Tools for diagnosing Alzheimer’s disease in early stage

Alzheimer’s disease is a slow and progressively wors-

ening disease of the brain, characterised by damage

to specific brain regions. Diagnosis of the disease at

the earliest possible stage has high priority because

medications are available to slow the symptoms of

its progress.

Approximately 70,000 people in Finland suffer from

Alzheimer’s disease.

Progressive memory disorders have become a major

challenge to health care in Europe and the United

States. It has been estimated that, among these diseases,

Alzheimer’s disease alone causes costs equivalent to

about one percent of the world’s GNP. The number of

these patients is expected to double in the next 20 years.

As many as 120,000 people in Finland suffer from the

syndrome of mild cognitive impairment.

Sensory gating and Alzheimer’s diseaseA group of researchers in SalWe’s Mind and Body Pro-

gramme has been studying the presence of the sen-

sory gating deficit in mild cognitive impairment and

Alzheimer’s disease by using auditory event-related

potentials. The group consists of researchers from the

hospital district of Helsinki and Uusimaa, the Univer-

sity of Helsinki and Aalto University.

A project launched in SalWe’s Mind and Body Programme has focused on studying the diagnosis of mild cognitive impairment and Alzheimer’s disease, by using auditory event-related potentials.

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SalWe - Strategic Centre for Science, Technology and Innovation in Health and Well-being

“The brain’s ability to inhibit incoming repetitive and

irrelevant sensory inputs, and thus to avoid sensory

overload, is known as sensory gating. The mechanism

is thought to be related to the cholinergic deficit that

is a feature of Alzheimer’s disease,” says Sara Lil-jander, a specialising medical physicist at the depart-

ment of clinical neurophysiology of Jorvi Hospital.

When brief changes in the electrical activity of the

brain, caused by an external stimulus, are linked to

a task given to the subject and the subject’s men-

tal state, the responses are called event-related po-

tentials, or ERPs. Cognitive potentials are generated

in connection with a memory task, recognition of a

stimulus or some other cognitive process.

“ERPs offer an objective, non-invasive and cost-ef-

fective method for testing cognitive processes and

sensory gating.”

Towards a diagnostic solutionThe research was carried out on three groups: patients

with mild cognitive impairment, patients with incipi-

ent Alzheimer’s disease and a normal control group.

Audio stimuli were delivered to both ears via head-

phones and the state of brain electrical activity was

recorded with an electroencephalogram EEG.

“The study confirms that the brain’s sensory gating

mechanism is impaired among patients with mild cog-

nitive impairment and Alzheimer’s disease. The results

also suggest that auditory ERPs are applicable to in-

dividual diagnosis of organic brain diseases. It may

even be possible to use ERPs to distinguish incipient

Alzheimer’s disease from mild cognitive impairment,”

Sara Liljander explains.

It is possible that GE Healthcare Finland and Elekta

use the research findings in their existing measuring

technology.

Lisätietoja

Sara Liljander specialising medical physicist HUS Medical Imaging Center Jorvi hospitalClinical neurophysiologysara.liljander@hus.fi+358 50 428 4308

Juhani V. Partanen docent, chief physician HUS Medical Imaging CenterJorvi hospitalClinical neurophysiologyjuhani.v.partanen@hus.fi

“Sensory gating is impaired among patients with mild cognitive impairment and Alzheimer’s disease.”

Sara Liljander, HUS Medical Imaging Center

SalWe - Strategic Centre for Science, Technology and Innovation in Health and Well-being