Neurobiology and Genetics of Mental Disorders — MCQs
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All of the following are true about Kluver-Bucy syndrome except?
Specific genetic conditions account for a proportion of Autism Spectrum Disorder (ASD) cases. Which of the following are known to be associated with ASD ? I. Tuberous sclerosis II. Fragile X syndrome III. Prader-Willi syndrome IV. Patau syndrome Select the correct answer using the code given below :
A 14-year-old female patient presents to the ENT OPD and complains that she can hear sounds clearly but has difficulty processing and understanding what is being said. Her Pure tone audiometry and ABR are normal. What is the likely diagnosis in this patient?
Prosopagnosia is:
Brain areas involved with obsessive compulsive disorder include all except:
In juvenile myoclonic epilepsy (JME), which is the most common presentation?
A 48 year old male incurred a road traffic accident leading to a brain lesion. Now the patient feels euphoric, laughs uncontrollably, jokes & makes puns. Which of the following brain parts may be involved?
In which of the following diseases was decrease in levels of a single neurotransmitter first identified?
What is the concordance rate for schizophrenia in monozygotic twins?
Following are predispositions of Alzheimer's disease except:
Neurobiology and Genetics of Mental Disorders Indian Medical PG Practice Questions and MCQs
Question 11: All of the following are true about Kluver-Bucy syndrome except?
- A. Hypersexuality
- B. Hyperactivity (Correct Answer)
- C. Hypermetamorphosis
- D. Placidity
Explanation: **Kluver-Bucy Syndrome (KBS)** is a clinical triad of behavioral changes resulting from **bilateral lesions of the anterior temporal lobes**, specifically involving the **amygdala**. ### Why "Hyperactivity" is the Correct Answer (The Exception) In Kluver-Bucy syndrome, patients typically exhibit **placidity** (a marked decrease in aggression and fear) rather than hyperactivity. While they may constantly explore their environment (hypermetamorphosis), they lack the increased psychomotor speed or agitation associated with hyperactivity. In fact, the syndrome is characterized by a "taming" effect where previously wild or aggressive subjects become docile. ### Explanation of Other Options * **Hypersexuality (A):** Patients show a marked increase in sexual libido, often directed toward inappropriate objects (paraphilias) or species. * **Hypermetamorphosis (C):** This refers to an irresistible impulse to notice and react to every visual stimulus, leading to the compulsive exploration of objects. * **Placidity (D):** This is a hallmark feature. The destruction of the amygdala leads to a loss of the "fear response," resulting in a lack of emotional reactivity and anger. ### High-Yield Clinical Pearls for NEET-PG * **Core Features (The 6 'H's):** 1. **Hypersexuality** 2. **Hypermetamorphosis** (Compulsive exploration) 3. **Hyperorality** (Tendency to examine objects by mouth) 4. **Hyperphagia** (Bulimia/Overeating) 5. **Hypo-emotionality** (Placidity/Docility) 6. **Visual Agnosia** (Psychic blindness – inability to recognize objects visually). * **Anatomical Site:** Bilateral Amygdala (Temporal Lobe). * **Common Causes:** Herpes Simplex Encephalitis (most common), Head Trauma, Pick’s Disease, and Stroke. * **Key Distinction:** Do not confuse Hypermetamorphosis with Hyperactivity; the former is a sensory-driven compulsion to touch, while the latter is a motor-driven state.
Question 12: Specific genetic conditions account for a proportion of Autism Spectrum Disorder (ASD) cases. Which of the following are known to be associated with ASD ? I. Tuberous sclerosis II. Fragile X syndrome III. Prader-Willi syndrome IV. Patau syndrome Select the correct answer using the code given below :
- A. I and III
- B. II and III
- C. I and II (Correct Answer)
- D. I and IV
Explanation: ***I and II*** - Both **Tuberous sclerosis** and **Fragile X syndrome** are well-established genetic conditions with a strong association with Autism Spectrum Disorder (ASD). - Tuberous Sclerosis Complex (TSC) is a genetic disorder that causes **benign tumors** to grow in the brain and other organs, and approximately **40-50% of individuals with TSC also have ASD**. Fragile X syndrome is the **most common inherited cause of intellectual disability** and a leading known **single-gene cause of ASD**, with about **25-50% of affected males** meeting the diagnostic criteria for ASD. *I and III* - While Tuberous sclerosis is strongly associated with ASD, **Prader-Willi syndrome** has a less consistent and well-defined relationship with ASD despite some overlapping behavioral features. - Prader-Willi syndrome is characterized by **hyperphagia (insatiable appetite)**, intellectual disability, and behavioral problems, but the autistic-like features may represent a behavioral phenocopy rather than true ASD. *II and III* - **Fragile X syndrome** is strongly associated with ASD, but **Prader-Willi syndrome** is not considered a primary or well-established genetic cause of ASD. - While intellectual disability and behavioral difficulties can be present in both, their underlying genetic mechanisms and core features differ significantly regarding ASD classification. *I and IV* - **Tuberous sclerosis** is clearly linked to ASD, but **Patau syndrome (Trisomy 13)** is not associated with ASD. - Patau syndrome is a severe chromosomal disorder characterized by **multiple congenital abnormalities** and **profound developmental delays**, often leading to early mortality. The severe nature of the condition and high infant mortality rate preclude typical ASD presentation.
Question 13: A 14-year-old female patient presents to the ENT OPD and complains that she can hear sounds clearly but has difficulty processing and understanding what is being said. Her Pure tone audiometry and ABR are normal. What is the likely diagnosis in this patient?
- A. Auditory cortex lesion
- B. Central Auditory Processing Disorder (CAPD) (Correct Answer)
- C. Malingering
- D. Sensorineural hearing loss
Explanation: ***Central Auditory Processing Disorder (CAPD)*** - **CAPD** is characterized by difficulty processing and understanding auditory information despite normal peripheral hearing, as indicated by normal pure tone audiometry and ABR. - The patient's inability to comprehend spoken words despite hearing them clearly is a hallmark symptom of **CAPD**. *Auditory cortex lesion* - While an **auditory cortex lesion** could impair sound processing, it would likely result in more profound and specific deficits in sound localization, discrimination, or recognition, rather than just difficulty understanding speech with otherwise normal hearing tests. - **Unilateral lesions** might cause mild or transient auditory issues, but bilateral lesions typically lead to **cortical deafness**, which contradicts the patient's ability to "hear sounds clearly." *Malingering* - **Malingering** involves deliberately fabricating or exaggerating symptoms for secondary gain, which is unlikely given the consistent presentation of difficulty understanding speech despite normal, objective hearing tests like ABR. - There are no indications in the case of **inconsistent test results** or other behaviors suggestive of feigned symptoms. *Sensorineural hearing loss* - **Sensorineural hearing loss** involves damage to the inner ear or auditory nerve, which would result in abnormal pure tone audiometry results and/or abnormal ABR findings. - The patient's **normal pure tone audiometry and ABR** rule out sensorineural hearing loss as the primary cause of her symptoms.
Question 14: Prosopagnosia is:
- A. Inability to recognize face (Correct Answer)
- B. Inability to read
- C. Anosmia
- D. Inability to write
Explanation: ***Inability to recognize face*** - **Prosopagnosia**, or **face blindness**, is a cognitive disorder characterized by an impaired ability to recognize familiar faces, including one's own. - This condition is often associated with damage to the **fusiform face area** in the brain, typically in the right hemisphere. *Inability to read* - The inability to read is known as **alexia** or **dyslexia**, which is distinct from the visual recognition deficit seen in prosopagnosia. - Alexia primarily involves difficulties with processing written language, not the visual recognition of faces. *Anosmia* - **Anosmia** refers to the complete or partial loss of the sense of smell and is a disorder affecting the olfactory system. - It is unrelated to visual processing or face recognition. *Inability to write* - The inability to write is termed **agraphia** or **dysgraphia**, a neurological condition that impairs writing ability. - This condition affects motor skills and language processing related to writing, not visual face recognition.
Question 15: Brain areas involved with obsessive compulsive disorder include all except:
- A. Head of caudate nucleus
- B. Corpus callosum (Correct Answer)
- C. Orbitofrontal cortex
- D. Basal ganglia
Explanation: ***corpus callosum*** - The **corpus callosum** is primarily involved in **interhemispheric communication**, connecting the two cerebral hemispheres, and is not a core area implicated in the pathophysiology of **OCD**. - While damage to the corpus callosum can lead to neurological deficits, it is not directly associated with the obsessions and compulsions seen in OCD. *Head of caudate nucleus* - The **caudate nucleus**, particularly its head, is part of the **basal ganglia** and is highly implicated in **OCD**, with studies showing abnormal activity and volume. - It plays a crucial role in **goal-directed behavior** and **habit formation**, which are dysfunctional in OCD. *Orbitofrontal cortex* - The **orbitofrontal cortex (OFC)** is consistently identified in neuroimaging studies as being hyperactive in individuals with **OCD**. - It is involved in **decision-making**, **reward processing**, and **emotional regulation**, contributing to the characteristic symptoms of OCD. *Basal ganglia* - The **basal ganglia**, a group of subcortical nuclei including the **caudate nucleus**, **putamen**, and **globus pallidus**, are central to the neurocircuitry of **OCD**. - This region is critical for **motor control**, **habit learning**, and **executive functions**, and its dysfunction is thought to contribute to the repetitive behaviors and cognitive rigidity seen in OCD.
Question 16: In juvenile myoclonic epilepsy (JME), which is the most common presentation?
- A. Absence seizures
- B. GTCS on awake state
- C. GTCS during sleep
- D. Myoclonus (Correct Answer)
Explanation: ***Myoclonus*** - **Myoclonic jerks** are the hallmark and defining feature of JME, present in virtually all patients - These typically occur bilaterally, symmetrically, and primarily involve the **upper extremities** shortly after waking up - Most common and earliest seizure manifestation in JME *Absence seizures* - While **absence seizures** can occur in JME, they are present in only 10-30% of patients - They are characterized by **brief periods of impaired consciousness** without motor convulsions - When present, they usually manifest earlier in childhood *GTCS on awake state* - **Generalized tonic-clonic seizures (GTCS)** occur in 85-95% of JME patients and are often triggered by sleep deprivation - They typically occur shortly after awakening and usually develop after myoclonic jerks have already begun - GTCS are not the *most common* or defining seizure type in JME *GTCS during sleep* - GTCS in JME are characteristically associated with awakening, not during sleep itself - While GTCS can occur, they are less common than myoclonic jerks as the presenting feature - The typical pattern is seizures occurring shortly *after* waking up rather than *during* sleep
Question 17: A 48 year old male incurred a road traffic accident leading to a brain lesion. Now the patient feels euphoric, laughs uncontrollably, jokes & makes puns. Which of the following brain parts may be involved?
- A. Parietal lobe
- B. Cerebellum
- C. Prefrontal cortex (Correct Answer)
- D. Occipital lobe
Explanation: ***Prefrontal cortex*** - Lesions in the **prefrontal cortex**, particularly the **orbital frontal cortex**, can lead to disinhibition, euphoria, inappropriate jocularity (witzelsucht), and lack of insight. - This region is critical for **executive functions**, social behavior, and emotional regulation, and damage can result in personality changes like those described. *Parietal lobe* - The **parietal lobe** is primarily involved in processing sensory information, spatial orientation, and navigation. - Damage typically results in sensory deficits, **neglect syndromes**, or **apraxia**, not euphoria or exaggerated humor. *Cerebellum* - The **cerebellum** is mainly responsible for motor control, coordination, and balance. - Lesions typically cause **ataxia**, dysarthria, and gait disturbances, not changes in mood or personality as described. *Occipital lobe* - The **occipital lobe** is the primary visual processing center of the brain. - Damage to this area typically leads to **visual field deficits**, cortical blindness, or visual agnosias, and is not associated with behavioral changes like euphoria or inappropriate humor.
Question 18: In which of the following diseases was decrease in levels of a single neurotransmitter first identified?
- A. Parkinson's disease (Correct Answer)
- B. Schizophrenia
- C. Huntington's disease
- D. Alzheimer's disease
Explanation: ***Parkinson's disease*** - The discovery of **decreased dopamine levels** in the **substantia nigra** of Parkinson's patients was a seminal finding in neurobiology. - This identification in the 1960s was one of the first clear links between a **specific neurotransmitter deficit** and a neurological disorder. *Schizophrenia* - While associated with **dopamine dysregulation** (specifically an excess in some pathways), the primary identification was not of a simple decrease in a single neurotransmitter. - The understanding of neurotransmitter involvement in schizophrenia is more complex, involving multiple systems and potentially **excess activity** rather than a deficit. *Huntington's disease* - Characterized by the degeneration of neurons in the **striatum**, leading to a decrease in **GABA** (gamma-aminobutyric acid) and acetylcholine. - The initial identification of a neurotransmitter deficit primarily focused on **GABA**, but this came after the initial findings in Parkinson's. *Alzheimer's disease* - Primarily defined by a significant loss of **cholinergic neurons**, leading to a decrease in **acetylcholine** in the brain. - The discovery of this specific neurotransmitter deficit also occurred after the initial identification in Parkinson's disease.
Question 19: What is the concordance rate for schizophrenia in monozygotic twins?
- A. 1%
- B. 10%
- C. 50% (Correct Answer)
- D. 0.10%
Explanation: ***50%*** - The **concordance rate** for schizophrenia in **monozygotic (identical) twins** is approximately **50%**. - This high concordance rate indicates a strong **genetic predisposition** but also highlights the role of **environmental factors**, as it is not 100%. *1%* - A 1% risk is closer to the **general population prevalence** of schizophrenia, not the concordance rate in monozygotic twins. - This low percentage would significantly underestimate the genetic component observed in twin studies for schizophrenia. *10%* - A 10% concordance rate is a significant increase over the general population risk but is still substantially lower than what has been consistently found in studies of monozygotic twins. - This percentage might be more aligned with the risk for first-degree relatives or dizygotic twins, not identical twins. *0.10%* - A 0.10% concordance rate is an extremely low figure, far below the actual observed rate for monozygotic twins. - Such a low percentage would suggest virtually no genetic influence on schizophrenia, which contradicts extensive research findings.
Question 20: Following are predispositions of Alzheimer's disease except:
- A. Down's syndrome
- B. Head trauma
- C. Low education group
- D. Blood type O (Correct Answer)
Explanation: ***Blood type O*** - There is currently **no established scientific evidence** linking blood type O directly to an increased risk or predisposition for Alzheimer's disease. - Genetic factors associated with Alzheimer's, such as the **APOE4 allele**, are not correlated with blood type. *Down's syndrome* - Individuals with **Down's syndrome** (Trisomy 21) have three copies of chromosome 21, which includes the **APP (amyloid precursor protein) gene**. - This overexpression of APP leads to increased production of **amyloid-beta plaques**, predisposing them to early-onset Alzheimer's-like pathology. *Head trauma* - A history of **moderate to severe head trauma**, particularly if repeated, has been identified as a significant risk factor for developing Alzheimer's disease. - Head injuries can trigger mechanisms that lead to **amyloid plaque deposition** and **tau tangle formation**. *Low education group* - A lower level of education is associated with an **increased risk of Alzheimer's disease**, possibly due to differences in **cognitive reserve**. - Higher education is thought to build greater cognitive reserve, making the brain more resilient to the pathological changes of Alzheimer's.
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