This video explores the neuroscience behind imagination, focusing on how the brain forms mental images of objects and combines them to create new, unseen images. It delves into the Hebbian principle and the mental synthesis theory, highlighting the role of the prefrontal cortex in coordinating neuronal activity to enable imaginative thinking.

Pause the video now and read the transcript! Answer in 3. Answer in 2. Answer in 1. Answer in 0. Answer in 1. Out of a single object, thousands of neurons in your posterior cortex fire. These neurons encode various characteristics of the object: specky, fruit, brown, green, and yellow. This synchronous firing strengthens the connections between that set of neurons, linking them together into what's known as a neuronal ensemble—in this case, the one for pineapple. In neuroscience, this is called the Hebbian principle: neurons that fire together wire together. If you try to imagine a pineapple later, the whole ensemble will light up, assembling a complete mental image. Dolphins are encoded by a different neuronal ensemble. In fact, every object that you've seen is encoded by a neuronal ensemble associated with it, the neurons wired together by that synchronized firing. But this principle doesn't explain the infinite number of objects that we can conjure up in our imaginations without ever seeing them. The neuronal ensemble for a dolphin balancing a pineapple doesn't exist. So how come you can imagine it anyway? One hypothesis, called the mental synthesis theory, says that, again, timing is key. If the neuronal ensembles for the dolphin and pineapple are activated at the same time, we can perceive the two separate objects as a single image. But something in your brain has to coordinate that firing. One plausible candidate is the prefrontal cortex, which is involved in all complex cognitive functions. Prefrontal cortex neurons are connected to the posterior cortex by long, spindly cell extensions called neural fibers. The mental synthesis theory proposes that, like a puppeteer pulling the strings, the prefrontal cortex neurons send electrical signals down these neural fibers to multiple ensembles in the posterior cortex. This activates them in unison. If the neuronal ensembles are turned on at the same time, you experience the composite image just as if you'd actually seen it.