The impact of unilateral brain damage on weight perception, sensorimotor anticipation, and fingertip force adaptation

- Patients with right brain injury experienced a size- and material-weight illusion.
- Patients with left brain injury experienced only a size-weight illusion.
- Age-matched controls also experienced no material-weight illusion.
- Patients used material properties to guide the application of grip and lift forces.

Damage to the left parietal cortex can lead to apraxia - a selective deficit in tool use and action planning. There is conflicting evidence as to whether this disorder affects more fundamental motor parameters, such as applying the appropriate forces to lift objects based upon how heavy they look. Here we examined how individuals with left and right-lateralized brain damage lift and perceive the weight of objects of the same mass which vary in their size and material properties. No clear differences emerged between the groups in terms of how visual material properties affected their perceptions of object weight or their initial application of grip and load forces. There was, however, some evidence that unilateral brain injury impaired the use of size cues for the parameterization of grip forces.