**Question:** In the postnatal period the greatest growth in the grey matter of the C.N.S. is of

A. Infancy
B. Childhood
C. Adolescence
D. Adulthood

**Correct Answer:** A. Infancy

**Core Concept:**
The postnatal period refers to the time immediately following birth when the developing brain undergoes significant growth and maturation. The grey matter, which includes neurons and their dendrites, plays a crucial role in cognitive functions and intelligence. In this context, the grey matter refers to the cerebral cortex, which is primarily responsible for higher cognitive functions.

**Why the Correct Answer is Right:**
In the postnatal period, the greatest growth of grey matter occurs during infancy. During this stage, the cerebral cortex experiences a significant increase in the number of neurons and synapses, which contributes to the development of cognitive abilities such as learning, memory, and problem-solving. This growth is primarily due to the process of neuronal migration, proliferation, and differentiation, which results in an expansion of the cerebral cortex.

**Why Each Wrong Option is Incorrect:**
1. Childhood (Option B): Although grey matter growth continues in childhood, the rate of expansion slows down compared to infancy. The cognitive development during childhood is mainly influenced by synaptic pruning, myelination, and synaptic plasticity, which are less prominent compared to the rapid growth observed in infancy.
2. Adolescence (Option C): Grey matter growth in adolescence is also significant, but it occurs at a slower rate than infancy. The cognitive tasks during this phase involve social skills, decision-making, and emotional regulation, which are different from those during infancy.
3. Adulthood (Option D): Grey matter growth reaches a peak during infancy and subsequently declines. While grey matter volume may remain stable in adulthood, the cognitive functions during this phase focus on problem-solving, decision-making, and abstract thinking, which are different from those during infancy.

**Clinical Pearl:**
The early childhood period, particularly infancy, is crucial for brain development and cognitive abilities. This growth window allows for the establishment of neural connections and refinement of neural networks, which contributes to the foundation of intellectual abilities and behavior patterns associated with infancy. Understanding these developmental stages is essential for healthcare providers to provide appropriate care and support for infants and their families.