Brain stimulation for PTSD patients
Sweat response can make stimulators responsive
August 7, 2019
Science Daily/University of Houston
Electrical engineers report that the tiny beads of sweat, which appear in patients experiencing PTSD or other neuropsychiatric disorders can be measured and used to design and more responsive brain stimulator for therapy.
For 8-million adults who suffer from post-traumatic stress disorder in any given year, medication and cognitive therapy have been the treatment protocol. Now, University of Houston assistant professor of electrical engineering Rose T. Faghih is reporting in Frontiers in Neuroscience that a closed-loop brain stimulator, based on sweat response, can be developed not only for PTSD patients, but also for those who suffer an array of neuropsychiatric disorders.
"Sweat primarily helps maintain body temperature; however, tiny bursts of sweat are also released in response to psychologically arousing stimuli. Tracking the associated changes in the conductivity of the skin, which can be seamlessly measured using wearables in real-world settings, thus provides a window into a person's emotions," reports Faghih.
For people with movement disorders like Parkinson's disease and essential tremor, who have not responded to medication, application of high-frequency electric current to the brain, or deep brain stimulation, is regarded as most effective. Electrodes are placed in certain areas of the brain to regulate abnormal functions and a pacemaker-like device, placed in the upper chest, controls the amount of stimulation the brain receives. Open-loop stimulators, the most widely-used, deliver continuous stimulation until manually re-adjusted by a physician. Closed-loop stimulators, which provide stimulation in response to biomarkers of pathologic brain activity, have been developed for movement disorders, but are yet to be explored for the treatment of neuropsychiatric disorders.
Signaling the onset of a PTSD episode, skin develops the tiniest sheen of perspiration. That symptom of the body's fight or flight response signals a change in the skin's electrical conductivity and provides a window into the brain's state of emotional arousal. Using skin conductance to create the framework for a deep brain stimulator seemed logical to Faghih after reviewing group studies of Vietnam combat veterans with PTSD. Among the findings, PTSD subjects had the largest skin conductance responses when confronted with combat-related words. In a similar study comparing Vietnam combat veterans with and without PTSD and non-combat controls, PTSD veterans had the highest baseline skin conductance levels.
"Skin conductance additionally has the advantage of being easily measured with wearable devices that afford convenience, seamless integration into clothing and do not involve risk of surgically implanted sensors," said Faghih.
The ultimate goal will be to develop closed-loop prototypes that can eventually be used for treating patients in a variety of neuropsychiatric disorders. Faghih's graduate researchers Dilranjan Wickramasuriya and Md. Rafiul Amin were first and second authors, respectively, of the article.
https://www.sciencedaily.com/releases/2019/08/190807105630.htm
Mechanism of Hallucinogens' Effects Discovered
February 2, 2007
Science Daily/Cell Press
The brain mechanism underlying the mind-bending effects of hallucinogens such as LSD, mescaline, and psilocybin has been discovered by neuroscientists. They said their discoveries not only shed light on the longtime mystery of how hallucinogens work, but that the findings also offer a pathway to understanding the function of drugs used to treat neuropsychiatric disorders, which are now being used largely without an understanding of their fundamental mechanism.
Stuart Sealfon, Jay Gingrich, and colleagues published their findings in the February 1, 2007 issue of the journal Neuron, published by Cell Press.
Researchers have long known that hallucinogens activate specific receptors in the brain, called 5-HT2A receptors (2ARs), that are normally triggered by the neurotransmitter serotonin. Neurotransmitters are chemicals that one brain cell launches at receptors on another to trigger a nerve impulse in the receiving cell. However, a fundamental mystery has been why other compounds that activate the same receptors are not hallucinogenic.
In their studies, the researchers compared the differences between the effects of LSD and a nonhallucinogenic chemical that also activates 2AR receptors on the mouse neural machinery. Since the animals could not report the kinds of perception-altering effects that humans experience on hallucinogens, the researchers determined hallucinogenic properties by measuring a head twitch response the mice characteristically showed when under hallucinogens but not when under nonhallucinogens.
The scientists concentrated their studies on the cortex of the brain, which earlier studies had shown to be the center for action of the hallucinogens. Their analysis revealed that LSD produced genetic, electrophysiological, and internal cellular signaling responses that were distinctively different from those induced by a nonhallucinogenic compound.
They also explored whether 2ARs were central to the hallucinogenic effect of LSD by producing mice lacking the receptors, but in which receptor activity could be selectively restored in the cortex. The researchers found that mice without functioning receptors showed no hallucinogenic response to LSD, but restoring the receptors rendered LSD hallucinogenic in the animals.
The researchers wrote that "These studies identify the long-elusive neural and signaling mechanisms responsible for the unique effects of hallucinogens."
They also concluded that "The strategy we developed to elucidate [hallucinogen] action should be applicable to [central nervous system]-active compounds, with therapeutic potential in other disorders. Thus, our findings may advance the understanding of neuropsychiatric disorders that have specific pharmacological treatments whose mechanisms of action are not fully understood."
https://www.sciencedaily.com/releases/2007/01/070131135536.htm