Cerebral Cortex Functions — MCQs
Moro's reflex persisting for more than 6 months indicates damage to which of the following lobes?
Which structure connects Broca's area and Wernicke's area?
Frontal gyrus lesion leads to?
Visual processing center is located in -
Which of the following cells in the brain are responsible for handling information regarding ability to read the slide below? (Recent NEET Pattern 2016-17)
Which of the following is NOT true about the brainstem?
Which of the following has small representation in somatosensory area of cerebral cortex -
Identify the type of the fibre marked in the image of the internal capsule.
Damage to Auditory Cortex on one side causes:
All of the following cause the secretion of gastric juice during the cephalic phase EXCEPT:
Cerebral Cortex Functions Indian Medical PG Practice Questions and MCQs
Question 1: Moro's reflex persisting for more than 6 months indicates damage to which of the following lobes?
- A. Temporal
- B. Frontal (Correct Answer)
- C. Occipital
- D. Parietal
Explanation: ***Frontal*** - Persistence of primitive reflexes such as the **Moro reflex** beyond 6 months suggests **delayed cortical maturation** and failure of cortical inhibition. - The **frontal lobe** and its connections via the **corticospinal tract** play a key role in suppressing brainstem-mediated primitive reflexes as the CNS matures. - While persistence often indicates **generalized CNS dysfunction** (e.g., cerebral palsy, developmental delay), among cortical lobes, the frontal lobe's motor and inhibitory functions make it most relevant to reflex suppression. *Temporal* - The temporal lobe is primarily involved in **auditory processing**, **memory formation**, and **language comprehension**. - Damage typically presents with **aphasia**, **auditory deficits**, or **memory impairment**, not persistent primitive reflexes. *Occipital* - The occipital lobe is responsible for **visual processing** and **visual perception**. - Lesions result in **visual field defects**, **cortical blindness**, or **visual agnosia**, not reflex abnormalities. *Parietal* - The parietal lobe integrates **sensory information** and is involved in **spatial awareness** and **body sensation**. - Damage leads to **sensory deficits**, **neglect syndromes**, or **apraxia**, not persistence of primitive reflexes.
Question 2: Which structure connects Broca's area and Wernicke's area?
- A. Fornix
- B. Anterior commissure
- C. Corpus callosum
- D. Arcuate fasciculus (Correct Answer)
Explanation: ***Arcuate fasciculus*** - The **arcuate fasciculus** is a bundle of **association fibers** that connects the **Broca's area** (speech production) and **Wernicke's area** (speech comprehension) in the brain [1]. - Damage to this pathway can lead to **conduction aphasia**, where speech comprehension and production are relatively preserved, but repetition is severely impaired. *Fornix* - The **fornix** is a C-shaped bundle of nerve fibers in the brain that acts as the primary efferent (output) pathway of the **hippocampus**, a crucial structure for memory. - It carries signals from the hippocampus to the mammillary bodies and other subcortical structures, playing a key role in **episodic memory** and **spatial navigation**. *Anterior commissure* - The **anterior commissure** is a bundle of nerve fibers, located in front of the columns of the fornix, that connects the two **temporal lobes** and plays a role in pain sensation and memory. - It specifically connects parts of the **pyriform cortex** and **amygdalar nuclei** of the two hemispheres. *Corpus callosum* - The **corpus callosum** is a large, C-shaped nerve fiber bundle found beneath the cerebral cortex in the brain, connecting the **two cerebral hemispheres**. - It facilitates **interhemispheric communication**, allowing for the transfer of motor, sensory, and cognitive information between both sides of the brain [1].
Question 3: Frontal gyrus lesion leads to?
- A. Nominal aphasia
- B. Akinetic mutism
- C. Wernicke's aphasia
- D. Broca's aphasia (Correct Answer)
Explanation: ***Broca's aphasia*** - A lesion in the **frontal gyrus**, specifically **Broca's area** (Brodmann areas 44 and 45), leads to Broca's aphasia [1]. - This condition is characterized by **non-fluent speech**, difficulty with articulation, and telegraphic sentences, while comprehension remains relatively intact [1]. *Nominal aphasia* - This is also known as **anomic aphasia**, characterized primarily by difficulty with **word finding** (naming objects). - It results from lesions in various cortical areas, but typically not isolated to Broca's area in the frontal gyrus. *Akinetic mutism* - This condition involves a state of **unresponsiveness** where the patient is awake but does not move or speak. - It usually results from lesions in the **cingulate gyrus**, basal ganglia, or medial frontal lobes, often bilateral, not typically a solitary frontal gyrus lesion. *Wernicke's aphasia* - Wernicke's aphasia results from damage to **Wernicke's area**, located in the **posterior superior temporal gyrus** [1]. - It is characterized by **fluent but nonsensical speech** with impaired comprehension [1].
Question 4: Visual processing center is located in -
- A. Occipital lobe (Correct Answer)
- B. Frontal lobe
- C. Parietal lobe
- D. Temporal lobe
Explanation: ***Occipital lobe*** - The **occipital lobe** houses the **primary visual cortex**, which is responsible for processing and interpreting visual information received from the eyes [1]. - Damage to this lobe can lead to various visual deficits, including **cortical blindness** or **visual agnosia** [2], [3]. *Frontal lobe* - The **frontal lobe** is primarily involved in **executive functions**, such as decision-making, problem-solving, planning, and voluntary movement. - It also plays a key role in **personality** and social behavior. *Parietal lobe* - The **parietal lobe** integrates sensory information from various parts of the body, including touch, temperature, pain, and pressure. - It also plays a crucial role in **spatial awareness** and navigation. *Temporal lobe* - The **temporal lobe** is mainly associated with **auditory processing**, memory, and language comprehension. - It contains the **primary auditory cortex** and structures vital for forming memories, such as the hippocampus.
Question 5: Which of the following cells in the brain are responsible for handling information regarding ability to read the slide below? (Recent NEET Pattern 2016-17)
- A. Magnocellular cells
- B. Parvocellular cells (Correct Answer)
- C. Purkinje cells
- D. Pyramidal cells
Explanation: ***Parvocellular cells*** - **Parvocellular cells** (P-cells) are responsible for processing detailed visual information, including **color**, **form**, and fine **texture**. Reading the Ishihara test requires the ability to distinguish specific colors and fine patterns. - They have **small receptive fields** and transmit information about high spatial resolution and chromatic detail, crucial for tasks such as reading and recognizing fine visual cues. *Magnocellular cells* - **Magnocellular cells** (M-cells) are primarily involved in detecting **motion** and processing **low-spatial frequency information**, such as global shape and location. - They have **large receptive fields** and are not primarily responsible for detailed color or pattern discrimination needed for reading. *Purkinje cells* - **Purkinje cells** are a type of large, extensively branched neuron located in the **cerebellar cortex**. - Their primary function is motor coordination, balance, and motor learning, not visual processing or reading. *Pyramidal cells* - **Pyramidal cells** are excitatory neurons found in the cerebral cortex and hippocampus, characterized by their pyramidal-shaped cell bodies. - While they are involved in complex cognitive functions, including parts of visual perception, they are not the specific cells in the primary visual pathway responsible for initial processing of fine details and color as required for reading this type of visual test.
Question 6: Which of the following is NOT true about the brainstem?
- A. Controls involuntary functions
- B. Regulates auditory reflexes
- C. Contains cranial nerve nuclei
- D. Coordinates fine motor movement (Correct Answer)
Explanation: ***Coordinates fine motor movement*** - The **cerebellum** is primarily responsible for coordinating **fine motor movements**, balance, and posture, not the brainstem. - While the brainstem transmits motor signals, it does not directly coordinate the precision and timing of voluntary movements. *Controls involuntary functions* - The brainstem contains centers vital for regulating **involuntary functions** such as **breathing**, **heart rate**, and **blood pressure**. - These life-sustaining functions are controlled by nuclei located in the medulla oblongata and pons. *Regulates auditory reflexes* - The **inferior colliculi** within the midbrain (part of the brainstem) are crucial centers for processing **auditory information** and mediating **auditory reflexes**, such as the startle reflex. - The superior colliculi are involved in visual reflexes, illustrating the brainstem's role in sensory processing and reflex arcs. *Contains cranial nerve nuclei* - The brainstem houses the nuclei for most of the **cranial nerves (III through XII)**, which control sensory and motor functions of the head and neck. - These nuclei are distributed throughout the midbrain, pons, and medulla oblongata.
Question 7: Which of the following has small representation in somatosensory area of cerebral cortex -
- A. Lips
- B. Thumb/fingers
- C. Tongue
- D. Trunk (Correct Answer)
Explanation: ***Trunk*** - The representation size in the **somatosensory cortex** is proportional to the **density of sensory receptors** and the importance of sensory feedback from that body part, not its physical size. - The trunk, while large in physical size, has a relatively **sparse distribution of specialized sensory receptors** compared to areas like the hands, lips, or tongue, thus leading to a smaller cortical representation. *Lips* - The lips have an **extremely high density of touch receptors** and are critical for fine sensory discrimination, speech, and feeding. - This high sensory innervation results in a **very large representation** in the somatosensory cortex. *Thumb/fingers* - The thumb and fingers are crucial for **fine motor manipulation**, complex tactile exploration, and detailed sensory feedback. - They possess a **very rich supply of mechanoreceptors**, leading to a disproportionately large cortical area dedicated to their sensation. *Tongue* - The tongue is vital for **taste perception, speech articulation**, and manipulating food during chewing and swallowing. - Its diverse sensory functions and high receptor density ensure a **significant representation** within the somatosensory cortex.
Question 8: Identify the type of the fibre marked in the image of the internal capsule.
- A. Projection fibers (Correct Answer)
- B. Short association fibers
- C. Long association fibers
- D. Commissural fibers
Explanation: ***Projection fibers*** - The image shows the **internal capsule**, which is a white matter structure composed of **projection fibers** that connect the cerebral cortex to subcortical structures, brainstem, and spinal cord. - These fibers facilitate communication between different levels of the central nervous system, including motor and sensory pathways. *Short association fibers* - These fibers, also known as **U-fibers**, connect adjacent gyri within the **same cerebral hemisphere**. - They are typically located superficially in the cerebral cortex, not deep within the brain as shown in the internal capsule. *Long association fibers* - These fibers connect **different lobes** within the **same cerebral hemisphere**, such as the arcuate fasciculus connecting temporal and frontal lobes. - While they are white matter tracts, they do not constitute the internal capsule, which is specifically known for its extensive projection pathways. *Commissural fibers* - **Commissural fibers** connect corresponding areas in the **two cerebral hemispheres**, with the most prominent example being the **corpus callosum**. - The internal capsule, shown in the image, primarily consists of fibers projecting superiorly and inferiorly, rather than horizontally across hemispheres.
Question 9: Damage to Auditory Cortex on one side causes:
- A. Impaired localization of sound on the ipsilateral side
- B. Hearing loss and impaired tonal discrimination on the ipsilateral side
- C. No noticeable hearing loss or loss of tonal discrimination (Correct Answer)
- D. Hearing loss and impaired tonal discrimination on the contralateral side
Explanation: ***No noticeable hearing loss or loss of tonal discrimination*** - Due to the **bilateral projection** of auditory pathways, lesions in one auditory cortex do not typically cause significant hearing loss or loss of tonal discrimination. - Each ear's sensory input is processed by **both hemispheres**, providing a compensatory mechanism. - The auditory pathway from each ear projects to the **primary auditory cortex (Brodmann areas 41 and 42)** on both sides, making unilateral cortical lesions relatively silent in terms of basic hearing function. *Impaired localization of sound on the ipsilateral side* - While **sound localization** can be affected by unilateral cortical damage, it typically affects the **contralateral auditory field**, not ipsilateral. - Sound localization requires comparison of signals from both ears and involves higher-order auditory processing areas. - The primary auditory cortex is less critical for precise sound localization than association areas. *Hearing loss and impaired tonal discrimination on the ipsilateral side* - This is incorrect because auditory signals from one ear project to **both cerebral hemispheres**, minimizing the impact of a unilateral cortical lesion on basic hearing functions. - Unilateral damage to the auditory cortex does **not** cause ipsilateral hearing loss due to bilateral representation. *Hearing loss and impaired tonal discrimination on the contralateral side* - Significant **contralateral hearing loss** or loss of tonal discrimination is not a common consequence of unilateral auditory cortical damage due to bilateral innervation. - The extensive **crossing and bilateral projection** of auditory pathways ensures that both sides of the brain receive input from both ears, protecting against unilateral cortical lesions.
Question 10: All of the following cause the secretion of gastric juice during the cephalic phase EXCEPT:
- A. Thought of food
- B. Food in mouth
- C. Sight of food
- D. Food in stomach (Correct Answer)
Explanation: ***Food in stomach*** - The presence of **food in the stomach** primarily stimulates the **gastric phase** of digestion, which occurs after the cephalic phase. - This phase involves stimuli like **stomach distension** and the presence of digested proteins, leading to further gastric juice secretion. *Food in mouth* - The taste and chewing of **food in the mouth** stimulate the **cephalic phase** through neural signals to the brainstem. - This initiates anticipatory gastric juice secretion via the vagus nerve. *Sight of food* - The **sight of food** is a powerful sensory input that triggers the **cephalic phase** of digestion. - This visual stimulus sends signals to the cerebral cortex, which then activates the vagus nerve to stimulate gastric secretion. *Thought of food* - The **thought of food**, even without direct sensory contact, can initiate the **cephalic phase**. - This cognitive stimulation reflects a conditioned reflex, where the brain anticipates a meal and prepares the digestive system, including gastric secretion.
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