Ready…Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time
Center inset: BA18 (peak coordinates: 28 −92 −8) are the only regions that show a climbing signal during the readiness period at p<0.001. More broadly distributed areas, most significantly in cuneus (peak coordinates: −8 −92 0) show a sinking signal at p<0.001. Color bar indicates t-value with degree of freedom 19. (A) Time series of the fMRI signal in BA18 around the go signal. (B) fMRI signal in cuneus (inset) showing sinking activity. This region is a subset of the regions shown in the center inset with a more stringent threshold of p<10−8. The dynamics of the sinking signal appear to mirror the climbing signal, suggesting the possibility that the sinking signal results from resource sharing (draining) with nearby climbing areas; however, the differential sizes of these regions (center inset) calls such a hypothesis into question. (C) fMRI signal in BA18 in the passive control experiment in which the visual stimuli are identical to the first experiment (Figure 1A) but no button press is required. Here a similar climbing signal is evident, indicating that the climbing activity in BA18 is not due to motor preparation. (D) fMRI signal in the cuneus in the passive control condition, showing that the sinking signal, like the climbing signal, is independent of motor preparation. Error bars SEM.