Cognitive tasks and combined statistical methods to evaluate, model, and predict mental workload.

Mental workload (MWL) is a concept that is used as a reference for assessing the mental cost of activities. In recent times, challenges related to user experience are determining the expected MWL value for a given activity and real-time adaptation of task complexity level to achieve or maintain desired MWL. As a consequence, it is important to have at least one task that can reliably predict the MWL level associated with a given complexity level. In this study, we used several cognitive tasks to meet this need, including the N-Back task, the commonly used reference test in the MWL literature, and the Corsi test. Tasks were adapted to generate different MWL classes measured via NASA-TLX and Workload Profile questionnaires. Our first objective was to identify which tasks had the most distinct MWL classes based on combined statistical methods. Our results indicated that the Corsi test satisfied our first objective, obtaining three distinct MWL classes associated with three complexity levels offering therefore a reliable model (about 80% accuracy) to predicted MWL classes. Our second objective was to achieve or maintain the desired MWL, which entailed the use of an algorithm to adapt the MWL class based on an accurate prediction model. This model needed to be based on an objective and real-time indicator of MWL. For this purpose, we identified different performance criteria for each task. The classification models obtained indicated that only the Corsi test would be a good candidate for this aim (more than 50% accuracy compared to a chance level of 33%) but performances were not sufficient to consider identifying and adapting the MWL class online with sufficient accuracy during a task. Thus, performance indicators require to be complemented by other types of measures like physiological ones. Our study also highlights the limitations of the N-back task in favor of the Corsi test which turned out to be the best candidate to model and predict the MWL among several cognitive tasks.

Bicentre, randomized, parallel-arm, sham-controlled trial of transcranial direct-current stimulation (tDCS) in the treatment of palliative care patients with refractory cancer pain.

BACKGROUND: Pain is a common symptom in palliative care cancer patients and is often insufficiently relieved. In recent years, transcranial direct-current stimulation (tDCS) of the motor cortex has been shown to be effective to treat chronic pain, essentially neuropathic pain. We propose to test the efficacy of tDCS in patients experiencing cancer pain in the palliative care setting. METHOD/DESIGN: This article describes the protocol of a bicentre, randomized, parallel-arm, sham-controlled clinical trial evaluating tDCS in the treatment of palliative care patients with refractory cancer pain. Seventy patients between the ages of 18 and 80 years experiencing refractory pain with a pain score of 4/10 on a numerical rating scale (NRS) ranging from 0 to 10 will be enrolled in this trial. The main exclusion criteria are patients unable to fill in the various rating scales and life expectancy less than 3 weeks. Treatment consists of 5 consecutive tDCS sessions targeting the motor cortex (one daily session for 5 days) on the contralateral side to the pain. After randomization (1:1 ratio), 35 patients will receive active stimulation and 35 patients will receive sham stimulation. The primary endpoint is the NRS score and the primary objective is a significant improvement of this score between the baseline score recorded between D-3 and D-1 and the score recorded 4 days after stopping treatment (D8). The secondary objectives are to evaluate whether this improvement is maintained 16 days after stopping treatment (D21) and whether the following scores are improved on D14 and D21: Brief Pain Inventory, Edmonton Symptom Assessment System, Hospital Anxiety and Depression scale, State-Trait Anxiety Inventory and Medication Quantification Scale. DISCUSSION: Positive results of this trial would indicate that tDCS can improve pain and quality of life of cancer patients in the palliative care setting. Reduction of analgesic consumption and improvement of activities of daily living should allow many patients to return home with a decreased workload for caregivers.

Efficacy of Transcranial Direct Current Stimulation Combined with Cognitive Training in the Treatment of Apathy in Patients with Alzheimer's Disease: Study Protocol for a Randomized Trial.

BACKGROUND: Apathy, commonly defined as the loss of motivation, is a symptom frequently encountered in Alzheimer's Disease (AD). The treatment of apathy remains challenging in the absence of any truly effective medications. Transcranial Magnetic Stimulation (rTMS) or Transcranial Direct Current Stimulation (tDCS) can improve cognitive disorders, but do not appear to improve apathy. Isolated cognitive training also appears to have no effect on apathy. We propose to test the efficacy of a new procedure for the treatment of apathy in AD patients consisting of a combination of tDCS and cognitive training, based on the latest guidelines for the design of therapeutic trials in this field. METHODS/DESIGN: This article primarily describes the design of a monocentre, randomized, doubleblind trial to be conducted in France to evaluate the effect of the combination of tDCS and cognitive training on apathy compared to a group treated exclusively by cognitive training (sham tDCS). Twenty- four patients under the age of 90 years with mild-to-moderate Alzheimer's disease (Mini Mental State Examination score between 15 and 26/30) (MMSE)) presenting clinically significant apathy evaluated by the Apathy Inventory (AI) and the NeuroPsychiatric Inventory (NPI) apathy subscore will be enrolled. Severe depression will be excluded by using the NPI depression subscore. Treatment will comprise 10 sessions (D0-D11) including tDCS (bilateral prefrontal, temporal and parietal targets) and Cognitive Training (Cog) (6 simple tasks involving working memory, language and visuospatial function). After randomization (ratio 2:1), 16 patients will receive the complete treatment comprising tDCS and Cog (group 1) and 8 patients will be treated exclusively by Cog (sham tDCS) (group 2). The primary endpoint will be a significant improvement of the AI score by comparing baseline measures (D-15) to those recorded one month after stopping treatment (D44). Secondary endpoints will be an improvement of this score immediately after treatment (D14), 2 weeks (D29) and 2 months (D74) after stopping treatment and improvement of the MMSE score, NPI apathy subscore, ADAS Cog (Alzheimer Disease Assessment cognitive Scale subsection), ADCS-ADL (Alzheimer Disease Cooperative Study-Activities of Daily Living), FAB (Frontal Assessment Battery) and the latency of P300 evoked potentials at the same timepoints. CONCLUSION: The purpose of our study is to check the assumption of tDCS and cognitive training efficacy in the treatment of apathy encountered in AD patients and we will discuss its effect over time.