INSIGHT, A Comprehensive, Multidisciplinary Brain Training System

Cognitive Ability, General Clinical Trial

— INSIGHT  

Official title:

An Integrative System for Enhancing Fluid Intelligence (Gf) Through Human Cognitive Activity, Fitness, High-definition Transcranial Direct-current Brain Stimulation (HD-tDCS), and Nutritional Intervention

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT02780739
• Other study ID #: 2014-1312170004-Ph1a
• Secondary ID: 14212
• Status: Completed
• Phase: N/A
• First received: May 16, 2016
• Last updated: May 19, 2016
• Start date: March 2014
• Est. completion date: November 2014

Study information

• Verified date: May 2016
• Source: University of Illinois at Urbana-Champaign
• Contact: n/a
• Is FDA regulated: No
• Health authority: United States: Institutional Review Board
• Study type: Interventional

Clinical Trial Summary

Adaptive reasoning and problem-solving are critical skills that allow for accurate decisions to be made based on varying levels of information. In many situations these decisions must be made and communicated under stressful, time-sensitive conditions. In such contexts, an ability to apply inductive and deductive reasoning to complex, ambiguous, and/or novel problems is critical. The objective of the INSIGHT project is to establish a comprehensive and rigorous brain training protocol to significantly improve adaptive reasoning and problem solving. We will examine a variety of interventions (cognitive training, physical fitness training, physiological stimulation, , and combinations thereof) to assess their ability to improve adaptive reasoning and problem solving abilities. Multimodal interventions are hypothesized to act synergistically to significantly enhance fluid intelligence (Gf) and underlying brain structure and function.

Description:

Recent innovations in cognitive neuroscience have advanced understanding of the neurobiological foundations of fluid intelligence (Gf) and adaptive reasoning and problem solving (ARP). Rather than engaging a single brain structure (e.g., prefrontal cortex) or operating at a fixed level of performance throughout adulthood, emerging neuroscience evidence indicates that Gf and ARP are mediated by a distributed neural system whose functions can be significantly enhanced by specific types of interventions, including cognitive training, high-definition transcranial direct-current brain stimulation (HD-tDCS), and physical fitness training. The main objective of the INSIGHT project is to establish and validate a comprehensive and rigorous brain training protocol that incorporates the best available interventions for the enhancement of Gf and ARP.

The project was divided into two phases, with the first occurring in February -November 2014 and the second occurring February - December 2015. The two phases were similar in structure and goals/hypotheses, but had several methodological differences in terms of interventions, arms, and outcome measures. This document contains information pertinent to only the 2014 phase, which examined the relative contributions of physical fitness intervention, video-game based training, and high-definition transcranial direct-current brain stimulation (HD-tDCS) to the improvement of Gf/ARP, executive function, working memory, relational memory, physical fitness level, and brain structure/function.

Arms/groups completed 1 week of testing to establish baseline measurements of cognitive abilities, physical fitness, and brain structure/function. 16 weeks of various intervention protocols. These protocols could include single or multiple intervention type(s) with varying schedules. Three 70-min training sessions were completed per week, so all arms completed 56 hours of training, total. Following completion of the intervention period was 1 week of post-assessment to measure changes in cognitive abilities, physical fitness, and brain structure/function.

Technical Justification for Physical Fitness Intervention: The beneficial effects of physical fitness on cognitive performance and brain health have been documented in many studies. For example, this literature suggests that increased exercise leads to the birth of new neurons in the hippocampus (a key brain region underlying Gf), increased connections among neurons throughout the brain, the development of new vasculature structure, increased production of neurotrophic proteins, enhanced learning and memory, and enhanced executive control including attention and inhibition, working memory, mental flexibility, and action monitoring. In particular, (1) exercise effects are largest for tasks that involve executive control functions for working memory, planning, and problem solving - abilities that are essential for Gf and ARP; and (2) aerobic exercise training, when combined with strength and flexibility training, had a greater positive effect on cognition compared to exercise training programs that included only aerobic components. Such findings provide important justification for the physical activity intervention proposed here. Hence, the proposed fitness intervention employs a combined aerobic/resistance training program to further enhance the benefits of cognitive training on Gf and ARP.

Technical Justification for Video Game-Based Training: Training on five cognitive skills - (1) processing speed, (2) attention, (3) working memory, (4) relational memory, and (5) cognitive flexibility - has been shown to provide promising transfer results to Gf and other relevant constructs. This training regime is the basis for the design of the Mind Frontiers software platform. Mind Frontiers includes an integrated suite of mini-games that are designed to train these five core cognitive skills. The mechanics, as abstractions of the cognitive exercises, ensure that the scientific integrity and the training effect of the exercises are preserved, but the exercises are implemented as games with motivational features and adaptive difficulty.

Technical justification for HD-tDCS: It has been hypothesized that Gf and ARP are critically dependent on a fronto-parietal brain network, and thus that bilateral, specific stimulation of the frontal cortex with high definition transcranial direct current stimulation (HD-tDCS) would have an excitatory effect on neurons within that network, making them more likely to fire, and thereby enabling faster learning and facilitating transfer to Gf.

Technical Justification for Active Control: Change detection and visual search tasks were selected as the active control tasks because previous work had indicated that training low-level perceptual abilities did not transfer to Gf and ARP.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 521
• Est. completion date: November 2014
• Est. primary completion date: November 2014
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Both
• Age group: 18 Years to 44 Years

Eligibility

Inclusion Criteria:

• English fluency

• US citizen, US permanent resident, or student/work visa sponsored by UIUC

• Available for 18-20 weeks

• Ages 18 - 44

• Normal or corrected-to-normal vision

• Normal or corrected-to-normal hearing

Exclusion Criteria:

• Previous participant in studies with similar protocols

• Currently taking any medication affecting CNS

• Has taken medication affecting CNS in past 2 months

• Current or planned pregnancy

• Recurrent migraines

• Concussion in past 2 years

• History of stroke

• History of epilepsy/seizures

• Any medical condition affecting CNS (e.g., history of thyroid cancer)

• Any medical condition affecting capability to exercise (e.g., paralysis)

• Reading disability/dyslexia

• Prior brain surgery

• Known brain malformation

• Colorblindness

• Heart condition that requires physician approval for physical activity

• Chest pain (with OR without physical activity)

• Loss of balance/dizziness/loss of consciousness

• Bone or joint problem that could be made worse by a change in physical activity

• Medication for blood pressure or a heart condition

Study Design

Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Investigator, Outcomes Assessor)

Related Conditions & MeSH terms

• Cognitive Ability, General

Intervention

Behavioral:
• Cognitive Training - 48 sessions
Mind Frontiers cognitive training software (Aptima Inc.) is a Wild West-themed Android application played on Nexus 10 tablets. This intervention includes 20 70-min sessions (23.33 hrs) completed over 12 weeks: 1/wk weeks 5-8, 2/wk weeks 9-16. The 6 mini-games, played in random order for 10 min each session, are Ante Up (Tower of London, executive functioning); Irrigator (visuospatial reasoning); Pen 'Em Up (dual task switching, executive function); Supply Run (Keep Track, working memory updating); Riding Shotgun (visuospatial working memory); and Sentry Duty (dual n-back, working memory). There is also a meta-game in which players build a town using resources earned from the mini-games, played for 5 min each session.
• Fitness
Based on high intensity cardiovascular resistance training (HICRT), this intervention includes a combination of aerobic and strength training. Sessions are conducted in a group of =20 participants per class, with =5 participants per trainer. This intervention includes 28 70-min sessions (32.67 hrs) completed over 16 weeks: 3/wk weeks 1-4, 2/wk weeks 5-8, 1/wk weeks 9-16. At the first and last session, participants complete the Army Physical Readiness Test. All other sessions consist of: Warm-up; Walk/Run; 2 HICRT circuits with 3 sets of 3-4 exercises; 1-2 min jump rope and 4-min power series between HICRT segments; Drills & Skills; and Cool-down/stretch.
• Active Control
The active control condition consists of 2 tasks (change detection and visual search) with 3 variants each. This intervention includes 48 70-min sessions (56 hrs) completed over 16 weeks: 3/wk. The 6 tasks are played in random order for 10 min each session.

Device:
• active tDCS
Active HD-tDCS is administered during the first 30 minutes of each Mind Frontiers session. Therefore, the schedule is 20 30-min sessions (10 hrs) completed over 12 weeks: 1/wk weeks 5-8, 2/wk weeks 9-16. The HD-tDCS devices are Soterix Medical 2x2 models, using 4 electrodes (2 anodal and 2 cathodal). Electrodes are held in place with custom, 3D-printed electrode holders inserted into EEG caps, using EEG gel. Participants receive 2.0 mA current for 30 min, split over the 2 anodal electrodes, each drawing =1.0 mA. Stimulation is ramped up and ramped down over 30 sec at the beginning and end of the 30-min stimulation period.
• sham tDCS
Sham HD-tDCS is administered during the first 30 minutes of each Mind Frontiers session. Therefore, the schedule is 20 30-min sessions (10 hrs) completed over 12 weeks: 1/wk weeks 5-8, 2/wk weeks 9-16. The HD-tDCS devices are Soterix Medical 2x2 models, using 4 electrodes (2 anodal and 2 cathodal). Electrodes are held in place with custom, 3D-printed electrode holders inserted into EEG caps, using EEG gel. Participants do not receive sustained stimulation; it is ramped up and ramped down over 30 sec at the beginning and end of the 30-min stimulation period to elicit the sensation of simulation and make the sham condition more convincing.

Behavioral:
• Cognitive Training - 20 sessions
Mind Frontiers cognitive training software (Aptima Inc.) is a Wild West-themed Android application played on Nexus 10 tablets. This intervention includes 20 70-min sessions (23.33 hrs) completed over 12 weeks: 1/wk weeks 5-8, 2/wk weeks 9-16. The 6 mini-games, played in random order for 10 min each session, are Ante Up (Tower of London, executive functioning); Irrigator (visuospatial reasoning); Pen 'Em Up (dual task switching, executive function); Supply Run (Keep Track, working memory updating); Riding Shotgun (visuospatial working memory); and Sentry Duty (dual n-back, working memory). There is also a meta-game in which players build a town using resources earned from the mini-games, played for 5 min each session.

Locations

Country	Name	City	State
United States	University of Illinois at Urbana-Champaign	Urbana	Illinois

Sponsors (6)

Lead Sponsor	Collaborator
University of Illinois at Urbana-Champaign	Aptima, Inc., Autonomous University of Madrid, Spain, Circinnus LLC, Georgia Institute of Technology, The City College of New York

Country where clinical trial is conducted

United States, 

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* Note: There are 68 references in all — Click here to view all references

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Change in Bochum Matrices Test	BOMAT is a non-verbal, one-dimensional neuropsychological test of Gf. The test consists of a series of 5x3 matrices of patternswith each matrix missing one field. The participant selects one of six possible answers that complete the matrix. The problems range from simple to complex and are all in black-and-white. Participants complete a 15-min practice and have 45 min to complete as many problems as they can (29 total).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Letter Sets	This test is a measure of Gf. For each problem of the Letter Sets task, the participant is shown 5 sets of letters, with 4 letters in each set. Four of the sets of letters follow a rule, while the fifth set of letters is different from the rest. With the exception of sounds of the sets of letters, shapes of the letters, or potential word formation of the letters, the participant must determine which rule applies to 4 of the letter sets and indicate the 1 letter set that doesn't fit. Participants have 7 minutes to complete as many problems as they can (15 total), with each problem getting progressively more difficult.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Number Series	This test is a measure of Gf. Participants are shown a series of arithmetic number series and need to select the next number in the series from 5 possible answers at the bottom of the screen. The participant is given 5 practice problems at the beginning of instruction, and must complete as many problems as possible in 5 min (10 total).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Rotation Span	This is a test of working memory. Participants must remember a series of arrows presented (16 possible arrows varying in length and direction), while maintaining accuracy on an interleaved letter rotation task (determining if a letter is facing the correct direction after rotation).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Symmetry Span	This is a test of working memory. Participants must remember a series of blocks presented (from a 4x4 grid) while maintaining accuracy on an interleaved symmetry judgment task.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Reading Span	This is a test of working memory. Participants must remember a series of words presented (18 possible 4-letter words) while maintaining accuracy on an interleaved task where they judge sensible or nonsensical sentences.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Garavan	The Garavan task is a serial attention task that measures executive function, specifically task-switching ability. Participants are presented with a series of large and small squares, 10 series/trial in total. Subjects must keep a mental count of how many large and small squares have been presented. For each square, the participant rapidly updates this mental count and then presses the spacebar to see the next square. At the end of the sequence (length is random), a response screen appears and participants report their final count of large and small squares. On a given trial, 11-15 updates are made. Dependent measures are response time for consecutive trials of the same type (no-switch RT) and response time for consecutive trials that differ (switch RT). A cost RT metric can be computed by taking the difference between Switch and No-Switch RT as a measure of set shifting.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Stroop	The Stroop task is a measure of executive function, specifically inhibition. In this task, subjects are asked to indicate the color of each word stimulus. The stimulus may be congruent (the word meaning and text color match), or incongruent (the word meaning and text color differ).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Keep Track	The Keep Track task measures executive function, specifically updating items held in short-term memory. In the task, a series of word stimuli are presented, each belonging to a category. Subjects must remember only the last item presented from each category.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Immediate and Delayed Free Recall - Words	This is a relational memory task. Participants are shown a sequence of 12 words (all 4-letter nouns/verbs), 750 ms for each word. Afterwards, the participant has 30 sec to enter as many words as they can remember from the trial. They do 1 practice trial, followed by 5 test trials. Approximately 20-30 min later, participants are given 90 sec to recall as many words as they can from all 5 previous trials.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Immediate and Delayed Free Recall - Pictures	This is a relational memory task. Participants are shown a sequence of 12 images (all objects, no "action" images), 750 ms for each image. Afterwards, the participant has 30 sec to enter words to describe as many images as they recall from the trial (1 word/image). Each image has multiple words that could be accepted as a correct response (i.e., if shown an image of a chimpanzee, answers "chimpanzee" and "monkey" would both be acceptable). They do 1 practice trial of this task, followed by 5 test trials. Approximately 20-30 minutes later, the participant is given 90 sec to recall as many images as they can from all the previous trials.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Paired Associates	This is a relational memory task. In Paired Associates, a list of 6 unrelated word pairs are presented. At recall, only the first word from each pair is presented. Subjects must enter the second word in the pair. This procedure is repeated with a second list of 6 word pairs. Approximately 20-30 minutes later, the first words from all 12 word pairs are presented. Subjects must enter the second words from each pair.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in VO2 Max (relative, percentile)	Aerobic fitness, defined as maximal oxygen consumption (VO2 max), is assessed using an indirect computerized calorimetry system during a modified Balke treadmill test. During the test, participants' heart rates are monitored using a Polar heart rate monitor, and ratings of perceived exertion are assessed every 2 min. During the test, speed remains constant while incline increases 2-3% every 2 min. Average O2 consumption and respiratory exchange ratio are sampled every 15 sec using a mouthpiece. Relative VO2 max is reported relative to body weight, calculated as ml O2/kg/min. Maximum effort is defined using at least 2 of the following: (1) age-defined maximum heart rate norms (HR > 85% of predicted max HR), (2) respiratory exchange ratio (CO2/O2) >1.1, (3) subjective rate of perceived exertion >17 (of 20), and (4) leveling of VO2 despite increasing aerobic demand. VO2 max percentile is also be reported based on age norms.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Body Mass Index	BMI is calculated from measures of height and weight	2 administrations: within 2 weeks before beginning and after finishing the 16-week intervention period	No
Secondary	Change in brain structure	High-resolution structural MRI scan of brain anatomy using MPRAGE sequence, acquired in sagittal orientation (resolution: 0.9 mm, 192 slices, TR 1900 ms, TE 2.32 ms).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in BOLD signal at rest	Using functional MRI to measure blood-oxygen-level-dependent signal while the subject is at rest and not performing a task	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in BOLD signal during task	Functional MRI that measures brain activity (based on hemodynamic response and blood-oxygenation-level dependent signal) during an experimental task.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Object Location Task performance	Completed during fMRI scanning. In the task, an image with 4 objects is presented on a grid of 9 possible locations. Participants are instructed to memorize the spatial locations of all 4 objects and mentally rotate the grid 90°. Participants are then presented with a probe image containing the same 4 objects rotated 90°. Participants must indicate whether or not any of the objects changed location in the rotated probe image. There are three possible responses: either all objects match; 1 object moves to a new location; or 2 objects swap locations. This task is a measure of relational memory.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in 3-back Task performance	Completed during fMRI scanning. Participants are presented with a continuous stream of stimuli (either faces or words), and for every stimulus, the participant must indicate (yes/no) whether or not the current stimulus is the same as the one presented three trials back. This task is a measure of working memory.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Diffusion of Water in the brain	Diffusion tensor imaging (DTI) is a magnetic resonance imaging method that is sensitive to the diffusion of water molecules. Diffusion of water in the brain depends on the tissue type, structural architecture, and presence/absence of barriers within imaging voxels. Using this raw imaging information, diffusion-based properties can be estimated including: 1. fractional anisotropy (FA), which is a measure of whether or not the 3-dimensional diffusion is largely directional (e.g., within an axon; thus, anisotropic diffusion), or if the diffusion is equal in all directions (e.g., within CSF; thus isotropic diffusion); 2. radial diffusivity (RD), which is a measure of how diffusion in the plane transverse to the principal direction of diffusion (i.e., within a cross-section of an axon, rather than down the length of an axon).	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in single-voxel magnetic resonance spectroscopy (MRS)	Technique to measure cell metabolites within a single super voxel of the brain (20 mm3), such as N-acetyl aspartate (NAA)	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Cerebral Blood Flow	During magnetic resonance imaging scans, using the arterial spin labeling technique to acquire multi-slice cerebral blood flow maps	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Saliva-based Genetic Biomarkers	Saliva collected from passive drooling, to be analyzed for biomarkers related to fluid intelligence	One administration, within a week after finishing the 16-week intervention	No
Secondary	Height	Height measured to calculate BMI estimate	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Weight	Weight measured to calculate BMI estimate	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Demographics Questionnaire	Questionnaire that requests age, birth date, sex, race/ethnicity, occupation.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Big Five Inventory (BFI) Questionnaire	Personality assessment with five dimensions: openness, conscientiousness, extraversion, agreeableness, and neuroticism	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Grit Scale Questionniare	This questionnaire assesses the personality trait of grit, a characteristic associated with passion and adherence to long-term goals, along with strong motivation to achieve goals despite potential obstacles.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Pittsburgh Sleep Quality Index (PSQI)	The PSQI assesses sleep habits on eight dimensions over the past month with 11 open-ended and multiple choice questions. Relevant dimensions include sleep duration, disturbance, latency, day dysfunction, efficiency, quality, use of medications to sleep, and an overall binary score of sleep habits.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Godin-Shepard Leisure Time Physical Activity Questionnaire	This survey asks about level of physical activity during leisure time in the past month, from which longer-term exercise habits can be extrapolated. By collecting height, weight, and resting heart rate with this measure, a VO2 max estimation can be reliably calculated.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in UCLA Loneliness Scale	This survey asks about the frequency (never, rarely, sometimes, often) of 20 statements regarding feelings of loneliness and social connection.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Need for Cognition	This survey asks 45 Likert-type questions regarding the value an individual places upon cognition in daily life.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Change in Implicit Theories of Intelligence Survey (ITIS)	The ITIS asks 8 Likert-type questions regarding personal beliefs about the relative fixedness/malleability of intelligence.	2 administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Physical Activity Enjoyment Scale	The Physical Activity Enjoyment Scale (PACES) measures individuals' enjoyment with their current activity level.	Administered once, within a week after finishing the 16-week intervention period	No
Secondary	Post-Experiment Survey	This survey was customized for each arm to assess: participant feedback on the various interventions they experienced; strategies developed and used in cognitive training and active control training; expectancy effects of video game-training, physical fitness training, and mindfulness meditation training; and the contribution of external (outside-study) physical activity/exercise and video game play.	Administered once, within 2 weeks after finishing the 16-week intervention period	No
Secondary	Preference for and Tolerance of the Intensity of Exercise Questionnaire (PRETIE-Q)	The Preference and Tolerance of the Intensity of Exercise Questionnaire (PRETIE-Q) measures individuals' preferences for physical activity type and duration. For instance, does one prefer high-intensity activity for a brief period of time, or low-intensity activity for a longer duration? How does one respond to physical challenge and exhaustion?	Two administrations: within a week before beginning and after finishing the 16-week intervention period	No
Secondary	Game Feedback - Mind Frontiers	Game feedback surveys were developed in-house and administered to evaluate participant responses to cognitive training. These surveys were administered at Sessions 1, 24, and 48 for the 48-session intervention, or at Sessions 1 and 20 for the 20-session intervention. These surveys evaluated enjoyment, engagement, motivation, demand, and frustration with each mini-game.	Administered at Sessions 1, 20 (or 24), and 48 of the Mind Frontiers intervention	No
Secondary	Game Feedback - Active Control	Game feedback surveys were developed in-house and administered to evaluate participant responses to active control training. These surveys evaluated enjoyment, engagement, motivation, demand, and frustration with each task.	Administered at Sessions 1, 24, and 48 of Active Control intervention	No
Secondary	Army Physical Readiness Test (APRT)	The APRT is five exercises: (1) 60-yard shuttle run, (2) standing long jump, (3) one-minute of rowers, (4) one-minute of push-ups, and (5) a 1.5 mile run	Administered at Session 1 and Session 28 of the fitness intervention	No
Secondary	Heart rate	Participants' heart rates were monitored using Polar heart rate monitor E600 during all sessions of the fitness intervention	Data collected continuously during at all 28 fitness intervention sessions	No

External Links

•   Click here for more information about the study: An integrative system for enhancing fluid intelligence (Gf) through human cognitive activity, fitness, high-definition transcranial direct-current brain stimulation, and nutritional intervention