Brain functional alterations are investigated by using imaging technologies such as functional magnetic resonance imaging and electroencephalogram, and by assessing physical anomalies such as changes in chemical levels and bodily functions. Click on the tabs below, or navigate the topics via the section on the left.
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What are catecholamines? Catecholamines are a group of neurotransmitters that include dopamine, norepinephrine, also called noradrenaline, and epinephrine, also called adrenaline. The sympathetic nervous system stimulates the release of catecholamines to mediate adaptive responses to acute stress. Catecholamines are also linked to long-term memory of events that induce strong emotions, including fear. Stress-responsive neurotransmitters released during emotional arousal are thought to enhance the consolidation of fear memory. Hyperresponsiveness in the dopaminergic system is common in individuals who have been exposed to stress, which was associated with PTSD symptoms such as restlessness, nightmares, fear memory, and impulsivity. Over activation of noradrenaline…
What is EEG? Electroencephalography (EEG) uses electrodes on the scalp to measure electrical activity from the brain. Quantitative spectral EEG investigates several waveforms, and so the activity can be measured, but EEG also gives rise to event related potentials (ERP), which measure the EEG activity directly evoked by a stimulus, often using cognitive or perceptual stimuli. P300, also referred to as P3, may be the ERP most suitable for the assessment of PTSD, given that it is well documented, and, with the appropriate stimulus paradigm used, can convey information about attention and working memory processes. P300 refers to a spike…
fMRI and PET
What is fMRI and PET? Functional magnetic resonance imaging (fMRI) measures blood flow to determine activation and deactivation of the specific brain regions. Positron emission tomography (PET) is a nuclear based imaging technique that utilises a radioactive tracer to visualise functional brain activity. The radioisotope tracers are coupled with a biological molecule such as glucose, which is used during cellular metabolism and can be used to highlight areas with changes in metabolic activity. Single-photon emission computed tomography (SPECT) offers more limited spatial and temporal resolution than PET but is less expensive as it does not require a cyclotron in close…
What is GABA? GABA (gamma-aminobutyric acid) is the most important inhibitor of neurotransmitters in the central nervous system and is often dysfunctional in people with mood disorders. It has also been investigated in people with PTSD. GABA can be measured via peripheral levels in plasma, via central levels in cerebrospinal fluid, and in brain regions using proton magnetic resonance spectroscopy. What is the evidence for changes in GABA in people with PTSD? Moderate to low quality evidence found no significant differences in brain GABA levels between people with PTSD and controls. August 2021 Image: ©Molecular Science – stock.adobe.com
What is HPA? The biological response to stress is mediated through the Hypothalamic-Pituitary-Adrenal (HPA) axis and the sympathetic nervous system. Cortisol and the steroid hormone dehydroepiandrosterone (DHEA) and its sulfate form DHEA-S are important for elucidating the role of HPA dysfunctions in PTSD. Stress is a threat to the body’s ability to regulate internal processes following exposure to an adverse event. People adapt physiologically and behaviourally in response to stress to re-establish internal balance. Altered HPA axis activity can be detrimental to physical and psychological health. What is the evidence for HPA dysfunction in people with PTSD? Moderate to high…
What is the immune system? The immune system is the body’s first line of defense and predominantly uses proteins called cytokines that are secreted by immune cells and act to allow cell-to-cell communication. Cytokines include interleukins (IL), interferons (IFN), tumor necrosis factors (TNF), transforming growth factors (TGF), and chemokines. These have influence over many cell types, including T helper lymphocytes (Th cells, or white blood cells) and act to regulate immunological and inflammatory responses to pathogens. They are understood to function as intermediaries between the immune system and the central nervous system (CNS). Alterations of these immune-system mediators could have…
What are neurometabolites? Magnetic resonance spectroscopy has been used to measure levels of metabolites, such as N-acetylaspartate (NAA), creatine (Cr), trimethylamines/ choline containing compounds (Cho) and glutamine (Gln). These derivatives are indirect indicators of biochemical activity. Alteration in levels of NAA/Cr is associated with the protective myelin sheath surrounding neurons, which is used as a marker of neural cell viability. Decreased levels of NAA are associated with neuron death, or injury to the part of the neuron that connects to other cells, the axon. What is the evidence for neurometabolite alterations in people with PTSD? Moderate quality evidence found medium-sized…
What are neuropeptides? Neuropeptides are a class of signaling molecules. They are protein-like molecules that are used by neurons to communicate with each other. Different neuropeptides are involved in different brain functions such as reward, food intake, metabolism, reproduction, social behaviours, and learning. What is the evidence for neuropeptides in people with PTSD? Moderate quality evidence found a large effect of lower neuropeptide Y levels in people with PTSD compared to controls without PTSD. This effect was also found in non-medicated samples. High quality evidence found no significant differences in oxytocin levels between people with PTSD and controls. August 2021…
What are neurotrophins? Neurotrophins, such as brain-derived neurotrophic factor (BDNF), regulate neuronal survival and growth during development. Effects of neurotrophins on neuronal transmission in the hippocampus, cortex, cerebellum, and basal forebrain are important for learning and memory processes. What is the evidence for changes in neurotrophins in people with PTSD? Moderate to low quality evidence found no significant differences in BDNF levels between people with PTSD and controls. August 2021 Image: ©Giovanni Cancem – stock.adobe.com
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