Final answer:
Donald Hebb called the combinations of neurons 'cell assemblies' and suggested that these assemblies represent psychological processes like learning and memory formation.
Step-by-step explanation:
The question you're asking involves the concept of how neurons work together in the brain to perform complex processes like memory formation and learning. Canadian psychologist Donald Hebb proposed the theory that when neurons in the brain fire together, they wire together, meaning that the connections between neurons become stronger with repeated activation. This concept is synonymous with the idea of synaptic plasticity, which is the brain's ability to strengthen or weaken synapses based on experience or activity.
Among the options provided in your question, the correct answer is Option 4: Cell assemblies; psychological processes. Hebb coined the term cell assemblies to describe these networks of neurons that become associated with one another through repeated activity.
It's key to understand that these cell assemblies are integral to how the brain learns and forms memories. Each assembly is a group of neurons that tend to get activated simultaneously, which ultimately contributes to psychological processes, such as thought, emotion, and behavior.