Neurobiology and Genetics of Mental Disorders — MCQs

Neurobiology and Genetics of Mental Disorders Indian Medical PG Practice Questions and MCQs

Question 21: When previously learned information is interfered with by newly acquired information, it is called:

A. Proactive inhibition
B. Inhibition
C. Simple inhibition
D. Retroactive inhibition (Correct Answer)

Explanation: ***Retroactive inhibition*** - This occurs when **newly learned information interferes** with the recall of **previously learned information**. - It is a form of memory interference where **recent learning impairs older memories**. *Proactive inhibition* - This happens when **previously learned information interferes** with the recall of **newly learned information**. - For example, if you learn a new phone number, your old phone number might make it harder to remember the new one. *Inhibition* - This is a **general term** that refers to a process that **blocks or suppresses something**, often used in the context of cognitive processes or physiological responses. - It does not specifically describe the direction of interference (i.e., whether old information interferes with new, or vice-versa). *Simple inhibition* - This term is **not a standard or recognized concept** in the field of memory or cognitive psychology. - It lacks the specific meaning associated with proactive or retroactive interference.

Question 22: Hyperphagia, weight gain and hypersexuality is seen in ?

A. Stein-Leventhal syndrome
B. Kluver-Bucy syndrome (Correct Answer)
C. Bulimia nervosa
D. Kleine-Levin syndrome

Explanation: ***Kluver-Bucy syndrome*** - This syndrome is characterized by **docility**, **hypersexuality**, **hyperphagia**, and **oral tendencies**, which all align with the symptoms described. - It results from bilateral lesions of the **amygdala** and **temporal lobes**, often due to trauma, stroke, or herpes simplex encephalitis. - **Weight gain** occurs secondary to hyperphagia. *Stein-Leventhal syndrome* - Refers to **polycystic ovary syndrome (PCOS)**, which presents with reproductive and endocrine symptoms like **amenorrhea**, **hirsutism**, and **infertility**. - It does not typically involve the cluster of behavioral symptoms such as hyperphagia or hypersexuality. *Bulimia nervosa* - An eating disorder characterized by recurrent episodes of **binge eating followed by compensatory behaviors** like purging, excessive exercise, or fasting. - While it involves hyperphagia, it does not include hypersexuality or the neurological basis seen in Kluver-Bucy syndrome. *Kleine-Levin syndrome* - A rare disorder characterized by **recurrent episodes of hypersomnia**, **hyperphagia**, and **hypersexuality** in adolescent males. - Unlike Kluver-Bucy syndrome, it presents in **episodic cycles** (lasting days to weeks) with normal behavior between episodes, and does not result from structural brain lesions.

Question 23: Behavioural problems caused by senility, drug damage, brain injury or disease, and the toxic effects of poisons are classified as __________ disorders

A. Psychosomatic
B. Substance use
C. Organic (Correct Answer)
D. Psychotic

Explanation: ***Organic*** - **Organic disorders** are characterized by behavioral or psychological symptoms that are directly attributable to a **physiological dysfunction** or structural change in the brain. - This category includes conditions arising from **senility**, drug-induced damage, brain injury, disease (e.g., **dementia**), or exposure to **neurotoxins**. *Psychosomatic* - **Psychosomatic disorders** involve physical symptoms that are caused or aggravated by **psychological factors**, like stress. - The primary cause is not a direct physiological injury or disease of the brain itself. *Substance use* - **Substance use disorders** describe maladaptive patterns of substance use leading to clinically significant impairment or distress. - While drug damage is mentioned in the question, this category focuses specifically on the **addiction** and related behaviors, not the broad range of organic causes. *Psychotic* - **Psychotic disorders** are characterized by a significant loss of contact with reality, often involving **hallucinations** or **delusions**. - While some organic conditions can cause psychotic symptoms, the term "psychotic disorders" refers to a specific symptom cluster rather than the underlying physical cause.

Question 24: A 30-year-old shows delusions, hallucinations, and marked thought disorder. Labs reveal anti-NMDA receptor antibodies. Best initial treatment?

A. Immunotherapy (Correct Answer)
B. Benzodiazepines
C. ECT
D. Antipsychotics

Explanation: ***Immunotherapy*** - The presence of **anti-NMDA receptor antibodies** indicates an autoimmune etiology for the psychiatric symptoms, making **immunotherapy** (e.g., corticosteroids, IVIG, plasmapheresis) the definitive first-line treatment. - Immunotherapy aims to reduce inflammation and remove autoantibodies, thereby reversing the neurological and psychiatric manifestations. *Benzodiazepines* - While useful for acute agitation or catatonia in psychiatric disorders, **benzodiazepines** do not address the underlying autoimmune pathology of anti-NMDA receptor encephalitis. - They would provide only symptomatic relief and would not prevent disease progression or long-term neurological damage. *ECT* - **Electroconvulsive therapy (ECT)** is a treatment for severe, refractory mood disorders or catatonia, which might be present in anti-NMDA receptor encephalitis. - However, ECT is a symptomatic treatment and does not target the autoimmune cause, making it less appropriate as the **initial definitive treatment**. *Antipsychotics* - **Antipsychotics** are used to manage psychosis, delusions, and hallucinations, which are prominent in anti-NMDA receptor encephalitis. - However, they do not treat the underlying **autoimmune inflammation** and may worsen some symptoms, such as autonomic instability or seizures, in this specific condition.

Question 25: In schizophrenia, what role does dopamine play in the mesolimbic pathway?

A. It is decreased, leading to negative symptoms in schizophrenia.
B. It is stable, contributing to cognitive symptoms in schizophrenia.
C. It is decreased, contributing to mood symptoms in schizophrenia.
D. It is increased, leading to positive symptoms in schizophrenia. (Correct Answer)

Explanation: ***It is increased, leading to positive symptoms in schizophrenia.*** - An **excess of dopamine** in the **mesolimbic pathway** is strongly associated with the **positive symptoms** of schizophrenia, such as **hallucinations** and **delusions**. - This hyperactivity is a cornerstone of the **dopamine hypothesis** of schizophrenia, supported by the efficacy of dopamine receptor blocking antipsychotics. *It is decreased, leading to negative symptoms in schizophrenia.* - **Negative symptoms** (e.g., anhedonia, alogia, avolition) are more often linked to **decreased dopamine activity** in the **mesocortical pathway**, not the mesolimbic pathway. - The mesolimbic pathway's primary role is in reward and motivation, not the development of negative symptoms from dopamine reduction. *It is stable, contributing to cognitive symptoms in schizophrenia.* - Cognitive symptoms in schizophrenia (e.g., impaired working memory, executive dysfunction) are generally attributed to **dysfunction in the prefrontal cortex** and often involve **dopamine abnormalities in the mesocortical pathway**, specifically hypofunction, not stable levels. - While dopamine plays a role in cognition, its being "stable" wouldn't explain the cognitive deficits observed in schizophrenia, and these are not primarily linked to the mesolimbic pathway directly. *It is decreased, contributing to mood symptoms in schizophrenia.* - While dopamine dysfunction can contribute to mood symptoms (like depression or anhedonia) in various psychiatric conditions, the **mesolimbic pathway's primary role** in schizophrenia is linked to positive symptoms via **hyperactivity**, not decreased dopamine. - Mood symptoms in schizophrenia often have a more complex neurobiological basis, involving multiple neurotransmitter systems and brain regions, with decreased dopamine in the mesocortical pathway being more relevant for some aspects.

Question 26: A patient describes seeing colors when hearing certain sounds. This experience is best described as:

A. Perceptual distortion
B. Synesthesia (Correct Answer)
C. Psychosis
D. Sensory misperception

Explanation: ***Synesthesia*** - **Synesthesia** is a neurological phenomenon where stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. - In this case, hearing sounds (auditory stimulation) triggers the perception of colors (visual experience), which is a classic example of **audiovisual synesthesia**. *Perceptual distortion* - **Perceptual distortion** refers to an altered perception of real external stimuli, such as **macropsia** (objects appearing larger) or **micropsia** (objects appearing smaller). - This option does not accurately describe the cross-modal nature of the patient's experience, where one sense triggers another unrelated sensory input. *Psychosis* - **Psychosis** is a severe mental disorder in which thought and emotions are so impaired that contact is lost with external reality, often involving **hallucinations** or **delusions**. - Synesthesia is a consistent, involuntary, and often pleasant or neutral experience, not indicative of a loss of touch with reality or psychiatric illness. *Sensory misperception* - **Sensory misperception** is a broad term that could encompass various errors in interpreting sensory input, but it doesn't specifically capture the unique cross-modal aspect described. - While synesthesia technically involves a form of "misperception" in a neurological sense, the term **synesthesia** is far more precise and accurate for this specific phenomenon.

Question 27: What is the primary function of the corpus callosum, and what deficit results from its surgical sectioning (split-brain procedure)?

A. Coordinates motor function; results in hemiplegia.
B. Processes sensory input; results in hemisensory loss.
C. Stores memory; results in global amnesia.
D. Facilitates interhemispheric communication; leads to disconnection syndrome. (Correct Answer)

Explanation: ***Facilitates interhemispheric communication; leads to disconnection syndrome.*** - The **corpus callosum** is the largest commissural fiber bundle connecting the brain's two hemispheres, primarily responsible for **interhemispheric communication and integration**. - Surgical sectioning (corpus callosotomy), rarely performed for **refractory epilepsy**, results in **split-brain syndrome** or **disconnection syndrome**, where each hemisphere functions independently. - Classic deficits include **inability to name objects in the left visual field** (processed by right hemisphere, which lacks language), **alien hand syndrome**, and difficulty integrating bilateral sensory-motor information. *Coordinates motor function; results in hemiplegia.* - While the corpus callosum transmits motor planning information between hemispheres, its **primary role is not motor coordination itself**—that is handled by the corticospinal tracts and cerebellar pathways. - **Hemiplegia** (unilateral paralysis) results from damage to the motor cortex or corticospinal tract, **not from corpus callosum sectioning**. - Split-brain patients maintain normal motor function in both sides of the body. *Processes sensory input; results in hemisensory loss.* - Each cerebral hemisphere processes sensory input from the contralateral body, but the **corpus callosum does not primarily process sensory input**—it transmits already processed information between hemispheres. - **Hemisensory loss** results from damage to sensory pathways (thalamus, sensory cortex), not from callosal sectioning. - Split-brain patients retain normal sensory perception bilaterally. *Stores memory; results in global amnesia.* - Memory storage involves the **hippocampus, medial temporal lobe structures, and distributed cortical networks**, not the corpus callosum. - **Global amnesia** results from bilateral hippocampal damage (as in severe hypoxia or herpes encephalitis), not callosal sectioning. - Split-brain patients show subtle memory integration deficits but not amnesia.

Question 28: Which receptors are primarily implicated in the pathophysiology of schizophrenia?

A. Dopamine D2 (Correct Answer)
B. NMDA
C. GABA_A
D. 5-HT2A

Explanation: ***Dopamine D2*** - The **dopamine hypothesis of schizophrenia** posits that excess dopamine activity, particularly at **D2 receptors in the mesolimbic pathway**, contributes to positive symptoms (hallucinations and delusions). - Most typical and many atypical **antipsychotics** exert their primary therapeutic effects by **blocking D2 receptors**. - This is the **most established and clinically validated** mechanism in schizophrenia pathophysiology. *GABA_A* - While GABAergic dysfunction is implicated in some psychiatric disorders, **GABA_A receptors are not the primary receptors** in the core pathophysiology of schizophrenia. - Dysregulation of GABAergic interneurons may contribute to cognitive deficits, but it's not the central mechanism for hallmark symptoms. *NMDA* - **NMDA receptors** (a type of glutamate receptor) are implicated in pathophysiology, particularly regarding cognitive and negative symptoms, as **hypofunction** of these receptors contributes to glutamatergic dysfunction. - However, the **NMDA hypothesis is secondary** to the dopamine hypothesis, and D2 receptor overactivity remains the most widely accepted primary mechanism for positive symptoms. *5-HT2A* - **Serotonin 5-HT2A receptors** are significant targets for **atypical antipsychotics**, but they are **not the primary receptors** in the fundamental pathophysiology of schizophrenia. - Blockade of 5-HT2A receptors, combined with D2 blockade, helps ameliorate positive and negative symptoms and may reduce extrapyramidal side effects.

Question 29: Which of the following is a characteristic symptom of frontal lobe syndrome?

A. Indifference (Correct Answer)
B. Irritability
C. Euphoria
D. None of the options

Explanation: ***Indifference*** - **Indifference (apathy)** is one of the most **characteristic and consistent** symptoms of **frontal lobe syndrome**, particularly with **dorsolateral prefrontal cortex** damage. - Patients exhibit **reduced spontaneous activity**, **flat affect**, lack of concern for consequences, and **decreased motivation**. - This symptom is part of the classic **frontal lobe triad**: apathy, disinhibition, and executive dysfunction. *Euphoria* - While **euphoria** and inappropriate jocularity (moria) can occur with **orbitofrontal cortex** damage, it represents only one subtype of frontal lobe syndrome presentation. - More commonly associated with **mania** in primary mood disorders or substance-induced states. - Less consistent and characteristic compared to apathy/indifference. *Irritability* - **Irritability** can occur with frontal lobe dysfunction due to impaired emotional regulation, but it is **less specific** and seen in many other psychiatric and neurological conditions. - Often secondary to frustration from cognitive difficulties rather than a primary frontal lobe symptom. - Not as pathognomonic as apathy for frontal lobe syndrome. *None of the options* - Incorrect because **indifference (apathy)** is a well-established, characteristic symptom of **frontal lobe syndrome**. - The frontal lobes, especially the **dorsolateral** and **orbitofrontal** regions, are crucial for emotional regulation, executive functions, and motivated behavior.

Question 30: What is Prosopagnosia?

A. Impairment of consciousness
B. Being unaware of one's problems
C. Failure to identify objects
D. Difficulty in identifying known faces (Correct Answer)

Explanation: ***Difficulty in identifying known faces*** - **Prosopagnosia**, also known as **face blindness**, is a neurological disorder characterized by an inability to recognize familiar faces. - Individuals with prosopagnosia may have trouble recognizing even close family members or their own reflection, despite having intact vision and general intellectual function. - This is a specific type of agnosia limited to face recognition. *Impairment of consciousness* - Impairment of consciousness refers to a reduced state of awareness or responsiveness, often seen in conditions like coma or delirium. - This is a broad neurological state and does not specifically describe the inability to recognize faces. *Being unaware of one's problems* - This symptom is known as **anosognosia**, which is a lack of insight into one's own neurological deficits or illness. - Anosognosia is a problem of self-awareness, not specifically face recognition. *Failure to identify objects* - The inability to identify objects is a form of **agnosia**, specifically **associative visual agnosia** if the person can see the object but not recognize it. - While prosopagnosia is a type of agnosia, it is highly specific to faces, whereas object agnosia refers to a broader failure in object recognition.

Practice by Chapter

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Neurotransmitters and Receptors

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Neuroimaging in Psychiatry

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Neuropsychological Assessment

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Genetics of Psychiatric Disorders

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Epigenetics in Psychiatry

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Psychoneuroimmunology

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Circadian Rhythms and Psychiatry

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Neurodevelopmental Perspectives

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Stress and HPA Axis

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Gene-Environment Interactions

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Biomarkers in Psychiatry

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