When part of a person's brain is damaged due to a stroke, the patient often experiences impaired visual awareness, particularly of the space surrounding one side of their body. As a result, integrating vision is very difficult and the patient has trouble interacting with objects. This condition, called visual neglect or spatial neglect, is experienced by up to 60% of stroke patients and is commonly the result of injury to the right side of the brain (leading to impaired awareness of space on the left side of the body).
According to Dr David Soto of Imperial College London in the UK, who led the study, "Visual neglect can be a very distressing condition for stroke patients. It has a big effect on their day-to-day lives. For example, in extreme cases, patients with visual neglect may eat only the food on the right side of their plate, or shave only half of their face, thus failing to react to certain objects in the environment."
Visual neglect is an important area of scientific study, but until now, the importance of the individual's emotional state in modulating visual awareness has been neglected in research. In this latest study, the team examined three stroke patients who had lost awareness of half of their field of vision, asking them to complete tasks under three conditions: while listening to music they preferred; while listening to music they did not like; and in silence.
Listening to pleasant music has a positive effect on our emotions; this state is often referred to as a 'positive affect'. In healthy individuals, positive affect has been shown to enhance flexibility in problem solving and visual attention. So it was not altogether surprising that all three of the stroke patients were able to identify coloured shapes and red lights in their depleted side of vision much more accurately while they were listening to their preferred music, as compared with the other two conditions.
For example, in one of the tasks, the patients were asked to press a button when they could see a red light appear. One patient pressed the button correctly 65% of the time while listening to his preferred choice of music, but only recognised the light 15% of the time when there was silence or music playing that was not to his liking.
The music was chosen based on the patients' preferences, taking into account their individual tastes. After the study, to ensure that the music did in fact influence the patients' emotional state, they measured its effect on arousal using visual analogue scale ratings for enjoyment, mood and arousal.
Functional magnetic resonance imaging (fMRI) of one patient revealed that the brain was more active in areas linked to positive emotional responses to stimuli when the patient was listening to pleasant music. During this time, the patients' awareness of the visual world was markedly improved.
The researchers believe that positive emotions may result in more efficient signalling in the brain. According to the study: "This has important implications for attempts to remediate this clinically important disorder and, more generally, for understanding the interplay between attention and emotional states.
"We wanted to see if music would improve visual awareness in these patients by influencing the individual's emotional state," explained Dr Soto. While the results are indeed promising, he noted that it is important that a much larger group of patients with visual neglect and with other neuropsychological impairments also be examined.
"Our findings suggest that we should think more carefully about the individual emotional factors in patients with visual neglect and in [...] patients [suffering from other neurological conditions] following a stroke," said Dr Soto. "Music appears to improve awareness because of its positive emotional effect on the patient, so similar beneficial effects may also be gained by making the patient happy in other ways. This is something we are keen to investigate further."
CPA For more information, please visit:
- Imperial College London, http://www.imperial.ac.uk
- Proceedings of the National Academy of Sciences (PNAS), http://www.pnas.org
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