ObjectivesTo estimate the prevalence of long COVID symptoms in children with and without a history of SARS-CoV-2 infection and to evaluate factors associated with long COVID.DesignA nationwide cross-sectional study.SettingPrimary care.Participants3240 parents of children aged 5–18 with and without SARS-CoV-2 infection completed an online questionnaire (11.9% response rate); 1148 and 2092 with/without a history of infection, respectively.Primary and secondary outcome measuresPrimary outcome was the prevalence of long COVID symptoms in children with/without a history of infection. Secondary outcomes were the factors associated with the presence of long COVID symptoms and with failure to return to baseline health status in children with a history of infection including gender, age, time from illness, symptomatic illness and vaccine status.ResultsMost long COVID symptoms were more prevalent in children with a history of SARS-CoV-2 infection: headaches (211 (18.4%) vs 114 (5.4%), p<0.001), weakness (173 (15.1%) vs 70 (3.3%), p<0.001), fatigue (141 (12.3%) vs 133 (6.4%), p<0.001) and abdominal pain (109 (9.5%) vs 79 (3.8%), p<0.001). Most long COVID symptoms in children with a history of SARS-CoV-2 infection were more prevalent in the older age group (12–18) compared with the younger age group (5–11). Some symptoms were more prevalent in children without a history of SARS-CoV-2 infection, including attention problems with school malfunctioning (225 (10.8%) vs 98 (8.5%), p=0.05), stress (190 (9.1%) vs 65 (5.7%), p<0.001), social problems (164 (7.8%) vs 32 (2.8%)) and weight changes (143 (6.8%) vs 43 (3.7%), p<0.001).ConclusionThis study suggests that the prevalence of long COVID symptoms in children with a history of SARS-CoV-2 infection might be higher and more prevalent in adolescents than in young children. Some of the symptoms, mainly somatic symptoms, were more prevalent in children without a history of SARS-CoV-2 infection, highlighting the impact of the pandemic itself rather than the infection.

Previous studies showed that some dual tasks can be performed simultaneously without costs. Yet, a variable SOA between the inputs to such tasks leads to strategic, often involuntary, prioritization of one of the two tasks. Here we explore the boundary conditions for this involuntary or exogenous strategy. In Experiment 1, subjects were initially trained on dual task performance where the input to the two tasks is presented simultaneously (0 SOA). We used two tasks that under such conditions can be performed without costs and indeed subjects displayed perfect sharing of the tasks. Subjects then performed the same two tasks but with a variable SOA (0, 50, 150, 800 ms). This manipulation led to a serial-like performance of the two tasks even in trials with 0 SOA. In Experiment 2, subjects participated in eight sessions. Within each session, they performed in alternation blocks with a fixed 0 SOA and blocks with a variable SOA. Subjects displayed perfect sharing in the pure 0 SOA blocks but performed the two tasks serially in the mixed SOA blocks despite receiving identical instructions. These findings demonstrate that task context is a powerful factor in dual task performance and may lead subjects to involuntarily exhibit dual task costs even in conditions where they can perform the tasks without any costs. Moreover, these findings strongly suggest that costs observed in PRP studies reflect the use of such exogenous strategies rather than a general structural dual task limitation.

We hypothesize that a shared spatial attention mechanism is used for both perception and action. To this end we created a new dual-task version of the classical Simon task. In one task, the spatial-input task, associated with input spatial attention, participants named one shape out of two bilaterally presented colored shapes. In a second task, the spatial-output task, associated with output spatial attention, participants discriminated between high and low pitch tones by pressing either a left or a right key. In Experiment 1, input for both tasks appeared simultaneously, and participants were instructed not to prioritize either task. A between tasks Simon-like effect was found for responses to both tasks. Reaction times were shorter when the side of the relevant shape in the spatial-input task and the side of the correct response in the spatial-output task were congruent. In Experiment 2, we manipulated the stimulus-onset asynchrony (SOA) between the inputs for the two tasks and showed that the Simon-like effect remained intact at all SOAs. Experiment 3 was similar to Experiment 1 except that the vocal response for the spatial-input task was not speeded. A Simon-like effect was still observed. Experiment 4 was the same as Experiment 3 except that the non-speeded response for the spatial-input task was manual rather than vocal. No Simon-like effect was observed in this experiment. Our results support a shared spatial attention mechanism involved in the Simon effect and indicate that this spatial attention mechanism is shared by perception and action.

It has been suggested that personally significant (PS) information interferes with performance only when presented within the focus of attention. However, this claim was never tested by a systematic manipulation of attention, but only by using correlative measures of its locus. We addressed this issue in two experiments, utilizing a cued visual search paradigm that allowed us to directly manipulate attention and to measure behavioral and physiological responses. One of the stimuli in the search display had a higher luminance value (i.e., was cued), and, orthogonally, one of the stimuli could be a PS or neutral name. When the cue did not predict target location, PS distractors mildly interfered with task performance, regardless of the cue's location. However, when the cue predicted target location, responses were facilitated for cued targets, indicating that attention was shifted to the cue. Importantly, PS distractors interfered with task performance and elicited enhanced orienting responses only when they were cued. This implies that PS information affects performance only when presented within but not outside the focus of attention.

It is well established that processes of perception and action interact. A key question concerns the role of attention in the interaction between perception-action processes. We tested the hypothesis that spatial attention is shared by perception and action. We created a dual-task paradigm: In one task, spatial information is relevant for perception (spatial-input task) but not for action, and in a second task, spatial information is relevant for action (spatial-output task) but not for perception. We used endogenous pre-cueing, with two between-subjects conditions: In one condition the cue was predictive only for the target location in the spatial-input task; in a second condition the cue was predictive only for the location of the response in the spatial-output task. In both conditions, the cueing equally affected both tasks, regardless of the information conveyed by the cue. This finding directly supports the shared input-output attention hypothesis.