Article Figures & Data
Figures
- Figure 1.
Behavioral task and licking behavior. a, Task sequence. A stable display with two placeholders remains visible during the intertrial interval. A trial begins when the monkey achieves central fixation, bringing one of the placeholders into the RF (gray circle). After a fixation period, an RC appears, followed by a delay period and illumination of one of the placeholders. The monkey is required to make a saccade to the illuminated placeholder to receive the outcome predicted by the RC. If applicable (i.e., on a correct RC+ trial), the reward is given 350 ms after the end of the saccade; otherwise, no reward is given. b, Licking behavior during an example session. Trials are sorted off-line by RC type and plotted in chronological order, with the first trial on top. Blue horizontal lines indicate the times at which the monkey was licking during each trial. Rasters are aligned at the time of reward delivery on RC+ trials and at the corresponding time point (350 ms after saccade end) on RC− trials. The dots mark trial events as indicated in the legend. c, Frequency distribution of behavioral learn points for individual RC− during all 58 recording sessions.
- Figure 2.
The RCs exert spatial biases on saccade accuracy and RT. a, Angular saccade accuracy during all recording sessions (n = 58, mean ± SEM) as a function of RC type and spatial congruence between RC and target (congruent: thick lines; incongruent: thin lines). b, Saccade reaction times over all recording sessions in the same format as a. c, Endpoints of individual saccades for congruent trials in an example session. All saccades are included, regardless of whether they were scored as correct or errant. Saccade coordinates are normalized so that the target (indicated by the open square) was always mapped onto the point (1,0).
- Figure 3.
Response of a representative neuron to newly learned and overlearned RCs in its RF. In the raster displays, each tick represents an action potential and each row a single correct trial. Trials are aligned on RC onset and truncated at the end of the delay period, and they are shown in chronological order with the first presentation at the top. Trials with distinct RCs within a category are intermingled. The spike density traces (bottom) show the average firing rates for RC+ (blue) and RC− (red) trials, considering only trials after the learn point for each RC. Shading shows SEM. The black horizontal bar denotes RC duration.
- Figure 4.
Population analysis of reward modulation. a, Average normalized firing rates for the sample of neurons (n = 58) in response to RC− (red) and RC+ (blue) stimuli in the RF for newly learned (top) and overlearned (bottom) stimuli. Responses are aligned on RC onset (time 0) and are truncated at the end of the delay period. Shading indicates SE. Firing rates were normalized for each neuron by subtracting the baseline rate (50 ms before RC onset) and dividing by the peak response across all RC types. Stars denote 100-ms-firing-rate bins (beginning at 40 ms and shifted by 50 ms) with statistically significant differences between RC+ and RC− (Wilcoxon signed-rank test; p < 0.05). An apparent minor response peak at ∼400 ms is attributable to a subset of neurons that showed an off response to the disappearance of the RC. b, ROC analysis of reward modulation. Each row represents an individual neuron, and each pixel an ROC index in a 10 ms time bin. The white dashed line shows RC onset (time 0). ROC values of >0.5 (blue) signify preference for RC+, values of <0.5 (red) signify preference for RC−, and values close to 0.5 (black) signify no preference. Magenta crosses mark the latency at which each cell met the significance criterion for a reward effect. c, Cumulative distribution of the reward latencies for overlearned (green) and newly learned (goldenrod) RCs. d, Population average of the ROC values in b for overlearned and newly learned RCs. Circles denote time bins in which the value is significantly different from 0.5 (p < 0.05), and blue crosses denote bins with significant differences between overlearned and newly learned stimuli. Shading shows SEM.
- Figure 5.
Spatial effects of RC during the delay period. a, Population firing rates on trials in which the RC appeared in the RF (black) or opposite (opp.) the RF (gray) for each RC type. Shading shows SEM. The vertical scale is expanded and truncates the visual response to highlight delay period activity. b, Population ROC values for RC location in the last 300 ms of the delay period. All symbols show mean ± SEM. Circles indicate RC+ trials, and triangles, RC− trials. Filled symbols show values that are significantly different from 0.5 (t test; p < 0.05).
- Figure 6.
Spatial effects of the RC on presaccadic activity. a, Difference traces between activity on saccade into the RF and saccade of the RF trials. Trials are sorted by congruence (congruent: black; incongruent: gray) for each RC category and are aligned on the onset of the saccade target. Shading shows SEM. b, ROC for saccade direction 100–200 ms after target onset. All values are significantly more than 0.5 and are thus shown with filled symbols.
- Figure 7.
Probe task structure and licking behavior. a, Structure of probe trials. A single placeholder was present at the location opposite the RF during the intertrial interval, marking the location of the informative RC and the saccade target. A trial began as before with presentation of an informative RC followed by a 600 ms delay period. Simultaneous with target onset, a behaviorally irrelevant probe was flashed inside the RF. The probe was flashed for 80 ms and extinguished before the onset of the saccade. b, Licking behavior during the probe task. Percentage of time spent licking (mean ± SEM over all probe sessions; n = 34) immediately before juice delivery (or the equivalent time on RC− trials) as a function of the expected reward predicted by the informative RC (x-axis) and the valence of the probe (blue: probe RC+; red: probe RC−).
- Figure 8.
Neural responses and saccade reaction times during the probe task. a, Population neural response (n = 34) during the probe task (main panels) and standard task (same 34 neurons; insets). Trials were sorted by learning history (overlearned: top; newly learned: bottom) and the valence of the stimulus in the RF (blue: RC+; red: RC−). Responses to the probes are truncated at 250 ms—the average time at which the saccade moved the neuron's RF away from the probe location. Responses during the standard task are truncated at 250 ms as well for the sake of comparison. Shading is ±SEM. b, Average response of neurons with significant selectivity for the valence of overlearned probes (n = 15). Inset shows the responses of the same neurons for newly learned probes. c, Saccade reaction times during the probe task. Mean reaction times (±SEM) are plotted as a function of expected reward (x-axis) and probe valence (blue: probe+; red: probe−), separately for overlearned and newly learned probes.
Tables
- Table 1.
Firing rates (sp/s, mean ± SEM), according to RC training history and location, in the visual epoch (100–500 ms relative to RC onset) and at the end of the delay period (600–900 ms after RC onset)
Cue location Newly learned Overlearned Visual Delay Visual Delay RC+ In RF 45.96 ± 3.72** 21.96 ± 2.38** 41.06 ± 3.39** 21.16 ± 2.26* Opposite RF 14.75 ± 2.20** 18.16 ± 2.36 15.10 ± 2.24* 17.43 ± 2.28 RC− In RF 41.34 ± 3.58** 18.34 ± 2.15 33.02 ± 2.96** 14.04 ± 1.47* Opposite RF 17.96 ± 2.34 18.54 ± 2.17 21.37 ± 2.44 18.53 ± 1.94
Supplemental Data
Files in this Data Supplement:
- supplemental material - Supplemental Material
