Attention may influence the motor performance and frontal activity. This study will examine the effect of different attentional focus: internal, external and divided attention (dual task) on prefrontal cortical activation (fNIRS) and on gait performance. Thirty older adults and thirty PD will participate in this study.

The subjects will be guided to walk at a normal pace while maintaining the required attentional focus. Subjects will walk on 20 m four times in each of the four different focus conditions :

1. no instructions about the attentional focus
2. internal focus on their feet movements,
3. external focus on two lines drawn on the floor,
4. divided attention (walking while performing an arithmetic task).

A fNIRS system will be used for the prefrontal cortex activation evaluation and FeetMe soles for gait analyses.

Inclusion Criteria:

• For 2 groups :

  • Man or woman 60-85 years old
  • Informed consent obtained

• Group Parkinson : clinical diagnosis of idiopathic Parkinson's Disease, according to the UK Brain Bank criteria.

Exclusion Criteria:

• For 2 groups :

  • Assisted walker
  • Neurological (other than those resulting from Parkinson's disease), cardiologic, rheumatologic disorders
  • Disorders affecting gait.
  • Montreal Cognitive Assessment (MOCA) < 24.
  • Concomitant medication likely to interfere with the results.

• Group Parkinson:

  • freezing
  • Hoehn et Yahr > III