Neurons die as part of everyday life (about one neuron for each second), but the brain works on the principle of redundancy. Think of it this way: neurons are the same size. This means there are many more neurons in a big head than in a small human head. Yet head size doesn’t correlate with human mental capacity. Does this mean certain neurons in a big head are unused? No, but fewer neurons can evidently perform the same functions.
Axons aggregate in neural pathways; many go through the thalamus, which interconnects numerous brain regions. Neural pathways can be direct, diverging, converging, feed-forward or feedback. In a direct neural pathway, signaling goes from point A to point B without branching. In a diverging pathway, one neuron may cause two or more neurons to fire in parallel which, in turn, may cause many more to fire in a treelike fashion. In converging pathways, many neurons converge on a lesser number, such as when 100 million retinal receptors are funneled through one million nerve fibers exiting the eyeball. Feed-forward pathways go from early to later stages, such as when visual cortex signals traveling over the dorsal and ventral pathways diverge to a large number of other areas. There are also feedback pathways going from later to earlier stages. Lastly, there are circular pathways where signals travel around and around in central pattern generators. Such generators allow the rhythmic movement necessary for breathing, walking, and digesting food. Groups of neurons sometimes fire together even though they are in distant regions. It has been suggested that such synchronous firing has to do with focusing attention and binding perceptions into a whole. Francis Crick (1916-2004) and Christof Koch (1956-) suggested that the correlates of consciousness were neural structures firing synchronously at 60 hertz. However, there is an insufficient rationale and support for this hypothesis. Even if a correlation were found, there would remain the task of convincingly elaborating on how synchronous firing illuminates the question of consciousness. The same critique goes for claims of attention and perceptual binding. It remains unclear how sheer neural synchronicity would shed light on attention and perceptual unity. Observations of neural synchronicity with respect to mental phenomena call for further argumentative and experimental exploration.