The Oscillating Brain

To understand human behavior, we need to understand how the brain works. After all, human behavior is a product of brain function. “Reality” (the world as we experience it) is constructed by the brain. “Reality,” as our brain constructs it, is inherently oversimplified and heavily biased by our emotional reactions. A better understanding of brain function may help us to be a bit less dogmatic in our views (the word “humility” comes to mind) and more receptive to nuanced (diplomatic) solutions to human differences. This book provides an explanation of brain function. It brings together observations of clinical psychiatrists, neuroscientists, and complex systems theorists into an explanatory synthesis that addresses normal and abnormal brain function. The explanation of brain function presented in this book isn’t flawless or complete. Nonetheless, I believe that the overall explanation of brain function found in this book will stand up well to ongoing investigation. Dr. Dale Purves, in his book, Brains: How They Seem to Work indicates that the “conception of how brains work has not been substantiated despite an effort that now spans 50 years.” Dr. Purves is a distinguished neuroscientist. He suggests that part of the reason for delay is “the absence of some guiding principle or principles that would help to understand the neural underpinnings of perceptual, behavioral, and cognitive phenomenology in a more general way.” I believe that the guiding principles involved are those that underlie complex systems. Complex systems are patterns of activity that involve multiple variables and repetitive patterns of interaction. In the case of the brain, repetitive pattern of interaction refers to neural network oscillation -- a central theme of this book. Thanks to the meticulous work of neuroscientists our understanding of brain function has advanced to the point that I can offer a general explanation of brain function that integrates the experience of clinical psychiatry with the growing body of neuroscience information and our evolving understanding of complex systems. Nerve cells (neurons) are the workhorses of brain activity. When a nerve cell is stimulated, electrical activity is transmitted along the neuron’s outer membrane and down its axon. The axon is a long extension of the nerve cell that extends to other areas of the brain or body. Neural activity is transferred from one nerve cell to another through neurotransmitters. Neurotransmitters are chemicals released by neurons at the axon tip. They bridge the narrow gap (referred to as a synapse) that separates the axon tip of one neuron from the dendrites (short extensions) of the next neuron. Dendrites have neuroreceptors, proteins embedded in their surface membrane, which receive neurotransmitters and initiate electrical transmission in the receiving neuron. While transmission within a neuron is electrical in nature, transmission between neurons is chemical. This is an important distinction. Brain function requires the speed of electrical transmission to react rapidly to stimulation on a moment-to-moment basis. Chemical transmission between neurons, on the other hand, permits neural network transformation in response to experience, a process essential for forming memories. Continuous electrical activity is an essential feature of the living brain. Regardless of our state of awareness, an electroencephalogram will show the wave patterns of our brain’s ongoing electrical activity. Many of us have had an electrocardiogram (ECG) at one time or another. An electrocardiogram records the electrical activity of the heart through sensors placed on the chest. In death, our heart is no longer functioning and the lines of the ECG are flat. In brain death, the lines of the electroencephalogram are flat. Neural network oscillation is responsible for the brain’s sustained electrical activity. Neural oscillation is a form of repetitive activity. Repetitive activity is characteristic of complex systems. An individual nerve cell (neuron) transmits information in only one direction. Within the brain, however, communication is routinely bidirectional. For a unidirectional neuron to function in a bidirectional fashion, neural activity is directed back to a previously activated neuron. Reactivation of a previously fired neuron initiates a repetitive cycle of firing within a neuron loop involving only a limited number of neurons. Within a neuron loop, a stable pattern of repetitive firing can be indefinitely sustained. The pattern of repetitive firing within a loop of neurons is referred to as neural oscillation. Neural network oscillation is the product of reciprocal connections. Reciprocal connections are characteristic of brain architecture. The brain’s extensive reciprocal connections permit a variety of patterns of neural oscillation. While some patterns of neural oscillation are localized (restricted to specific regions of the brain), others involve reciprocal connections between geographically separate areas of the brain permitting more widespread neural network interaction. Neural network oscillation transforms the brain’s three-pound mass of grey matter into a dynamic medium. Sensory information is initially processed in specific local areas of the brain. Vision, for example, has its own visual processing area while hearing and somatic (bodily) perception each have independent processing areas. These specialized processing areas respond locally to visual, auditory, or somatic (bodily) sensation. Conscious experience involves the integrated interaction of both sensory areas of the brain and more forwardly located motor areas. I use the word “global” to refer to this type of widespread brain activity. This globalized pattern of neural network oscillation (involving both the sensory and motor areas of the cerebral cortex) involves an additional increase in oscillatory frequency. Global neural network oscillation enables the brain to integrate sensory information into our experience of reality as we move about. Our brain must also be able to monitor our integrated sensory experience and direct our behavior. The brain’s oscillatory neural network is a dynamic medium in which the oscillatory activity in one area of the brain can influence and be influenced by oscillatory activity in other areas. It permits virtually instantaneous interaction between different areas of the brain. Due to the bidirectional nature of brain oscillatory activity, the prefrontal cortex is able to receive sensory information, to focus sensory perception, and to guide behavior at the same time.