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In this study, the investigators examine the effects of low-dose ketamine on different oculomotor, perceptual and cognitive functions. They also examine effects on concurrent brain activity using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). A sample of N=25 healthy, male participants is required to complete the study. The design is within-subjects, placebo-controlled, double-blind and cross-over. A targeted ketamine level in plasma of 100ng/ml is applied. It is hypothesised that ketamine, compared to placebo, will lead to changes in task performance and brain activity similar to those observed in patients with schizophrenia.
The uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine has been proposed as a model system of the symptoms of schizophrenia. To complement this model system and to allow neurobiological as well as translational studies, biomarkers are often applied to people under the influence of ketamine. Here, we apply oculomotor, perceptual and cognitive biomarkers to healthy human volunteers whilst they undergo BOLD fMRI at 3 Tesla field strength. We use a counter-balanced, placebo-controlled, double-blind, within-subjects design. A sample of 25 healthy participants is required. Participants will receive intravenous (IV) racemic ketamine (with a 100ng/ml target plasma concentration) on one of two assessment days and they will receive placebo (intravenous saline) on the other assessment day. BOLD fMRI will be carried out on a Siemens Trio scanner at the Life&Brain Centre, Bonn. In addition to brain functional and cognitive, perceptual and oculomotor responses, we will also measure self-ratings of psychosis-like experiences. These will be obtained using the Psychotomimetic States Inventory (PSI; Mason et al 2008).
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Ketamine-Saline | Other | Each participant receives both ketamine and placebo (saline) in randomised order in a repeated-measures design. In this arm, ketamine is administered on the first assessment and placebo (saline) is administered on the second assessment. |
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| Saline-Ketamine | Other | Each participant receives both ketamine and placebo (saline) in randomised order in a repeated-measures design. In this arm, placebo (saline) is administered on the first assessment and ketamine is administered on the second assessment. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Ketamine | Drug | Racemic ketamine, intravenous, at a concentration of 10mg ketamine per 50ml infusion |
|
| Measure | Description | Time Frame |
|---|---|---|
| Brain activity in cortical and subcortical areas as assessed using BOLD (blood oxygen level dependent) functional magnetic resonance imaging (fMRI) at 3 Tesla field strength | within 1 hour of start of IV infusion |
| Measure | Description | Time Frame |
|---|---|---|
| Psychotomimetic State Inventory (PSI) | within 1 hour of start of IV infusion | |
| Visual Analogue Rating Scales (VARS) from Norris 1971; self-rating scores of the subscales "mental sedation", "physical sedation", "tranquillisation" and "other feelings and attitudes" |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Ulrich Ettinger, PhD | Department of Psychology, University of Bonn | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| University of Bonn | Bonn | North Rhine-Westphalia | 53111 | Germany |
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| ID | Term |
|---|---|
| D007649 | Ketamine |
| D012965 | Sodium Chloride |
| ID | Term |
|---|---|
| D003510 | Cyclohexanes |
| D003516 | Cycloparaffins |
| D006840 | Hydrocarbons, Alicyclic |
| D006844 | Hydrocarbons, Cyclic |
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| Saline | Drug | Saline, intravenous infusion |
|
|
| within 1 hour of start of IV infusion |
| d2 Attention Test, a measure of sustained attention | The test requires the crossing out of the letter d combined with two dashes amidst letters d and p combined with one, two, three or four dashes and is a well-established measure of sustained attention | within 1 hour of start of IV infusion |
| Recognition memory performance (latencies in ms) | after 5 days of washout period |
| Recognition memory performance (percent correct responses) | after 5 days of washout period |
| Smooth pursuit gain (%) | within 1 hour of start of IV infusion |
| Smooth pursuit root mean square error (RMSE) | within 1 hour of start of IV infusion |
| Smooth pursuit saccadic frequency (number per second) | within 1 hour of start of IV infusion |
| Prosaccade latency (ms) | within 1 hour of start of IV infusion |
| Prosaccade gain (%) | within 1 hour of start of IV infusion |
| Prosaccade spatial error (%) | within 1 hour of start of IV infusion |
| Prosaccade velocity (degrees per second) | within 1 hour of start of IV infusion |
| Prosaccade error rate (%) | within 1 hour of start of IV infusion |
| Antisaccade latency (ms) | within 1 hour of start of IV infusion |
| Antisaccade gain (%) | within 1 hour of start of IV infusion |
| Antisaccade spatial error (%) | within 1 hour of start of IV infusion |
| Antisaccade velocity (degrees per second) | within 1 hour of start of IV infusion |
| Antisaccade error rate (%) | within 1 hour of start of IV infusion |
| D006838 |
| Hydrocarbons |
| D009930 | Organic Chemicals |
| D002712 | Chlorides |
| D006851 | Hydrochloric Acid |
| D017606 | Chlorine Compounds |
| D007287 | Inorganic Chemicals |
| D017670 | Sodium Compounds |