Fig 1.
Design of the experimental procedure.
A) Timeline of the different experimental steps. The pre-training visual cortical responses to visual stimulation were recorded 4 days (d5) after the implantation of the electrodes and guide cannulas. Visual training was provided for 10 min/day for 7 days (d7-d14) and followed by the recording of the post-training VEPs (d16) (see text for details). B) Schematic diagram illustrating the chronic implantation of the recording electrode and the push-pull guide cannula in V1. The stimulating electrode was implanted in the HDB. C) Schematic representation of the areas of pharmacological agent injection and electrophysiological recording. D) Representative VEP signal traces in response to a 0.12 CPD grating for the sham, pre- and post-training VS/HDB groups. The VEP was evoked by phase inversion after 2 seconds of stimulus presentation (0.25 Hz), and the amplitude was measured by subtracting the negative peak (a or a’) from the positive peak (b or b’). Note that the visual cortical response increased after the VS/HDB training (b’-a’) compared to sham (b-a).
Table 1.
Experimental groups.
Fig 2.
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.
Fig 3.
Change in VEP amplitudes following pharmacological modulation during visual/cholinergic stimulation (VS/HDB).
The histograms represent the VEP difference of amplitude (Post-Pre training) for the different groups for the trained spatial frequency of 0.12 CPD (A) and 0.3 CPD (B). Note that the VEP amplitude enhancement following the visual/cholinergic training was blocked by MEC, AFDX, or PTX injection. (*; one-way ANOVA, post-hoc Dunnett, p < 0.05, compared to VS/HDB group, †; post-hoc Dunnett, p <0.05, compared to VS group). The error bars represent the average deviation. (Abbreviations; PZP: pirenzepine; MEC: mecamylamine; AFDX: AF-DX 116; MUS: muscimol and PTX: picrotoxin).
Fig 4.
A) Representative comparison of the power spectral densities (PSDs) of the pre- and post-training VEPs from the VS/HDB group as analyzed with the short-time Fourier transformation. B) Comparison of the PSDs in the 200–250 ms time window after the stimulus presentation. Only the VS/HDB group exhibited an increase in gamma band oscillations (†, one-way ANOVA, p < 0.05). Gamma (C) and beta band (D) power during VEP recording. There was an increase of beta (15–30 Hz) and gamma band (30–90 Hz) power 200–250 ms after stimulus onset.