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Linking brain hemisphere alterations to behaviour and cognition

The brain is an important organ; not only to sustain life, but also for cognition, language, learning, emotion and other functions. It is divided into two cerebral hemispheres connected by the corpus callosum; these hemispheres are apparently interchangeable in terms of structure and function.
Linking brain hemisphere alterations to behaviour and cognition
Funded by the EU, the project 'A cognitive neuroscientific model of impulsivity and anxiety' (CNMIA) undertook groundbreaking research to study the relation between brain hemispheres and their role in language and behaviour. In particular, the effect of impulsivity and anxiety on linguistic perception and attention control were assessed in normal and clinical patients.

The dichotic listening to words and affects (DLWA) test was used to assess hemisphere function in terms of attentional control and language cognition. The study included normal people as well as those with high impulsivity or anxiety. Results revealed that high anxiety and high impulsivity reduced accuracy and increased distraction when exposed to interference. The left hemisphere (LH) was found to demonstrate perceptual deficits, whereas the right hemisphere (RH) was associated with decreased cognition control in these emotional states. In attention control studies, the LH showed more susceptibility to attention switching and stronger involvement in word processing, while the RH was associated with emotion processing.

During the next stage of the project, an electroencephalogram (EEG) was performed on a patient with left hemispherectomy using words with emotional prosodies. Prosody represents the rhythm, stress and intonation in speech and hemispherectomy is the disconnection or removal of one hemisphere of the brain. An interesting finding was that the RH mimicked LH patterns to enable recovery of language-processing ability in this patient.

Functional magnetic resonance imaging (fMRI) and diffusion MRI were combined with EEG to study differences in hemisphere activity in response to emotionally charged words. Interestingly, results revealed that word processing for emotional intonation has different brain patterns in comparison to a neutral tone. Also, people with low impulsivity had balanced hemisphere activity in response to emotional prosody, unlike the high-impulsivity patients. However, both groups were susceptible to interference when exposed to sad prosody.

Such measures of behaviour, emotion, cognition and other responses could be used as neuro-feedback for normalising behaviour in people with attention and self-control deficits. People suffering from anxiety, attention deficit hyperactivity and other such disorders could then have corrective therapy for a better quality of life.

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