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Chapter III. The Neurological Basis of Conscious Experience >> Definition of mental synthesis on a neuronal level

Definition of mental images on a neuronal level

Recall that a mental image is a visual image generated from memory. Let us start by looking at how the brain generates a mental image of an object. Every object is represented in our brain by an ensemble of neurons characterizing this object. Some neurons characterize the object’s shape, some its color, and others its texture. Tens of thousands of neurons characterize each object. There is strong evidence that when the brain generates a mental image of an object from memory, the neurons characterizing the object are activated to fire action potentials in synchrony (discussed below).

Note that one neuron can belong to multiple neuronal ensembles. For example, a neuron encoding a certain shape, such as a horizontal line, can be a part of the encoding mechanism for millions of objects photographed by our memory, each of which contain such a shape. Firing of that neuron alone may not generate any meaningful mental image. However, when that neuron fires as part of a synchronized ensemble of neurons, we experience a complete mental image.

Definition of mental synthesis on a neuronal level

According to the theory put forth in this book, mental synthesis (creating a new, never-before-seen mental image) involves the synchronization of two ensembles of neurons, each ensemble representing an object stored in memory. For example, when you imagine a cup on top of a keyboard, your brain first generates a mental image of a cup by activating the ensemble of neurons representing the cup (color, shape, curvature, brightness, texture, etc.) to fire synchronous action potentials. Then the brain recalls a keyboard by activating the ensemble of neurons representing the keyboard (color, shape, curvature, brightness, texture, etc.) to fire synchronous action potentials. Finally the brain synchronizes the two ensembles of neurons together. At that moment you experience a new, never-before-seen mental image of a cup on top of a keyboard.

In Chapter I of this book, we hypothesized that the fundamental difference between modern humans and animals is that animals lack the ability to perform mental synthesis. In other words, they lack the apparatus for voluntary synchronization of two ensembles of neurons that represent two objects stored in memory. Animals have no problem recalling one object at a time, but they cannot synchronize two objects in one mental frame.

In order to understand the process of mental synthesis we need to (1) identify the neuronal ensembles that form mental images, (2) identify the process of synchronization between those neurons, and (3) identify the mechanism for synchronization between two neuronal ensembles.