Abstract
Using a common set of mindfulness exercises, mindfulness based stress reduction (MBSR) and mindfulness based cognitive therapy (MBCT) have been shown to reduce distress in chronic pain and decrease risk of depression relapse. These standardized mindfulness (ST-Mindfulness) practices predominantly require attending to breath and body sensations. Here, we offer a novel view of ST-Mindfulness's somatic focus as a form of training for optimizing attentional modulation of 7–14 Hz alpha rhythms that play a key role in filtering inputs to primary sensory neocortex and organizing the flow of sensory information in the brain. In support of the framework, we describe our previous finding that ST-Mindfulness enhanced attentional regulation of alpha in primary somatosensory cortex (SI). The framework allows us to make several predictions. In chronic pain, we predict somatic attention in ST-Mindfulness “de-biases” alpha in SI, freeing up pain-focused attentional resources. In depression relapse, we predict ST-Mindfulness's somatic attention competes with internally focused rumination, as internally focused cognitive processes (including working memory) rely on alpha filtering of sensory input. Our computational model predicts ST-Mindfulness enhances top-down modulation of alpha by facilitating precise alterations in timing and efficacy of SI thalamocortical inputs. We conclude by considering how the framework aligns with Buddhist teachings that mindfulness starts with “mindfulness of the body.” Translating this theory into neurophysiology, we hypothesize that with its somatic focus, mindfulness' top-down alpha rhythm modulation in SI enhances gain control which, in turn, sensitizes practitioners to better detect and regulate when the mind wanders from its somatic focus. This enhanced regulation of somatic mind-wandering may be an important early stage of mindfulness training that leads to enhanced cognitive regulation and metacognition.
Highlights
As a form of mental training, mindfulness meditation has been practiced for over two millennia
The fine topographically specific arrangement of thalamocortical connections from VPm is well suited to adjust alpha rhythmicity locally, while the more diffuse connections from non-lemniscal sources to supragranular layers and SI and other cortical areas is ideal for broader modulations such that refined control of thalamocortical drive enables finer top-down attentional control and filtering of both spatially localized sensory information and whole sensory areas in neocortex (Jones, 2001)
A candidate area for the non-lemniscal thalamic nucleus that projects to SI is the Ventral Medial (VM) thalamus, as depicted in Figure 4, which has been shown to project nearly exclusively to the supragranlular layers in SI (Herkenham, 1980; Desbois and Villanueva, 2001; Rubio-Garrido et al, 2009; Sherman and Guillery, 2009; Theyel et al, 2010)
Summary
As a form of mental training, mindfulness meditation has been practiced for over two millennia. ST-Mindfulness training in a highly extendable mechanism of alpha modulation may account for how ST-Mindfulness, which is centered on a specific set of low-level sensory-attentional meditative tasks, achieves such a general range of positive therapeutic outcomes, possibly by engaging prefrontal cortical areas known to be crucial regulators of thalamocortical circuits during attentionally demanding tasks This view of localized SI alpha modulation training as an enhancer of prefrontal attentional control is consistent with studies showing long-term changes in ST-Mindfulness practitioners in prefrontal cortex (Davidson et al, 2003; Farb et al, 2007, 2010). ST-MINDFULNESS ENHANCES ATTENTIONAL MODULATION OF ALPHA IN OTHER SENSORY AREAS Alpha rhythms in other sensory systems in the cortex (e.g., visual and auditory systems) follow the same general principles as those described above for the somatosensory system with TMS studies causally linking experimentally induced changes in alpha in changes in perception (Romei et al, 2008, 2010), suggesting that our ST-Mindfulness theoretical framework should be generalizable to include top-down modulation of alpha rhythms across sensory neocortex (see Figure 1 for a summary of the framework)
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