An Alpha and Theta Intensive and Short Neurofeedback Protocol for Healthy Aging Working-Memory Training

Abstract

The present study tested the effects of an intensive and short alpha and theta neurofeedback (NF) protocol in working memory (WM) performance in a healthy elder population and explored the effects of a multimodal approach, by supplementing NF with cognitive tasks. Participants were allocated to four groups: NF (N = 9); neurofeedback supplemented with cognitive training (NFCT) (N = 8); cognitive training (CT) (N = 7) and sham neurofeedback (Sham-NF) (N = 6). The intervention consisted in 30-min sessions for 8 days. The NF group presented post intervention increases of alpha and theta relative power as well as performance in the matrix rotation task. In addition, a successful up training of frontal theta showed positive correlation with an improvement of post-training alpha and a better performance in the matrix rotation task. The results presented herein suggest that an intensive and short NF protocol enables elders to learn alpha and theta self-modulation and already presents moderate improvements in cognition and basal EEG. Also, CT group showed moderate performance gains on the cognitive tasks used during the training sessions but no clear improvements on neurophysiology and behavioral measurements were observed. This study represents a first attempt to study the effects of an intensive and short NF protocol in WM performance of elders. The evidence presented here suggests that an intensive and short NF intervention could be a valid alternative for introduction of older populations to NF methodologies.

Keywords: EEG; alpha; cognitive training; healthy aging; neurofeedback; theta; working memory.

FIGURE 1

Experimental design (A) representation of the different phases of the intervention protocol featuring a traditional neuropsychological assessment, a pre- and post-training sessions for EEG assessment simultaneously to the performance of a computerized test battery, and 8 days of intensive training. (B) Representative screenshots of the four computerized tests applied on pre- and post-training assessment sessions, featuring the Auditory Backward Digit Span Test (D. Span), the Matrix Rotation Test (M. Rot), the Stroop Test and the Trail-Making Test (TMT).

FIGURE 2

Representation of the implemented 8-days training intensive and short NF protocol featuring four groups: NF, NFCT, CT and Sham-NF. The NF group (i) performed 4 days of alpha and 4 days of theta training. Each day involved an active baseline followed by six blocks of NF (A). The NFCT group (ii) performed NF supplemented with cognitive tasks [Corsi Block-Tapping Task (B) and n-Back Task (C)]. Each day consisted in an active baseline followed by 3 blocks of NF (similar to A) and 5 blocks of NC tasks. The CT group (iii) performed, each day, 10 blocks of the abovementioned NC tasks. The Sham-NF group (iv) followed the same protocol structure as applied to the NF group.

FIGURE 3

Representation of the mean difference between pre- and post-training performance in the cognitive tests. (A) Digit Span Test Score and (B) Matrix Rotation Test Accuracy, for all experimental groups: NF (N = 8), NFCT (N = 8), CT (N = 7) and Sham-NF (N = 6). NF group presented a statistically significant increase in Matrix Rotation Accuracy (p-value = 0.039). ^#p < 0.05.

FIGURE 4

Representation of the 4-day variation of alpha and theta gradients during training; (A) absolute PSD and (B) relative PSD, for NF (N = 9), NFCT (N = 8) and Sham-NF (N = 6) groups. NF group presented a statistically significant increase in absolute alpha (p-value = 0.014) and in relative alpha and theta (p-value = 0.027 and 0.006, respectively). ^#p < 0.05, ^##p < 0.01.

FIGURE 5

Evolution of frontal EEG power spectral density (PSD) and frontal spectral coherence from pre- to post-training phase; (A) alpha and (C) theta PSD, on baseline and activity periods, in Fz channel, for NF (N = 9), NFCT (N = 8), CT (N = 7) and Sham-NF (N = 6) groups; NF group presented a statistically significant increase in basline alpha (p-value = 0.049) and both baseline and activity theta (p-value = 0.037 and 0.010, respectively, ^#p < 0.05, ^##p < 0.01); for (B) alpha and (D) theta frontal spectral coherence (between FL and FR channel pools), for all four experimental groups. NF group presented a statistically significant increase in both baseline and activity alpha (p-value = 0.037 and 0.027, respectively) and in both baseline and activity theta (p-value = 0.049 and 0.049, respectively, ^#p < 0.05).

FIGURE 6

Correlations between the Fz relative theta gradients, accuracy gains on the Matrix Rotation Test and improvements of post-training Fz alpha PSD for all NF group’s participants (N = 8). Specifically, the positive correlations between (A) relative theta gradient and M. Rot. accuracy (Kendall′s τ = 0.617, p-value = 0.040) (B) relative theta gradient and post-training alpha PSD during activity periods (τ = 0.556, p-value = 0.037) and (C) M. Rot. accuracy gains and post-training alpha PSD (τ = 0.694, p-value = 0.021); Additionally, there is a non-represented positive correlation between the relative theta training gradient and score gains in the D. Span task (τ = 0.718, p-value = 0.016); In-plot dots represent participants.

FIGURE 7

Cognitive training performance for NFCT and CT groups. (A) The participants from CT experimental group have shown performance gains during both forward (p-value: 0.004) and backward (p-value: 0.004) Corsi tasks as well as during 1-back (p-value: 0.007) and 2-back (p-value: 0.004) tasks. (B) The participants from NFCT group only presented performance gains for the forward version of Corsi task (p-value: 0.006). CT participants over performed NFCT participants in the 2-back task (p-value: 0.016).