This study will investigate whether odors can be conditioned to fearful events and themselves elicit fear in humans. Fear conditioning will be tested on two odors: a pleasant odor and an unpleasant odor. The research questions are 1) can odors be…
ID
Source
Brief title
Condition
- Other condition
- Anxiety disorders and symptoms
Synonym
Health condition
Meervoudige Chemische Overgevoeligheid
Research involving
Sponsors and support
Intervention
Outcome measures
Primary outcome
The CS is the presentation of an odor with a duration of 6 seconds. The US is
an electrical shock, delivered 500 ms to the fingers, presented directly
following the CS+. Per condition, 25 participants will be tested (N = 50 in
total). As dependent variable, the electrodermal response will be measured via
electrodes attached to two fingers.
Secondary outcome
As a secundary physiological measures heart rate frequency as a second
indicator of phsyiological arousal assessed via a clip on one finger of the
hand, and sniffing behavior, via the assessment of air presssure differences
through a cannula in the nose, will be investigated during each phase of the
experiment. Evaluation of odor intensity and odor pleasantness will be
completed after each odor presentation by means of Visual Analogue Scales
(VAS), to investigate how odor evaluation develops during the expected
classical conditioning process. Explicit expectation of the shock will be
assessed by means of a VAS on expectation for both odors. Finally,
questionnaires will be administered containing questions about demographics,
general health, and neuroticism.
Background summary
Specific symptoms of Multiple Chemical Sensitivity (MCS), such as headache,
dizziness and chest palpitations, may result from learning by classical fear
conditioning. In classical conditioning, a neutral stimulus is paired with an
unconditioned stimulus (US) that causes fear. The neutral stimulus may
thereupon provoke fear as a conditioned stimulus (CS). In MCS sufferers, a
representation of a fearful encounter (US) with an odor is activated when the
odor (CS) is smelled again, which causes fear as a conditioned response (CR).
Physiological changes resulting from fear might subsequently cause several
symptoms typical for MCS.
Study objective
This study will investigate whether odors can be conditioned to fearful events
and themselves elicit fear in humans. Fear conditioning will be tested on two
odors: a pleasant odor and an unpleasant odor. The research questions are 1)
can odors be conditioned to fear and elicit fear themselves, and 2) can
unpleasant odors be conditioned to fear better than pleasant odors?
Study design
An experimental study will be conducted using a differential conditioning
paradigm. This holds that both a target odor (CS+) and a control odor (CS-)
will be presented, but only the target odor will be occasionally paired with an
electrical shock (US). For fifty percent of the participants (randomized) the
CS+ will be the pleasant odor and the CS- will be the unpleasant odor. For the
other fifty percent the CS+ and CS- are swapped. A habituation phase will
investigate baseline measures. This is followed by an acquisition phase, in
which only the CS+, not the CS-, will be paired with shocks. In a test phase,
physiological responses to the presentation of both CS-types alone (not
followed by shocks) will be investigated. We predict increased arousal to the
CS+, but not the CS-, presentation.
Study burden and risks
The main burden for the participant consists of having to undergo six
presentations of the electric shock. This will startle the participants.
However, the intensity of the shocks will be tailored to the participant*s pain
threshold in a work-up procedure that involves the presentation of shocks at
increasing levels until the participant experiences the shock as uncomfortable
but not painful. In addition, an electric current of 0.5 Volts will be
maintained between the electrodes measuring the elctrodermal response. The risk
of being exposed to an electric current in case of short circuiting is minimal,
because patient safe conditions will be maintained. Time investment will be
only a single visit of 1 - 1.5 hours. This research will yield an insight into
the role of odors as possible triggers of fear and subsequent symptoms in
humans, a topic about which still little is known.
Heidelberglaan 1
3508 TC Utrecht
Nederland
Heidelberglaan 1
3508 TC Utrecht
Nederland
Listed location countries
Age
Inclusion criteria
Students who are 18 years or older, are generally healthy, do not have a psychiatric condition or anxiety disorder, epilepsy, heart condition, a pacemaker, who are not pregnant or possibly pregnant, have a good (self-reported) sense of smell, no severe allergies, no asthma, and no scores of 4 or higher on 3 or more items of the modified Chemical Intolerance Index (which is indicative of MCS), will be accepted into the study. Participants who have a severe cold or the flu at the moment of the lab visit will be rescheduled.
Exclusion criteria
Students who are younger than 18 year, who are not generally healthy, who have a psychiatric condition or anxiety disorder, who have either epilepsy, or a heart condition, or a pacemaker, who are pregnant or possibly pregnant, have a bad (self-reported) sense of smell, who have severe allergies, or asthma, or scores of 4 or higher on 3 or more items of the modified Chemical Intolerance Index (which is indicative of MCS), will be not accepted into the study. In addition, participants who have a severe cold or the flu at the moment of lab visit will not be included in the experiment that same day.
Design
Recruitment
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In other registers
| Register | ID |
|---|---|
| CCMO | NL25646.041.08 |