Brain stem reticular formation and activation of the eeg

Brain stem reticular formation and activation of the EEG.

brain stem reticular formation and activation of the eeg

Brain stem reticular formation and activation of the EEG. Moruzzi G, Magoun HW. 1. Stimulation of the reticular formation of the brain stem evokes changes in the.

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Stimulation of the reticular formation of the brain stem evokes changes in the EEG, consisting of abolition of synchronized discharge and introduction of low voltage fast activity in its place, which are not mediated by any of the known ascending or descending paths that traverse the brain stem. The alteration is a generalized one but is most pronounced in the ipsilateral hemisphere and, sometimes, in its anterior part. This response can elicited by stimulating the medical bulbar reticular formation, pontile and midbrain tegmentum, and dorsal hypothalamus and subthalamus. The bulbar effect is due to ascending impulses relayed through these more cephalic structures. The excitable substrate possesses a low threshold and responds best to high frequencies of stimulation. Some background synchrony of electrocortical activity is requisite for manifestation of the response.

The brainstem reticular formation RF represents the archaic core of those pathways connecting the spinal cord and the encephalon. It subserves autonomic, motor, sensory, behavioral, cognitive, and mood-related functions. Its activity extensively modulates cortical excitability, both in physiological conditions i. Such a wide variety of effects arises from the long course and profuse axonal branching of isodendritic reticular neurons, which allows the neuronal message to travel toward the entire cerebral cortex and downstream to the spinal cord. On the other hand, the isodendritic architecture featuring a monoplanar branching allows most RF neurons to cover roughly half of the brainstem and to be impinged by ascending and descending pathways.

The term was coined at a time when the functional identity of the many brainstem structures had not been explored. This view is no longer valid because we now know that many units within the so-called reticular formation have their distinct chemical identity, anatomical connectivity, and function, and thus may not fit into the mold of a unitary formation such as the reticular formation. This article is intended to give an overview of the structure and function of the structures that once believed to be part of the brainstem reticular formation. We will aim at providing a big picture to aid the intended audience, and put the structure and function of the brainstem reticular formation structures in the context of the architectural and operational organization of the brainstem as a whole. The brainstem is the stem of the brain.

The Discovery of the Ascending Reticular Activating System

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Scientific Research An Academic Publisher. Moruzzi, G. Electroencephalography and Clinical Neurophysiology, 1, ABSTRACT: Normal aging and depression both slow information processing speed which leads to poorer attentional control, shallower inhibition monitoring, poorer encoding, poorer updating of short term memory, and subsequent poorer learning, set-shifting, error monitoring, inhibition control, and cognitive planning. A combination of aging and depression amplifies these cognitive effects. Deterioration in frontal brain functioning in normal aging is irreversible, but altering of frontal brain function due to depression may be reversible.

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation is not anatomically well defined because it includes neurons located in different parts of the brain. The neurons of the reticular formation make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. Neurons of the reticular formation, particularly those of the ascending reticular activating system, play a crucial role in maintaining behavioral arousal and consciousness. The functions of the reticular formation are modulatory and premotor. The modulatory functions are primarily found in the rostral sector of the reticular formation and the premotor functions are localized in the neurons in more caudal regions. The reticular formation is divided into three columns: raphe nuclei median , gigantocellular reticular nuclei medial zone , and parvocellular reticular nuclei lateral zone.

Reticular formation

In the organization of the central nervous system the role of Ascending Reticular Activating System ARAS comprising the reticular formation, thalamus and thalamo-cortical system of bi-directional projection which governs the activities of wakefulness and vigilance does not correspond to a hierarchical superiority with respect to the cerebral hemispheres. The ARAS is not limited to the brain stem: it projects upwards towards the cerebral hemispheres and downwards towards the spinal cord. Its functions are much more complex than simple cortical desynchronization, even though this is essential in the state of alertness and attention. Its thalamo-cortical projections, which are a-specific with a high oscillatory frequency, are fundamental for some essential functions of consciousness. Unable to display preview. Download preview PDF. Skip to main content.


J Neuropsychiatry Clin Neurosci. Spring;7(2) Brain stem reticular formation and activation of the EEG. Moruzzi G, Magoun HW.
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