A. Kane York’s research while affiliated with University of Michigan and other places

The preoptic area of the hypothalamus is key for the control of sleep onset and sleep homeostasis. Although traditionally considered exclusively somnogenic, recent studies identified a group of preoptic glutamatergic neurons that promote wakefulness. Specifically, our previous investigations demonstrated that chemogenetic stimulation of glutamatergic neurons within the medial-lateral preoptic area (MLPO_VGLUT2) promotes wakefulness, fragments non-rapid eye movement sleep (NREMs), and suppresses REM sleep (REMs). This evidence is further supported by recent work showing that preoptic glutamatergic neurons are activated during microarousals that fragment sleep in response to stress, and optogenetic stimulation of these neurons promotes microarousals and wakefulness. Thus, while the wake-promoting function of MLPO_VGLUT2 is clear, their role in sleep homeostasis has not been assessed. We tested the hypothesis that MLPO_VGLUT2 are wake-active, and their activation will increase wakefulness and disrupt sleep homeostasis via projections to arousal-promoting systems. Using fiber photometry, we found that MLPO_VGLUT2 were highly active during REMs, wakefulness and brief arousals, and remained minimally active during NREMs. Chemogenetic stimulation of MLPO_VGLUT2 inhibited REMs onset – independent of NREMs fragmentation produced by simultaneous hypothermia – and suppressed the REMs homeostatic response after total sleep deprivation. Chemogenetic inhibition of MLPO_VGLUT2 increased REMs time (during the light phase only) but did not influence REMs and NREMs homeostasis. Anterograde projection mapping revealed that MLPO_VGLUT2 innervate central regions that promote wakefulness and inhibit REMs. We conclude that MLPO_VGLUT2 powerfully suppress REMs and that exogenous —and possibly pathologic— activation of these neurons disrupts REMs recovery, presumably by directly or indirectly activating REMs-inhibitory mechanisms.

Abrupt onsets are commonly assumed to be a class of stimuli with high physical salience. This high salience has been used to explain past findings showing abrupt onsets captured attention more strongly compared to other types of distractors, such as color singletons. However, there has been a lack of consensus about the definition and measurement of physical salience. As a result, it is unclear if abrupt onsets capture attention more strongly simply because they are more salient than other types of stimuli. Using a psychophysical technique recently developed by Stilwell et al. (2023), we explicitly quantified the level of physical salience of abrupt onsets, color singletons, and color singleton onsets. Surprisingly, abrupt onsets were the least salient among the three types of items examined. Despite this, only abrupt onsets captured attention in a subsequent visual search task, whereas color singletons and color singleton onsets were both suppressed. Thus, abrupt onsets tend to capture attention more strongly than color singletons, but this is not apparently because of high physical salience. Indeed, high physical salience may make an object easier to suppress during visual search.

Abrupt onsets are commonly assumed to be a class of stimuli with high physical salience. Presumably because of this, abrupt onsets tend to capture attention even when other types of distractors, such as color singletons, do not. However, there has been a lack of consensus on the definition and measurement of physical salience. As a result, it is unclear if high physical salience is indeed the reason why abrupt onsets tend to capture attention more strongly than other types of stimuli. Using a psychophysical technique recently developed by Stilwell et al. (2023), we explicitly quantified the level of physical salience of abrupt onsets, color singletons, and color singleton onsets. Surprisingly, abrupt onsets were the least salient among the three types of items. Despite this, only abrupt onsets captured attention in a subsequent visual search task, whereas the other two types of distractors were suppressed. These results indicate that high physical salience is neither a necessary nor a sufficient condition for abrupt onsets to capture attention.

The study of attentional allocation due to external stimulation has a long history in psychology. Early research by Yantis and Jonides suggested that abrupt onsets constitute a unique class of stimuli that captures attention in a stimulus-driven fashion unless attention is proactively directed elsewhere. Since then, the study of visual attention has evolved significantly. This article revisits the core conclusions by Yantis and Jonides in light of subsequent findings and highlights emerging issues for future investigation. These issues include clarifying key concepts of visual attention, adopting measures with greater spatiotemporal precision, exploring how past experiences modulate the effects of abrupt onsets, and understanding individual differences in attentional allocation. Addressing these issues is challenging but crucial, and we offer some perspectives on how one might choose to study these issues going forward. Finally, we call for more investigation into abrupt onsets. Perhaps due to their strong potential to capture attention, abrupt onsets are often set aside in pursuit of other conditions that show attenuation of distractor interference. However, given their real-world relevance, abrupt onsets represent the exact type of stimuli that we need to study more to connect laboratory attention research to real life.

The preoptic area of the hypothalamus is key for the control of sleep onset and sleep homeostasis. Although traditionally considered exclusively somnogenic, recent studies identified a group of preoptic glutamatergic neurons that promote wakefulness. Specifically, our previous investigations demonstrated that chemogenetic stimulation of glutamatergic neurons within the medial-lateral preoptic area (MLPO_VGLUT2) promotes wakefulness, fragments non-rapid eye movement sleep (NREMs), and suppresses REM sleep (REMs). This evidence is further supported by recent work showing that preoptic glutamatergic neurons are activated during microarousals that fragment sleep in response to stress, and optogenetic stimulation of these neurons promotes microarousals and wakefulness. Thus, while the wake-promoting function of MLPO_VGLUT2 is clear, their role in sleep homeostasis has not been assessed. We tested the hypothesis that MLPO_VGLUT2 are wake-active, and their activation will increase wakefulness and disrupt sleep homeostasis via projections to arousal-promoting systems. Using fiber photometry, we found that MLPO_VGLUT2 were highly active during REMs, wakefulness and brief arousals, and remained minimally active during NREMs. Chemogenetic stimulation of MLPO_VGLUT2 inhibited REMs onset and suppressed the REMs homeostatic response after total sleep deprivation. Chemogenetic inhibition of MLPO_VGLUT2 increased REMs time (during the light phase only) but did not influence REMs and NREMs homeostasis. Anterograde projection mapping revealed that MLPO_VGLUT2 innervate central regions that promote wakefulness and inhibit REMs. We conclude that MLPO_VGLUT2 powerfully suppress REMs and that exogenous —and possibly pathologic— activation of these neurons disrupts REMs recovery, presumably by directly or indirectly activating REMs-inhibitory mechanisms. SIGNIFICANCE STATEMENT The preoptic area of the hypothalamus has been extensively studied and its role in sleep regulation is well-established. Importantly, recent work identified a group of preoptic glutamatergic neurons (MLPO_VGLUT2) that are wake-active and promote wakefulness. However, whether these neurons influence sleep homeostasis remains unknown. We demonstrate that MLPO_VGLUT2 are maximally active during REM sleep (REMs), wakefulness and brief arousals from sleep, and innervate wake-promoting and REMs-inhibitory regions. MLPO_VGLUT2 stimulation inhibits REMs and REMs rebound after sleep deprivation, whereas their inactivation increases REMs but does not alter REMs homeostatic response. We thus identified a preoptic mechanism that powerfully suppresses REMs, which we propose may engage during normal sleep-to-wake transitions to block REMs intrusions into subsequent wakefulness.

Abrupt onsets are commonly assumed to be a class of stimuli with high physical salience. Presumably because of this, abrupt onsets tend to capture attention even when other types of distractors, such as color singletons, do not. However, there has been a lack of consensus on the definition and measurement of physical salience. As a result, it is unclear if high physical salience is indeed the reason why abrupt onsets tend to capture attention more strongly than other types of stimuli. Using a psychophysical technique recently developed by Stilwell et al. (2023), we explicitly quantified the level of physical salience of abrupt onsets, color singletons, and color singleton onsets. Surprisingly, abrupt onsets were the least salient among the three types of items. Despite this, only abrupt onsets captured attention in a subsequent visual search task, whereas the other two types of distractors were suppressed. These results indicate that high physical salience is neither a necessary nor a sufficient condition for abrupt onsets to capture attention.

Abrupt onsets are commonly assumed to be a class of stimuli with high physical salience. This high salience has been used to explain past findings showing abrupt onsets captured attention more strongly compared to other types of distractors, such as color singletons. However, there has been a lack of consensus about the definition and measurement of physical salience. As a result, it is unclear if abrupt onsets capture attention more strongly simply because they are more salient than other types of stimuli. Using a psychophysical technique recently developed by Stilwell et al. (2023), we explicitly quantified the level of physical salience of abrupt onsets, color singletons, and color singleton onsets. Surprisingly, abrupt onsets were the least salient among the three types of items examined. Despite this, only abrupt onsets captured attention in a subsequent visual search task, whereas color singletons and color singleton onsets were both suppressed. Thus, abrupt onsets tend to capture attention more strongly than color singletons, but this is not apparently because of high physical salience. Indeed, high physical salience may make an object easier to suppress during visual search.

The study of attentional allocation due to external stimulation has a long history in psychology. Early research by Yantis and Jonides suggested that abrupt onsets constitute a unique class of stimuli that captures attention in a stimulus-driven fashion unless attention is proactively directed elsewhere. Since then, the study of visual attention has evolved significantly. This article revisits the core conclusions by Yantis and Jonides in light of subsequent findings and highlights emerging issues for future investigation. These issues include clarifying key concepts of visual attention, adopting measures with greater spatiotemporal precision, exploring how past experiences modulate the effects of abrupt onsets, and understanding individual differences in attentional allocation. Addressing these issues is challenging but crucial, and we offer some perspectives on how one might choose to study these issues going forward. Finally, we call for more investigation into abrupt onsets. Perhaps due to their strong potential to capture attention, abrupt onsets are often set aside in pursuit of other conditions that show attenuation of distractor interference. However, given their real-world relevance, abrupt onsets represent the exact type of stimuli that we need to study more to connect laboratory attention research to real life.