Engram Physical Changes Explained

An engram, or memory trace, involves physical modifications in the brain that represent learned information. Let's analyze the given points:

• 1. Change in number of receptor sites: This is a known mechanism. Synapses can increase or decrease the number of receptors to strengthen or weaken connections, facilitating memory storage.
• 3. Changes in the sensitivity of the synapse through repeated stimulation: Synaptic plasticity, like Long-Term Potentiation (LTP) and Long-Term Depression (LTD), involves altering synaptic sensitivity with repeated use, which is crucial for engram formation.
• 4. Changes in the dendrites: Dendrites, the receiving parts of neurons, can undergo structural changes, such as the growth of new dendritic spines or alterations in existing ones, to accommodate new connections and store information.

Points 2 (Change in the transmission system) and 5 (Changes in the neuron structure) are too general. While transmission and structure are involved, points 1, 3, and 4 describe specific, well-established physical changes directly linked to memory encoding (engram formation).

Therefore, the physical changes involved in engrams are primarily changes in the number of receptor sites, changes in synaptic sensitivity, and changes in dendrites.

Selected Engram Components

Based on the analysis, the correct components representing physical changes in engrams are:

• 1. Change in number of receptor sites
• 3. Changes in the sensitivity of the synapse through repeated stimulation
• 4. Changes in the dendrites

This corresponds to Option A.