amplitudes in the repetitive VS/HDB stimulation (training) animals in response to different orientations and spatial frequencies. Visual/cholinergic training induced increases in VEP amplitudes in response to the exposure of the stimulus (0.12 CPD) and higher spatial frequency stimuli (0.3 CPD). D) VEP amplitude difference (post training—pre training) for X°-0.12 CPD (left) and 0.3 CPD (right). VEP difference of VS/HDB was significantly enhanced compared to sham and VS group. (*, ANOVA, post-hoc Tukey, p < 0.05). VS/HDB = sinusoidal grating screen with HDB stimulation, VS = sinusoidal grating screen without HDB stimulation, and Sham = grey screen without HDB stimulation. The error bars represent the average deviation.
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pone.0141663.g002: Effects of repetitive Visual/cholinergic stimulation (VS/HDB) on VEP amplitudes.A) Basal VEPs in response to 30°, 45° and 60° stimuli orientation recorded prior to any experimental procedure. There were no differences in VEP amplitudes between the orientations, which were subsequently pooled into the X° and X+90° groups. B) VEP amplitudes from the sham (grey screen/no HDB stimulation) animals in response to different orientations and spatial frequencies. There were no significant differences between the pre- and post-training values. C) VEP amplitudes in the repetitive VS/HDB stimulation (training) animals in response to different orientations and spatial frequencies. Visual/cholinergic training induced increases in VEP amplitudes in response to the exposure of the stimulus (0.12 CPD) and higher spatial frequency stimuli (0.3 CPD). D) VEP amplitude difference (post training—pre training) for X°-0.12 CPD (left) and 0.3 CPD (right). VEP difference of VS/HDB was significantly enhanced compared to sham and VS group. (*, ANOVA, post-hoc Tukey, p < 0.05). VS/HDB = sinusoidal grating screen with HDB stimulation, VS = sinusoidal grating screen without HDB stimulation, and Sham = grey screen without HDB stimulation. The error bars represent the average deviation.

Mentions: The VEP response and amplitude were similar across all orientations tested (30°, 45°, and 60°, collectively termed "X°") (Fig 2A), as well as across all X+90° stimuli (i.e., 120°, 135° and 150°; data not shown). These values were thus further pooled together for the X° and X+90° analysis. The VEP responses in the pre-training/sham recordings were largest for 0.08 and 0.12 CPD both for the X° and X+90° stimuli (Fig 2B). The threshold of detection of the contrast inversion was 0.5 CPD because cortical responses were not significantly different from the baseline level (field potential during grey stimulus presentation) above this spatial frequency in the sham group (grey screen: 0.03 ± 0.019 mV v. 0.5 CPD: 0.25 ± 0.14; paired t-test, p = 0.081; average ± average deviation). Thus, 0.5 CPD was determined to be the cortical visual acuity in these experiments.


Pharmacological Mechanisms of Cortical Enhancement Induced by the Repetitive Pairing of Visual/Cholinergic Stimulation.

Kang JI, Huppé-Gourgues F, Vaucher E - PLoS ONE (2015)

Effects of repetitive Visual/cholinergic stimulation (VS/HDB) on VEP amplitudes.A) Basal VEPs in response to 30°, 45° and 60° stimuli orientation recorded prior to any experimental procedure. There were no differences in VEP amplitudes between the orientations, which were subsequently pooled into the X° and X+90° groups. B) VEP amplitudes from the sham (grey screen/no HDB stimulation) animals in response to different orientations and spatial frequencies. There were no significant differences between the pre- and post-training values. C) VEP amplitudes in the repetitive VS/HDB stimulation (training) animals in response to different orientations and spatial frequencies. Visual/cholinergic training induced increases in VEP amplitudes in response to the exposure of the stimulus (0.12 CPD) and higher spatial frequency stimuli (0.3 CPD). D) VEP amplitude difference (post training—pre training) for X°-0.12 CPD (left) and 0.3 CPD (right). VEP difference of VS/HDB was significantly enhanced compared to sham and VS group. (*, ANOVA, post-hoc Tukey, p < 0.05). VS/HDB = sinusoidal grating screen with HDB stimulation, VS = sinusoidal grating screen without HDB stimulation, and Sham = grey screen without HDB stimulation. The error bars represent the average deviation.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4626033&req=5

pone.0141663.g002: Effects of repetitive Visual/cholinergic stimulation (VS/HDB) on VEP amplitudes.A) Basal VEPs in response to 30°, 45° and 60° stimuli orientation recorded prior to any experimental procedure. There were no differences in VEP amplitudes between the orientations, which were subsequently pooled into the X° and X+90° groups. B) VEP amplitudes from the sham (grey screen/no HDB stimulation) animals in response to different orientations and spatial frequencies. There were no significant differences between the pre- and post-training values. C) VEP amplitudes in the repetitive VS/HDB stimulation (training) animals in response to different orientations and spatial frequencies. Visual/cholinergic training induced increases in VEP amplitudes in response to the exposure of the stimulus (0.12 CPD) and higher spatial frequency stimuli (0.3 CPD). D) VEP amplitude difference (post training—pre training) for X°-0.12 CPD (left) and 0.3 CPD (right). VEP difference of VS/HDB was significantly enhanced compared to sham and VS group. (*, ANOVA, post-hoc Tukey, p < 0.05). VS/HDB = sinusoidal grating screen with HDB stimulation, VS = sinusoidal grating screen without HDB stimulation, and Sham = grey screen without HDB stimulation. The error bars represent the average deviation.
Mentions: The VEP response and amplitude were similar across all orientations tested (30°, 45°, and 60°, collectively termed "X°") (Fig 2A), as well as across all X+90° stimuli (i.e., 120°, 135° and 150°; data not shown). These values were thus further pooled together for the X° and X+90° analysis. The VEP responses in the pre-training/sham recordings were largest for 0.08 and 0.12 CPD both for the X° and X+90° stimuli (Fig 2B). The threshold of detection of the contrast inversion was 0.5 CPD because cortical responses were not significantly different from the baseline level (field potential during grey stimulus presentation) above this spatial frequency in the sham group (grey screen: 0.03 ± 0.019 mV v. 0.5 CPD: 0.25 ± 0.14; paired t-test, p = 0.081; average ± average deviation). Thus, 0.5 CPD was determined to be the cortical visual acuity in these experiments.

Bottom Line: The post-training VEP amplitude was significantly increased compared to the pre-training values for the trained spatial frequency and to adjacent spatial frequencies up to 0.3 CPD, suggesting a long-term increase of V1 sensitivity.However, the M1 mAChR antagonist blocked the increase of the VEP amplitude only for the high spatial frequency (0.3 CPD), suggesting that M1 role was limited to the spread of the enhancement effect to a higher spatial frequency.These findings demonstrate that visual training coupled with cholinergic stimulation improved perceptual sensitivity by enhancing cortical responsiveness in V1.

View Article: PubMed Central - PubMed

Affiliation: École d'optométrie, Université de Montréal, CP 6128 succursale centre-ville, Montréal, Qc, H3C 3J7, Canada; Département de Neuroscience, Université de Montréal, CP 6128 succursale centre-ville, Montréal, Qc, H3C 3J7, Canada.

ABSTRACT
Repetitive visual training paired with electrical activation of cholinergic projections to the primary visual cortex (V1) induces long-term enhancement of cortical processing in response to the visual training stimulus. To better determine the receptor subtypes mediating this effect the selective pharmacological blockade of V1 nicotinic (nAChR), M1 and M2 muscarinic (mAChR) or GABAergic A (GABAAR) receptors was performed during the training session and visual evoked potentials (VEPs) were recorded before and after training. The training session consisted of the exposure of awake, adult rats to an orientation-specific 0.12 CPD grating paired with an electrical stimulation of the basal forebrain for a duration of 1 week for 10 minutes per day. Pharmacological agents were infused intracortically during this period. The post-training VEP amplitude was significantly increased compared to the pre-training values for the trained spatial frequency and to adjacent spatial frequencies up to 0.3 CPD, suggesting a long-term increase of V1 sensitivity. This increase was totally blocked by the nAChR antagonist as well as by an M2 mAChR subtype and GABAAR antagonist. Moreover, administration of the M2 mAChR antagonist also significantly decreased the amplitude of the control VEPs, suggesting a suppressive effect on cortical responsiveness. However, the M1 mAChR antagonist blocked the increase of the VEP amplitude only for the high spatial frequency (0.3 CPD), suggesting that M1 role was limited to the spread of the enhancement effect to a higher spatial frequency. More generally, all the drugs used did block the VEP increase at 0.3 CPD. Further, use of each of the aforementioned receptor antagonists blocked training-induced changes in gamma and beta band oscillations. These findings demonstrate that visual training coupled with cholinergic stimulation improved perceptual sensitivity by enhancing cortical responsiveness in V1. This enhancement is mainly mediated by nAChRs, M2 mAChRs and GABAARs. The M1 mAChR subtype appears to be involved in spreading the enhancement of V1 cortical responsiveness to adjacent neurons.

No MeSH data available.


Related in: MedlinePlus