Disorders in semantic memory or so called memory of things and matters have until now been little observed in MS. Neuropsychologist Sari Laatu’s doctoral thesis published in the summer 2003 ascertains that disorders in this memory area, that is an area combined of things and matters, are possible in MS. On the other hand, all affected do not experience disorders.

Laatu’s research deepens knowledge about cognitive disorders in MS. Cognitive disorders include difficulties in remembering, learning, concentration, drawing conclusions, finding and identifying words.

Difficulty in remembering has known to be one of the most typical cognitive symptoms in MS. However, more often researched than semantic memory has been episodic memory, which is a combination of all events during a lifetime.

Now researched semantic memory is a partial area of the memory and it includes all general knowledge about the world gathered during a lifetime. This knowledge is based on concepts. For example based on this we know what a certain animal looks like, what is the taste of a strawberry, how household machines are functioning and what do the words comedy and daughter-in-law mean.

In quality research, the experience of understanding the knowledge was emphasised. The approach is new, because interest in research has generally been targeted on unconscious memory.

‘It was important to me to research how a person consciously experiences the remembering of things. Conscious understanding gives a meaning to the activities and to the content of a discussion.’

Disorders of semantic memory are individual
Two different MS studies included 42 persons affected by MS, some of whom had cognitive disorders and some who were without cognitive symptoms. All in the study had been affected for a relatively short time, several years only.

Two different methods were used in the study. In linguistic exercises the persons were asked to describe and explain different concepts (e.g. what does a peach look like or a penguin, what does a notion bachelor or news mean). In addition the people evaluated the importance of a quality of the concept (e.g. is a diamond always a jewel, a metal, expensive or hard) and connections between the concepts (e.g. is a tomato a fruit, a vegetable or a root).

In visual exercises impulses were given as pictures on a computer. The aim was to examine the speed and accuracy of the person to recognise the pictures of items and animals.

The study reinforces the fact that disorders in semantic memory can belong to the MS disease.

‘Many people experienced some sort of difficulty during the exercise, but some did not experience at all. It is important to observe that disturbances in semantic memory vary between patients. Different exercises were difficult to different patients.’

It is assumed that disturbance in semantic memory is not the first cognitive symptom of MS. All who seemed to have difficulties in semantic memory exercises also had other cognitive symptoms.

The research study does not give a direct answer concerning the frequency and propagation of disturbances. They are however thought to be quite general, because they were distinctly appearing in so a small experiment. In general it is estimated that about half of persons with MS have cognitive, other than semantic, disturbances of different degree.

‘New tests used in this research were extremely sensitive and found even slight disturbances. Although the disturbances were noticed in exact tests, slight disturbances do not have a marked effect in practice’.

There have not been earlier direct and sensitive methods to study semantic memory. Dr Laatu hoped to exploit her study and develop the methods used into simpler versions suitable to a larger clinical work with the patients.

Knowledge has diminished bewilderment
For many patients who participated in the study, knowledge about semantic disorders has been a relief - perhaps a small surprise, but now the cause is clear. Difficulties in remembering what had happened are easier to accept, but when one does not find the right item on the shelves of a store, or cannot interpret a traffic sign or when understanding conversation and self expression are difficult, bewilderment is usually major.

'Many studied persons had been shy to talk about these odd symptoms. An explanation has been found for these during the research, which has facilitated the understanding of own symptoms', Dr Laatu explains.

Sometimes in the background of memory disorders there can be found some other cause like exacerbation, stress, fatigue or depression, which can momentarily weaken cognitive functions. The most important thing is to always take care of memory disorders, if a person affected mentions them. Research diminishes uncertainty and if disorders occur, research can help to together study whether they have an impact in a daily life.


Neuropsychologist Satu Laatu works in the Masku Neurological Rehabilitation Centre, Finland. She received her PhD in psychology in Turku University, in June.