Effects of stimulation frequency on evoked components.

<p>(<b><i>A</i></b>) Representative responses of one mouse to various stimulus trains (30 stimuli per train) at frequencies between 0.2 and 50 Hz (indicated at left). Each trace shows the mean local field potential (averaged over the last 20 stimuli) recorded near the Purkinje cell layer of the Crus I/II area. In control conditions, the stimuli were delivered every 10±3 s. To facilitate visual comparison, dotted lines have been placed to indicate the locations of the N1, N2, and N3 peaks observed before stimulation. The arrowheads indicate shifts in the peak latencies. (<b><i>B</i></b>) Superimposed traces of mean averaged local field potentials obtained at stimulation frequencies from control to 8 Hz. Traces were aligned with the stable N1 component. Dotted lines indicate the locations of the N1, N2, and N3 peaks observed before stimulation. (<b><i>C</i></b>) Single-trial traces that correspond to the local field potentials in response to the first 10 stimuli (8 Hz) in a train (numbered at left). Single control stimuli responses were recorded just before the train (top) and just after (bottom) the 10^th stimulus (8 Hz).</p

Experimental design and electrophysiological responses during the collision testing.

<p><i>(</i><b><i>A</i></b><i>)</i> Diagram of the neural pathways concerned in the direct stimulation (Stim.) applied on the top of the parallel fiber (PF). This stimulation produced a negative LFP (superimposed traces on the right corner) recorded by a microfiber placed in the dendritic tress of Purkinje cells (PC). The small arrows indicate the propagation of the orthodromic action potentials (black arrows) and the antidromic action potentials (red arrows) producing collision (red star). The peripheral input coming from the whisker pad is transmitted to the granule cells (GC) via the mossy fiber. (<b><i>B</i></b>) Superimposition of the average LFP (n = 10 stimulations) in control (black trace) and during the collision (red trace, red star). The gray vertical arrow indicates the direct stimulation of the PFs while the black vertical arrow indicates the peripheral stimulation of the whisker pad. (<b><i>C</i></b>) Evolution of the N2 (blue lines) and N3 (red lines) amplitudes during the collision testing with respect to the control situation recorded before (control 1) and after the collision (control 2).</p

Time course of the effects induced by an 8-Hz stimulation train on evoked field potential components.

<p>(<b><i>A</i></b>) Time course of amplitude changes for N1 (black circles), N2 (blue squares), and N3 (red triangles) before (negative time periods) and after (positive time periods) the 8-Hz stimulation protocol (not shown). Mean normalized values were calculated for each 5-min interval of data from 15 alert animals. Data points are mean±SEM. (<b><i>B</i></b>) Time course of N1 (black circles), N2 (blue squares), and N3 (red triangles) latency changes before (negative time periods) and after (positive time periods) the 8-Hz stimulation protocol (not shown). Mean data represent the time difference at peak latency between each 5-min interval and the mean value measured in control conditions (negative time periods). Significant differences from control are indicated with asterisks. A small but significant (*) difference observed in the N1 presynaptic component showed recovery to control values after the first 5 min. (<b><i>C</i></b>, <b><i>D</i></b>) Controls were performed in different animals (n = 10) for which the 10-min period at 8 Hz was replaced by 10 min at the same frequency as the control situation. No significant changes were observed in the amplitude or latency compared to the control condition. (p<0.001, ***; p<0.01, **; p<0.05, *). Data points are mean±SEM.</p

Relationships between evoked local field potential components and Purkinje cell firing behavior.

<p>(<b><i>A</i></b>) Recording of spontaneous firing behavior of a Purkinje cell (PC) shows the presence of single spikes (SS) and complex spikes (CS). The presence of a CS followed by a pause in the SS firing (asterisk) identifies this neuron as a PC. (<b><i>B</i></b>) Single trials, superimposed (n = 11), show spontaneous firing before the whisker electrical stimulation (Stim) and the temporal reorganization of the firing after the stimulus. SS firing occurred at the low points of the N2 and N3 components and later. The evoked CS occurred at a latency of 9–13 ms after the stimulus onset (arrowhead). The single trace appears in color to facilitate the identification of SS and CS. (<b><i>C</i></b>) Histogram (bin size = 1 ms) of a PC recording shows the typical SS (top) and CS (bottom) response to whisker pad electrical stimulation (n = 37). After stimulus onset (arrowhead), the PC showed an initial SS burst at N2–N3 latencies, followed by a CS, followed by a silent period. (<b><i>D</i></b>) Superimposition (n = 43) of a PC recording triggered by CS (dotted line) during spontaneous firing. (<b><i>E</i></b>) Superimposition (n = 58) of the same PC presented in (<b><i>C</i></b>) in response to electrical whisker stimulation (arrowheads). The figure shows that SS and CS waveforms were preserved during whisker stimulation. (<b><i>F</i></b>) The SS latency distribution, in response to whisker pad electrical stimulation, combined from 45 PCs. The two major peaks correspond to the occurrence times of the N2 (black bars) and N3 (gray bars) postsynaptic components. Bin sizes are 0.2 ms. (<b><i>G</i></b>) Latency of the complex spike (CS) for the same population of PCs. The CS always occurred after SS evoked potentials. Bin sizes are 0.5 ms.</p

Simple and complex spike firing behavior before and during the 8-Hz electrical stimulus train.

<p>(<b><i>A</i></b>) Superimposed single stimulus (Stim, open arrow) trials under control conditions, before the 8-Hz stimulation. Note the SS evoked responses at the latency of the N2–N3 local field potential components (N2–N3, filled arrow). (<b><i>B</i></b>, <b><i>C</i></b>) Superimposed single traces during two 8-Hz stimulation protocols. In each case (<b><i>A</i></b>–<b><i>C</i></b>), the stimulations (Stim, open arrow) are aligned for comparisons. Single trace appears in color to facilitate the identification of SS and CS. Of note, (<b><i>B</i></b>) the early evoked SS is absent, and (<b><i>C</i></b>) the evoked SS is desynchronized compared to the control situation (<b><i>A</i></b>). (<b><i>D</i></b>) Raster sweeps (top) and related histograms (bin size = 1 ms, bottom) of the CS (upper part) and SS (lower part) evoked responses in control conditions. (<b><i>E</i></b>, <b><i>F</i></b>) Raster sweeps (top panels) and histograms (bin size = 1 ms, bottom panels) of (<b><i>E</i></b>) the CS and (<b><i>F</i></b>) SS evoked responses during the 8-Hz stimulation.</p

Experimental design and electrophysiological response to electrical stimulation of mouse whiskers.

<p>(<b><i>A</i></b>) Animals were prepared for chronic recordings of local field potentials and unitary extracellular activity in the Purkinje cell layer of the Crus I/II area. Facial dermatomes of the whisker region were electrically or tactilely stimulated with a pair of needles under the skin (Stim.) or an air puff pulse, respectively. Sensory information comes into the Crus I/II area from the trigeminal nucleus (Tn) in the brainstem, which receives afferent signals from the trigeminal ganglion (Tg). The LFP recorded in the alert animal induced by tactile stimuli consisted of two major negative waves corresponding to trigeminal (T) and cortical (C) responses (upper trace). (<b><i>B</i></b>) In some of the recordings, the T component appeared as two separate components (N2 and N3). The figure shows superimposed LFPs (upper trace, n = 7) and the corresponding mean average (with error bars in gray at bottom) for the LFP acquired after tactile stimulation of the whisker. (<b><i>C</i></b>) Superimposed LFPs (upper trace, n = 7) and the corresponding mean average (with error bars in gray at bottom) for the LFP acquired at the same recording place shown in <i>B</i> but after electrical stimulation of the whisker. A major reproducibility of the T-related components in the superimposed traces and a decrement in the error bars in the mean average of LFP were observed after electrical stimulation in comparison to air puff stimulation. (<b><i>D</i></b>) The lower trace shows T-related components enlarged from a representative local field potential recording from the Crus II area in the Purkinje cell layer in response to a single-pulse electrical stimulation of the whisker pad (Stim. trace). Early response associated with sensory input in the cerebellum via the trigeminal nucleus is characterized by P1-N1-N2-P2-N3 components.</p

Event-related spectral perturbation (ERSP) and intertrial coherency (ITC) (grand average, n = 8 subjects) recorded at the O2 electrode.

<p>A: ERSP related to checkerboard stimulation preceded and followed by gray page condition, the related ERP traces are overlapping and indicate P100, P200, P300. B: ITC map corresponding to the same situation as A. C: Same display as in A but for the 3D tunnel stimulation. D: same display as in B, but for the 3D-tunnel stimulation.</p

Superimposition of the event-related potentials (grand average, n = 8 subjects) evoked by the checkerboard (red traces) and the 3D-tunnel (blue traces) presentation recorded at the O2 electrode.

<p>A: The vertical arrow corresponds to image presentation (Checkerboard or 3D tunnel) highlighting the P100, P200 and P300 components. The lower raster line represents the statistical significance of ERP difference between the two conditions (<i>P</i> < 0.05, permutation test). B: Same display as in A, but here the vertical arrow indicates the presentation of the uniform gray image highlighting the P135 component. Note the occurrence of a sinusoidal profile in the delta frequency range. C: Scalp topographies of the power of delta oscillation (1Hz) corresponding to the checkerboard and the 3D-tunnel stimulation between 360 and 460 ms. Only the significant periods are illustrated and the significant electrodes (<i>P</i> < 0.05, permutation test) are displayed in the far right column.</p

Short-term EEG dynamics and neural generators evoked by navigational images - Fig 6

<p>Event-related spectral perturbation (ERSP) evoked by the gray image in the context of the checkerboard (GrayCheck)(A,D,G) and the 3D-tunnel (GrayTun)(B,E,H) in the same display as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178817#pone.0178817.g005" target="_blank">Fig 5</a>. The statistical differences observed between these two situations are indicated in C, F, I for the ERSP recorded in Fz, Cz, and Oz, respectively. The red arrows point to increased beta ERS in case of the GrayTun centered around 450 ms (F) and increased alpha ERS just after the onset of the GrayCheck. These ERPS analysis are corroborated by FFT topographies of the 10 Hz (J) and 15 Hz oscillations (K) where only the statistical periods are illustrated from respectively -40 ms before the gray image presentation to + 250 ms and from +240 ms after the gray image to + 50 ms after the image presentation. J and K maps are vertically adjusted in order to highlight the time transition marked by a rectangular frame between the 10 and 15 Hz maps. Note that significant electrodes (third column of J, K) are mainly bilaterally situated in the parieto-occipital areas (J) for the 10 Hz and mainly lateralized in the left side for the 15 Hz (K).</p

Effects of directional change in the 3D-tunnel presentation (grand average, n = 12 subjects).

<p>A: Event-related spectral perturbation in occipital locus (O2 electrode) evoked by the same 3D-tunnel direction (1Dir) (left side) and the 4 different directions (4Dir) (middle) showing a significant theta ERS between 370–500 ms for the 3D-tunnel with 4 different directions (middle map) with respect to the 3D-tunnel with single direction (left map). The statistical map (permutation with Holms test <i>P</i> < 0.05) is given on the right side of A. B: Event-related potential recorded (O2 electrode) evoked in the same condition as in A. The statistical difference (<i>P</i> < 0.05, permutation test) centered on the P200 component is marked by the vertical gray rectangle in the third column. C: Topography of the delta oscillation during the presentation of only one direction of the 3D-tunnel (left column) and during the 4 different directions of the 3D-tunnel presentation (middle column). The third column represents the statistical map (permutation with Holms). D: Same displays as in C but for the theta oscillation. Only the significant periods are illustrated.</p