Neural evidence for impaired action selection in right hemiparetic cerebral palsy M. van Elka, C. Crajé, M.E.G.V. Beeren, B. Steenbergen, H.T. van Schie, H. Bekkering Brain research (2010)

Cerebral palsy An umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement

Cerebral palsy Risk factors – Premature – Birth defect – Abnormal fetal position – Low birth weight

Cerebral palsy Classification – Hemiplegia – Diplegia – Quadriplegia Type of CP – Spastic – Athetoid/dyskinetic – Ataxic – Hytonic

Cerebral palsy Associated problems – Muscle spastic, abnormal muscle tone – Ataxia – Sensory problem – Seizures – Articulation problem

EEG & ERPs Electroencephalography (EEG) – A procedure that measures electrical activity of the brain through the skull and scalp Event-related potential (ERPs) – A part of potential in the EEG record after stimulus or event – Use to see the brain response to the stimulus actiCAP

ERPs Visual sensory responses – P1: Visual, direction of spatial attention – N1: Discrimination task – P2: Target discern Auditory sensory responses – N1 – N2 Family – P3 Family

Introduction Action planning – The ability to anticipate upcoming actions when preparing a movement – Involves the selection of the correct motor program Andersen et. al., 2009

Introduction Left hemisphere is dominance for action planning. Therefore planning problems are more severe in CP with right side body involvement Craje et al., 2009; Mutsaarts et al., 2007 HCP failed to anticipate the fingertip forces required for smoothly grasping an object Duff et. al., 2003

Introduction HCP often grasped objects with an initial comfortable grip, even if that resulted in an awkward end posture or task failures Mutsaarts et al., 2006; Steenbergen et al., 2004 HCP have poor action selection ability Chen et. al., 2007; Steenbergen et. al., 2004

Introduction A larger P2 amplitude is observed for stimuli with a to-be-attended and the evaluation of task-relevant stimuli Kenemans et al., 1993; Potts, 2004; Smid et al., 1999 P2 reflects an action selection mechanism, action preparation, stimulus evaluation and the organization of the up coming motor response Kuhn et al., 2009; Makeig et al., 1999; Potts, 2004

Hypothesis Action planning of more complex actions might be accompanied by a stronger anterior P2 component HCP may have a smaller anterior P2 amplitude than control participants HCP may be related to an impaired process of action selection

Method 20 participants : – 10 diagnosis right HCP (3 females, mean age: 18.3 y/o, SD: 1.2 y/o) – 10 neurologically healthy control participants (2 males, mean age: 19.7 y/o, SD: 2.2 y/o) Hand function test – Box and Blocks test – Purdue Pegboard test 13

Hand function test

Experimental setup Device consisted of: – A wooden disk (diameter 40 cm) with 6 LEDs – A hexagonal knob (diameter 11 cm, depth 6 cm) freely rotate on the vertical axis – A button Mutsaarts et al., 2005,

Experimental setup Rotation angle – Clockwise (CW): 60°, 120° and 180° – Counterclockwise (CCW): 60°, 120° and 180° 180 ° 60° 120° 16

Pressed the button LEDs switched on (indicate the angle and direction) Decide how to grasp the knob Release the button Start to rotate the knob 17

Grip types 5 different grip types

Two blocks Action blocks a combination of LEDs – To rotate the disk with a specific angle in a specific direction Verbal blocks a combination of LEDs – To report the number of LEDs that were lighted, after the LEDs switched off

Two blocks

EEG & ERPs EEG measured while participants were preparing actions of varying difficulty The task difficulty were explored by measuring event-related potentials (ERPs)

EEG & ERPs EEG setting – 61 active electrodes placed in an actiCAP – Electrode positions were based on the M-10 – Equidistant 61-Channel-Arrangement ERPs – Cz & FCz

Analysis Analysis of behavioral responses focused on – Reaction times – Grasping times – Rotation times – Errors times ERPs – P2 amplitude

Results - Behavioral results Reaction times – LEDs lighted → release the button Grasping times – Release the button → detection of grasping Rotation times – Detection of grasping → release the hexagon Rotation errors

Reaction times RTs ↑ with rotation angles ↑ Counter-clockwise rotations (777 ms, SE=119 ms) > clockwise rotations (738 ms, SE=104ms)

Grasping times Grasping times ↑ with rotation angles ↑ Counter-clockwise rotations (2077 ms, SE=190ms) > clockwise rotations (1925ms, SE=188ms)

Rotation times Rotation times ↑ with rotation angles ↑ Counter-clockwise rotations (3471 ms, SE=196ms) > clockwise rotations (3198 ms, SE=176ms)

Rotation errors Rotation errors ↑ with rotation angles No effect between groups

Selection of grip types Average number of selection of Grip 3 – HCP > control Control subjects have more anticipatory grip planning HCP subjects often persisted in grasping the hexagon with the same initial comfortable grip, and failing to anticipate the upcoming action

Results – ERPs (Action blocks) P2 amplitude: – P2 amplitude ↑ with rotation angle ↑ – Control subjects (average amplitude=11.7 μV, SE=1.2 μV) > HCP subjects (average amplitude=4.1 μV, SE=1.2 μV)

Results – Peak correlation analysis Functional relation between the P2 amplitude and the behavioral of Cz and FCz P2 amplitude X grasping time: – Significant negative correlations in 60°,120° and 180° rotations

Source analysis Dorsal posterior cingulate cortex (dPCC)

Results – ERPs (Verbal blocks) P2 amplitude – Control subjects (average amplitude=10.1 μV, SE=1.3 μV) > HCP subjects (average amplitude=4.4 μV, SE=1.2 μV) – The amplitude ↑ with rotation angle ↑ in both groups – Amplitude differences slightly more in posterior sites for 180° rotations

Discussion The posterior cingulate cortex (dPCC) – The P2 were localized – Part of the dorsal visual pathway involved in visual processing for action and the control of action – Involved in making predictions of actions, eye- hand coordination and spatial navigation Goodale et al., 2004; Blakemore et al., 1998

Discussion P2 has been suggested to reflect – Action selection process – Relevant visual information – Selection mechanism – Action preparation – Stimulus evaluation Kuhn et al., 2009; Smid et al., 1999

Discussion The stronger P2 amplitude reflects – An increased action selection process incase amore difficult action – Action planning is further supported by our finding – Associated with successful action planning – More efficient grasping

Discussion Action planning–control framework Glover, 2004 The action selection process in HCP is impaired already at an early stage (the visual information and the selection of appropriate action)

Discussion Action planning deficits in hemiplegic due to an impaired process of action selection These findings are line with previous studies, indicating that individuals with HCP show anticipatory action planning deficits Mutsaarts et al., 2006; Steenbergen et al., 2004

Conclusion The anticipatory planning deficits in HCP is due to – Impairments in action selection (at an early stage during action preparation) – Impairments in stimulus evaluation