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Conditional associative learning examined in a paralyzed patient with amyotrophic lateral sclerosis using brain-computer interface technology.

Iversen I, Ghanayim N, Kübler A, Neumann N, Birbaumer N, Kaiser J - Behav Brain Funct (2008)

Bottom Line: A smiley was presented as a reward when he hit the correct target.In contrast, the patient showed clear evidence that A-B and B-C training had resulted in formation of equivalence classes.The brain-computer interface technology combined with the matching to sample method is a useful way to assess various cognitive abilities of severely paralyzed patients, who are without reliable motor control.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Medical Psychology, Goethe-University, Frankfurt am Main, Germany. j.kaiser@med.uni-frankfurt.de.

ABSTRACT

Background: Brain-computer interface methodology based on self-regulation of slow-cortical potentials (SCPs) of the EEG (electroencephalogram) was used to assess conditional associative learning in one severely paralyzed, late-stage ALS patient. After having been taught arbitrary stimulus relations, he was evaluated for formation of equivalence classes among the trained stimuli.

Methods: A monitor presented visual information in two targets. The method of teaching was matching to sample. Three types of stimuli were presented: signs (A), colored disks (B), and geometrical shapes (C). The sample was one type, and the choice was between two stimuli from another type. The patient used his SCP to steer a cursor to one of the targets. A smiley was presented as a reward when he hit the correct target. The patient was taught A-B and B-C (sample - comparison) matching with three stimuli of each type. Tests for stimulus equivalence involved the untaught B-A, C-B, A-C, and C-A relations. An additional test was discrimination between all three stimuli of one equivalence class presented together versus three unrelated stimuli. The patient also had sessions with identity matching using the same stimuli.

Results: The patient showed high accuracy, close to 100%, on identity matching and could therefore discriminate the stimuli and control the cursor correctly. Acquisition of A-B matching took 11 sessions (of 70 trials each) and had to be broken into simpler units before he could learn it. Acquisition of B-C matching took two sessions. The patient passed all equivalence class tests at 90% or higher.

Conclusion: The patient may have had a deficit in acquisition of the first conditional association of signs and colored disks. In contrast, the patient showed clear evidence that A-B and B-C training had resulted in formation of equivalence classes. The brain-computer interface technology combined with the matching to sample method is a useful way to assess various cognitive abilities of severely paralyzed patients, who are without reliable motor control.

No MeSH data available.


Top: Schematic of the sequences of screens that the patient faced at trial start (left), during SCP-controlled cursor movement toward a target (middle, shows the path of cursor movement), and the final, brief reward screen of a "smiley" on correct trials. Bottom: Schematic of the logic of SCP control. The average EEG during the last 0.5 s of the first 2 s following trial start was used as a baseline for subsequent EEG changes during the next 3 s. EEG was assessed relative to baseline during the last 0.3 s of the feedback phase to determine which target the cursor had reached.
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Figure 2: Top: Schematic of the sequences of screens that the patient faced at trial start (left), during SCP-controlled cursor movement toward a target (middle, shows the path of cursor movement), and the final, brief reward screen of a "smiley" on correct trials. Bottom: Schematic of the logic of SCP control. The average EEG during the last 0.5 s of the first 2 s following trial start was used as a baseline for subsequent EEG changes during the next 3 s. EEG was assessed relative to baseline during the last 0.3 s of the feedback phase to determine which target the cursor had reached.

Mentions: Each training session (run) consisted of a series of 70 trials that each lasted 5 s. There were no inter-trial intervals. The patient faced the screen on the notebook computer that showed the sample at left, two targets at right, and a cursor between the targets (Fig. 2, top left). The onset of a trial was indicated by the presentation of stimulus material on the monitor and a 50 ms high-pitched tone. The cursor remained stationary on the monitor for 2 s (the preparatory phase). A within-trial baseline of SCP was recorded for the last 0.5 s of the 2-s preparatory phase (Fig. 2, bottom). This baseline served as an online immediate reference for SCP changes in the subsequent feedback phase, which lasted 3 s and was initiated by a 50 ms low-pitched tone [22]. The cursor began to move at a constant speed from left to right, 0.5 s into the 3-s feedback phase and moved for 2.5 s. The cursor's vertical movement was determined by the average SCP change relative to the 0.5-s baseline SCP value. During the feedback phase, SCP was updated every 62.5 ms and smoothed by a 500 ms moving average. If the patient produced a negative SCP change relative to the immediately preceding baseline the cursor moved up, and if the patient produced a positive SCP change relative to baseline the cursor moved down (Fig. 2, top middle frame). If the SCP remained the same as during the baseline, then the cursor did not move vertically. When the patient steered the cursor to the correct target, a "smiley" face appeared on the monitor as rewarding feedback during the last 0.2 s of a trial (Fig. 2, top right frame). The smiley did not appear if the cursor hit the incorrect target or if no selection was made or if a trial was rejected due to an eye-movement artifact or other artifacts such as from swallowing occurred [22]. A trial was repeated when the trial was rejected or when the cursor did not hit either target.


Conditional associative learning examined in a paralyzed patient with amyotrophic lateral sclerosis using brain-computer interface technology.

Iversen I, Ghanayim N, Kübler A, Neumann N, Birbaumer N, Kaiser J - Behav Brain Funct (2008)

Top: Schematic of the sequences of screens that the patient faced at trial start (left), during SCP-controlled cursor movement toward a target (middle, shows the path of cursor movement), and the final, brief reward screen of a "smiley" on correct trials. Bottom: Schematic of the logic of SCP control. The average EEG during the last 0.5 s of the first 2 s following trial start was used as a baseline for subsequent EEG changes during the next 3 s. EEG was assessed relative to baseline during the last 0.3 s of the feedback phase to determine which target the cursor had reached.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2599893&req=5

Figure 2: Top: Schematic of the sequences of screens that the patient faced at trial start (left), during SCP-controlled cursor movement toward a target (middle, shows the path of cursor movement), and the final, brief reward screen of a "smiley" on correct trials. Bottom: Schematic of the logic of SCP control. The average EEG during the last 0.5 s of the first 2 s following trial start was used as a baseline for subsequent EEG changes during the next 3 s. EEG was assessed relative to baseline during the last 0.3 s of the feedback phase to determine which target the cursor had reached.
Mentions: Each training session (run) consisted of a series of 70 trials that each lasted 5 s. There were no inter-trial intervals. The patient faced the screen on the notebook computer that showed the sample at left, two targets at right, and a cursor between the targets (Fig. 2, top left). The onset of a trial was indicated by the presentation of stimulus material on the monitor and a 50 ms high-pitched tone. The cursor remained stationary on the monitor for 2 s (the preparatory phase). A within-trial baseline of SCP was recorded for the last 0.5 s of the 2-s preparatory phase (Fig. 2, bottom). This baseline served as an online immediate reference for SCP changes in the subsequent feedback phase, which lasted 3 s and was initiated by a 50 ms low-pitched tone [22]. The cursor began to move at a constant speed from left to right, 0.5 s into the 3-s feedback phase and moved for 2.5 s. The cursor's vertical movement was determined by the average SCP change relative to the 0.5-s baseline SCP value. During the feedback phase, SCP was updated every 62.5 ms and smoothed by a 500 ms moving average. If the patient produced a negative SCP change relative to the immediately preceding baseline the cursor moved up, and if the patient produced a positive SCP change relative to baseline the cursor moved down (Fig. 2, top middle frame). If the SCP remained the same as during the baseline, then the cursor did not move vertically. When the patient steered the cursor to the correct target, a "smiley" face appeared on the monitor as rewarding feedback during the last 0.2 s of a trial (Fig. 2, top right frame). The smiley did not appear if the cursor hit the incorrect target or if no selection was made or if a trial was rejected due to an eye-movement artifact or other artifacts such as from swallowing occurred [22]. A trial was repeated when the trial was rejected or when the cursor did not hit either target.

Bottom Line: A smiley was presented as a reward when he hit the correct target.In contrast, the patient showed clear evidence that A-B and B-C training had resulted in formation of equivalence classes.The brain-computer interface technology combined with the matching to sample method is a useful way to assess various cognitive abilities of severely paralyzed patients, who are without reliable motor control.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Medical Psychology, Goethe-University, Frankfurt am Main, Germany. j.kaiser@med.uni-frankfurt.de.

ABSTRACT

Background: Brain-computer interface methodology based on self-regulation of slow-cortical potentials (SCPs) of the EEG (electroencephalogram) was used to assess conditional associative learning in one severely paralyzed, late-stage ALS patient. After having been taught arbitrary stimulus relations, he was evaluated for formation of equivalence classes among the trained stimuli.

Methods: A monitor presented visual information in two targets. The method of teaching was matching to sample. Three types of stimuli were presented: signs (A), colored disks (B), and geometrical shapes (C). The sample was one type, and the choice was between two stimuli from another type. The patient used his SCP to steer a cursor to one of the targets. A smiley was presented as a reward when he hit the correct target. The patient was taught A-B and B-C (sample - comparison) matching with three stimuli of each type. Tests for stimulus equivalence involved the untaught B-A, C-B, A-C, and C-A relations. An additional test was discrimination between all three stimuli of one equivalence class presented together versus three unrelated stimuli. The patient also had sessions with identity matching using the same stimuli.

Results: The patient showed high accuracy, close to 100%, on identity matching and could therefore discriminate the stimuli and control the cursor correctly. Acquisition of A-B matching took 11 sessions (of 70 trials each) and had to be broken into simpler units before he could learn it. Acquisition of B-C matching took two sessions. The patient passed all equivalence class tests at 90% or higher.

Conclusion: The patient may have had a deficit in acquisition of the first conditional association of signs and colored disks. In contrast, the patient showed clear evidence that A-B and B-C training had resulted in formation of equivalence classes. The brain-computer interface technology combined with the matching to sample method is a useful way to assess various cognitive abilities of severely paralyzed patients, who are without reliable motor control.

No MeSH data available.