Mental training as a tool in the neuroscientific study of brain and cognitive plasticity

Abstract

Although the adult brain was once seen as a rather static organ, it is now clear that the organization of brain circuitry is constantly changing as a function of experience or learning. Yet, research also shows that learning is often specific to the trained stimuli and task, and does not improve performance on novel tasks, even very similar ones. This perspective examines the idea that systematic mental training, as cultivated by meditation, can induce learning that is not stimulus or task specific, but process specific. Many meditation practices are explicitly designed to enhance specific, well-defined core cognitive processes. We will argue that this focus on enhancing core cognitive processes, as well as several general characteristics of meditation regimens, may specifically foster process-specific learning. To this end, we first define meditation and discuss key findings from recent neuroimaging studies of meditation. We then identify several characteristics of specific meditation training regimes that may determine process-specific learning. These characteristics include ongoing variability in stimulus input, the meta-cognitive nature of the processes trained, task difficulty, the focus on maintaining an optimal level of arousal, and the duration of training. Lastly, we discuss the methodological challenges that researchers face when attempting to control or characterize the multiple factors that may underlie meditation training effects.

Keywords: brain; cognition; meditation; mental training; neuroimaging; plasticity; training.

Figure 1

Effects of FA meditation. (A) Intensive mental training reduced intra-individual variability of behavioral performance. Average SD of reaction time in response to target (attended deviant) tones, separately for each session (time 1, time 2) and group [practitioners (Pract), novices (Nov)]. (B) Intensive mental training increased trial-to-trial consistency of brain responses to attended deviant tones. The scalp maps show the spatial distribution of the mental training-related increase in theta-band (4–7 Hz) phase consistency (indexed by normalized PLF) to target tones, as indexed by a three-way interaction between group, session, and condition (attended, unattended deviant tones). F values are averaged between 300 and 500 ms. The time course of normalized PLF values averaged across the electrodes sites showing this significant three-way interaction is shown separately for each group, session, and attended (Att) and unattended (Unatt) deviant tones. Note that the observed increase in phase consistency to attended deviant tones over time was only observed for the practitioner group. (C) The correlation plot shows that the observed change in the trial-to-trial variability of brain responses predicted the observed behavioral change in the trial-to-trial variability of the RT. (D) Mental training selectively reduced cognitive effort as indexed by ERD. Time course of the ERD for attended and unattended deviant tones (Dev.) shown for the practitioners and novices separately. The scalp maps show the spatial distribution of the mental training-related decrease in beta-band (13–30 Hz) ERD to attended vs. unattended deviant tones [three-way interaction between group, session, and condition]. F values are averaged between 580 and 750 ms. Figure is adopted from Lutz et al. (2009).

Figure 2

Effects of OM meditation. (A) Brain potentials from electrode Pz, time-locked to T1 onset in short-interval trials as a function of session (time 2 vs. 1), T2 accuracy (no-blink vs. blink), and group (practitioners vs. novices). This figure panel illustrates that intensive OM meditation was associated with a selective reduction in T1-elicited P3b amplitude, a brain potential index of resource allocation, in no-blink trials in the practitioner group. The scalp map shows electrode sites where this three-way interaction between session, T2 accuracy, and group was significant between 420 and 440 ms. Adopted from Slagter et al. (2007); (B) Target locking of the theta frequency band phase at electrodes Fz and FT8, time-locked to T1 onset, shown for short-interval no-blink trials and separately for each session and group. Neural activity in the theta frequency band phase-locked robustly to consciously perceived target stimuli over frontal scalp regions. Importantly, a significant meditation-related increase in T2 phase consistency was observed over midline frontal and right lateral frontal and centro-parietal scalp regions (see scalp map). This increase in phase consistency over time was only observed for the practitioner group, indicating that intensive OM meditation may have reduced trial-to-trial variability in the recruitment of processes leading toward the conscious perception of T2. Adopted from Slagter et al. (2009); (C) Relationship between the observed change in brain resource allocation to T1, as indexed by T1-elicited P3b amplitude (for no-blink trials), and the corresponding the change in attentional blink magnitude over time. Note that those individuals that showed the largest decrease in T1-elicited P3b amplitude over time generally showed the largest increase in T2 accuracy over time. Adopted from Slagter et al. (2007); together, these data support the notion that the ability to accurately identify T2 depends upon the efficient processing of T1, and that OM meditation may reduce elaborate object processing.