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Unit 5 - Notes

PSY291

Unit 5: Cognitive Dysfunction and Psychological Testing

1. Introduction to Cognitive Dysfunction

Cognitive dysfunction (or cognitive impairment) refers to a deficit in one or more of the core cognitive domains that affects an individual's ability to process information, apply knowledge, and function independently. These deficits can range from Mild Cognitive Impairment (MCI) to severe dementia.

Core Cognitive Domains

To understand dysfunction, one must understand the domains being assessed:

  • Complex Attention: Sustained attention, divided attention, selective attention, and processing speed.
  • Executive Function: Planning, decision making, working memory, responding to feedback, inhibition, and mental flexibility.
  • Learning and Memory: Immediate memory, recent memory (including free recall and cued recall), and very-long-term memory.
  • Language: Expressive language (naming, word finding, grammar) and receptive language.
  • Perceptual-Motor: Visual perception, visuo-constructional reasoning, and perceptual-motor coordination.
  • Social Cognition: Recognition of emotions, theory of mind.

Types of Cognitive Dysfunction

  1. Delirium:

    • Nature: Acute, fluctuating disturbance in attention and awareness.
    • Onset: Sudden (hours to days).
    • Reversibility: Often reversible if the underlying cause (e.g., infection, medication toxicity) is treated.

  2. Mild Cognitive Impairment (MCI):

    • Nature: Cognitive decline greater than expected for an individual’s age and education level but does not interfere significantly with activities of daily living (ADLs).
    • Significance: Often a prodromal stage of dementia.

  3. Major Neurocognitive Disorder (Dementia):

    • Nature: Significant cognitive decline interfering with independence in everyday activities.
    • Subtypes:
      • Alzheimer’s Disease: Primarily affects memory and learning first.
      • Vascular Dementia: Step-wise decline often associated with strokes; affects executive function/speed.
      • Lewy Body Dementia: Fluctuating cognition, visual hallucinations, parkinsonism.
      • Frontotemporal Dementia: Behavioral/personality changes or language deficits.

  4. Traumatic Brain Injury (TBI):

    • Dysfunction resulting from external force. Deficits depend on the site of impact (e.g., frontal lobe damage affects executive function).

  5. Substance/Medication-Induced:

    • Cognitive deficits persisting beyond the immediate intoxication or withdrawal period (e.g., Korsakoff’s syndrome from alcohol).

Causes (Etiology)

  • Neurodegenerative: Accumulation of proteins (amyloid plaques, tau tangles, Lewy bodies) causing neuronal death.
  • Vascular: Ischemia, hemorrhage, or hypoperfusion restricting blood flow to the brain.
  • Traumatic: Concussions, contusions, Diffuse Axonal Injury (DAI).
  • Infectious: HIV-associated neurocognitive disorder, meningitis, encephalitis.
  • Metabolic/Endocrine: Thyroid dysfunction, B12 deficiency, hepatic encephalopathy.
  • Psychiatric: "Pseudodementia" (cognitive slowing caused by severe depression).

2. Psychological Tests for Assessing Cognitive Deficits

Assessment typically follows a hierarchical approach: Screening General Intelligence/Battery Domain-Specific Testing.

A. Screening Instruments

Used to determine if further, more comprehensive testing is necessary.

  • Mini-Mental State Examination (MMSE):
    • Focus: Orientation, registration, attention, calculation, recall, language.
    • Pros: Widely known, quick.
    • Cons: Low sensitivity for MCI; heavily influenced by education level; ceiling effect.
  • Montreal Cognitive Assessment (MoCA):
    • Focus: Visuospatial, naming, memory, attention, language, abstraction, delayed recall, orientation.
    • Pros: More sensitive than MMSE for mild impairment and frontal lobe dysfunction.

B. Comprehensive Neuropsychological Batteries

Fixed sets of tests designed to provide a holistic view of brain-behavior relationships.

  • Halstead-Reitan Neuropsychological Battery (HRNB):
    • Purpose: Detects brain damage and determines its location/nature.
    • Components: Category Test (abstraction), Tactual Performance Test, Speech Sounds Perception, Finger Tapping.
    • Characteristics: Lengthy (6–8 hours), strictly standardized.
  • Luria-Nebraska Neuropsychological Battery (LNNB):
    • Purpose: Assesses neuropsychological functioning using qualitative and quantitative methods.
    • Characteristics: Shorter than Halstead-Reitan; emphasizes the process of problem-solving rather than just the score.

C. General Intelligence Tests

  • Wechsler Adult Intelligence Scale (WAIS-IV):
    • Provides a Full-Scale IQ but specifically useful for cognitive dysfunction via its indices:
    • Processing Speed Index (PSI): Often first to decline in TBI or aging.
    • Working Memory Index (WMI): Sensitive to attention deficits and executive dysfunction.

D. Domain-Specific Tests

1. Attention and Concentration

  • Trail Making Test (Part A): Measures visual scanning and processing speed.
  • Digit Span (Forward): Measures basic auditory attention capacity.

2. Memory

  • Wechsler Memory Scale (WMS-IV): Assess auditory and visual memory, immediate and delayed recall.
  • Rey Auditory Verbal Learning Test (RAVLT): Assesses verbal learning curves and susceptibility to interference.
  • Benton Visual Retention Test: Assesses visual memory and visual perception.

3. Executive Functioning

  • Wisconsin Card Sorting Test (WCST): The "gold standard" for executive function. Measures abstract reasoning and the ability to shift cognitive strategies (mental flexibility) in response to feedback.
  • Stroop Color and Word Test: Measures inhibition (the ability to suppress a habitual response).
  • Trail Making Test (Part B): Measures cognitive flexibility and set-shifting.

4. Visuospatial/Constructional

  • Bender Visual-Motor Gestalt Test: Screening for visual-motor integration and neurological impairment.
  • Clock Drawing Test: Simple screen for parietal/frontal lobe dysfunction.

3. Application of Cognitive Assessment

Cognitive assessments are not merely diagnostic; they serve multiple applied functions in clinical, legal, and educational settings.

1. Differential Diagnosis

  • Differentiating Depression from Dementia: Cognitive profiles can distinguish between true memory loss (amnestic disorder) and concentration deficits caused by depression (pseudodementia).
  • Localizing Lesions: Specific patterns of deficits (e.g., right vs. left hemisphere) can corroborate MRI findings or suggest damage where imaging is inconclusive.

2. Treatment Planning and Rehabilitation

  • Baseline Measurement: Establishing a pre-treatment baseline to measure the effectiveness of interventions (e.g., post-surgery or post-medication).
  • Strengths-Based Approach: Identifying preserved cognitive abilities to compensate for deficits. (e.g., if verbal memory is impaired but visual memory is intact, use visual aids for rehabilitation).

3. Forensic and Legal Applications

  • Competency to Stand Trial: Assessing if a defendant has the cognitive capacity to understand proceedings.
  • Guardianship/Capacity: Determining if an older adult with dementia can manage their own finances or make medical decisions.
  • Personal Injury: Quantifying cognitive loss in lawsuits regarding TBI or malpractice.

4. Monitoring Progression

  • Tracking the rate of decline in degenerative diseases (e.g., Alzheimer’s) to assist families in planning for future care needs (e.g., when to stop driving).

4. Ethical Considerations in Testing Individuals with Cognitive Impairments

Testing individuals with cognitive dysfunction presents unique ethical challenges requiring strict adherence to APA guidelines and beneficence.

1. Informed Consent and Capacity

  • The Dilemma: The very condition being tested (e.g., dementia) may compromise the ability to give informed consent.
  • Protocol:
    • Determine if the client has the legal capacity to consent.
    • If not, obtain proxy consent from a legal guardian or power of attorney.
    • Always seek the client's assent (willingness to participate), even if legal consent is provided by a third party.

2. The Feedback Process

  • Delivering Bad News: Results often indicate irreversible decline. Psychologists must balance honesty with compassion.
  • Clarity: Avoid jargon. Explain how the results translate to daily life (e.g., "This score means you may struggle with managing medication," rather than "You have a low working memory score").
  • Who receives the data: Clarify strictly beforehand who receives the report (e.g., the patient, the family, or the insurance company).

3. Test Selection and Standardization Issues

  • Sensory Impairments: Many elderly clients have hearing or vision loss. Using standard tests without accommodation invalidates results, but modifying tests breaks standardization. This must be noted in the report.
  • Fatigue: Individuals with brain injury or dementia fatigue easily. Testing should be broken into shorter sessions to ensure scores reflect ability, not exhaustion.

4. Cultural and Linguistic Fairness

  • Education Bias: Many cognitive tests (like the MMSE) are biased toward those with higher education. Low scores may reflect lack of schooling rather than brain damage.
  • Language: Testing a client in their non-native language for cognitive dysfunction yields high false-positive rates for impairment. Use non-verbal tests or culturally validated norms where possible.

5. Labeling and Stigma

  • A diagnosis of "Dementia" or "Brain Damage" carries heavy social stigma and legal implications (e.g., loss of driver's license). Psychologists must ensure the diagnosis is supported by converging evidence (history + observations + test data) to avoid false labeling.