The Center for Investigating Healthy Minds

Theta phase synchrony and conscious target perception: Impact of intensive mental training.
Slagter et al., 2009, Journal of Cognitive Neuroscience

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 et al., 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.

Empathy is associated with dynamic change in prefrontal brain electrical activity during positive emotion in children.
Light et al., 2009, Child Development

This manuscript presents data from a study involving a large sample of children (N=128) aged 6 to 10 years old from whom measures of brain electrical activity were recorded in response to a novel task that evokes pleasure in a substantial subset of children as they engage in play with an experimenter and then their parent. We sought to determine the extent to which a child's ability to experience positive emotion—as reflected by (1) changes in prefrontal electroencephalographic (EEG) asymmetry during a positive affect inducing task, and (2) parent's report of their child's tendency to experience contentment (i.e. calm happiness)—related to the child's ability to be empathic in a separate situation. We predicted that empathy and contentment would predict change in prefrontal EEG asymmetry during the pleasurable task.

The "empathy task," adapted from Zahn-Waxler, Radke-Yarrrow, Wagner & Chapman (1992) was used to assess empathy. The task begins when an experimenter simulates pain after pretending to catch his/her finger in a clipboard. Then the experimenter simulates relief/happiness. All children were video recorded and vocal, bodily and facial indicators were used to rate children on empathic concern (the ability to vicariously relate to the negative emotion of the experimenter) and a newly operationalized construct: positive empathy. We identified 2 forms of positive empathy, and each child was scored on both: (a) empathic happiness—the ability to vicariously relate to the positive emotion expressed by the experimenter during the relief period, and (b) empathic cheerfulness—the child's attempts to cheer up the experimenter during the pain simulation period.

We used hierarchical linear modeling (HLM) to characterize the second-by-second growth curves of prefrontal EEG activation asymmetries during the pleasurable task using empathy (i.e. empathic concern, empathic cheerfulness and empathic happiness) and contentment scores as predictors of EEG asymmetry growth over time.

The results provide novel evidence that shows for the first time that changes in prefrontal brain electrical asymmetries during a positive incentive in children are related to behavioral measures of empathy obtained during a separate experimental session. Children's brain activity during a pleasure-inducing task is predicted by their empathy level. Children who demonstrated high empathic concern during the empathy task activated first the right and then the left prefrontal cortex during the pleasurable task. A child's ability to flexibly shift between negative and positive emotional states based upon contextual information may provide an optimal substrate for the expression of certain forms of empathy (e.g. empathic concern) that call for the generation of a combination of positive (i.e. feelings of goodwill) and negative (i.e. sadness) emotion in response to the emotional displays of another person. Children who demonstrated high empathic happiness during the empathy task exhibited relatively symmetrical prefrontal activity during the pleasurable task, indicating that these children maintained equal amounts of left-sided and right-sided prefrontal activation (i.e. co-activation) during the course of the task. The sustained maintenance of equal amounts of left and right prefrontal cortex activity over the course of a positive stimulus may indicate that these children generally maintain a relatively neutral emotional set-point that may tend to make them particularly willing to (or susceptible to) vicariously absorb the positive emotion exuded by others because they have "emotional space" available to fill. Children who exhibited high empathic cheerfulness during the empathy task demonstrated an ability to exhibit consistent left prefrontal activity during the course of the pleasurable task. Dual activity in left dorsolateral and left frontopolar cortex may be suggestive of an ability to generate a high level of positive emotion, which can be readily used in an empathic manner.

Dynamic variation in pleasure in children predicts non-linear change in lateral frontal activity.
Light et al., 2009, Developmental Psychology

This manuscript presents data from a  study involving a large group of children (N=128) approximately 8 years of age from whom measures of brain electrical activity were recorded in response to a naturalistic task (that is part of a well-established battery to assess temperamental qualities with behavioral measures) that evokes strong positive affect in a substantial subset of children.  We used hierarchical linear modeling to characterize the growth curves of prefrontal activation asymmetries during this task and found that children expressing objective signs of positive affect showed increasing levels of left prefrontal activity over time.  These are the first data of which we are aware to perform growth curve modeling on EEG measures in this way and provide strong new evidence to show that the change in left lateral prefrontal activation reflects both anticipatory and consummatory positive affect in children.  Furthermore, we found that children who showed less intense forms of positive emotion, i.e. contentment, exhibited increasing levels of right lateral prefrontal activity over the course of the pleasure-inducing task.  This suggests that right lateral prefrontal activity can track non-approach related positive emotions such as contentment (in addition to withdrawal related negative emotions such as sadness), just as left lateral prefrontal activity can track approach related negative emotions such as anger (in addition to approach-related positive emotions such as joy).

Neural correlates of attentional expertise in long-term meditation practitioners.
Brefczynski-Lewis et al., 2007, Proceedings of the National Academy of Sciences

Concentration meditation is a way to increase attentional focus and concentration.  In this meditation one tries to focus all one's attention upon one object, keep it on that object, and bring it back to that object when one finds that one has been distracted (i.e. by outer perceptions or inner thoughts).

As scientists, we wondered whether the brain activation patterns during concentration meditation would be different in experienced Buddhist practitioners compared to normal people without prior meditation experience, and also whether practitioners with different levels of training would show different activation patterns. We hoped that our results would tell us some important things about what brain regions are involved in this meditation, and what brain regions might show effects of training.  The first thing we did was to choose participants that were “the crème de la crème” of Buddhist practitioners.  These participants had at least 10,000 hours of meditation retreat practice, and some had more than 50,000 hours of practice.  These were Buddhist monks and lamas who were often flown in from Nepal, India, the U.S., Europe and Canada.   For comparison, the “novice” participants were normal people who had an interest in meditation, but no prior meditative training.  We worked only with volunteers who were well motivated to learn the meditation techniques, and willing to practice them every day for a week before the actual scan.  

Both the experienced practitioners and the newly trained novices performed the same meditation task while undergoing functional Magnetic Resonance Imaging (fMRI) scans. The fMRI scan is sensitive to changes in blood flow, and can thus detect active brain regions.  In addition to just looking at the meditation vs. a normal resting state, we presented sounds in order to test how distractible participants were during the meditation vs. rest.  The object of focus in the fMRI scanner was a small dot on the computer screen that the participants could view with special goggles.   Participants were to focus all their attention, without distraction on this dot during the meditation blocks.  If participants were drowsy or distracted either by the distracting sounds or own thoughts, they were instructed to simply bring the focus back to the dot.

What we found is that both the expert and the novice meditators were using the same brain regions (regions related to attention) during the concentration meditation.  However, the degree of expertise made a difference in the amount of activation.  Experts as a group had more activation than the novices, which might be expected since novices were likely to struggle with concentration.  There was also a delay in activation such that novices often took 10 seconds or more to show significant activation. In contrast, experts with the most hours of practice (over 40,000 hours of retreat practice) had only about 20 seconds of activation in some brain regions at the beginning of the meditation that then dropped back to zero.  This decreased activation was possibly due to reduced effort necessary to maintain concentration for these very seasoned practitioners.  This “inverted u-shaped curve” is similar to that seen in other learning-related studies such as when one learns a second language.

As for the distracting sounds presented in the meditation, we investigated how brain response to the sounds differed between novices and experts, and how brain response in certain regions varied with hours of practice among the experts.  For an emotionally disturbing sound (a woman screaming) there was less activation in regions related to emotion and cognitive discursiveness in experts vs. novices.  Those with the most hours of practice showed the least activation suggesting that they were the least disturbed by these sounds.   

In sum, concentration meditation activated attention-related brain regions in both expert meditation practitioners and novices. Meditators with more practice initially recruited stronger activation in attention regions, but those with the most practice (over 40,000 hours) had activity drop after less than half a minute, when their concentration may have settled into a tranquil but alert awareness, as is the goal of the meditation practice.  Furthermore, the most practiced meditators showed the least reaction to distracting sounds presented during medititation. The results from this study give promising evidence that concentration meditation may be an effective way to train attention, with results that one can see in brain scans.  Since concentration meditation itself can be a secular practice done completely outside of a religious context, it has broad applications for training attention.  Those with attentional deficits as well as those with attentionally demanding jobs such as surgeons and air traffic controllers may find benefits from this type of meditation. 

Mental training affects distribution of limited brain resources.
Slagter et al., 2007, PLoS Biology

Meditation includes the mental training of attention, which involves the selection of goal-relevant information from the array of inputs that bombard our sensory systems. One of the major limitations of the attentional system concerns the ability to process two temporally close, task-relevant stimuli. When the second of two target stimuli is presented within a half second of the first one in a rapid sequence of events, it is often not detected. This so-called ‘‘attentional-blink’’ deficit is thought to result from competition between stimuli for limited attentional resources. We measured the effects of intense meditation on performance and scalp-recorded brain potentials in an attentional-blink task. We found that three months of intensive Vipassana meditation reduced brain-resource allocation to the first target, enabling practitioners to more often detect the second target with no compromise in their ability to detect the first target. These findings demonstrate that meditative training can improve performance on a novel task that requires the trained attentional abilities. Furthermore, they support the idea that plasticity in brain and mental function exists throughout life and illustrates the usefulness of systematic mental training in the study of the human mind.