Drivers may be more likely to crash if an obstacle appears at the same time as a heartbeat.
To investigate how the beat of our hearts influences our reaction times, Sarah Garfinkel at the University of Sussex, UK, and her colleagues designed a virtual reality driving game. While participants were driving, obstacles would appear in the road, either in time with a heartbeat or between beats.
When objects coincided with heartbeats, drivers’ reaction times were slower and they were more likely to crash. Garfinkel presented the results, where she discussed the possible effect of systoles – the squeezing of the heart ventricles that occurs in the middle of a heartbeat – on driving.
“If you’re driving and you’re in a highly aroused state and your heart is beating strong and fast, you will have more cardiac systoles, and that is going to impair your reaction time and ability to avoid objects,” she said.
The research adds to a series of studies showing that systoles have an inhibitory effect on the brain’s ability to process stimuli. For example, painful stimuli are perceived as less painful if they coincide with a heartbeat.
Garfinkel previously found an effect on memory, too. If participants are shown words either in time with heartbeats or between beats, they are more likely to forget words that appeared on a beat when tested later.
These effects are thought to be mediated by baroreceptors, blood pressure sensors located in the major arteries. These receptors fire in bursts every time the heart contracts, but as well as helping to regulate blood pressure, they appear to have an inhibitory effect on certain cognitive functions.
According to this hypothesis, “you activate the baroreceptors and you inhibit the brain activity within the cardiac cycle,” says Christopher Ring at the University of Birmingham, UK. Some studies have detected fluctuations in electrical activity in the brain according to the phase of the cardiac cycle.
But our heartbeats may also enhance some neural functions. For example, Garfinkel has found that fearful stimuli are perceived to be more frightening if they appear during a heartbeat.
“There seem to be ‘better’ and ‘worse’ cardiac phases for sensory processing. It’s unclear, however, whether that’s a bug or a feature,” says Michael Gaebler at the Max Planck Institute for Human Cognitive and Brain Sciences in Germany. Noise in the brain may hamper processing of stimuli, or the brain may make use of rhythmic fluctuations in cardiac activity to optimise sensory processing, he says.
Sensory processing is just one step in a complex cascade of events while driving, says Gaebler. “My guess would be that while cardiac-related perceptual fluctuations may contribute [to accidents], a lot of other things have to go wrong to lead to an accident.”Source:Web
