Present Tense

Lately, The Neurocritic (and recent neuronews) has been focused on the past and the future. But what about the present? What happens to the brain when we are truly focused on the present moment? Overlapping brain areas activated while remembering the past/imagining the future include medial prefrontal cortex, posterior cingulate, and parahippocampal gyrus (Okuda et al., 2003; Addis et al., 2007; Szpunar et al., 2007). Are these regions (and others specific to past or future) deactivated when one resides in the present moment? And what does this state entail, phenomenologically speaking? Mindfulness is now a very popular topic of academic study, and numerous universities have centers for research on mindfulness and the application of mindfulness techniques in clinical practice.

The Centre For Mindfulness Research And Practice (University of Wales, Bangor)

Center for Mindfulness in Medicine, Health Care, and Society (University of Massachusetts Medical School)

Mindfulness Practice Center (University of Vermont)

UCSD Center for Mindfulness

etcetera...

What is mindfulness? According to Wikipedia, mindfulness is

the practice whereby a person is intentionally aware of his or her thoughts and actions in the present moment, non-judgmentally. Mindfulness is applied to both bodily actions and the mind's own thoughts and feelings.

One of the pioneers in this area is Richie Davidson, director of the Laboratory for Affective Neuroscience at the University of Wisconsin. Certainly, this topic can cover an entire blog, but in terms of neuroimaging studies, the literature on mindfulness-based meditation is sparse. However, two preliminary experiments were reported at conferences and summarized by Cahn and Polich (2006) in their comprehensive review, Meditation States and Traits: EEG, ERP, and Neuroimaging Studies. One of these fMRI studies (Baerentsen, 2001), and another one by Ritskes et al. (2003), employed 45 sec on/45 sec off bouts of meditation/rest (not entirely conducive to entering the appropriate state). At any rate, Baerentsen (2001) reported activations in the dorsolateral prefrontal cortex (PFC), anterior cingulate cortex (ACC), hippocampus, and right temporal lobe, and deactivations in the visual cortex. Ritskes et al. (2003) also reported increased activity in dorsolateral PFC (R>L) plus the basal ganglia. They saw decreased activity in the occipital lobe but also in the anterior cingulate (in contrast to Baerentsen, 2001). Hmm. Anyway. Commonalities include deactivation in the occipital cortex (which is activated in the past/future studies, presumably due to imagery) and activation in dorsolateral PFC.

At first glance, the latter finding seems curious because dorsolateral PFC is involved in attention, working memory, and other executive control-type functions. Although meditation is relaxing, it is

a state of concentrated attention on some object of thought or awareness.

This point was stressed by Lazar and colleagues (2000), who reported greater activity in dorsolateral PFC, parietal lobe, ACC, striatum, hippocampus/parahippocampus, etc. during the practice of Kundalini meditation, which involves a focus on breathing and silent repetition of phrases during inhalation and exhalation.

Another unpublished study compared two forms of meditation: Kundalini (mantra-based) or Vipassana (mindfulness-based). These were contrasted with control conditions of rest, random number generation, and paced breathing (Lazar et al., 2003). Similar (but nonoverlapping) regions in frontal and parietal cortices and some subcortical areas were more active during the two types of meditation than during the control conditions. A common area of activation was in the dorsal ACC. Overall, these findings suggest a focused state of attention during meditation, which engages an attentional network (mostly) unlike what is seen in studies of past and future time travel. Areas common to reflecting upon the past, present, and future include the hippocampus and parahippocampal gyrus.

References

Addis DR, Wong AT, Schacter DL. (2007). Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration. Neuropsychologia 45: 1378-1385.

Baerentsen KB. (2001). Onset of meditation explored with fMRI. Neuroimage 13: S297.

Cahn BR, Polich J (2006). Meditation States and Traits: EEG, ERP, and Neuroimaging Studies. Psych Bull. 132: 180-211.

Lazar SW, Rosman IS, Vangel M, Rao V, Dusek, H, Benson H, et al. (2003, November). Functional brain imaging of mindfulness and mantra-based meditation. Paper presented at the meeting of the Society for Neuroscience, New Orleans, LA.

Lazar SW, Bush G, Gollub RL, Fricchione GL, Khalsa G, Benson H. (2000). Functional brain mapping of the relaxation response and meditation. NeuroReport 11: 1581-1585.

Okuda J, Fujii T, Ohtake H, Tsukiura T, Tanji K, Suzuki K, et al. (2003). Thinking of the future and the past: The roles of the frontal pole and the medial temporal lobes. Neuroimage 19: 1369–1380.

Ritskes, R., Ritskes-Hoitinga, M., Stodkilde-Jorgensen, H., Baerentsen, K., & Hartman, T. (2003). MRI scanning during Zen meditation: The picture of enlightenment? Constructivism in the Human Sciences 8: 85-90.

Szpunar KK, Watson JM, McDermott KB. (2007). Neural substrates of envisioning the future. Proc. Natl. Acad. Sci. Published online before print January 3, 2007.