November 5, 2010

6 More Reasons to Meditate

From: Psychology Today

Why meditate? Outside of religious contexts, the most common reason is stress management. But as these latest research findings demonstrate, meditation is much more than just a relaxation technique. Here are a half-dozen more good reasons to take up meditation.

To enhance concentration
Meditation has an undeserved reputation for being esoteric and difficult to learn. In truth, it’s really nothing more than the practice of focusing the mind intently on a particular thing or activity. It seems logical that regular meditation would hone a person’s powers of concentration, and a recent study in the Journal of Neuroscience found just that. In the study, three months of intensive meditation training led to improvements in attentional stability – the ability to sustain attention without frequent lapses.

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February 17, 2009

The Default Mode Network and Self-Referential Processes in Depression

In a recent study, Sheline and colleagues examined whether patients with major depression were impaired in their ability to regulate the activity of the default mode network, which is characterized by self-referential functions.  To do so, they used fMRI to measure changes in brain activity occurring within this network in 20 individuals with major depression and 21 demographically similar control participants.  The depressed and healthy control participants were asked to examine negative pictures passively and also to reappraise them actively. 

In contrast to the depressed participants, the healthy control participants demonstrated reduced activity in widely distributed regions of the default mode network (ventromedial prefrontal cortex, prefrontal cortex, anterior cingulate, lateral parietal cortex, and lateral temporal cortex) while looking at the negative pictures and reappraising them.  Moreover, compared to the healthy control participants, the depressed participants demonstrated a larger increase in activity in other default mode network regions (amygdala, parahippocampus, and hippocampus) while they looked at negative pictures. 

Based on these data, Sheline and colleagues suggest that depression is characterized by both a stimulus-induced increase in brain activity and a failure to broadly decrease the activity of the default mode network.  Further, the authors suggest that these findings provide a brain network framework within which to consider the pathophysiology of depression.

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January 31, 2009

Hyperactivity and Hyperconnectivity of the Default Network in Schizophrenia and in First-degree Relatives of Persons with Schizophrenia

Susan Whitfield-Gabrieli, Heidi W. Thermenos, Snezana Milanovic, Ming T. Tsuang, Stephen V. Faraone, Robert W. McCarley, Martha E. Shenton, Alan I. Green, Alfonso Nieto-Castanon, Peter LaViolette, Joanne Wojcik, John D. E. Gabrieli and Larry J. Seidman
Article in PNAS

We examined the status of the neural network mediating the default mode of brain function, which typically exhibits greater activation during rest than during task, in patients in the early phase of schizophrenia and in young first-degree relatives of persons with schizophrenia. During functional MRI, patients, relatives, and controls alternated between rest and performance of working memory (WM) tasks. As expected, controls exhibited task-related suppression of activation in the default network, including medial prefrontal cortex (MPFC) and posterior cingulate cortex/precuneus. Patients and relatives exhibited significantly reduced task-related suppression in MPFC, and these reductions remained after controlling for performance. Increased task-related MPFC suppression correlated with better WM performance in patients and relatives and with less psychopathology in all 3 groups. For WM task performance, patients and relatives had greater activation in right dorsolateral prefrontal cortex (DLPFC) than controls. During rest and task, patients and relatives exhibited abnormally high functional connectivity within the default network. The magnitudes of default network connectivity during rest and task correlated with psychopathology in the patients. Further, during both rest and task, patients exhibited reduced anticorrelations between MPFC and DLPFC, a region that was hyperactivated by patients and relatives during WM performance. Among patients, the magnitude of MPFC task suppression negatively correlated with default connectivity, suggesting an association between the hyperactivation and hyperconnectivity in schizophrenia. Hyperactivation (reduced task-related suppression) of default regions and hyperconnectivity of the default network may contribute to disturbances of thought in schizophrenia and risk for the illness.

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January 12, 2008

Neuronal correlates of “free will” are associated with regional specialization in the human intrinsic/default network

Ilan Goldberg, Shimon Ullman and Rafael Malach
In press article in Consciousness & Cognition

Recently, we proposed a fundamental subdivision of the human cortex into two complementary networks-an ‘‘extrinsic” one which deals with the external environment, and an ‘‘intrinsic” one which largely overlaps with the ‘‘default mode” system, and deals with internally oriented and endogenous mental processes. Here we tested this hypothesis by contrasting decision making under external and internally-derived conditions. Subjects were presented with an external cue, and were required to either follow an external instruction (‘‘determined” condition) or to ignore it and follow a voluntary decision process (‘‘free-will” condition). Our results show that a well defined component of the intrinsic system-the right inferior parietal cortex-was preferentially activated during the ‘‘free-will” condition. Importantly, this activity was significantly higher than the base-line resting state. The results support a self-related role for the intrinsic system and provide clear evidence for both hemispheric and regional specialization in the human intrinsic system.

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