A brain–computer interface tool to assess cognitive functions in completely paralyzed patients with amyotrophic lateral sclerosis

Brain-computer interface methodology based on self-regulation of slow-cortical potentials (SCPs) of the EEG was used to assess cognitive abilities of two late-stage ALS patients.A monitor presented visual information in two targets. Patients used their SCPs to steer a cursor to one of the targets. Within-subject methodology tested the ability to differentiate odd/even numbers, consonants/vowels, nouns/verbs, large/small numbers, and the ability to perform simple computations. One patient had a short-term memory task with delays up to 15s.Both patients reached accuracy near 90% correct on simple tasks showing that they understood the instructions, discriminated the visual stimuli, and could use the SCP to control the cursor. Both patients showed some deficit on the task that involved computations. The patient with the short-term memory task showed a large reduction in accuracy on delay trials but retained high accuracy on non-delay trials.The fully computerized method is a useful tool for presenting a variety of two-choice tasks to assess certain cognitive functions in the severely paralyzed patient.The task can potentially be used to examine maintenance or decline of cognitive abilities in individual ALS patients.