Example of the activity of a typical neuron in the PPTN that exhibited periodic firing during the FX-condition.

<p>(<b>A</b>) Rastergrams (<i>top</i>) and spike density functions (<i>bottom</i>). Data are aligned to the appearance of the FT and sorted by relative timing of the centering saccade. This example neuron exhibited periodic firing pattern during the FX-condition. Green, yellow, and blue markers indicate the timing of centering saccades, saccades to target stimulus, and reward delivery, respectively. Black and red bars indicate the FV- and FX-conditions, respectively. (<b>B-D</b>) Plots of ISI (<b>B</b>), CV (<b>C</b>), and power spectrum (<b>D</b>) during the FX- (red) and FV-conditions (black).</p

Relationship between the periodic firing pattern with anatomical and physiological properties of neurons.

<p>(<b>A-C</b>) Distribution of neurons that showed periodic firing during the FX-condition (<b>A</b>), FV-condition (<b>B</b>), and both conditions (<b>C</b>) for monkey 1. Red downward triangles, green squares, and blue upward triangles indicate neurons that showed higher activity during the FV-condition, no significant changes in firing rate, and higher activity during the FX-condition, respectively. (<b>D</b>) Distribution of neurons that did not show periodic firing are shown. (<b>E</b>) Distribution of the recording location for monkey 1 and (<b>F</b>) the duration of spikes for neurons that exhibited periodic firing (solid line) and those that did not (dashed line). (<b>G</b>) Relationship between periodic firing frequency and spike duration of recorded neurons. Frequency of periodic firing during the FX-condition plotted against spike duration for the 119 neurons that showed periodic firing during the FX-condition.</p

Relationship between firing rate and CV.

<p><b>(A, B)</b> Plot of mean CV vs. firing rate of neurons recorded during the FX-condition (<b>A</b>, r = 0.02, p = 0.29) or during the FV-condition (<b>B</b>, r = -0.04, p = 0.15). Red lines indicate the mean and 1 SD of CV simulated from the random spike trains over a range of mean firing rates between 5 and 100 spikes/s. (<b>C</b>) Plot of the modulation of mean CV vs. firing rate as the monkeys’ behavior moved from the FV- to FX-conditions (r = -0.46, p < 0.001), indicating a tendency for increased regularity with increased firing rate.</p

Summary of task-related changes in firing rate and firing regularity.

<p>Values are number of neurons. Higher regularity was indicated by lower CV.</p><p>Summary of task-related changes in firing rate and firing regularity.</p

Summary of periodic firing patterns and task-related tonic changes in activity.

<p>Values are number of neurons.</p><p>Summary of periodic firing patterns and task-related tonic changes in activity.</p

Distributions of firing rate and regularity of PPTN neuron.

<p>Summary histograms and scatter plots of the distributions of firing rate (<b>A</b>) and regularity (<b>B</b>) of PPTN neuron firing during the FX- (<i>right</i>) and FV-conditions (<i>top</i>).</p

Summary of the frequencies of periodic firing of PPTN neurons.

<p>(<b>A, B</b>) Summary histograms of the frequency of periodic firing defined by Fourier analysis. Gray bars indicate neurons that exhibited periodic firing only during the FX-condition (<b>A</b>) or the FV-condition (<b>B</b>), and unfilled bars indicate neurons that exhibited periodic firing throughout the entire behavioral conditions. (<b>C, D</b>) Plots of the mean firing rate vs. frequency of periodic firing during the FX- (<b>C</b>) or FV-conditions (<b>D</b>). Gray circles indicate neurons that exhibited periodic firing only during the FX- (<b>C</b>) or FV-conditions (<b>D</b>), and open circles indicate neurons that exhibited periodic firing throughout the entire behavioral conditions.</p