## 2 Methods
### Experimental Protocol  
The experiments with the patient were conducted at her home. The patient was in a wheelchair, in a reclined position. The visits to the patient were done in the late morning when the patient showed longer attention spans, according to information provided by the husband. Each visit lasted no longer than two hours. We performed 16 visits to the patient for data acquisition and testing. At each visit, we performed one or more sessions, where we tested the same or different interfaces. A total of 31 sessions were conducted during the 16 visits.  
The developed interfaces comprised visual (text, symbols, and images), auditory (spoken words and white noise), or hybrid stimuli (combining visual and auditory stimuli). The visual stimuli were presented via a screen located at approximately 1 m from the patient's line of sight, and the auditory stimuli were presented through earphones. The stimuli differed on the different interfaces, as explained in Section 2.4.1, but the number of symbols remained the same during our experiments. The BCIs evaluated in this study consisted of a P300 oddball paradigm (1 Target and 6 standards (non-Targets)), consisting of seven stimuli that provide a small Portuguese lexicon, namely 'SIM' (Yes), 'NAO' (No), 'TOSSE' (Cough), 'TV', 'AJUDA' (Help), 'SONO' (Sleep), and 'STOP', which, according  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Characteristic** & **Patient** \\ \hline Age & 54 \\ Gender & Female \\ ALSFRS-R & 1 \\ Diagnosis/onset & ALS/Limb \\ Time since onset & 57 months \\ Ventilation/nutrition & Tracheotomy/Gastrostomy \\ Movement control & No \\ Hearing & Yes \\ Tactile sensitivity & Yes \\ Understands what is asked & Authors believe so \\ Attention spans & Unknown \\ Medication & Fluoxetine \\ \hline \hline \end{tabular}
\end{table}
Table 2: CLIS patient characteristics.  
to the patient's family members, were the main needs of the patient. The stimuli had a duration of 550 ms and an interstimulus interval (ISI) of 100 ms.  
Each online session was preceded by a calibration to obtain training data for fitting the classification model. The calibration process (Figure 1a) consisted of the patient focusing on one word at a time and mentally counting the number of times each word appeared on the screen and/or was spoken. Each target word was repeated 9 times interleaved with the non-target words, according to the oddball paradigm, to induce the target-related potentials. In total, there were 12 words in the training sequence, corresponding to 108 (12 \(\times\) 9) target trials and 648 (12 \(\times\) 9 \(\times\) 6) non-target trials.  
During the online session (Figure 1b), the patient was asked to perform a copy-paste task, wherein she was instructed with one word and required to mentally count the number of times the specified word occurred. The number of repetitions for each selection was adjusted to 9, although different numbers of repetitions were tested in some sessions for comparison. Each copy task consisted of 10 selections.  
After the fourth visit to the patient, due to the very low BCI performance achieved, two modifications were introduced to the experimental procedure: (1) only the words 'SIM' and 'NAO' were used in the training sequence, while the P300 oddball paradigm with the seven symbols remained the same; and (2) in the copy task, we started applying a filter in the classification algorithm, limiting the selections to 'SIM' and 'NAO' choices, i.e., transforming the 7-class problem into a binary classification. The oddball paradigm with the seven symbols remained the same as in calibration.  
The control group performed the experiments in a laboratory environment, always using the 7-class BCI.