Objective: We used emotional (images from the International Affective Picture System – IAPS)¹ and cognitive inputs(visual perturbation in a stepping-over-the-obstacle task) with the aim to investigate the hypothesis of a cognitive and affective processing overload in the genesis of freezing of gait (FoG) in Parkinson’s disease (PD).

Background: FoG is one of the most severe symptoms in PD. It appears as an unpredictable stopping phenomenon during gait and locomotor tasks. The underlying mechanism of freezing is still largely unknown. An emerging hypothesis explores freezing as an information processing overload problem produced by a basal ganglia faulty output control in cognitive, limbic and motor neural networks²

Method: We recruited 12 PD patients with FoG, 11 patients without FoG, and 15 healthy elderly controls. Participants underwent neurological, neuropsychological, and affective state assessments. The emotional stimuli were 20 different images taken from the IAPS system (10 with positive valence, 10 with negative valence, all with a medium level of rating in the arousal). The cognitive stimulus was the obstacle with a light placed on the top.
Participants were placed at the beginning of a walkway and were asked to look at a screen placed at the other end, where the IAPS images were presented. The obstacle was positioned in the middle of the walkway (set at 10% of participants’ height). The participants were asked to walk and step over the obstacle, and in half of the trials, when the subject began the last step before overcoming the obstacle, the light on the top was turned on randomly.

Results: In PD with FoG, the clearance (vertical distance between the foot and the obstacle during the crossing step) was modulated by the valence of the emotional image when the light was off (lower step clearance in response to unpleasant images p=0.020), but not when the light was on.
Moreover, results showed slower reaction times in response to unpleasant images (p=0.028), and longer times to approach (p=0.012) and cross (p=0.023) the obstacle when unpleasant images were presented. A similar slowing is present in the mean velocity of the crossing step in response to unpleasant images ((p=0.044).

Conclusion: Our data support the hypothesis that the increase of cognitive and emotional information processing³, could be relevant in the genesis of freezing episodes during planning and motor control.

References: 1. Lang PJ, Bradley MM, Cuthbert BN. International Affective Picture System (IAPS): affective ratings of pictures and instruction manual.Technical Report A-8. https://doi.org/10.1016/j.epsr.2006.03.016 2. Weiss D, Schoellmann A, Fox MD, Bohnen NI, Factor SA, Nieuwboer A, Hallett M, Lewis SJG. Freezing of gait: understanding the complexity of an enigmatic phenomenon. Brain. 2020 Jan 1;143(1):14-30. doi: 10.1093/brain/awz314. Erratum in: Brain. 2020 Mar 1;143(3):e24. PMID: 31647540; PMCID: PMC6938035. 3. Lagravinese G., Pelosin E., Bonassi G., Carbone F., Abbruzzese G., Avanzino L. Gait Initiation Is Influenced by Emotion Processing in Parkinson’s Disease Patients With Freezing Mov Disord. 2018 Apr;33(4):609-617. doi: 10.1002/mds.27312. Epub 2018 Feb 2

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MDS Abstracts - https://www.mdsabstracts.org/abstract/emotional-and-cognitive-information-processing-in-obstacle-negotiation-in-patient-with-parkinsons-disease-and-freezing/