Article Figures & Data
Figures
- Figure 1.
Task design. A, Target-mapping task: monkeys fixated for 500 ms, after which a target appeared at a location randomly chosen from a 40 × 40° grid of locations in the visual field, with 5° spacing in most cases (C). After 500 ms, a distractor was flashed briefly (<50 ms) at the RF center. After a 550 ms delay, the fixation spot was turned off, and the monkey made a saccade to the target to obtain the reward. B, The no-saccade control task was otherwise identical, except that the fixation spot was never turned off, and monkeys maintained fixation throughout the trial to obtain the reward. C, Grid of potential target locations. D, Suppression of example LIP neuron by a saccade plan to the surround. Grayscale map of response to the distractor (average firing rate from 30 to 300 ms after distractor onset) as a function of saccade target location with respect to the central fixation point. Target locations with yellow/cyan dots are significantly suppressed (yellow) or enhanced (cyan) relative to the no-saccade control (p < 0.05, t test with Bonferroni correction for 80 simultaneous comparisons). Boxed locations indicate saccade target locations defined as the RF (magenta) and Smax (red) for the rasters and PSTHs in E. X at −20, 20 indicates distractor location. E, PSTHs and rasters from the example neuron, aligned to distractor onset: saccade plan to the Smax leads to a reduced distractor response (red) compared to both the no-saccade control response (blue) and the response when saccade is planned to the RF (magenta). Rasters are sorted by trial type. Dashed vertical lines indicate time of saccade target onset (left), distractor onset (middle), and time of saccade go-cue (right). F, Distractor response varies with distance of saccade target from the RF center. An example neuron's distractor response during the target-mapping task (minus the response during the no-saccade control, horizontal dashed line at 0) is plotted as a function of the distance between the saccade target and the RF center. Error bars show SEMs (n = number of locations contributing to each data point).
- Figure 2.
A, Population average PSTH reveals significant suppression of both baseline and distractor response when a saccade is planned to the Smax (red) compared to the no-saccade control (blue). Only the one-third of trials that were not used to calculate the Smax contribute to the response in red. Black crosses mark the centers of non-overlapping 100 ms time bins with a significant difference between responses (paired t test, p < 0.05, n = 72 neurons). B, Scatter plot of each neuron's response to the distractor (30–300 ms after distractor onset, gray bar in A) during the no-saccade control (abscissa) and the saccade plan to Smax condition (ordinate). Paired t test: p < 0.0001, n = 72. Green, black, and magenta circles indicate neurons from monkeys I, D, and Z, respectively. C, Distractor response varies with distance of saccade target from the RF center. Population-averaged distractor response during the target-mapping task (minus the response during the no-saccade control, horizontal dashed line at 0) is plotted as a function of the distance between the saccade target and the RF center. Averaged tuning curves were first calculated for each neuron and then averaged together to produce the population average. Error bars show SEMs. n = number of neurons contributing to each data point. D, Population-averaged suppression extends in all directions from the RF. A polar plot shows average level of suppression in 8 binned angular directions (bin size = 45°) around the RF center. Polar tuning plots were first computed for each neuron and then averaged together. Error bars are as in C. The magnitude of suppression (spikes/s) is plotted as a function of absolute direction around the RF center (black), and after rotating all target angles so that the center of Smax lies at 0° (gray). The four circles in the polar plot lie at −15, −10, −5, and 0 spikes/s. See also supplemental Figures 1 and 2 (available at www.jneurosci.org as supplemental material).
- Figure 3.
Suppression can be maintained without the presence of the saccade target. A, Task design: Identical to the target-mapping task, except that monkeys planned a memory-guided saccade to a single fixed location within the surround. The distractor was flashed at the RF center. B, Population average PSTH reveals significant suppression of both baseline and distractor response when a memory-guided saccade is planned to the surround (red) compared to the no-saccade control (blue). Bin width = 15 ms. C, Scatter plot of each neuron's response to the distractor (gray bar in B) during the no-saccade control (abscissa) compared to the saccade plan to the surround (ordinate). One point (control response = 131.70, saccade plan = 59.64) was omitted for visibility. Paired t test: p < 0.0001, n = 48. The figure format for B and C is otherwise identical to Figure 2, A and B, respectively.
- Figure 4.
A flashed distractor elicits suppression. A, Distractor-mapping task: identical to the target-mapping task (Fig. 1A), except that the saccade target location was fixed at the RF center, and the distractor location was chosen randomly on each trial from the 40 × 40° grid of locations (Fig. 1C). In interleaved no-distractor controls, the distractor was not flashed. B, Distractor onset in the surround evokes transient suppression. Population average PSTHs show the no-distractor control (blue) and the population average response when the distractor was flashed within DSmax calculated from the bottom-up response map (red). Trials used to calculate DSmax not included in the PSTH. PSTHs are aligned to saccade target onset. Black crosses are as in Figure 2A. Bin width = 25 ms. C, Scatter plot of each neuron's response to the distractor during the no-distractor control (abscissa) compared to the response with the distractor within DSmax (ordinate). Paired t test: p = 0.007, n = 37. Two points (control response = 176.02, 134.35 and saccade plan = 189.92, 123.28) were omitted for visibility. D, Distractor appearance leads to slowed saccadic latencies: scatter plot of mean saccadic latency during the no-distractor control (abscissa) versus the mean saccadic latency with the distractor flashed either within DSmax (ordinate, filled circles) or anywhere in the visual field (ordinate, plus signs). Each point represents data from the recording of one neuron. Paired t tests for both comparisons: p < 0.0001, n = 37. The figure format for B and C is otherwise identical to Figure 2, A and B, respectively.
- Figure 5.
Increasing motivation enhances suppression. A, Distractor response is lower during large-reward trials: With distractor in RF and target in the suppressive surround, population average PSTH shows reduced distractor response in large-reward trials (red), compared to small-reward trials (blue). Black crosses are as in Figure 2A. B, Scatter plot of each neuron's response to the distractor during small-reward (abscissa) and large-reward (ordinate) trials. Paired t test: p < 0.0001, n = 46. One point (small-reward: 105.63, large-reward: 79.00) was omitted for visibility. C, Target response is larger during large-reward trials: With target in RF and distractor in the suppressive surround, population average PSTH shows enhanced target response in large-reward trials (red), compared to small-reward trials (blue). Black crosses are as in Figure 2A. D, Scatter plot of each neuron's response to the target (−400 to 30 ms after distractor onset, gray bar in C) during small-reward (abscissa) and large-reward (ordinate) trials. Paired t test: p < 0.0001, n = 38. PSTH bin widths: 15 ms. Two points (small-reward: 150.26 and 153.30, large-reward: 184.38, 149.44) were omitted for visibility. The figure format for PSTHs and scatter plots is as in Figure 2. E, Correlates of LIP neurons with saccadic behavior in the cued-reward task: Larger LIP neuronal responses are associated with faster saccades to the RF and slower saccades to the surround. In the small-reward condition (blue bars), correlation coefficients were significantly negative (paired t test: p = 0.0005, n = 38) with target in RF and distractor in the surround, while slopes were significantly positive with distractor in RF and target in the surround (paired t test: p = 0.0006, n = 46). Effect sizes were smaller in the large-reward condition (red bars) and only significant with the target in RF (paired t test: p = 0.0132, n = 38) and not with the distractor in the RF (paired t test: p = 0.2266, n = 46). See also supplemental Figure 3 (available at www.jneurosci.org as supplemental material).
- Figure 6.
Target and distractor responses predict saccadic targeting during small-reward error trials. A lower target response predicts saccades away from the target. A higher distractor response on such trials predicts a distractor-directed saccade. A, Schematic depicting distractor-directed error trials. B, Population average PSTH shows larger distractor responses on distractor-directed error trials (red) than on correct trials (blue). C, Scatter plot of each neuron's response to the distractor during correct trials (abscissa) and distractor-directed error trials (ordinate). Paired t test: p = 0.0003, n = 18 neurons. D, Schematic depicting small-reward error trials where monkey saccades away from the target. E, Population average PSTH shows reduced target responses on these error trials (red) compared to correct trials (blue). Black crosses are as in Figure 2A. F, Scatter plot of each neuron's response to the target (−400 to 300 ms relative to distractor onset, gray bar in E) during correct trials (abscissa) and error trials (ordinate). Paired t test: p < 0.0001, n = 31 neurons. PSTH bin widths = 25 ms. Only errors made at least 350 ms after distractor onset included. Figure format for PSTHs and scatter plots as in Figure 2.
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Supplemental Material
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- supplemental material - Supplemental Figures
