Theta phase synchrony and conscious target perception: impact of intensive mental training - PubMed (original) (raw)

Theta phase synchrony and conscious target perception: impact of intensive mental training

Heleen A Slagter et al. J Cogn Neurosci. 2009 Aug.

Abstract

The information processing capacity of the human mind is limited, as is evidenced by the attentional blink-a deficit in identifying the second of two targets (T1 and T2) presented in close succession. This deficit is thought to result from an overinvestment of limited resources in T1 processing. We previously reported that intensive mental training in a style of meditation aimed at reducing elaborate object processing, reduced brain resource allocation to T1, and improved T2 accuracy [Slagter, H. A., Lutz, A., Greischar, L. L., Francis, A. D., Nieuwenhuis, S., Davis, J., et al. Mental training affects distribution of limited brain resources. PloS Biology, 5, e138, 2007]. Here we report EEG spectral analyses to examine the possibility that this reduction in elaborate T1 processing rendered the system more available to process new target information, as indexed by T2-locked phase variability. Intensive mental training was associated with decreased cross-trial variability in the phase of oscillatory theta activity after successfully detected T2s, in particular, for those individuals who showed the greatest reduction in brain resource allocation to T1. These data implicate theta phase locking in conscious target perception, and suggest that after mental training the cognitive system is more rapidly available to process new target information. Mental training was not associated with changes in the amplitude of T2-induced responses or oscillatory activity before task onset. In combination, these findings illustrate the usefulness of systematic mental training in the study of the human mind by revealing the neural mechanisms that enable the brain to successfully represent target information.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Attentional-blink task. On every trial, between 15 and 19 items were presented at the center of the screen, preceded by a 1780-msec fixation cross. Most of the items were letters, presented for 50 msec each and followed by a 34-msec blank. On T2-present trials, there were two target numbers (T1 and T2) among the items, which participants had to detect and report at the end of the trial. The temporal distance between T1 and T2 could be short (336 msec) or long (672 msec).

Figure 2

Figure 2

Effects of intensive mental training on the attentional blink. Average T2 accuracy (plus standard error) for each session, T1—T2 interval, and group (at-chance participants excluded). Note that both groups showed an attentional blink at Time 1: lower T2 accuracy at short- compared to long-interval trials. Note further that, as predicted, the practitioner group showed a significantly larger reduction in attentional-blink size over time than the novice group. Adapted from Slagter et al. (2007).

Figure 3

Figure 3

Effects of intensive mental training on target phase locking. (A, C, D, E) Target locking of the theta frequency-band phase at electrodes FT7, Fz, and FT8, time-locked to T1 onset, shown separately for short-interval no-blink (A), blink (C), and T2-absent (D) trials and long-interval no-blink trials (E), and for each session and group. In combination, these data indicate that neural activity in the theta frequency band phase-locked robustly to consciously perceived target stimuli over frontal scalp regions. In addition, they show a significant mental training-related increase in T2 phase locking over midline frontal and right lateral frontal and centro-parietal scalp regions (B). This increase in phase consistency over time was only observed for the practitioner group, indicating that intensive mental training may have reduced trial-to-trial variability in the recruitment of processing leading toward the conscious perception of T2.

Figure 4

Figure 4

The efficient processing of T1 reduces variability in the recruitment of processes related to conscious T2 perception. Relationship between the change in T1-elicited P3b amplitude and the corresponding change in T2 locking of the theta frequency-band phase at electrodes Fz (top) and T8 (bottom) (for no-blink trials). Note that those individuals that showed the largest decrease in T1-elicited P3b amplitude over time generally showed the largest reduction in theta phase variability over time.

Figure 5

Figure 5

Changes in target-induced amplitude over time. Changes in target-induced amplitude (μV) over time in no-blink versus blink trials are shown for each group (practitioners, novices) and frequency band separately, for electrode POz. Between —31 msec and 160 msec post-T1 (black rectangular box), the practitioners compared to the novices showed a significant increase in alpha power over time over occipital scalp regions in no-blink compared to blink trials. No other significant mental training-related changes in target-induced responses related to the detection of T2 were observed.

Similar articles

Cited by

References

    1. Arend I, Johnston S, Shapiro K. Task-irrelevant visual motion and flicker attenuate the attentional blink. Psychonomic Bulletin & Review. 2006;13:600–607. - PubMed
    1. Bastiaansen M, Hagoort P. Event-induced theta responses as a window on the dynamics of memory. Cortex. 2003;39:967–992. - PubMed
    1. Brefczynski-Lewis JA, Lutz A, Schaefer HS, Levinson DB, Davidson RJ. Neural correlates of attentional expertise in long-term meditation practitioners. Proceedings of the National Academy of Sciences, U.S.A. 2007;104:11483–11488. - PMC - PubMed
    1. Bullock TH, McClune MC, Enright JT. Are the electroencephalograms mainly rhythmic? Assessment of periodicity in wide-band time series. Neuroscience. 2003;121:233–252. - PubMed
    1. Chun MM, Potter MC. A two-stage model for multiple target detection in rapid serial visual presentation. Journal of Experimental Psychology: Human Perception and Performance. 1995;21:109–127. - PubMed

Publication types

MeSH terms

Grants and funding

LinkOut - more resources