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Top>Research>Focusing on Hypersensitivity


Focusing on Hypersensitivity

Akira Midorikawa
Professor, Faculty of Letters, Chuo University
Area of Specialization: Neuropsychology

The symptoms of dementia

As mentioned in the definition[i], dementia is a brain disease causing gradual decrease in higher functions of the brain such as memory, thought, and recognition.

Though dementia has been depicted in novels and films for a long time, all of the characters in these works view the possibility of suffering from dementia as something to be abhorred and feared.

Unfortunately, even with advances in modern medicine and technology, we are still unable to treat dementia.

The symptoms observed in people with dementia are quite complex. In addition to forgetfulness, which is a disturbance in memory, and executive function disorder, which is a disturbance in thought, symptoms include delusion of something being stolen and wandering. The former are a direct reflection of brain illness; previously, they were known as core symptoms, while recently they are called cognitive impairment. These symptoms are believed to be caused when functions which were supported by specific regions of the brain are lost due to brain illness. On the other hand, the latter are known as peripheral symptoms; more recently, they are called behavioral and psychological symptoms of dementia (BPSD)[ii]. A portion of these symptoms are thought to occur due to interaction between cognitive impairment and the environment surrounding the individual.

For example, in the case of delusion of something being stolen, the cognitive impairment of forgetfulness occurs against a background of uneasiness and loss of family role which had been fulfilled until that point. BPSD is known for affecting the feeling of nursing care burden. Conversely, BPSD can sometimes be alleviated by revising family roles and reducing feelings of uneasiness. Therefore, this means that the claim that “dementia is not treatable” actually refers to cognitive impairment, and the possibility of dealing with BPSD still remains, and effective measures can be taken by family members.

Hypersensitivity hidden behind dementia

Our research group believes that hypersensitivity of the senses is one cause of BPSD. We formed this hypothesis based on measures taken by the family of a certain patient. In that family, the husband had always been gentle and kind; however, together with the progress of dementia, he grew irritable toward his beloved grandchildren. Initially, his wife couldn’t understand the reason for his sudden grumpiness. Nevertheless, she surmised that her husband might be annoyed by the voices of his grandchildren. She decided to spend time together only as a couple, placing some distance between themselves and the rest of their family. Upon making this change, her husband’s irritableness disappeared and they were able to spend peaceful time together. Although the sound of energetic children’s voices had previously made him happy, it seems that it now caused him great distress.

Drawing upon this case example, we started an attempt to understand changes from the onset of dementia through “positive” aspects. As a result, we clarified that many patients experienced sensory changes (hypersensitivity) and positive changes in recognition (refer to graphs below) [iii].

(Abbreviations) AD: Alzheimer’s Disease, bvFTD: behavioral variant frontotemporal dementia

The positive areas of the graphs are functions which increased with the onset of dementia. The negative areas are functions which decreased. It is clear that the onset of symptoms from Alzheimer’s disease and behavioral variant frontotemporal dementia causes an increase in sensory hypersensitivity. Also, in some patients, we observe an increase in visuospatial activities; for example, activities such as puzzles or drawings.

Understanding through similarity

Hypersensitivity is not limited to dementia. In some people with developmental disability (DD) have long been known to suffer from hypersensitivity. Compared to people with typical development, people with DD have acutely sensitive hearing, vision, and touch. In many cases, these acute senses cause distress.

When viewed from the perspective of hypersensitivity, there may be similarities between dementia and DD. On a slightly different note, people who suffer from headaches may be subject to feeling of unpleasantness by specific visual stimuli. In this respect, hypersensitivity may be more common than previously thought.

From April 2018, based on support from JSPS Grant-in-Aid for Scientific Research (A), we started a project entitled “Continuous Understanding of Developmental Disabilities and Dementia through Hypersensitivity” (joint research with Professor Shinichi Koyama of the University of Tsukuba and Dr. Masakazu Ide of the Research Institute of National Rehabilitation Center for Persons with Disabilities). Through this research, we seek to understand the subjective world of people with these illnesses, to explore methods for alleviating their symptoms, and to construct comfortable environments.

  1. ^ “Syndrome normally occurring due to chronic or progressive brain disease, consisting of disturbances to multiple higher brain functions such as memory, consciousness, orientation, understanding, calculation, learning, language, and judgment.” The ICD-10 Classification of Mental and Behavioural Disorders: Clinical descriptions and diagnostic guidelines (Igaku-Shoin Ltd., 2005)
  2. ^ Dementia Disease Diagnosis Guidelines 2017 (Igaku-Shoin Ltd., 2017)
  3. ^ Midorikawa, Akira, et al. "All is not lost: positive behaviors in Alzheimer’s disease and behavioral-variant frontotemporal dementia with disease severity." Journal of Alzheimer's Disease 54.2 (2016): 549-558.
Akira Midorikawa
Professor, Faculty of Letters, Chuo University
Area of Specialization: Neuropsychology
Akira Midorikawa was born in Tokyo in 1971. He graduated from the Chuo University Faculty of Letters in 1995. He completed the Doctoral Program in the Chuo University Graduate School of Letters in 2002. He holds a PhD in education. He is currently researching both positive and negative changes associated with brain functional disorders. His major written works include Clinical Neuropsychology (co-written/edited; Ishiyaku Pub, Inc. 2018), The Neuropsychology of Music (Igaku-Shoin Ltd., 2013), as well as the thesis The Emergence of Artistic Ability Following Traumatic Brain Injury (co-written; Neurocase, 2014) and more.

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