Resource: Guido, Frank K.W, Megahn Shott, Carrie Keffler, and Marc-Andre Cornier. “Extremes of Eating Are Associated with Reduced Neural Taste Discrimination.” International Journal of Eating Disorders 49:6 (2016): 603-612.
Taste amongst other senses are important components of food intake. The brains primary taste cortex “the insula” may be altered resulting in how patterns of information regarding food intake is interpreted. The insula connects to higher order brain structures that control how much we eat. Thus the insula could have a role in the pathophysiology of disordered eating regarding taste information transmission. The insula is important for responding to body cues such as hunger or fullness which tend to be altered in eating disorders. In eating disorders, the size and function of the insula is altered. Functional brain imaging typically studies strength of brain activation in response to specific stimuli.
Study 106 women, 27 healthy comparison women, 21 restricting type AN, 19 recovered from AN 20 women BN, and 19 with obesity. Participants completed breakfast based on their meal plan and resonance brain imagining (fMRI) was performed upon completion of meal. The fMRI measured brain activity in regions of the brain. During the fMRI participants were also given 3 test stimuli to evaluate taste- sucrose solution, no solution, and artificial saliva.
This study indicated that Anorexia Nervosa and obesity are associated with reduced taste quality in the insula. In recovered Anorexia Nervosa and Bulimia Nervosa, there was no difference when compared to the healthy comparison group. When contrasting two of the test taste stimuli to remove effects of texture and other sensory stimulation in the mouth there was evidence of encoding differences of the brain specific to taste quality. Thus presenting the possibility of deficits in neuronal encoding of distinct taste qualities in Anorexia Nervosa and obesity. Leptin and other hormones are altered with eating disorders and obesity by affecting taste perception and reducing insula pattern classification due to primary structural changes within the insula or within signaling pathways from other regions of the brain to the insula. The insula is also connected to other pathways that are responsible for internal emotional states. The insula has also been associated with self-recognition (abstract representation with one’s self) as well as gastric distention and self-reported fullness. As a result, many intertwined functions are used for processing and altered on different levels within the insula when presenting with eating disorders or obesity. If normal taste is disturbed, this could possibly lead to altering the normal insula inputs which in turn, may lead to altering other processing centers affect taste and influencing the drive to eat or not to eat. Anorexia Nervosa and obesity also have altered dopamine function, elevated or reduced cognitive control as well as high anxiety resulting in a change in eating pathology when the insula is altered. Therefore, in eating disorders, if there is a diminished insula signal in response to taste, than dopamine levels could have a stronger impact on food choices.