BrailleBCI/README.md

Braille BCI EEG experiment

Brief experiment description

10 blind and 10 sighted subjects were using tactile P300 BCI, implemented with Alva 640 comfort Braille display.

4 fingers on each hand were placed on separate Braille cells, serving as stimuli. Each stimulus was activated 10 times in random order. Participant's task was to count activations of target cell.

For blind subjects, Braille proficiency was assessed with the reading test before the experiment. The experiment included BCI sessions with large (8 dots) and small (1 dot) stimuli.

The present analysis is focused on the comparison of BCI performance for large and small stimuli in blind and sighted individuals.

For more details, see our preprint at https://doi.org/10.1101/2020.06.16.155796

Complete analysis is available at https://github.com/eegdude/erp_analysis/tree/brlbci The scripts are designed to work with contents of sourcedata folder

Sourcedata description

Per-record markup is provided in sourcedata. Per-epoch markup is calculated at preprocessing step. Various stimuli parameters for each epoch are descriped in events.tsv files

Per-record markup

column name	description
user	user id
folder	folder with a record inside the user folder
reg	BCI mode. 'large' for large stimuli, 'small' for small
targets	list of target stimuli for all learning and stimuli selection cycles
fingers	which finger corresponds to specific stimuli code. right hand 0 - pinky, 1 - ring, 2 - middle, 3 - index left hand 4 - index, 5 - middle, 6 - ring, 7 - pinky
ecg_r_peak_direction	1 if R-peak is up, -1 if R-peak is down, 0 or 2 if no ECG
leading_hand	'r' if right, 'l' if left
ignore_events_id	list of events to not include into analysis
reading_finger	list of fingers used for Braille reading
blind	1 if blind, 0 if sighted
order	index of the record in the experiment. Failed sessions that have not made it into the dataset are counted.
blindness_age	age of complete vision loss
reading_time	time of reading Braille text of standard informed consent
braille_display_user	1 if the subject uses Braille display in daily life
daily_braille_time	self-reported daily Braille usage, hours
age	user's age
music	1 if the subject has musical experience (except vocal), 0 if not
remaining_vision	1 if the user has residual vision, 0 if not
sex	male or female
blind_years	years passed from total vision loss
congenitaly_blind	1 if congenital blindness, 0 if acquired

Per-epoch markup

The preprocessed dataset has some added columns, which are calculated during the preprocessing stage.

column name	description
id	unique epoch id
event	epoch event (activated stimuli id)
target	id of current target stimuli
is_target	1 if epoch is target, 0 if not
session_id	stimuli selection cycle index inside experiment
epoch_id	epoch index inside stimuli selection cycle (from 0 to 79)
ms_after_r	milliseconds after R-peak
ms_before_r	milliseconds before next R-peak

Sourcedata folder structure

\
└── markup.csv                               # metadata for all records
└── user 
    └── record
        └── _data_$MODE__play_$TIME.npy      # Raw EEG data
        └── _events_$MODE__play_$TIME.npy    # BCI events
        └── _photocell_$MODE__play_$TIME.npy # sync events
        └── Rpeaks.npy                       # preprocessed R-peaks, if availible

users are numbered from 6 to 26

$MODE can be 'large' for large stimuli and 'small' for small stimuli

Preprocessed data folder structure

\
└── markup.csv                               # metadata for all epochs, created at preprocessing stage
└── 0.pickle                                 # pickle files, corresponding to single epochs

...

└── $N.pickle