Article Type : Research Article
Authors : Antonis T, George S, Maria S, Margarita H, Konstantinos T, Grigoris K, Konstantinos F, Ioannis N and Charalampos P
Keywords : Schizophrenia; Mental imagery of movement
Schizophrenia patients often present with
neurological signs such as left/right confusion, impaired coordination of
movements, and motor abnormalities may occur secondary to antipsychotic
medications. Neuropsychological tests identify various dysfunctions, such as
difficulty in focusing attention, difficulty in abstract thinking or difficulty
in changing the response frame, while Neurophysiological tests show slowing
down of reaction time, problems with eye tracking, etc. There are no studies in
the international literature dealing with the investigation of mental imagery
of movement in Greek patients with schizophrenia. Also, the position that
patients with schizophrenia – regardless of their symptom profile, age, sex,
and chronicity of the disease – have a permanent difficulty in creating and
manipulating an internal model of their movement prediction, has not been
substantiated enough to date.
Aim: In the present study we examine the
function of visual-motor coordination and the time to achieve the goal-directed
movement of the dominant hand of patients with schizophrenia
Method: The sample we used in our research
consisted of patients with diagnosed schizophrenia and healthy individuals.
Schizophrenia patients belonged to the experimental group and healthy subjects
to the control group. The number of examined patients was 39 and the healthy
51. The assessment of the movement and its mental representation was carried
out with the real and mental movement of the dominant hand between two square
targets located at a distance of 20 cm, on white paper of A4 size.
Conclusions: Visuomotor coordination of a
specific hand movement differs between patients with schizophrenia and the
normal population. In particular, the means of the goal-directed hand movement
achievement time in the actual execution condition and in the mental execution
condition of the patients were significantly higher than the corresponding
times of the standard population.
Neuropsychological deficits are recognized as primary
symptoms of psychotic disorders, since they are detected even in the early
stages, with some of them showing a more significant decline (e.g. executive
functions, memory, attention) and others a smaller but significant one (e.g.
language , movement perception, psychomotor). A wealth of neuropsychological
research over the past decade has contributed to elucidating the nature and
significance of cognitive dysfunction in schizophrenia. Today we know that patients
with schizophrenia show lower performance in all known neuropsychological tests
compared to healthy controls.
Schizophrenic deficits
in psychomotor speed
We know that schizophrenia is governed by deficits in
psychomotor speed [1,2]. Psychomotor speed refers to the time to process a
stimulus, prepare the response to that stimulus, and execute the response. It
has been shown that patients with schizophrenia are disadvantaged compared to
healthy individuals in tests of psychomotor speed [3]. However, this difference
does not always reach the significance level [4]. Of interest is the result of
the research by Riley and his colleagues (2000) that deficits in psychomotor
speed in schizophrenia appear as early as the first episode, reinforcing the
view that this area is greatly damaged by the presence of psychotic symptoms
[5]. Sweeney et al.'s (1991) study found improvement in psychomotor speed in
both first-episode schizophrenia patients and patients with a previous history
of psychosis, which is consistent with the view that neurocognitive deficits in
patients with schizophrenia remain relatively stable across the lifespan [6].
The depiction of
movement
Movement imagery is a mental process in which a
specific movement is internally simulated without actually performing the
movement. According to simulation theory, mental movements are essentially
movements that do not take place [7]. Much research has highlighted the
relationship between real movement and its corresponding mental representation
as well as common brain areas that are activated during planning and execution
in both cases, while both mental and real movement follow the same rules (e
.e.g. speed-accuracy, speed-curvature relationship) and maintain the same
temporal structure [8-12]. In addition, mental training improves motor
performance and enhances muscle strength [13-19]. Neuroimaging studies have
revealed a common activation of specific brain regions during both motor and
mental execution of a movement (parietal and prefrontal cortex, primary cortex,
basal ganglia and cerebellum) [20-24]. Research using movement imagery tests is
a useful and sensitive method of investigating the unconscious process of
representation [25]. Movement imagery has been widely used to investigate the
movement system in both healthy and clinical populations. The advantage of
investigating kinesthetic imaging is that the internal processes of real
movement that involve planning and planning can be studied. This element is
very important for the study of the production and execution of the movement
and the related deficits shown by patients of various categories such as
patients with psychiatric or neurological syndromes. In these patient cases the
ability or inability to produce or perform a movement can indicate whether the
relevant brain function has begun to be affected, to what extent it is
deficient, and the degree of progressive impairment. Deficits in mental imagery
of movement have been assessed in Parkinson's disease, prefrontal cortex
syndrome, motor - sensory cortex, and in multiple sclerosis [26-31].
Investigating the mental imagery of movement also helps psychomotor retardation
(Psychomotor retardation -PMR-) which is a central factor in the assessment of
clinical and therapeutic effects and can seriously affect the psychosocial
functioning of patients. Psychomotor rehabilitation modifies all of the
person's actions, including mobility, mental activity, and speech [32].
Schizophrenics' deficits
in motor mental imagery
Kinetic imagery is about being able to create
internal/mental images before they are executed. Patients with schizophrenia
have difficulty accurately tracking mental images of movement, and are unable
to produce accurate mental images of their own movements. Research has shown
that many of the first-order symptoms of schizophrenia, for example delusions
of control in which the patient believes that external forces are controlling
their thoughts or actions, can be characterized as deficits in reality
monitoring or self-monitoring of internally generated thoughts. For the
schizophrenic patient a self-control deficit, which manifests as an inability
to recognize his thoughts or actions as his own, is also auditory
hallucinations when these manifest as an inability to recognize inner speech as
self-generated. However, patients with schizophrenia are a heterogeneous group
of patients with deficits in attention, memory, and executive functions. Thus,
a difficulty to examine the hypothesis that they present difficulties and
deficits in motor mental imagery, is the use of neuropsychological tests that
usually concern cognitive abilities (such as attention and memory) that in one
way or another are presented as deficits in this group of patients. From a
neuropsychological point of view the parietal cerebral cortex is an interesting
area for research in patients with schizophrenia, since it receives information
from multiple sensory inputs, is crucial for the control of directed limb and
eye movements, and plays an important role in proprioception (somatotopographic
recognition). The two brain regions of the parietal cortex are involved in
different cognitive functions with the left region involved in speech and
movement processes, and the right region involved in processing spatial
representations and focusing attention on specific environmental stimuli.
Previous research has shown deficits in eye movement control and visual
attention in patients with schizophrenia, suggesting deficits in parietal lobe
function [33]. Frontal and parietal brain structures play an important role not
only in the control and execution of goal-directed movements but also in the
ability to recognize movements as individual. Neuroimaging studies
investigating the recognition of self-generated movements versus other
movements have shown increased activation in regions of the parietal and
frontal cortex that are critical for the control of goal-directed movements.
Interestingly, when hallucinating schizophrenics are asked to discriminate
between self-made hand movements and movements of a "foreign" hand,
they mistake the foreign movements as their own in 80% of trials. Also, the
conscious control of certain movements for patients with schizophrenia presents
particular difficulties. However, the question that has not been sufficiently
answered to date is whether these difficulties are exclusively related to
visual feedback of information or are related to a central deficiency in the
ability to visually motor coordination for the execution of goal-directed
movements of patients with schizophrenia. Motor mental imagery presupposes the
creation of an internal mental image of a movement and its mental projection
with successive individual images of the intended action. Tasks requiring motor
imagery are a good means of studying goal-directed movement for patients with
schizophrenia as well. Typically, when subjects are asked to imagine a movement
at a mental level the time required to mentally perform that movement will be
the same as the time to actually perform the movement.
Research case
Based on the preceding literature review, it became
clear that patients with schizophrenia present many cognitive deficits, the
most important of which are related to executive functions, memory, and
attention. The aim of our own research was to investigate the target-directed
movement ability of the dominant hand of schizophrenics and to compare this
ability with healthy individuals in order to clarify the possible difference
between the two groups. Our research question has not been answered in any research
in the Greek area and we hope that it will be another important element in
being able to clarify with the greatest possible precision the deficits in the
cognitive functions of schizophrenic patients.
Sample
The sample we used in our research consisted of patients with diagnosed schizophrenia and healthy individuals. Schizophrenia patients belonged to the experimental group and healthy subjects to the control group. The number of patients examined was 39 and the healthy 51. The age range of the patients was from 28 to 64 years with a mean age of 45.3 years. Nine were men and six were women. Seven had completed secondary education, five tertiary and three primary. The group of healthy subjects was matched based on all the above elements with the group of schizophrenics. All participants had normal vision and were right-handed. The patients had previously been treated at the 3rd University Psychiatric Clinic of the ACHEPA Hospital in Thessaloniki and participated in the study during their scheduled visit to the clinic's outpatient clinics. Exclusion criteria from the study were: depression, neurological disease, severe organic disease, substance use. Also, those patients receiving medication (Haloperidol, Risperidone, Biperidone) which can affect movement were excluded. The patients in the sample were receiving second generation antipsychotics (Second Generation Antipsychotics SGAs – Clozapine up to 900mg/24h, Olanzapine up to 20mg/24h, Aripiprazole up to 30mg/24h, Cariprazine up to 6mg/24h, Amisoulpride, Lourasidone, Ziprasidone). Control group participants were free from any neurological, cognitive and organic impairment and were randomly selected from the community. All participants gave written consent to participate in the study. The research protocol was approved by the Ethics Committee of the Faculty of Medicine of the A.P.Th. and conducted in accordance with the principle set out in the Declaration of Helsinki.
In the present study, the function of visual-motor coordination and the time to achieve the goal-directed movement of the dominant hand of patients with schizophrenia was investigated. The questions to be answered were:
The hypotheses of the research
Data collection took place in a quiet office. In order
to limit the influence of circadian rhythms on motor and mental performance,
all experiments were performed in the morning (between 9 and 11 AM).
Participants were seated comfortably in an adjustable chair in front of a table
whose edge was aligned with their chest at the level of the diaphragm. In the
middle of the table, the pieces of paper (A4 format) were placed at a distance
of 20 cm from the chest of the participants. Three targets (black squares) and
a starting point (abference) were printed on each sheet. We used four different
target sizes (0.5 cm, 1 cm, 1.5 cm, 2 cm) and the distances between the targets
were (15 cm) to model the test according to Fitts' law (Fitts, 1954).
Participants had to perform (actual movement) or
imagine themselves performing the movement (mental movement) between the
targets as accurately and as quickly as possible (i.e., we adapted Fitts' law
motor paradigm, while the presentation of the targets was randomized to exclude
the learning process. After the instructions were briefed and explained,
participants were free to initiate the real or mental movements when they felt
ready. /s. Each real or mental movement was performed eight times between targets
for each trial (0.5 cm, 1 cm, 1.5 cm, 2 cm). For mental movements, participants
were asked to place their pencil over the original target (starting point),
hold it still throughout the trial, and feel that they are performing the task
(motor) as they would in reality. of a movement at the mental level is a
necessary condition for the motor system to be involved [34-38]. For each
actual test, we measured the reaching time as well as the accuracy of the
movements. Participants were told that if they missed more than two targets
during a trial, it would be cancelled (invalid trial) and repeated at the end
of the session. No tests had to be repeated. Each test was performed on
separate sheets. The main experiment was preceded by a series of practice
trials, which allowed participants to familiarize themselves with the task. The
targets used in practice were of different sizes (3 cm and 2.5 cm) than those
used in the experiment. After this practice phase, all participants verbally
reported that they were able to generate motor imagery after having practiced
9–10 times. During the experiment, all participants performed eight real and
eight mental trials for each different target dimension (64 trials per
participant) in random order. When participants completed eight consecutive
trials, they rested for ?1
min to avoid physical and mental fatigue. After achieving the experimental
protocol, none of the participants reported mental or physical fatigue and any
difficulty in internally simulating the movements.
Regarding gender, the sample consists of 42 men (46.7%) and 48 women (53.3%). Regarding the disease, 51 normal (56.7%) and 39 patients with schizophrenia (43.3%) participated. Of all the participants in the research, 2 people had completed primary education (2.2%), 12 people (13.3%) high school, 23 people high school (25.6%) 37 people (41.1%) the university while 16 people had also completed postgraduate education (17.8%). 27 people (30%) were aged 19 to 29, 19 people (21%) were aged 30 to 39, 12 people (13%) were aged 40 to 49, 23 people (26%) were aged 50 to 59 and 9 people (10%) belonged to the age group of 60 to seventy years.
Control of
performance averages
We calculated the averages of the time to achieve the
specific goal-directed real and mental movement to targets of different
dimensions (square targets with dimension: 0.5X0.5 cm, 1X1 cm, 1.5X1.5 cm, and
2X2 cm). Testing the means with the t-test for independent samples showed that
reaching time was significantly associated with schizophrenia in all cases
(real and mental movement and different goal dimensions). Patients with
schizophrenia perform this movement in a longer period of time than the normal
population.
?he execution time of both real and mental movement in
all subtests (target size) is longer for patients with schizophrenia compared
to the corresponding times of normal subjects. As the dimension of the target
increases, the time to achieve the movement decreases for both conditions (real
and mental movement) and for both groups (normal population - patients with
schizophrenia). Schizophrenia patients show larger differences between the mean
execution time between the actual and mental execution of the movement than the
corresponding differences of the normal population. ?he difference in the
averages of the time to achieve the movement is smaller between the two groups
(normal - schizophrenic) for the condition of mental execution of the specific
movement.