Tonic and phasic alertness training: a novel behavioral therapy to improve spatial and non-spatial attention in patients with hemispatial neglect

Abstract

Hemispatial neglect is a debilitating disorder marked by a constellation of spatial and non-spatial attention deficits. Patients' alertness deficits have shown to interact with lateralized attention processes and correspondingly, improving tonic/general alertness as well as phasic/moment-to-moment alertness has shown to ameliorate spatial bias. However, improvements are often short-lived and inconsistent across tasks and patients. In an attempt to more effectively activate alertness mechanisms by exercising both tonic and phasic alertness, we employed a novel version of a continuous performance task (tonic and phasic alertness training, TAPAT). Using a between-subjects longitudinal design and employing sensitive outcome measures of spatial and non-spatial attention, we compared the effects of 9 days of TAPAT (36 min/day) in a group of patients with chronic neglect (N = 12) with a control group of chronic neglect patients (N = 12) who simply waited during the same training period. Compared to the control group, the group trained on TAPAT significantly improved on both spatial and non-spatial measures of attention with many patients failing to exhibit a lateralized attention bias at the end of training. TAPAT was effective for patients with a range of behavioral profiles and lesions, suggesting that its effectiveness may rely on distributed or lower-level attention mechanisms that are largely intact in patients with neglect. In a follow-up experiment, to determine if TAPAT is more effective in improving spatial attention than an active treatment that directly trains spatial attention, we trained three chronic neglect patients on both TAPAT and search training. In all three patients, TAPAT training was more effective in improving spatial attention than search training suggesting that, in chronic neglect, training alertness is a more effective treatment approach than directly training spatial attention.

Keywords: attention; hemispatial neglect; neurological disorders; rehabilitation; visual.

Figures

Figure 1

MRI and CT scans of patients’ lesions in neurological convention (excluding patient JS).

Figure 2

TAPAT task. Each day, the training session began with the patients familiarizing themselves with a new target scene while reading the following instructions as the experimenter read them aloud: “You will see many scenes over the next 12 min. Your job is to hit the spacebar as fast as you can for each scene except when the scene is the target scene. When you see the target scene, do not hit the spacebar. The target scene for today is the following [Example Target Scene]. Please take a minute to memorize this scene.” Each 12-min round contained 360 trials: 36 target scenes (10%) and 324 non-target scenes (90%) randomly ordered. Each scene subtended a visual angle of 4° (vertical) × 6° (horizontal). On each trial, scenes were presented for 500 ms and between trials a blank screen with a fixation “+” at the center was shown for either 1000 ms (33.3% of trials), 1500 ms (33.3% of trials), or 2000 ms (33.3% of trials). After completion of a round of 360 trials, patients took a short break (approximately 2 min) before beginning the next 12-min round of 360 trials. Each day, patients performed three of these 12-min rounds for a total of 1080 trials.

Figure 3

Group (A) and individual (B) results of performance on the training task during the first and last day of training (error bars represent the standard error of the mean). There were no significant group changes with training (A), though individuals demonstrated significant improvements and decrements on different aspects of the training task (highlighted in gray and black). This was determined by performing Wilcoxon signed rank test on each component of training and assessing the calculated Z-score statistic at the p < 0.05 level.

Figure 4

Original conjunction search results for TAPAT group (A) and control group (B). The display time is the amount of time that the target (red square) had to be shown for patients to correctly identify it 75% of the time. This was calculated separately for right and left targets (error bars represent the standard error of the mean). (C) is an example of a left target present trial.

Figure 5

Alternative conjunction search results for TAPAT group. The display time is the amount of time that the target (blue triangle) had to be shown for patients to correctly identify it 75% of the time. This was calculated separately for right and left targets (error bars represent the standard error of the mean).

Figure 6

Group landmark results for TAPAT (A) and Control (B) groups. The pixel deviation from center measures patients’ subjective perception of the center of the black line compared to the actual center (left is negative, right is positive). Error bars represent the standard error of the mean. (C) is an example of a landmark display.

Figure 7

Group attentional blink results for TAPAT (A) and Control (B) groups. Correct Time 2 discrimination accuracy is the percentage of correct identifications of the second target (in the example, 7) when correctly identifying the first target (in the example, 3). This is calculated for when the second target lags the first target by two positions (see example) or six positions. Error bars represent the standard error of the mean. (C) is an example of a lag 2 attentional blink trial: 3 is the first target (T1) and 7 is the second target (T2).

Figure 8

Correlations between pre-training impairment and post-pre improvement scores for the original conjunction search (A), landmark task (B), and attentional blink task for lag 2 (C) and lag 6 (D).

Figure 9

Results of stepwise regressions predicting assessment improvement from training task improvement. (A) Shows the regression results predicting the post-pre improvement scores from improvements on components of the training task. ** indicates that the training component significantly predicted the particular assessment improvement (p<.05). (B–D) Show plots of the assessments with significant improvement-training component relationships.

Figure 10

Results of TAPAT training and search training in three chronic neglect patients for the conjunction search task and landmark task. Error bars represent the standard error of the mean. For the conjunction search, the display time is the amount of time that the target (red square) had to be shown for patients to correctly identify it 75% of the time. This was calculated separately for right and left targets. For the landmark task, pixel deviation was collapsed across right starting and left starting trials to give an average pixel deviation to the right (positive values) or left (negative values).