GPe neurons exhibit negligible interactions between pairs of neurons.

<p>Cross-correlations in the two species. Below the blue line: cross-correlations during a time window of ±1 s in four units recorded simultaneously in primates. Above the blue line: same in rats. Red lines in every cross-correlogram represent the lower and upper confidence levels (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045421#s2" target="_blank">Methods</a>).</p

Neuronal classification and firing properties in primates and rats.

<p>A and B: 3 dimensional presentation of firing properties leading to the formation of distinct clusters in primates (A) and rats (B). C–H: Bar plots representing parameters of the two groups (HFP - blue, LFB - red) in the two species (left two bars - primates, right two bars - rats).</p

Waveform characteristics.

<p>A and B: normalized average waveforms of HFP (blue) and LFB (red) neurons in primates (A) and rats (B). Inset: X represents the valley to peak duration, Y the valley width and Z the zero-cross parameter. C and D Bar plots representing waveform parameters in HFP (blue) and LFB (red) neurons in primates (C) and in rats (D).</p

Typical firing patterns observed in rats (A–C) and primates (D–F).

<p>Left panel: autocorrelation using a time window of ±1 s, middle panel: autocorrelation with x-axis expanded to ±0.1 s, right panel: spike train of the example neuron. A: example of HFP neuron exhibiting tonic Poisson firing without pauses. B: HFP neuron displaying pauses (pauser). C: LFB neuron (burster). D–F: same type of neurons as in A–C but in primates.</p

Verification of electrode placement in the Globus Pallidus of rats.

<p>A: a 60 micron slice showing electrode placement in a rat GPe following electrolytic lesion. B: Appropriate coronal section from atlas (Bregma: −2.28 mm; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045421#pone.0045421-Paxinos1" target="_blank">[47]</a>). C: Recording sites marked (grey rectangle) for all animals on a planar rat atlas slice (Bregma: −6.82 mm; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045421#pone.0045421-Paxinos1" target="_blank">[47]</a>).</p

Average parameters of GP neurons.

<p><i>Ai</i>, Voltage-current curves for type A neurons (n = 14). <i>Bi</i>, Voltage-current curves for type B neurons (n = 24). <i>Ci</i>, Voltage-current curves for type C neurons (n = 38). In Ai, Bi and Ci, • - data measured to calculate input resistance; ○ - data measured to estimate the influence of I_h on membrane potential. <i>Aii</i>, lines plotted by exponential fitting to curves from action potential frequency vs. injected currents. F_max and current required to reach 63% of maximal firing rate were extracted by exponential fit for type A neurons. Values and error bars are mean ± S.E. Bii, As in Aii but for type B neurons. Cii, As in Aii but for type C neurons.</p

Extracellular properties of different cellular populations of the primate GPe.

<p><b>A</b>. Traces from representative neurons from the two major neuron types in the GPe: high frequency pauser (HFP–left) and low frequency burster (LFB–right), shown at long and short time scales (top, 1 s trace; bottom, 100 ms trace). <b>B</b>. Autocorrelation functions of the neurons in A (maximal offset ±1 s). <b>C</b>. Mean firing rate of the two groups. <b>D</b>. Mean ISI distribution coefficient of dispersion of the two groups. <b>E</b>. Mean spike shape of the neurons shown above (HFP–black, LFB–gray). <b>F</b>. Mean spike duration of the two groups, Error bars indicate SEM, ** p≪0.01 Mann-Whitney U-test.</p

The width of the intracellular AP can be extracted from extracellular recordings.

<p><b>A</b>, The intracellular AP recorded in the whole-cell mode (top trace) and the transmembrane current recorded in the cell-attached mode (bottom trace, black line). The first derivative of the intracellular trace is superimposed on the extracellular trace (bottom trace, gray line). The half-width of the intracellular AP is indicated by the horizontal line. The vertical lines locate the half-width of the intracellular AP on the extracellular trace. <b>B</b>, Correlation between the half-width of the extracellular and intracellular recordings of the AP for all neurons recorded (n = 76). <b>C</b>, Distribution of the intracellular AP half-width for all neurons recorded. <b>D</b>, Distribution of the extracellular AP half-width for all neurons recorded.</p

Representative recordings from GP neurons of three visually separated subgroups.

<p><i>Ai</i>, <i>Bi</i>, and <i>Ci</i>, responses of GP cells to depolarizing current steps (50 pA increment, 600 ms) applied from 0 to 550 pA using whole-cell configuration of the patch-clamp technique. Representative membrane potentials recorded in response to 100 pA are given for each cell type. Sampled at 20 kHz and filtered at 10 kHz. <i>Aii</i>, <i>Bii</i>, and <i>Cii</i>, responses of GP cells to hyperpolarizing current steps applied from 0 to −450 pA (50 pA increment, 600 ms) using the whole-cell configuration of the patch-clamp technique.</p

Spontaneous firing of GP neurons in acute rat brain slices.

<p><b>A</b>, Population average of the spontaneous firing frequency recorded from GP neurons in the cell-attached mode (n = 76). <b>B</b>, Population average of the spontaneous firing frequency recorded from GP neurons in the whole-cell mode (n = 76). <b>C</b>, Distribution of the average firing frequency recorded in the cell-attached mode across the population. The frequency value used to construct the histogram was taken 200 s after the start of the recording to ensure stability. <b>D</b>, Distribution of the average firing frequency recorded in the whole-cell mode across the population. The frequency value used to construct the histogram was taken 200 s after the start of the recording to ensure stability. <b>E</b>, Correlation between the values used to generate C and D.</p