Current Projects

Control of fingertip forces in object lifting and weight perception

When picking up an object, the forces applied by the fingertips have to be scaled to the weight of the object. Object information, such as size or material, can be used to make a motor plan. If the initially planned forces are incorrect, online sensory feedback loops can be used to correct the movement. This project investigates how visual and haptic information is used to plan and control fingertip forces in object lifting and how this interacts with how you perceive the weight of this object. To do this, I use differently weighted cubes, force sensors and a virtual reality environment.

Figure An object is lifted in virtual reality (left) or from force sensors (right) to measure the force scaling towards objects of different weights.

Role of motor and sensory brain areas: use of TMS

To study the role of brain areas that are important for motor control and object perception, I use transcranial magnetic stimulation (TMS). With this tool, I can temporarily disrupt or measure processes in a specific brain area. If this area is involved in a specific task, such as force control or sensory processing, a change in behavioural performance can be measured.

Figure A TMS coil placed on a participant’s head.

PhD Projects

Haptic perception of object properties

When perceiving an object using your sense of touch, some object properties are processed more efficiently than others. Such properties are immediately detected among others whereas other properties are much more difficult to perceive. As part of my PhD thesis, I have found that the haptic properties movability, hardness and softness were processed very efficiently. In addition, I found that combining information about texture and shape could improve object detection, but salient properties could also disrupt the detection of other properties.

Figure Search tasks can be used to investigate the processing efficiency of properties. The presence of a target object with a specific property has to be detected among distractor objects. Objects can be held in the hand, or placed on a surface.

Haptic exploration of object properties

Haptic perception is an active process: you move your hand to better perceive the properties of the object you are exploring. These exploration movements are adapted to the properties you want to perceive. How these movements are adapted when searching for a specific object among others is a question that was investigated in this project.

Figure If the object property is easy to perceive, the movement will be more efficient and quick (light blue trace) compared to a property that is difficult to perceive for which a more detailed exploration is needed (dark blue trace).