Neurobiology and Genetics of Mental Disorders — MCQs

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

Question 41: Which of the following techniques is associated with the term 'MERMER' in the context of memory recognition?

A. Brain fingerprinting (Correct Answer)
B. Narcoanalysis
C. DNA fingerprinting
D. Polygraph test

Explanation: ***Brain fingerprinting*** - **MERMER** (**Memory and Encoding Related Multifaceted Electroencephalographic Response**) is a key component of **brain fingerprinting**, which uses **EEG** to detect brain responses to specific information. - This technique aims to determine if an individual has specific knowledge or memories related to an event, by measuring electrical activity in the brain. *Narcoanalysis* - Involves administering psychoactive drugs (e.g., **sodium pentothal**) to induce a semi-conscious state, under the premise that it might facilitate recall of hidden memories. - It does not involve the measurement of **EEG responses** or the specific MERMER phenomenon. *DNA fingerprinting* - A technique used to identify individuals based on their unique **DNA profiles**, often used in forensics and paternity testing. - It is a **molecular biology** technique and has no association with brainwave patterns or memory recognition. *Polygraph test* - Measures physiological responses such as **heart rate**, **blood pressure**, **respiration rate**, and **skin conductivity** to assess deception. - While it attempts to infer truthfulness, it does not directly measure memory recall through EEG patterns like MERMER.

Question 42: Which of the following is NOT typically associated with Korsakoff's psychosis?

A. Long Term Memory Loss
B. Confabulation
C. Immediate/Working Memory Loss (Correct Answer)
D. Mammillary Bodies Involved

Explanation: ***Immediate/Working Memory Loss*** - Korsakoff's psychosis is primarily characterized by **profound anterograde amnesia** (inability to form new long-term memories) and significant **retrograde amnesia** (loss of past memories). - **Immediate/working memory** (the ability to hold information for seconds, such as digit span) is **relatively preserved** in Korsakoff's syndrome, unlike the severe deficits in forming and retrieving long-term memories. - The core deficit is the inability to transfer information from working memory to long-term storage (consolidation failure), not impairment in immediate recall itself. - This preservation of immediate memory with profound long-term memory loss is a key distinguishing feature of the syndrome. *Confabulation* - **Confabulation** (fabrication of memories without intent to deceive) is a **classic and common symptom** of Korsakoff's psychosis. - Patients spontaneously generate false narratives to fill in memory gaps, arising from severe anterograde and retrograde amnesia. - This is a pathognomonic feature used in clinical diagnosis. *Long Term Memory Loss* - **Severe long-term memory loss** (both anterograde and retrograde) is the **defining hallmark** of Korsakoff's psychosis. - Anterograde amnesia prevents formation of new long-term memories, while retrograde amnesia causes loss of previously stored memories, typically with a temporal gradient. - This profoundly impacts daily functioning and is central to diagnosis. *Mammillary Bodies Involved* - Damage to the **mammillary bodies** and **dorsomedial nucleus of the thalamus** due to **thiamine (B1) deficiency** is the **neuropathological basis** of Korsakoff's psychosis. - These structures are critical components of the **Papez circuit** (hippocampus-fornix-mammillary bodies-thalamus-cingulate-hippocampus), essential for memory consolidation. - Often preceded by Wernicke's encephalopathy (acute confusional state, ataxia, ophthalmoplegia).

Question 43: Which of the following neurotransmitters is NOT suspected to be involved in the pathophysiology of schizophrenia?

A. Ascorbic acid (Correct Answer)
B. Serotonin (5-HT)
C. Norepinephrine
D. Glutamate

Explanation: ***Ascorbic acid*** - **Ascorbic acid (Vitamin C)** is an important antioxidant and cofactor, but it is **not a neurotransmitter**. - While it may have neuroprotective roles, there is **no significant theory** suggesting ascorbic acid dysregulation is involved in the core pathophysiology of schizophrenia. - Unlike the other options, ascorbic acid is not part of any major neurotransmitter hypothesis of schizophrenia. *Serotonin (5-HT)* - The **serotonin hypothesis** of schizophrenia suggests an imbalance in serotonergic activity, particularly involving **5-HT2A receptors**. - Serotonin is targeted by **atypical antipsychotics** (e.g., risperidone, olanzapine) which block 5-HT2A receptors. - Serotonin dysregulation is believed to contribute to both **positive and negative symptoms** of schizophrenia. *Norepinephrine* - Dysregulation of **norepinephrine** has been implicated in the **cognitive and negative symptoms** of schizophrenia. - Alterations in noradrenergic systems contribute to deficits in **attention, working memory, and motivation** in affected individuals. - The prefrontal cortex noradrenergic system is particularly relevant to schizophrenia pathophysiology. *Glutamate* - The **NMDA receptor hypofunction hypothesis** is a major theory in schizophrenia pathophysiology. - **Glutamate** dysfunction, particularly involving NMDA receptors, can explain positive, negative, and cognitive symptoms. - NMDA receptor antagonists (like PCP and ketamine) can **induce psychotic symptoms** similar to schizophrenia, supporting this hypothesis.

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