Background: Attention-Deficit Hyperactivity Disorder (ADHD) is defined as the most

Magnetoencephalography (MEG) allows the real-time recording of neural activity and oscillatory activity in distributed neural networks. We applied a non-linear complexity analysis to resting-state neural activity as measured using whole-head MEG. Recordings were obtained from 20 unmeditated patients with major depressive disorder and 19 matched healthy controls. Subsequently, after 6 months of pharmacological treatment with the antidepressant mirtazapine 30mg/day, patients received a second MEG scan. A measure of the complexity of neural signals, the Lempel-Ziv Complexity (LZC), was derived from the MEG time series. We found that depressed patients showed higher pre-treatment complexity values compared with controls, and that complexity values decreased after 6 months of effective pharmacological treatment, although this effect was statistically significant only in younger patients. The main treatment effect was to recover the tendency observed in controls of a positive correlation between age and complexity values. Importantly, the reduction of complexity with treatment correlated with the degree of clinical symptom remission. We suggest that LZC, a formal measure of neural activity complexity, is sensitive to the dynamic physiological changes observed in depression and may potentially offer an objective marker of depression and its remission after treatment.

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Over three months of intensive training with a tactile stimulation device, 18 blind and 10 blindfolded seeing subjects improved in their ability to identify geometric figures by touch. Seven blind subjects spontaneously reported ‘visual qualia’, the subjective sensation of seeing flashes of light congruent with tactile stimuli. In the latter subjects tactile stimulation evoked activation of occipital cortex on electroencephalography (EEG). None of the blind subjects who failed to experience visual qualia, despite identical tactile stimulation training, showed EEG recruitment of occipital cortex. None of the blindfolded seeing humans reported visual-like sensations during tactile stimulation. These findings support the notion that the conscious experience of seeing is linked to the activation of occipital brain regions in people with blindness. Moreover, the findings indicate that provision of visual information can be achieved through non-visual sensory modalities which may help to minimize the disability of blind individuals, affording them some degree of object recognition and navigation aid.

The brain magnetic activity patterns in a high load probe-letter (targets and distractors) memory task were examined in patients with Alzheimers's disease (AD) and elderly controls. Control subjects showed a higher number of activity sources over the temporal and parietal cortex between 400 and 700 ms after stimulus onset. However, AD patients showed a higher number of sources over the frontal motor areas, including Broca's and the insula. The number of activity sources on the left parietal areas in response to the target stimuli predicted the AD score oncognitive (MMSE, CAMCOG) and functional staging (FAST) scales. These results suggest that a high information load reveals a deficient functioning of phonological store and reduced task-related activity in temporal and parietal areas, manifesting in a rapid information trace decay. The increased levels of activity in motor areas may reflect a compensatory strategy in an attempt to facilitate rehearsal speed.