Temporal expectation weights visual signals over auditory signals

Shielding working-memory representations from temporally predictable external interference

Protecting working-memory content from distracting external sensory inputs and intervening tasks is an ubiquitous demand in daily life. Here, we ask whether and how temporal expectations about external events can help mitigate effects of such interference during working-memory retention. We manipulated the temporal predictability of interfering items that occurred during the retention period of a visual working-memory task and report that temporal expectations reduce the detrimental influence of external interference on subsequent memory performance. Moreover, to determine if the protective effects of temporal expectations rely on distractor suppression or involve shielding of internal representations, we compared effects after irrelevant distractors that could be ignored vs. interrupters that required a response. Whereas distractor suppression may be sufficient to confer protection from predictable distractors, any benefits after interruption are likely to involve memory shielding. We found similar benefits of temporal expectations after both types of interference. We conclude that temporal expectations may play an important role in safeguarding behaviour based on working memory - acting through mechanisms that include the shielding of internal content from external interference.

Rhythm Violation Enhances Auditory-Evoked Responses to the Extent of Overriding Sensory Adaptation in Passive Listening

Sensory systems utilize temporal structure in the environment to build expectations about the timing of forthcoming events. We investigated the effects of rhythm-based temporal expectation on auditory responses measured with EEG recorded from the frontocentral sites implicated in auditory processing. By manipulating temporal expectation and the interonset interval (IOI) of tones, we examined how neural responses adapted to auditory rhythm and reacted to stimuli that violated the rhythm. Participants passively listened to the tones while watching a silent nature video. In Experiment 1 (n = 22), in the long-IOI block, tones were frequently presented (80%) with 1.7-sec IOI and infrequently presented (20%) with 1.2-sec IOI, generating unexpectedly early tones that violated temporal expectation. Conversely, in the short-IOI block, tones were frequently presented with 1.2-sec IOI and infrequently presented with 1.7-sec IOI, generating late tones. We analyzed the tone-evoked N1-P2 amplitude of ERPs and intertrial phase clustering in the theta-alpha band. The results provided evidence of strong delay-dependent adaptation effects (short-term, sensitive to IOI), weak cumulative adaptation effects (long-term, driven by tone repetition over time), and robust temporal-expectation violation effects over and above the adaptation effects. Experiment 2 (n = 22) repeated Experiment 1 with shorter IOIs of 1.2 and 0.7 sec. Overall, we found evidence of strong delay-dependent adaptation effects, weak cumulative adaptation effects (which may most efficiently accumulate at the tone presentation rate of ∼1 Hz), and robust temporal-expectation violation effects that substantially boost auditory responses to the extent of overriding the delay-dependent adaptation effects likely through mechanisms involved in exogenous attention.

Probability-driven and stimulus-driven orienting of attention to time and sensory modality

The timing and the sensory modality of behaviorally relevant events often vary predictably, so that it is beneficial to adapt the sensory system to their statistical regularities. Indeed, statistical information about target timing and/or sensory modality modulates behavioral responses-called expectation effects. Responses are also facilitated by short-term repetitions of target timing and/or sensory modality-called priming effects. We examined how the expectation and priming effects on target timing (short vs. long cue-to-target interval) and target modality (auditory vs. visual) interacted. Temporal expectation was manipulated across blocks, while modality expectation was manipulated across participants. Responses were faster when targets were presented at the expected timing and/or in the expected modality in an additive manner, suggesting that temporal and modality expectation operate relatively independently. Similarly, responses were faster when the timing and/or modality of targets was repeated across trials in an additive manner, suggesting that temporal and modality priming operate relatively independently. Importantly, the interactions between expectation and priming were domain specific. In the temporal domain, temporal-expectation effects were observed only when temporal-priming effects were absent. In the modality domain, modality-priming effects predominated for auditory targets whereas modality-expectation effects predominated for visual targets. Thus, the interactions between probability-driven expectation and stimulus-driven priming processes appear to be controlled separately for the mechanisms that direct attention to specific temporal intervals and for the mechanisms that direct attention to specific sensory modalities. These results may suggest that the sensory system concurrently optimizes attentional priorities within temporal and sensory-modality domains.

Comparing the effects of implicit and explicit temporal expectation on choice response time and response conflict

People can use temporally structured sensory information to anticipate future events. Temporal information can be presented implicitly through probability manipulation without participants' awareness of the manipulation, or explicitly conveyed through instructions. We examined how implicit and explicit temporal information established temporal expectations that influenced choice response times and response conflict (measured as flanker effects). We implicitly manipulated temporal structure by block-wise varying the likely timing of a target. In the short-interval block, a target was presented frequently (80 % of trials) after a short (400 ms) cue-to-target interval and infrequently (20 % of trials) after a long (1200 ms) interval; the probability assignment was reversed in the long-interval block. Building on this baseline condition (Experiment 1), we augmented the temporal information by filling the cue-to-target intervals with tones (Experiment 2), explicitly informed participants of the prevalent time interval (Experiment 3) and provided trial-by-trial reminders of the prevalent time interval (Experiment 4). The temporal probability manipulation alone (of which participants were unaware) influenced choice response times but only when the temporal information was augmented with tones, whereas providing the explicit knowledge of the temporal manipulation, with or without trial-by-trial reminders, robustly influenced choice response times. Response conflict was unaffected by these conditions. These results suggest that temporal expectation can be established by the implicit learning of a temporal structure given that sufficiently strong temporal information is presented as well as by the explicit knowledge of the temporal structure. This established temporal expectation influences choice response times without necessarily affecting the strength of response conflict.