Is apathy associated with poor effort during neuropsychological assessment in patients with Alzheimer*s disease or Parkinson*s disease?

Psychological tests are assumed to yield objective and standardized measures of
an individual*s mental ability. However, neuropsychological test performance
can be influenced by other factors than cognitive ability, such as a primary
motivational deficiency as a consequence of cerebral pathology, unwillingness
to undergo the assessment, and exaggeration out of a psychological need to
demonstrate cognitive deficits and to adapt the sick role. All these factors
may lead to insufficient effort.
Effort is defined by Bush, Ruff, Troster, Barth, Koffler, Pliskin, Reynolds and
Silver (2005; p. 120) as *the individual*s investment at performing at capacity
levels*. Hence, insufficient effort leads to performing below one*s capacities
(e.g. underperformance) and this withholds conclusions to be drawn from the
traditional cognitive tests about cognitive abilities or deficits. Therefore,
it is important to control for effort when interpreting cognitive test results
to avoid the risk of drawing errounous conclusions about a person's cognitive
capacities and giving inappropriate advice.

Since research convincingly showed that the clinician*s view is unreliable in
detecting insufficient effort (Heaton et al., 1978; Wedding and Faust, 1989),
many Symptom Validity Tests (SVTs) have been developed to measure effort. An
SVT appears to tap cognitive function, most often memory, when in fact it is an
easy task even for patients with quite marked cognitive impairment. Effort
testing has been primarily developed and examined in medico-legal and forensic
settings. In such settings, external incentives may play an important role and
demonstrating cognitive deficit may lead to a more favorable outcome of the
legal procedure (e.g. a higher financial compensation or a diminished
punishment). In this domain, underperformance is often used as a behavioral
proxy of malingering. However, as mentioned above, there are several other
explanations why a patient does not put sufficient effort in test. SVTs can
only tap underperformance on cognitive tests. The underlying reason for poor
effort must be inferred by the clinician.

To date there are no objective measures or strategies available to the
clinician to interpret insufficient effort and little scientific research has
been conducted into exploring the possible factors operating behind
insufficient effort. One important question that remains unresolved is whether
a motivational deficiency as a consequence of cerebral pathology may lead to
insufficient effort on neuropsychological assessment and if so, how it can be
distinguished from a lack of motivation to perform optimally based on a
psychological need or secondary gains to demonstrate cognitive deficits. This
question is important because not being able to perform optimally out of a
motivational deficiency requires a different treatment approach than not
performing optimally out of need to demonstrate cognitive deficits.

The general aim of this study is to explore how a motivational deficiency (i.e.
apathy) related to neurodegenerative diseases is associated with effort and how
it can be distinguished from intentional underperformance. We will investigate
whether there is a difference in performance on SVTs and cognitive tests
between patients with Parkinson Disease (PD) and Alzheimer dementia with and
without apathy. If it can be shown that there is a difference in SVT
performance between patients with and without apathy, then this will be a first
clue that a motivational disorder can lead to underperformance on cognitive
tests.

A secondary aim is to investigate whether apathy is associated with a low
endorsement of complaints. We anticipate that the typical malinger pattern of
underperformance on cognitive tests and overendorsement of complaints (Iverson,
2006) is not present in patients with apathy. If so, then this would provide
clinicians with an important clue as to how to differentiate between
intentional underperformance as seen in malingering and apathy related
underperformance. However, we also anticipate that patients might as a
consequence of their cognitive deficits not fully comprehend the questionnaires
measuring cognitive complaints and non-credible psychological and neurological
complaints, and thus undermining the reliability of these questionnaires. To
overcome this we will separately analyze the results for the group AD patients,
who per definition have cognitive deficits, and the group Parkinson patients,
in which patients with co morbid dementia are excluded.


Hypotheses:
1. Patients with Alzheimer*s or Parkinson*s disease that suffer from apathy
score lower on SVTs than those that do not suffer from
apathy.
2. Apathetic patients report fewer cognitive complaints than non-apathetic
patients.
3. Scores on the SVTs are related to the traditional cognitive test (e.g., IQ
etc.) scores.
4. Neither apathetic nor non-apathetic patients report non-credible
psychological and neurological complaints.

we will use a cross-sectional, between-subjects design. Basically, the design
follows the 2 (apathetic versus non-apathetic) x 2 (PD versus early dementia
patients) between-subjects Analysis of Variance (ANOVA) set-up.

The risks of participating in this study are considered minimal. The two
questionnaires and two tests that are added to the regular assessment protocol
are non-invasive and scarcely stressful. These instruments will be administered
during the routine neuropsychological assessment, so patients are not asked to
make an extra visit to the hospital. The burden in our study stems from the
fact that the regular assessment is extended for approximately 40 minutes. The
participants will not directly benefit from the study.

When taken into consideration that the patients have to be mental competent to
give informed consent and that the risks of participating in this study are
minimal, we feel that the burden of 40 minutes extra testing time is justified,
in order to gain more insight into the relationship between apathy and effort
during testing.