The structural neuroanatomy of music emotion recognition: Evidence from frontotemporal lobar degeneration

Reference:

Rohani, Omar, Susie M.D. Henley, Jonathan W. Bartlett, Julia C. Hailstone, Elizabeth Gordon, Disa A. Sauter, Chris Frost, Sophie K. Scott, and Jason D. Warren. "The structural neuroanatomy of music emotion recognition: Evidence from frontotemporal lobar degeneration." Neuroimage 2011, June 1; 56(3): 1814-1821.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3092986/?tool=pmcentrez

Summary:

Despite growing interest in the neurobiology of music, the brain mechanisms that are critical for processing emotion in music remain incompletely understood. Music is universal and highly valued for the powerful emotional responses it engenders: indeed, music activates brain circuitry associated with pleasure and reward and musical emotion judgments and brain responses are consistent amongst members of a musical culture. Certain music can specifically induce an intense arousal response in normal listeners, and this response is mediated by brain structures such as the amygdala and insula that have been implicated in other kinds of salient emotional stimuli. Deficits of musical emotion comprehension have been reported following focal damage of these same structures, located in the medial prefrontal and anterior temporal lobe.

Frontotemporal lobar degeneration (FTLD) is the name for a group of clinically, pathologically and genetically heterogeneous disorders associated with atrophy in the frontal lobe and temporal lobe of the brain. In the over 65 age group, FTLD is probably the fourth most common cause of dementia after Alzheimer’s disease, dementia with Lewy bodies and vascular dementia. Patients with FTLD frequently exhibit derangements of complex social and emotional behaviour. From a clinical perspective, investigation of musical emotion processing and its cerebral associations in FTLD has the potential to improve the understanding of the disease’s phenomenology, and the intrinsic network connectivity in the working brain.

A human brain showing frontotemporal lobar degeneration.

The idea behind this research was to investigate critical neuroanatomical associations of emotion recognition from music using FTLD as a disease model of brain network breakdown. The research included 26 patients with FTLD and 21 healthy control subjects with no history of neurological, or psychiatric illness. Recognition of four emotions (happiness, sadness, anger, and fear) from music, facial expressions and nonverbal vocal sounds was assessed using a procedure in which subjects were required to match each target stimulus with the most appropriate verbal emotion label in a four-alternative-forced-choice model. The music stimuli were short (approx. 11 s) non-vocal (orchestral and chamber) excerpts drawn from the Western classical canon and film scores. MR brain images were acquired in all FTLD patients at the time of behavioural testing, as well as voxel-based morphometry, a neuroimaging analysis technique that allows investigation of focal differences in brain anatomy.

On neuropsychological evaluation, patients with FTLD showed deficient recognition of canonical emotions (happiness, sadness, anger and fear) from music as well as emotional signals conveyed by facial and vocal expressions compared with healthy control subjects. Impaired recognition of emotions from music was specifically associated with grey matter loss in a distributed cerebral network including insula, orbitofrontal cortex, anterior cingulate and medial prefrontal cortex, anterior temporal and more posterior temporal and parietal cortices, amygdala and the subcortical mesolimbic system. This network of the brain is essential for recognition of musical emotion that overlaps with brain regions previously implicated in coding emotional value, behavioural context, conceptual knowledge and theory of mind. The study also found that amygdala damage was associated with impaired emotion recognition only from music, as opposed to emotion recognition of facial and verbal expressions.

Reflexion:

The ability that music has to affect and manipulate emotions and the brain is undeniable, and yet largely inexplicable. This research identified regions of the brain associated with music emotion recognition, including insula, orbitofrontal cortex, anterior cingulate and medial prefrontal cortex, anterior temporal and more posterior temporal and parietal cortices, amygdala, and striatum. Identifying the neural mechanisms of musical emotion helps us understand how the brain codes emotional value, and how emotional signals acquire meaning.

Following a similar idea, Petr Janata, associate professor of psychology at UC Davis' Center for Mind and Brain, mapped the brain activity of a group of subjects while they listened to music, and found that the region of the brain where memories of our past are supported and retrieved also serves as a hub that links familiar music, memories and emotion. His research may help to explain why music can elicit strong responses from people with Alzheimer's disease. The hub is located in the medial prefrontal cortex region — right behind the forehead — and one of the last areas of the brain to atrophy over the course of the disease.

In Rohani & al.’s study, subjects with frontotemporal lobar degeneration did not respond well to recognition of emotion in music, unlike Alzheimer’s patients in Janata’s study. This was caused by grey matter loss, including the medial prefrontal cortex region, which is linked to memories and emotion. Does memory affect music emotion recognition, or is it just contained in the same medial prefrontal cortex region as is emotion? How does music succeed in prompting emotions within us? And why are these emotions often so powerful?