Historical Discoveries:
– Richard Caton discovered electrical activity in cerebral hemispheres of rabbits and monkeys in 1875.
– Adolf Beck observed spontaneous electrical brain activity in rabbits and dogs in 1890.
– Vladimir Vladimirovich Pravdich-Neminsky published the first animal EEG and evoked potential in a dog before Hans Berger.
– Neural oscillations in humans were first observed in 1924 by Hans Berger.
– Intrinsic oscillatory behavior in vertebrate neurons was discovered over 50 years later.
Characteristics and Functions:
– Neural oscillations are present throughout the central nervous system at all levels.
– Oscillations are characterized by frequency, amplitude, and phase.
– Changes in synchronization within neural ensembles lead to amplitude changes in large-scale oscillations.
– Linked to cognitive functions like information transfer and memory.
– EEG signals show specific frequency bands like alpha, delta, theta, beta, low gamma, and high gamma.
Neural Activity Patterns:
– Neurons can generate rhythmic patterns of action potentials or spikes.
– Bursting is a form of rhythmic spiking.
– Spiking patterns are fundamental for information coding.
– Oscillatory activity can be observed in subthreshold membrane potential oscillations.
– Synchronous spiking of neurons can lead to oscillations in local field potentials.
Physiological Levels of Oscillations:
– Micro-scale: Single neuron activity generating action potentials for neural coding.
– Meso-scale: Local groups of neurons generating oscillatory activity through synchronized firing patterns.
– Macro-scale: Activity of brain regions interacting through structural connectome to produce neural oscillations.
Mechanisms and Modulation:
– Intrinsic neuronal properties like voltage-gated ion channels critical for oscillation generation.
– Neuromodulators regulate oscillatory activity.
– Balance between excitation and inhibition crucial for oscillations.
– Influence of neurotransmitters on physiological state and brain wave amplitudes.
– Oscillations linked to cognitive processes, information processing, and sensory perception.
Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.
Neural oscillations in humans were observed by researchers as early as 1924 (by Hans Berger). More than 50 years later, intrinsic oscillatory behavior was encountered in vertebrate neurons, but its functional role is still not fully understood. The possible roles of neural oscillations include feature binding, information transfer mechanisms and the generation of rhythmic motor output. Over the last decades more insight has been gained, especially with advances in brain imaging. A major area of research in neuroscience involves determining how oscillations are generated and what their roles are. Oscillatory activity in the brain is widely observed at different levels of organization and is thought to play a key role in processing neural information. Numerous experimental studies support a functional role of neural oscillations; a unified interpretation, however, is still lacking.