Neuropsychologia 39 (2001) 173–183
The preparation and execution of saccadic eye and goal-directed
hand movements in patients with Parkinson’s disease
Harold Bekkering
a,
*, Sebastiaan F.W. Neggers
a
, Robin Walker
b
, Brigitte Gleißner
a
,
Winand H. Dittrich
c
, Christopher Kennard
c
a
Department of Cognition and Action, Max-Planck-Institute for Psychological Research, Amalienstr.
33
, D-
80799
Munich, Germany
b
Department of Psychology, Royal Holloway Uni6ersity of London Egham, Surrey TW
20
OEX, UK
c
Department of Sensorimotor Systems, Di6ision of Neuroscience and Psychological Medicine, Imperial College School of Medicine,
London, W
68
RF, UK
Received 22 March 1999; received in revised form 17 March 2000; accepted 12 July 2000
Abstract
The oculomotor and manual motor systems were studied in a two-segment movement task in a group of patients with
Parkinson’s disease and in age matched normal controls. In order to avoid reflexive motor movements the selection of the correct
motor sequence was derived from the interpretation of symbolic (coloured) cues. The latencies and dynamics of eye and hand
(pointing) movements performed during the first (fixed) movement segment were measured and the planning and execution
processes were manipulated by varying the complexity of the second movement segment relative to the first (with regard to
direction and amplitude). The results showed that the eye and hand movements made by patients with Parkinson’s disease were
not impaired in the initiation of the first movement segment. Interestingly, both Parkinson’s patients and controls showed
increased eye and hand reaction time latencies for the first movement when the second movement was in the direction opposite
to the first. This indicates that the complexity of the second movement influences the execution of the first movement, and
importantly that complexity affects motor initiation and execution processes in both normal subjects and in patients with
Parkinson’s disease. The execution of hand movements was found to be impaired in patients with Parkinson’s disease as indicated
by a reduced peak velocity of manual pointing responses when compared to age matched controls. By contrast, no differences
were found in the dynamics of saccadic eye movements. This dissociation is consistent with the notion that the skeletomotor loop
passes through the functionally corresponding portions of the basal ganglia independently of the oculomotor loop. Together, these
results demonstrate that Parkinson’s patients are able to generate multiple non-reflexive eye and hand movements and that the
observed (manual) motor deficits are specific to the processes of motor execution. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords
:
Basal ganglia; Bradykinesia; Saccade; Pointing; Internal control; Movement sequences
www.elsevier.com/locate/neuropsychologia
1. Introduction
There has been considerable interest in the deficits
associated with Parkinson’s disease (PD), particularly
because they may illuminate the functions of the basal
ganglia, the brain region thought to be most impaired
by the degeneration of nigrostriatal neurones resulting
in a reduction of the neurotransmitter, dopamine
[25,26]. Although many researchers have investigated
cognitive deficits in patients with PD [12,30,34,35,37]
the main focus of interest has centred on the sensorimo-
tor impairments [5,17,27,43– 46]. The interest in the
sensorimotor impairments arises because movement ex-
ecution is known to be a principal manifestation of the
disease and such deficits may be directly related to
basal ganglia dysfunction. In particular, studies have
investigated the integrity of the initiation and execution
processes of oculomotor (saccadic) and the goal-di-
rected hand movements to visual stimuli in PD.
Studies of oculomotor function in patients with PD
have demonstrated mild abnormalities in the initiation
or execution of saccades made to novel peripheral
visual stimuli, so-called reflexive saccades [7,40]. How-
* Corresponding author.
E-mail address
:
bekkering@mpipf-muenchen.mpg.de (H. Bekker-
ing).
0028-3932/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0028-3932(00)00092-0