Neurobiology and Genetics of Mental Disorders Practice Questions

Q: Ribot's law deals with which of the following?

Retrograde amnesia. **Explanation:** **Ribot’s Law** (also known as the Law of Regression) states that in cases of organic memory loss, there is a specific chronological order to the dissolution of memory. It posits that **recent memories are lost first, while remote (older) memories are better preserved.** 1. **Why Retrograde Amnesia is Correct:** Ribot’s Law specifically describes the pattern of **Retrograde Amnesia**. It suggests that memories undergo a process of "consolidation" over time. Older memories are more stable and resistant to brain injury or decay because they have been more firmly ingrained in the neural architecture. Therefore, in conditions like head trauma or early neurodegeneration, a patient may forget events leading up to the injury (recent) but vividly remember their childhood (remote). 2. **Why Other Options are Incorrect:** * **Anterograde Amnesia:** This refers to the inability to form *new* memories after an inciting event. Ribot’s Law focuses on the gradient of loss for *pre-existing* memories. * **Dementia:** While Ribot’s Law is clinically observed in dementia (e.g., Alzheimer’s, where recent memory fails first), the law itself is a principle of memory dissolution, not a diagnosis. * **Delirium:** This is an acute disturbance of consciousness and attention, not primarily a disorder of graded memory loss. **High-Yield Clinical Pearls for NEET-PG:** * **Jost’s Law:** States that if two memories are of equal strength, the older one will decay more slowly. * **Wernicke-Korsakoff Syndrome:** Characterized by profound anterograde amnesia and retrograde amnesia (often following Ribot’s Law), typically associated with thiamine deficiency. * **Memory Consolidation:** The hippocampus is essential for forming new memories, but over time, memories are transferred to the neocortex for long-term storage (explaining why remote memories survive hippocampal damage).

Q: Signs of organic brain damage are evident on which of the following tests?

Bender Gestalt test. **Explanation:** The correct answer is **A. Bender Gestalt test.** The **Bender Visual-Motor Gestalt Test** is a neuropsychological assessment used to evaluate visual-motor maturity and to screen for **organic brain damage**. It involves asking the patient to copy nine geometric designs. Patients with organic brain lesions (such as those in the parietal lobe) often demonstrate "signs of organicity," including rotation of figures, perseveration (repeating parts of the design), fragmentation, and inability to integrate the figures. It is highly sensitive to deficits in visuospatial processing and fine motor coordination. **Why the other options are incorrect:** * **B. Rorschach Test:** This is a **projective personality test** using inkblots. It is primarily used to assess personality structure, emotional functioning, and thought disorders (like schizophrenia), rather than structural brain damage. * **C. Sentence Completion Test:** This is a **projective verbal test** where patients finish incomplete stems. It is used to uncover internal conflicts, motivations, and personality dynamics. * **D. Thematic Apperception Test (TAT):** This is a **projective test** where patients create stories based on ambiguous pictures. It evaluates a person's underlying needs, motives, and interpersonal relationships. **High-Yield Clinical Pearls for NEET-PG:** * **Projective Tests:** Rorschach, TAT, Sentence Completion, and Draw-A-Person test (used for personality/psychodynamics). * **Neuropsychological Tests for Organicity:** Bender Gestalt, **Luria-Nebraska Battery**, and **Halstead-Reitan Battery**. * **Memory Assessment:** PGI Memory Scale and Wechsler Memory Scale. * **Intelligence:** Wechsler Adult Intelligence Scale (WAIS) is the gold standard for IQ. * **Mini-Mental State Examination (MMSE):** A bedside screening tool for cognitive impairment/dementia (Max score 30; <24 suggests impairment).

Q: A 32-year-old woman is diagnosed with major depression. What is the chance that her identical twin sister will develop the same disease?

70%. ### Explanation **1. Understanding the Correct Answer (D: 70%)** The question tests the concept of **concordance rates** in psychiatric genetics. Concordance refers to the probability that if one twin has a disorder, the other will also develop it. For Major Depressive Disorder (MDD), studies on Monozygotic (identical) twins—who share 100% of their genetic material—show a concordance rate of approximately **50% to 70%**. This high percentage highlights a significant genetic predisposition, although environmental factors also play a role. **2. Analysis of Incorrect Options** * **Option A (5%):** This is closer to the lifetime prevalence of MDD in the general population (approx. 5-12% for men). * **Option B (20%):** This represents the concordance rate for **Dizygotic (fraternal) twins**, who share only 50% of their genes. It is also the approximate risk for a first-degree relative of a patient with MDD. * **Option C (50%):** While some older studies cite 50%, modern psychiatric literature and NEET-PG patterns frequently use the upper limit (70%) to emphasize the high genetic load in identical twins compared to fraternal twins. **3. NEET-PG Clinical Pearls & High-Yield Facts** * **Bipolar Disorder (BPAD):** Has an even higher genetic link than MDD. Monozygotic twin concordance is **70-90%**, while Dizygotic is **15-25%**. * **Schizophrenia:** Monozygotic twin concordance is approximately **40-50%**. * **General Rule:** If a question asks for twin concordance in major psychiatric illnesses, BPAD > MDD > Schizophrenia. * **First-degree relatives:** The risk for MDD in a first-degree relative of an affected individual is roughly **2 to 3 times** higher than the general population.

Q: Which of the following symptoms is likely to be of organic origin?

Prominent visual hallucination. **Explanation:** In psychiatry, distinguishing between **Functional Psychosis** (e.g., Schizophrenia) and **Organic Psychosis** (e.g., Delirium, metabolic encephalopathy, or brain lesions) is a critical clinical skill. **Why Option D is correct:** **Visual hallucinations** are the hallmark of organic brain syndromes. While they can occur in functional disorders, their presence—especially when prominent, vivid, or occurring in a clear sensorium—should immediately raise suspicion of an underlying medical cause, such as substance withdrawal (Delirium Tremens), epilepsy, or neurotoxicity. **Analysis of Incorrect Options:** * **A. Delusion of Guilt:** This is a classic feature of **Psychotic Depression** (Functional). Patients believe they have committed unforgivable sins or are responsible for disasters. * **B. Auditory Hallucinations:** These are the most common type of hallucinations in functional psychiatric disorders, particularly **Schizophrenia** (specifically Schneiderian First Rank Symptoms). * **C. Formal Thought Disorder (FTD):** Characterized by disorganized thinking (e.g., loosening of associations), FTD is a core feature of **Schizophrenia** and is rarely the primary presentation of an organic condition. **High-Yield Clinical Pearls for NEET-PG:** * **Visual Hallucinations = Organic** until proven otherwise. * **Auditory Hallucinations = Functional** (Schizophrenia) until proven otherwise. * **Olfactory/Gustatory Hallucinations:** Strongly associated with **Temporal Lobe Epilepsy** (Uncinate fits). * **Tactile (Formication) Hallucinations:** Classically seen in **Cocaine** use (Cocaine bugs) or Alcohol withdrawal. * **Clouding of consciousness** is the most reliable indicator of an organic etiology (Delirium).

Q: Which of the following neurotransmitters/factors increases on Electroconvulsive therapy?

Brain derived neurotrophic factor. **Explanation:** **Correct Answer: D. Brain-derived neurotrophic factor (BDNF)** The therapeutic efficacy of Electroconvulsive Therapy (ECT) is increasingly attributed to its **neuroplastic effects**. ECT significantly increases the levels of **Brain-derived neurotrophic factor (BDNF)** in the hippocampus and prefrontal cortex. BDNF is a protein that promotes the survival of existing neurons and encourages the growth and differentiation of new neurons and synapses (neurogenesis). Chronic depression is associated with hippocampal atrophy and low BDNF levels; ECT reverses this by stimulating BDNF expression, which is considered a primary mechanism for its rapid antidepressant action. **Analysis of Incorrect Options:** * **A. 5-hydroxy-indole-acetic acid (5-HIAA):** This is the primary metabolite of serotonin. Studies show that ECT does not consistently increase 5-HIAA levels in the cerebrospinal fluid. * **B. Dopamine:** While ECT may increase postsynaptic dopamine receptor sensitivity, it does not consistently increase the overall levels of the neurotransmitter itself. * **C. Serotonin:** Similar to antidepressants, ECT modulates the serotonergic system (specifically increasing 5-HT2A receptor sensitivity), but it does not significantly increase the absolute concentration of serotonin. **Clinical Pearls for NEET-PG:** * **Gold Standard:** ECT remains the most effective treatment for **severe treatment-resistant depression** and **catatonia**. * **Mechanism:** The therapeutic effect requires a **generalized tonic-clonic seizure** lasting at least 25–30 seconds. * **Neurobiology:** Beyond BDNF, ECT is known to **decrease** hyperconnectivity in the "Default Mode Network" (DMN) of the brain. * **Contraindications:** There are no absolute contraindications, but **increased intracranial pressure (ICP)** is the most significant relative contraindication due to the risk of herniation.

Q: In a youngster with a history of seizures, which of the following would be most suggestive of a nonorganic or hysterical etiology?

Changing pattern of the seizure. **Explanation:** The distinction between **Epileptic Seizures (ES)** and **Psychogenic Non-Epileptic Seizures (PNES)**—formerly termed "hysterical seizures"—is a high-yield topic in neuropsychiatry. **Why "Changing pattern of the seizure" is correct:** Organic epilepsy typically follows a stereotyped, consistent semiology because the electrical discharge follows a specific anatomical pathway in the brain. In contrast, PNES often presents with a **polymorphic or changing pattern**. During a single episode, the movements may shift from side-to-side head shaking to pelvic thrusting or out-of-phase limb movements. This lack of a fixed pattern is a hallmark of non-organic etiology. **Analysis of Incorrect Options:** * **A. Postictal sleep:** This is a classic feature of true epilepsy. The massive neuronal discharge leads to a period of cortical inhibition, resulting in drowsiness, confusion, or deep sleep. * **C. Biting of the tongue:** While tongue biting can occur in PNES (usually the tip), **lateral tongue biting** is highly specific for generalized tonic-clonic seizures (GTCS). * **D. Urinary incontinence:** This occurs due to the loss of sphincter control during the tonic/clonic phases of an organic seizure. While it can rarely be feigned, its presence strongly points toward an organic cause. **NEET-PG Clinical Pearls:** * **Gold Standard Diagnosis:** Video-EEG (V-EEG) monitoring is the investigation of choice to differentiate ES from PNES. * **Prolactin Levels:** Serum prolactin rises significantly 15–30 minutes after a true tonic-clonic seizure; it remains normal in PNES. * **Eyes:** In PNES, eyes are often **tightly closed** and resistant to opening; in organic seizures, eyes are usually open or deviated. * **Duration:** PNES episodes often last longer (>2 minutes) compared to typical organic seizures.

Question 1

Ribot's law deals with which of the following?

Accepted Answer

Retrograde amnesia

Answer

Dementia

Answer

Delirium

Answer

Anterograde amnesia

Question 2

Signs of organic brain damage are evident on which of the following tests?

Accepted Answer

Bender Gestalt test

Answer

Rorschach test

Answer

Sentence completion test

Answer

Thematic Apperception Test

Question 3

In which of the following chronic conditions are degenerative changes in the brain seen, which are not part of normal aging?

Accepted Answer

Amnestic syndrome

Answer

Dementia

Answer

Delirium

Answer

Pseudodementia

Question 4

Which of the following is NOT a common characteristic of psychiatric symptoms associated with brain tumors?

Accepted Answer

More common with brainstem lesions

Answer

More common with supra- than infratentorial tumors

Answer

More common with slow-growing tumors

Answer

More common with temporal than frontal lobe tumors

Question 5

A 32-year-old woman is diagnosed with major depression. What is the chance that her identical twin sister will develop the same disease?

Accepted Answer

70%

Answer

5%

Answer

20%

Answer

50%

Question 6

Antegrade amnesia is seen in:

Accepted Answer

Post-traumatic head injury

Answer

Drug induced

Answer

Electroconvulsive therapy

Answer

Stroke

Question 7

Which of the following symptoms is likely to be of organic origin?

Accepted Answer

Prominent visual hallucination

Answer

Delusion of guilt

Answer

Auditory hallucinations

Answer

Formal thought disorder

Question 8

Which of the following neurotransmitters/factors increases on Electroconvulsive therapy?

Accepted Answer

Brain derived neurotrophic factor

Answer

5-hydroxy-indole-acetic acid

Answer

Dopamine

Answer

Serotonin

Question 9

The presence of delusion, hallucination, and disturbed cognitive functions indicate which of the following?

Accepted Answer

Organic Brain Syndrome

Answer

Paranoid Psychosis

Answer

Obsessive-Compulsive Disorder

Answer

Dissociative disorder

Question 10

In a youngster with a history of seizures, which of the following would be most suggestive of a nonorganic or hysterical etiology?

Accepted Answer

Changing pattern of the seizure

Answer

Postictal sleep

Answer

Biting of the tongue during an episode

Answer

Urinary incontinence during an episode

Neurobiology and Genetics of Mental Disorders — MCQs

Neurobiology and Genetics of Mental Disorders — MCQs

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