The human brain is able to process information flexibly, depending on a person's task. The mechanisms underlying this ability to initiate and maintain a task set are not well understood, but they are important for understanding the flexibility of human behavior and developing therapies for disorders involving attention. Here we investigate the differential roles of early visual cortical areas in initiating and maintaining a task set.
Using functional Magnetic Resonance Imaging (fMRI), we characterized three different components of task set-related, but trial-independent activity in retinotopically mapped areas of early visual cortex, while human participants performed attention demanding visual or auditory tasks. These trial-independent effects reflected: (1) maintenance of attention over a long duration, (2) orienting to a cue, and (3) initiation of a task set. Participants performed tasks that differed in the modality of stimulus to be attended (auditory or visual) and in whether there was a simultaneous distractor (auditory only, visual only, or simultaneous auditory and visual). We found that patterns of trial-independent activity in early visual areas (V1, V2, V3, hV4) depend on attended modality, but not on stimuli. Further, different early visual areas play distinct roles in the initiation of a task set. In addition, activity associated with maintaining a task set tracks with a participant's behavior. These results show that trial-independent activity in early visual cortex reflects initiation and maintenance of a person's task set.
Objective: Test the effectiveness of a 6-week functional electrical stimulation (FES)-assisted rowing intervention to increase aerobic fitness and decrease shoulder pain in manual wheelchair users with spinal cord injury (SCI) Methods: Ten adults with SCI (47 ± 12 years, 86 ± 19.7 kg, 175.5 ± 13.2 cm) 18 ± 14 years since injury, AIS classification A-C who had pain in one or both shoulders for >6 months took part in a pre-test, post-test experiment in our human performance laboratory. Participants took part in 30 minutes of FES-assisted rowing, 3 days/week × 6 weeks. Participants were evaluated for VO 2 peak (FES-row and arm bike), distance rowed, arm power output, Wheelchair User Shoulder Pain Index (WUSPI), upper extremity isokinetic strength, scapular stabilization, participation (LIFE-H), quality of life (QOL-SCI), qualitative exit interview. Results: Participants increased distance rowed by 257 ± 266 m and increased arm power output by 6.7 ± 7.9 W. An 8% increase in VO 2 peak and 10.5 ± 4.4 point decrease in shoulder pain were observed (all P < 0.05). There were no changes in upper extremity strength, scapular stabilization, or survey-based measures of participation or quality of life. Qualitative interviewing indicated overall enjoyment of the intervention and improvement in perceived quality of life. Conclusions: FES-assisted rowing is effective to increase aerobic fitness and decrease shoulder pain in manual wheelchair users with SCI. Further research is necessary to determine if rowing without FES can provide similar benefits, and to determine mechanisms driving improvements in shoulder pain, as no changes in measures of upper extremity strength or scapular stabilization were observed.
One approach to encourage and facilitate exercise is through interaction with virtual environments. The present study assessed the utility of Microsoft Kinect as an interface for choosing between multiple routes within a virtual environment through body gestures and voice commands. The approach was successfully tested on 12 individuals post-stroke and 15 individuals with cerebral palsy (CP). Participants rated their perception of difficulty in completing each gesture using a 5-point Likert scale questionnaire. The "most viable" gestures were defined as those with average success rates of 90% or higher and perception of difficulty ranging between easy and very easy. For those with CP, hand raises, hand extensions, and head nod gestures were found most viable. For those post-stroke, the most viable gestures were torso twists, head nods, as well as hand raises and hand extensions using the less impaired hand. Voice commands containing two syllables were viable (>85% successful) for those post-stroke; however, participants with CP were unable to complete any voice commands with a high success rate. This study demonstrated that Kinect may be useful for persons with mobility impairments to interface with virtual exercise environments, but the effectiveness of the various gestures depends upon the disability of the user.
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