Card Sorting Test for Evaluation of Psychomotor Activity in a Healthy Volunteer

Overview

Purpose in Drug Evaluation

• Impairs or enhances executive functioning (higher cognitive processing)
• Affects cognitive flexibility (ability to shift mental strategies)
• Alters psychomotor speed (integration of cognitive processing with motor response)
• Produces sedation or CNS depression (e.g., anxiolytics, hypnotics, antipsychotics)
• Produces CNS stimulation (e.g., stimulants, nootropics)

The Wisconsin Card Sorting Test - Structure

Parameters Measured

Primary Measures

Secondary / Composite Measures

• Conceptual level responses (% of correct answers that are part of a run of 3+ correct)
• Learning-to-learn (improvement across categories, reflects adaptability)

Psychomotor Speed - Related Tests Often Co-administered

• Digit Symbol Substitution Test (DSST) - the classic measure of psychomotor speed; uses a number-to-symbol matching key filled in as rapidly as possible; sensitive to sedation and CNS depression
• Trail Making Test Part A & B - measures motor speed, scanning, and set-shifting
• Finger Tapping Test - pure motor speed
• Reaction Time tests - simple and choice reaction time
• Critical Flicker Fusion (CFF) - measures CNS sedation/arousal

What Psychomotor Activity Means in This Context

"The term 'psychomotor speed' reflects the fact that test performance is determined not only by the speed with which one thinks but also by the integration of those thoughts with the motor response... tests in this domain tend to be among the most sensitive to virtually any form of neurocognitive injury or dysfunction."

• Decreased psychomotor activity (drug impairment) = increased errors, increased perseverative errors, fewer categories completed, slowed reaction time
• Increased psychomotor activity (stimulant effect) = faster responses, possibly fewer errors but also more impulsive errors

Administration Protocol in Healthy Volunteer Studies

1. Baseline assessment - CST administered before drug dosing (pre-drug)
2. Post-dose assessments - Repeated at pharmacokinetically relevant time points (e.g., Tmax, 2h, 4h, 8h post-dose)
3. Crossover design - Volunteer receives drug and placebo on separate occasions (washout period between)
4. Blinding - Double-blind, placebo-controlled
5. Standardized instructions - Examiner gives identical instructions each session
6. Scoring - Computerized scoring preferred for reliability

Drugs Commonly Evaluated with Card Sorting / Psychomotor Tests

Interpretation of Results

• Drug impairs performance if statistically significant increase in perseverative errors or decrease in categories completed vs. placebo
• Effect size and time course of impairment maps the drug's CNS pharmacodynamic profile
• Recovery of performance back to baseline = duration of psychomotor impairment
• Correlation with plasma concentration establishes a PK/PD relationship

Key Points

• The WCST is primarily a test of executive function and cognitive flexibility, mediated by the prefrontal cortex
• It is most sensitive to frontal lobe dysfunction and CNS-active drugs
• For pure psychomotor speed, the Digit Symbol Substitution Test is more sensitive
• A full psychomotor battery (WCST + DSST + Reaction Time + CFF) provides the most complete picture of drug CNS effects in healthy volunteers
• Results must be compared to age-matched normative data and within-subject placebo baselines

Card Sorting Test - Step-by-Step Guide for Pharmacology Practical Exam

What You Need to Know First

Materials Required

• A standard deck of cards (or specially prepared test cards) with variations in:
  • Color (red, blue, yellow, green)
  • Shape (circle, triangle, star, cross)
  • Number (1, 2, 3, or 4 symbols)
• 4 stimulus (reference) cards placed face-up on the table
• A response deck of 64 or 128 cards
• A stopwatch
• A score sheet (to record correct responses, errors, perseverative errors)
• Pen and paper for recording

Step-by-Step Procedure

STEP 1 - Prepare the Environment

• Seat the volunteer at a quiet table, free from distractions
• Place the 4 stimulus cards face-up in a row in front of the volunteer, in this order:
  • Card 1: 1 red triangle
  • Card 2: 2 green stars
  • Card 3: 3 yellow crosses
  • Card 4: 4 blue circles
• These 4 cards remain visible throughout the entire test - they do not move

STEP 2 - Establish Baseline (Pre-drug Assessment)

STEP 3 - Give Instructions to the Volunteer

"I am going to show you a card. I want you to place it under one of these four cards at the top. I will tell you whether each choice is right or wrong. Try to get as many correct as possible."

STEP 4 - Begin the Test

• Show the volunteer one response card at a time from the shuffled deck
• The volunteer places it under one of the 4 stimulus cards
• You say "Right" or "Wrong" after each placement
• The hidden sorting rule changes after every 10 consecutive correct responses - without telling the volunteer
  • Rule sequence: Color → Form/Shape → Number → Color → Form → Number...
• Continue until all cards are used OR 6 categories are completed (whichever comes first)

STEP 5 - Record Responses in Real Time

STEP 6 - Administer the Drug

• Give the drug to the volunteer (as per exam protocol - usually a pre-determined dose, e.g., diazepam 5 mg oral or simulated in exam)
• Wait for the drug to take effect - this depends on the drug:
  • Diazepam oral: wait 30-60 minutes (Tmax ~1-1.5 hours)
  • In practical exams, the examiner may give you the "post-drug" results directly

STEP 7 - Repeat the Test Post-Drug

• Repeat the exact same procedure with a different set of shuffled response cards (to avoid learning effect)
• Record all responses again on a separate score sheet

STEP 8 - Score the Test

STEP 9 - Compare and Interpret

• CNS depressant (e.g., diazepam): Perseverative errors increase, categories completed decrease, time taken increases - volunteer cannot shift rules, thinking becomes rigid and slow
• CNS stimulant (e.g., caffeine, amphetamine): May improve performance (fewer errors, faster) at low doses; may cause impulsive random errors at high doses
• Antipsychotic: Significant slowing, more errors across all types

What to Say in Your Viva After the Test

• It means the volunteer is unable to shift cognitive strategy when the rule changes - a sign of frontal lobe/executive dysfunction induced by the drug.

• Because the test measures the ability to form concepts and adapt to change using only feedback - telling the rule would eliminate the cognitive challenge.

• Executive function (specifically cognitive flexibility) + psychomotor speed (time taken, response speed)

• The prefrontal cortex - this area governs planning, flexibility, and executive control.

Quick Memory Aid

WCST = Watch, Correct, Shift, Track

• Watch the volunteer sort
• Correct them ("Right/Wrong") after each card
• Shift the hidden rule every 10 correct sorts
• Track perseverative errors - these are your key pharmacological endpoint

Viva Questions & Answers - Card Sorting Test (Pharmacology Practical)

CATEGORY 1 - About the Test Itself

• Whether a drug impairs or enhances psychomotor activity
• Degree of sedation, cognitive slowing, or cognitive enhancement
• To establish a pharmacodynamic (PD) profile of CNS-active drugs
• To study dose-response relationships for cognitive effects
• Mandatory component of Phase I clinical trials for CNS drugs

• Planning and working memory
• Cognitive flexibility and set-shifting
• Abstract reasoning and concept formation
• Executive control of behavior

1. 1 red triangle
2. 2 green stars
3. 3 yellow crosses
4. 4 blue circles

1. Color (match by color)
2. Form/Shape (match by shape)
3. Number (match by number of symbols)

1. Concept formation - the ability to independently figure out the correct rule
2. Cognitive flexibility - the ability to detect when the rule has changed and shift strategies
3. Response to feedback - learning from "right" or "wrong" cues

• It specifically indicates inability to shift cognitive strategy (set-shifting failure)
• It reflects frontal lobe/executive dysfunction
• It is the most sensitive marker of CNS drug impairment
• A significant increase in perseverative errors post-drug = drug impairs executive function

• Complete 5-6 categories
• Make few perseverative errors (can shift rules easily)
• Show improvement across categories (learning-to-learn)
• Complete the test in approximately 12-20 minutes

CATEGORY 2 - Drug Effects

• Increase in perseverative errors (rigid thinking, cannot shift rules)
• Decrease in categories completed
• Increase in total errors
• Increased time taken (psychomotor slowing)
• Increased failure to maintain set (attention lapses due to sedation)

• Low dose: May improve performance - fewer errors, faster completion, more categories completed
• High dose: May cause impulsive errors (rushing through without thinking), increased non-perseverative errors
• Perseverative errors typically decrease (more flexible thinking)

• Increasing the frequency of chloride channel opening
• Causing chloride influx into the neuron
• Leading to neuronal hyperpolarization
• Result: Reduced neuronal excitability throughout the CNS

• α1 subunit - sedation, anterograde amnesia, anticonvulsant
• α2 subunit - anxiolysis and muscle relaxation

• Route: Oral, IV, IM, rectal
• Bioavailability: ~100% orally
• Tmax: ~1-1.5 hours after oral dose
• Protein binding: ~98%
• Half-life (diazepam): 20-100 hours (long-acting)
• Metabolism: Hepatic - primarily by CYP2C19 and CYP3A4
• Active metabolite: N-desmethyldiazepam (nordiazepam) - half-life up to 200 hours; further metabolized to oxazepam
• Excretion: Renal (as glucuronide conjugates)
• Affected by: Age (elderly have reduced clearance), obesity, liver disease

• Reversal of benzodiazepine-induced sedation (e.g., post-procedural)
• Diagnosis and treatment of benzodiazepine overdose
• Reversal of excessive sedation in ICU

• Predictable, well-characterized CNS depressant effect
• Short onset (effects visible within 30-60 min orally)
• Dose-dependent impairment - easy to see effect vs. placebo
• Primarily impairs prefrontal cortex function - directly affecting the domain measured by the card sorting test
• Reversible with flumazenil if needed (safety)
• Well-established pharmacokinetic profile for correlation studies

CATEGORY 3 - Study Design

• They have a normal baseline CNS function - any change is clearly due to the drug
• No confounding factors from disease, existing medications, or pathology
• Allows accurate measurement of the drug's intrinsic CNS pharmacodynamic effect
• Ethical - drug effects are reversible in a healthy person
• This corresponds to a Phase I clinical trial - safety and pharmacodynamic characterization in healthy subjects

• Randomized - order of drug/placebo allocation randomized to avoid bias
• Double-blind - neither volunteer nor examiner knows which is drug or placebo
• Placebo-controlled - direct comparison eliminates observer and expectation bias
• Crossover - same volunteer receives both drug AND placebo on different occasions (separated by a washout period); this controls for inter-individual variability

• Using alternate/parallel forms of the test (different card sets)
• Randomizing which session comes first (drug vs. placebo)
• Sufficient practice trials at baseline before testing begins

CATEGORY 4 - Broader Concepts

• Speed of thinking
• Speed and accuracy of executing that thought as a motor action
• Attention, reaction time, and coordination

• Sedation = reduction in arousal and alertness - the volunteer feels drowsy, wants to sleep
• Psychomotor impairment = reduction in the speed and accuracy of cognitive-motor tasks - the volunteer may be awake but makes more errors, reacts more slowly, and cannot shift mental strategies

1. A cognitive enhancer (nootropic) - genuinely improving executive function
2. A drug that reduces anxiety just enough to improve concentration in an anxious volunteer (anxiolytic effect at low dose)
3. A stimulant at low-to-moderate dose