Top-down control of visual sensory cortex has long been tied to the orienting of visual spatial attention on a rapid, moment-to-moment basis. Here, we examined whether sensory responses in visual cortex are also modulated by natural and comparatively slower fluctuations in whether or not one is paying attention to the task at hand. Participants performed a simple visual discrimination task at fixation as the ERPs to task-irrelevant probes in the upper visual periphery were recorded. At random intervals, participants were stopped and asked to report on their attentional state at the time of stoppage-either "on-task" or "off-task." ERPs to the probes immediately preceding these subjective reports were then examined as a function of whether attention was in an on-task versus off-task state. We found that sensory-evoked responses to the probes were significantly attenuated during off-task relative to on-task states, as measured by the visual P1 ERP component. In two additional experiments, we replicated this effect while (1) finding that off-task sensory attenuation extends to the auditory domain, as measured by the auditory N1 ERP component, and (2) eliminating state-dependent shifts in general arousal as a possible explanation for the effects. Collectively, our findings suggest that sensory gain control in cortex is yoked to the natural ebb and flow in how much attention we pay to the current task over time.

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Mind wandering episodes have been construed as periods of “stimulus-independent” thought, where our minds are decoupled from the external sensory environment. In two experiments, we used behavioral and event-related potential (ERP) measures to determine whether mind wandering episodes can also be considered as periods of “response-independent” thought, with our minds disengaged from adjusting our behavioral outputs. In the first experiment, participants performed a motor tracking task and were occasionally prompted to report whether their attention was “on-task” or “mind wandering.” We found greater tracking error in periods prior to mind wandering vs. on-task reports. To ascertain whether this finding was due to attenuation in visual perception per se vs. a disruptive effect of mind wandering on performance monitoring, we conducted a second experiment in which participants completed a time-estimation task. They were given feedback on the accuracy of their estimations while we recorded their EEG, and were also occasionally asked to report their attention state. We found that the sensitivity of behavior and the P3 ERP component to feedback signals were significantly reduced just prior to mind wandering vs. on-task attentional reports. Moreover, these effects co-occurred with decreases in the error-related negativity elicited by feedback signals (fERN), a direct measure of behavioral feedback assessment in cortex. Our findings suggest that the functional consequences of mind wandering are not limited to just the processing of incoming stimulation per se, but extend as well to the control and adjustment of behavior.

Engaging in progressive RT may reduce WML progression.

Mind wandering is a natural, transient state wherein our neurocognitive systems become temporarily decoupled from the external sensory environment as our thoughts drift away from the current task at hand. Yet despite the ubiquity of mind wandering in everyday human life, we rarely seem impaired in our ability to adaptively respond to the external environment when mind wandering. This suggests that despite widespread neurocognitive decoupling during mind wandering states, we may nevertheless retain some capacity to attentionally monitor external events. But what specific capacities? In Experiment 1, using traditional performance measures, we found that both volitional and automatic forms of visual-spatial attentional orienting were significantly attenuated when mind wandering. In Experiment 2, however, ERPs revealed that, during mind wandering states, there was a relative preservation of sensitivity to deviant or unexpected sensory events, as measured via the auditory N1 component. Taken together, our findings suggest that, although some selective attentional processes may be subject to down-regulation during mind wandering, we may adaptively compensate for these neurocognitively decoupled states by maintaining automatic deviance-detection functions.

ImportanceA stroke doubles one’s risk for dementia. How to promote cognitive function among persons with chronic stroke is unclear.ObjectiveTo evaluate the effect of exercise (EX) or cognitive and social enrichment activities (ENRICH) on cognitive function in adults with chronic stroke.Design, Setting, and ParticipantsThis was a 3-group parallel, single-blinded, single-site, proof-of-concept randomized clinical trial at a research center in Vancouver, British Columbia, Canada. Participants included community-dwelling adults with chronic stroke, aged 55 years and older, able to walk 6 meters, and without dementia. The trial included a 6-month intervention and a 6-month follow-up. Randomization occurred from June 6, 2014, to February 26, 2019. Measurement occurred at baseline, 6 months, and 12 months. Data were analyzed from January to November 2021.InterventionsParticipants were randomly allocated to twice-weekly supervised classes of: (1) EX, a multicomponent exercise program; (2) ENRICH, a program of cognitive and social enrichment activities; or (3) balance and tone (BAT), a control group that included stretches and light-intensity exercises.Main Outcomes and MeasuresThe primary outcome was the Alzheimer Disease Assessment Scale-Cognitive-Plus (ADAS-Cog-Plus), which included the 13-item ADAS-Cog, Trail Making Test Parts A and B, Digit Span Forward and Backward, Animal Fluency, and Vegetable Fluency.ResultsOne-hundred and twenty participants, with a mean (range) of 1.2 (1-4) strokes, a mean (SD) of 66.5 (53.8) months since the most recent stroke, mean (SD) baseline age of 70 (8) years, mean (SD) baseline ADAS-Cog-Plus of 0.22 (0.81), and 74 (62%) male participants, were randomized to EX (34 participants), ENRICH (34 participants), or BAT (52 participants). Seventeen withdrew during the 6-month intervention and another 7 during the 6-month follow-up. Including all 120 participants, at the end of the 6-month intervention, EX significantly improved ADAS-Cog-Plus performance compared with BAT (estimated mean difference: −0.24; 95% CI, −0.43 to −0.04; P = .02). This difference did not persist at the 6-month follow-up (estimated mean difference: −0.08; 95% CI, −0.29 to 0.12; P = .43). For the 13-item ADAS-Cog, the EX group improved by 5.65 points over the 6-month intervention (95% CI, 2.74 to 8.57 points; P < .001), exceeding the minimally clinical difference of 3.0 points.Conclusions and RelevanceThese findings suggest that exercise can induce clinically important improvements in cognitive function in adults with chronic stroke. Future studies need to replicate current findings and to understand training parameters, moderators, and mediators to maximize benefits.Trial RegistrationClinicalTrials.gov identifier: NCT01916486

BackgroundFalls are a ‘geriatric giant’ and are the third leading cause of chronic disability worldwide. About 30% of community-dwellers over the age of 65 experience one or more falls every year leading to significant risk for hospitalization, institutionalization, and even death. As the proportion of older adults increases, falls will place an increasing demand and cost on the health care system. Exercise can effectively and efficiently reduce falls. Specifically, the Otago Exercise Program has demonstrated benefit and cost-effectiveness for the primary prevention of falls in four randomized trials of community-dwelling seniors. Although evidence is mounting, few studies have evaluated exercise for secondary falls prevention (that is, preventing falls among those with a significant history of falls). Hence, we propose a randomized controlled trial powered for falls that will, for the first time, assess the efficacy and efficiency of the Otago Exercise Program for secondary falls prevention.Methods/DesignA randomized controlled trial among 344 community-dwelling seniors aged 70 years and older who attend a falls prevention clinic to assess the efficacy and the cost-effectiveness of a 12-month Otago Exercise Program intervention as a secondary falls prevention strategy. Participants randomized to the control group will continue to behave as they did prior to study enrolment. The economic evaluation will examine the incremental costs and benefits generated by using the Otago Exercise Program intervention versus the control.DiscussionThe burden of falls is significant. The challenge is to make a difference – to discover effective, ideally cost-effective, interventions that prevent injurious falls that can be readily translated to the population. Our proposal is very practical – the exercise program requires minimal equipment, the physical therapist expertise is widely available, and seniors in Canada and elsewhere have adopted the program and complied with it. Our innovation includes applying the intervention to a targeted high-risk population, aiming to provide the best value for money. Given society’s limited financial resources and the known and increasing burden of falls, there is an urgent need to test this feasible intervention which would be eminently ready for roll out.Trial registrationClinicalTrials.gov Protocol Registration System: NCT01029171; registered 7 December 2009.