29 research outputs found
Stochastic Resonance Modulates Neural Synchronization within and between Cortical Sources
Neural synchronization is a mechanism whereby functionally specific brain regions establish transient networks for perception, cognition, and action. Direct addition of weak noise (fast random fluctuations) to various neural systems enhances synchronization through the mechanism of stochastic resonance (SR). Moreover, SR also occurs in human perception, cognition, and action. Perception, cognition, and action are closely correlated with, and may depend upon, synchronized oscillations within specialized brain networks. We tested the hypothesis that SR-mediated neural synchronization occurs within and between functionally relevant brain areas and thus could be responsible for behavioral SR. We measured the 40-Hz transient response of the human auditory cortex to brief pure tones. This response arises when the ongoing, random-phase, 40-Hz activity of a group of tuned neurons in the auditory cortex becomes synchronized in response to the onset of an above-threshold sound at its “preferred” frequency. We presented a stream of near-threshold standard sounds in various levels of added broadband noise and measured subjects' 40-Hz response to the standards in a deviant-detection paradigm using high-density EEG. We used independent component analysis and dipole fitting to locate neural sources of the 40-Hz response in bilateral auditory cortex, left posterior cingulate cortex and left superior frontal gyrus. We found that added noise enhanced the 40-Hz response in all these areas. Moreover, added noise also increased the synchronization between these regions in alpha and gamma frequency bands both during and after the 40-Hz response. Our results demonstrate neural SR in several functionally specific brain regions, including areas not traditionally thought to contribute to the auditory 40-Hz transient response. In addition, we demonstrated SR in the synchronization between these brain regions. Thus, both intra- and inter-regional synchronization of neural activity are facilitated by the addition of moderate amounts of random noise. Because the noise levels in the brain fluctuate with arousal system activity, particularly across sleep-wake cycles, optimal neural noise levels, and thus SR, could be involved in optimizing the formation of task-relevant brain networks at several scales under normal conditions
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Diet modulates brain network stability, a biomarker for brain aging, in young adults
Epidemiological studies suggest that insulin resistance accelerates progression of age-based cognitive impairment, which neuroimaging has linked to brain glucose hypometabolism. As cellular inputs, ketones increase Gibbs free energy change for ATP by 27% compared to glucose. Here we test whether dietary changes are capable of modulating sustained functional communication between brain regions (network stability) by changing their predominant dietary fuel from glucose to ketones. We first established network stability as a biomarker for brain aging using two large-scale (n = 292, ages 20 to 85 y; n = 636, ages 18 to 88 y) 3 T functional MRI (fMRI) datasets. To determine whether diet can influence brain network stability, we additionally scanned 42 adults, age < 50 y, using ultrahigh-field (7 T) ultrafast (802 ms) fMRI optimized for single-participant-level detection sensitivity. One cohort was scanned under standard diet, overnight fasting, and ketogenic diet conditions. To isolate the impact of fuel type, an independent overnight fasted cohort was scanned before and after administration of a calorie-matched glucose and exogenous ketone ester (D-β-hydroxybutyrate) bolus. Across the life span, brain network destabilization correlated with decreased brain activity and cognitive acuity. Effects emerged at 47 y, with the most rapid degeneration occurring at 60 y. Networks were destabilized by glucose and stabilized by ketones, irrespective of whether ketosis was achieved with a ketogenic diet or exogenous ketone ester. Together, our results suggest that brain network destabilization may reflect early signs of hypometabolism, associated with dementia. Dietary interventions resulting in ketone utilization increase available energy and thus may show potential in protecting the aging brain
Neuroepigenetic signatures of age and sex in the living human brain
Age- and sex-related alterations in gene transcription have been demonstrated, however the underlying mechanisms are unresolved. Neuroepigenetic pathways regulate gene transcription in the brain. Here, we measure in vivo expression of the epigenetic enzymes, histone deacetylases (HDACs), across healthy human aging and between sexes using [11C]Martinostat positron emission tomography (PET) neuroimaging (n = 41). Relative HDAC expression increases with age in cerebral white matter, and correlates with age-associated disruptions in white matter microstructure. A post mortem study confirmed that HDAC1 and HDAC2 paralogs are elevated in white matter tissue from elderly donors. There are also sex-specific in vivo HDAC expression differences in brain regions associated with emotion and memory, including the amygdala and hippocampus. Hippocampus and white matter HDAC expression negatively correlates with emotion regulation skills (n = 23). Age and sex are associated with HDAC expression in vivo, which could drive age- and sex-related transcriptional changes and impact human behavior
Evaluation as a Tool for Research and Development: Issues and Trends in Its Applications in Educational Technology
Functional Connectivity Estimated from Intracranial EEG Predicts Surgical Outcome in Intractable Temporal Lobe Epilepsy
Aberrant Neuromagnetic Activation in the Motor Cortex in Children with Acute Migraine: A Magnetoencephalography Study
Bottom-up communication: Identifying opportunities and limitations through an exploratory field-based evaluation
Full article available via Springerlink.comCommunication to promote behaviours like
energy saving can use significant resources. What is less
clear is the comparative value of different approaches
available to communicators. While it is generally agreed
that ‘bottom-up’ approaches, where individuals are actively
involved rather than passive, are preferable to
‘top-down’ authority-led projects, there is a dearth of
evidence that verifies why this should be. Additionally,
while the literature has examined the mechanics of the
different approaches, there has been less attention paid
to the associated psychological implications. This paper
reports on an exploratory comparative study that examined
the effects of six distinct communication activities.
The activities used different communication approaches,
some participative and others more top-down informational.
Two theories, from behavioural studies and communication,
were used to identify key variables for
consideration in this field-based evaluation. The evaluation
aimed to assess not just which activity might be
most successful, as this has limited generalisability, but
to also gain insight into what psychological impacts
might contribute to success. Analysis found support for
the general hypothesis that bottom-up approaches have
more impact on behaviour change than top-down. The
study also identified that, in this instance, the difference
in reported behaviour across the activities related partly
to the extent to which intentions to change behaviour
were implemented. One possible explanation for the
difference in reported behaviour change across the activities
is that a bottom-up approach may offer a supportive
environment where participants can discuss
progress with like-minded individuals. A further possible
explanation is that despite controlling for intention at
an individual level, the pre-existence of strong intentions
may have an effect on group success. These suggestive
findings point toward the critical need for
additional and larger-scale studies. The challenges associated
with field-based evaluative research and the role
of theory are discussed. The design approach and measures
used in this study may be useful to other evaluations
that seek to compare different communicative
approaches.The research discussed in this article was funded by a bursary from the UK Engineering and Physical Sciences Research Council