Treatment for the most common mental health problems could be ineffective or even detrimental to about half the population. Photo / 123RF
Treatment for the most common mental health problems could be ineffective or even detrimental to about half the population. Photo / 123RF
Treatment for the most common mental health problems could be ineffective or even detrimental to about half the population, according to a radical new model of emotion in the brain.
Since the 1970s, hundreds of studies have suggested that each hemisphere of the brain is home to a specific type of emotion.
Emotions linked to approaching and engaging with the world - like happiness, pride and anger - lives in the left side of the brain, while emotions associated with avoidance - like disgust and fear - are housed in the right.
But those studies were done almost exclusively on right-handed people.
That simple fact has given us a skewed understanding of how emotion works in the brain, argues Cornell University's Associate Professor Daniel Casasanto.
That longstanding model is, in fact, reversed in left-handed people, whose emotions like alertness and determination are housed in the right side of their brains, Casasanto suggests in a new study.
Even more radical: the location of a person's neural systems for emotion depends on whether they are left-handed, right-handed or somewhere in between, the research shows.
According to a new theory, called the "sword and shield hypothesis", the way we perform actions with our hands determines how emotions are organised in our brains.
Sword fighters of old would wield their swords in their dominant hand to attack the enemy - an approach action - and raise their shields with their non-dominant hand to fend off attack - an avoidance action.
Consistent with these action habits, results show that approach emotions depend on the hemisphere of the brain that controls the dominant "sword" hand, and avoidance emotions on the hemisphere that controls the non-dominant "shield" hand.
The work has implications for a current treatment for recalcitrant anxiety and depression called neural therapy.
Similar to the technique used in the study and approved by the US Food and Drug Administration, it involves a mild electrical stimulation or a magnetic stimulation to the left side of the brain, to encourage approach-related emotions.
But Casasanto's work suggests the treatment could be damaging for left-handed patients. Stimulation on the left would decrease life-affirming approach emotions.
"If you give left-handers the standard treatment, you're probably going to make them worse," Casasanto said.
"And because many people are neither strongly right- nor left-handed, the stimulation won't make any difference for them, because their approach emotions are distributed across both hemispheres," he said.
"This suggests strong righties should get the normal treatment, but they make up only 50 per cent of the population.
"Strong lefties should get the opposite treatment, and people in the middle shouldn't get the treatment at all."
However, Casasanto cautions that this research studied only healthy participants and more work is needed to extend these findings to a clinical setting.
Experts have written a major series of review papers on the past, present, and future of the search for life on other planets. Photo / 123RF
If you're looking for a manual on the hunt for alien life, you're in luck.
Some of the leading experts in the field have written a major series of review papers on the past, present, and future of the search for life on other planets.
Scientists have identified more than 3500 planets around other stars, called exoplanets, and many more will be discovered in the coming decades.
Some of these are rocky, Earth-sized planets that are in the habitable zones of their stars, meaning it's neither too hot nor too cold for liquid water - and possibly life - to exist.
The five papers will serve as a reference for scientists searching for signs of life, called biosignatures, in the data they collect from future telescope observations.
"In less than 30 years, we've gone from not knowing whether planets existed outside our solar system to being able to pinpoint potentially habitable planets and collect data that will enable us to look for the signatures of life," said Edward Schwieterman, a postdoctoral researcher at the University of California.
"These advances offer unprecedented opportunities to answer the age-old question, 'are we alone?', but at the same time demand that we move forward with great care by developing robust models that allow us to seek and identify life with a high degree of certainty."
Schwieterman's paper reviews three types of biosignatures that astrobiologists have previously proposed as markers for life on other planets, all of which must be remotely detected since exoplanets orbit distant stars that we cannot reach in person.
The markers include gaseous biosignatures, which are byproducts of life that can be detected in the atmosphere, such as oxygen; surface biosignatures, which life-induced changes in the absorption and reflection of light on the surface of a planet; and temporal biosignatures, which are time-dependent fluctuations in gaseous or surface biosignatures.
Schwieterman is part of a Nasa-funded group now developing a "search engine" for life on other worlds by delving into our own planet's dynamic, 4.5-billion-year history.
Though dramatically different in terms of atmospheric composition and climate, the different chapters of Earth's history have one thing in common: oceans teeming with a remarkable diversity of simple and complex life.
"We are using Earth to guide our search for life on other planets because it is the only known example we have," explained Distinguished Professor Timothy Lyons, who collaborated on the new papers.
"But Earth actually offers us a great diversity of possibilities.
"Rather than being constrained to a study of present-day life, we use geological and geochemical analyses to examine the billions of years that life survived, evolved, and thrived on Earth under conditions that are very different than today's, hence the concept of 'alternative Earths'."
