Chapter 66 Neuromodulation of the brain gamma band oscillatory systems

Abstract

Publisher Summary Cortical resonance and regional coherence are achieved through the harmonization of the neuronal firing pattern and membrane/field potentials. According to models and experiments, these synchronized oscillatory activities serve as “carrier” signals in functional instances, provide a spatiotemporal coding system, and characterize the neuronal assemblies binding common sensory features at discrete cortical areas into unified object representation. In the cat visual cortex, the stimulus-specific oscillatory activity synchronizes between the adjacent cells, cortical columns or visual areas, and hemispheres. The time dynamics depend on contiguity and cell interaction, influenced by the stimulus coherence, and the oscillatory activity in visual cortex reflects the global properties of stimulus. These synchronized, stimulus-specific oscillations result in summated oscillatory mass responses to transient stimulation in animals and man. Oscillatory response in man and cat phase-locked to stimulus anticipates the low frequency visual evoked potentials (VEP) components and reflects the stimulus physical properties, with a “tuning,” matching the contrast sensitivity function of visual system. Gamma band oscillatory activities also mediate in cognitive processes, such as selective attention, focused arousal, multistable or ambiguous perceptive conditions, induced visual illusions, visuomotor integration, associative learning, sensorimotor processing, or short-term memory. This chapter discusses the oscillatory activity and neuronal function correlation, corticothalamic regulation, brain functional states and neuromodulation. Inhibition appears to be a mechanism in the synchronization of large assemblies of excitatory pyramidal cells engaged in oscillatory activities. Tonically excited networks of (gamma-aminobutyric acid (GABA)ergic) cortical interneurons mediate by entraining each other into sustained inhibitory connections and contribute to determine when pyramidal cells would fire. Excitatory (cholinergic) synaptic events also participate during the network oscillation in a temporal pattern and interact with GABAergic interneurons. The cholinergic systems, projecting to cortex, increase the excitability and firing rate of thalamocortical neurons and regulate the brain function.