The experiment was conducted and responses were collected using custom written code in matlab 7.10.0 (The MathWorks LDE225 molecular weight Inc., Natick, MA, USA). The goal of the study was to examine the effects of attention to time and modality. To achieve this goal we adopted a discrimination task, in which we manipulated the participants’

expectations about the onset time and modality of an upcoming target. The experiment was conducted in a sound-attenuated room with dim illumination (1.595 cd/m2). Participants sat in an armchair with their hands resting on a table and covered from view by a cardboard box that bore the fixation and stimulation LEDs (Fig. 1A). Every trial started with the delivery of an auditory warning tone [1.0 kHz, 100 ms, 60 dB(A)], via headphones, and was followed by masking white noise [55 dB(A)] throughout the trial. Either 1 or 2.5 s after the warning tone, a target stimulus could appear (Fig. 1B); this could be either visual or tactile and could also be single- or double-pulse stimulation. The task was to discriminate between single- and double-pulse stimulation regardless of modality or time point of presentation. Responses were delivered by releasing one of the two foot pedals (toe or heel) to indicate double or single stimulus (respectively). Participants were informed before every block about

the most likely time point of target appearance and the most likely modality, but they were also told to always deliver a response and instructed to answer as fast and as accurately as C646 manufacturer possible. After the response (or after the response timeout of 1.5 s), an intertrial

interval of 2 s led to the beginning of the next trial. When no stimulus was presented at one of the possible onset times a gap in the background white noise occurred (20 ms, 10-ms ramps envelope) as provision of additional temporal information. Within GBA3 the experiment, the participants’ expectations about the onset time and target modality were manipulated by adjusting probabilities for the two factors (Fig. 1C). Temporal expectation was manipulated across blocks of trials, whereas modality probability was a between-participants factor. At the beginning of each experimental block, participants were informed which time interval (1 or 2.5 s) would be more likely to contain the target and we will refer to this point as the expected time point. If the early stimulus onset was expected, 55% of all trials contained a target after 1 s and 22.5% of all trials contained a target after 2.5 s. This pattern was inverted for the blocks in which the late stimulus onset was expected. In all cases, 22.5% of trials in the block were catch trials without a target in either of the time intervals, in which case participants were instructed to withhold the response. In addition to the temporal attention manipulation described above, attention to modality was manipulated by making one modality more likely overall (primary; 66%) than targets in the other modality (secondary; 33%).