Misdirected attentional focus in functional tremor, 2021, Huys, Edwards et al

Abstract

A characteristic and intriguing feature of functional neurological disorder is that symptoms typically manifest with attention and improve or disappear with distraction. Attentional phenomena are therefore likely to be important in functional neurological disorder, but exactly how this manifests is unknown. The aim of the study was to establish whether in functional tremor the attentional focus is misdirected, and if this misdirection is detrimental to the movement, or rather reflects a beneficial compensatory strategy.

Patients with a functional action tremor, between the ages of 21-75, were compared to two age and gender matched control groups: healthy controls and patients with an organic action tremor. The groups included between 17 and 28 participants. First, we compared the natural attentional focus on different aspects of a reaching movement (target, ongoing visual feedback, proprioceptive-motor aspect). This revealed that the attentional focus in the functional tremor group, in contrast to both control groups, was directed to ongoing visual feedback from the movement. Next, we established that all groups were able to shift their attentional focus to different aspects of the reaching movement when instructed. Subsequently, the impact of attentional focus on the ongoing visual feedback on movement performance was evaluated under several conditions: the reaching movement was performed with direct, or indirect visual feedback, without any visual feedback, under three different instruction conditions (as accurately as possible/very slowly/very quickly), and finally as a preparatory movement that was supposedly of no importance. Low trajectory length and low movement duration were taken as measures of good motor performance.

For all three groups, motor performance deteriorated with attention to indirect visual feedback, to accuracy, and when instructed to move slowly. It improved without visual feedback and when instructed to move fast. Motor performance improved, in participants with functional tremor only, when the movement was performed as a preparatory movement without any apparent importance.

In addition to providing experimental evidence for improvement with distraction, we found that the normal allocation of attention during aimed movement is altered in functional tremor. Attention is disproportionately directed towards the ongoing visual feedback from the moving hand. This altered attentional focus may be partly responsible for the tremor, since it also worsens motor performance in healthy controls and patients with an organic action tremor. It may have its detrimental impact through interference with automatic movement processes, due to a maladaptive shift from lower- to higher-level motor control circuitry.

Paywall, https://academic.oup.com/brain/advance-article-abstract/doi/10.1093/brain/awab230/6305827

 

Ah, yes, it only rains when I notice that it rains therefore my noticing of raining is what brings rain. Give me unlimited funding please and thank you.

Do these people actually think it's possible to experience tremors without noticing them? Is this what they really believe?

 

One of my nephews couldn't speak when he was young. He had the words in his head, but he couldn't get them out. I forget now what the diagnosis was. However, on rare occasions he would speak a few words and it was because he was so focused on what he was doing at the time that he wasn't thinking about trying to talk. Over time with the help of a speech therapist he was able to learn how to speak by working on rewiring his brain.

I'm finding with myself since having an adverse reaction to the covid vaccine that my arms and legs don't feel as shaky when I am immersed in whatever I am doing. For instance when I'm just doing short walks around the house or yard, I'm very aware of how my legs feel, however, when I'm walking around the grocery store concentrating on shopping, I don't notice that my legs feel strange. It's once I stop that I become aware again of the tingling and shaky feeling.

 

No, I don't see any indication that they think that.
They are studying the effects of focusing on control or action on tremor. Such effects are basic to diagnosis all sorts of tremor and known to all medical students. The intention tremor of cerebellar disease only appears with attempted movement whereas the tremor of Parkinson's disease can vanish during voluntary movement.

I have not read the paper in full but studying the effects of attention of feedback on tremor is a very reasonable way of trying to analyse what is going on. It is likely to give quite a good idea of what level within hindbrain/midbrain or cortex the problem lies.

 

Maybe it's just something completely different but I get what I call the shakes quite badly if I'm not careful. It can affect all limbs - especially ones used most often as part of PEM. It is most annoying and noticeable in the arms and hands.

I soon learnt that when this happens it is absolutely vital to pay attention to the hand/arm with the tremor. Stabbing oneself in the face with your fork while trying to eat will certainly help focus the mind.