Reticular Formation Summary

Activation by Attention of the Human Reticular
Formation and Thalamic Intralaminar Nuclei

In the article Activation by Attention of the Human Reticular Formation and Thalamic Intralaminar Nuclei by Shigeo Kinomura, Jonas Larsson, Balázs Gulyás, and Per E. Roland (1996), they address whether or not the midbrain reticular formation and the thalamic intralaminar nuclei of the brain actually cause arousal and vigilance. They do this by conducting a series of experiments.
The reticular formation is a system of nerves whose main job is to send alert signals of the higher parts of the brain (Morris & Maisto, 2009). Proving that the MRF (Midbrain Reticular Formation) and the Thalamic Intralaminar Nuclei are responsible for arousal and alertness
has been difficult because injuries to these areas of the brain have failed to impair the ability to become alert (Shigeo Kinomura et al. 1996). Although electrocoagulation, a technique that uses radio waves to increase the temperature of blood cells within a tissue, of the MRF was found to induce a comatose state in animals. Similar results have been difficult to reproduce with more refined methods of electrocoagulation, in which only the neuronal perikarya of the MRF are destroyed (Kinomura et al. 1996).
The authors measured which parts of the brain had an increased blood flow, or regional cerebral blood flow (rCBF), of ten normal volunteers while at rest, and while they were engaged in two sensory and visual reaction-time tasks.
The authors hypothesized that going from a resting state to a state of high attention would increase the synaptic activity in the MRF and also increase the rCBF in these areas. The ten volunteers were hooked up to a Positron emission tomography (PET) scan and monitored while they completed these tasks. Nine of the volunteers were right handed and one was ambidextrous. During the “at rest” activities, the volunteers were supine with their eyes closed holding a response key in their right hand. During visual timed response task the volunteers were instructed to click the response key when the yellow light they were fixated on increased in brightness. The light was set to increase its brightness in random intervals. During the somatic response time task, the volunteers were still fixated on the yellow light but were instructed to press the response key as soon as they felt a stylus poke their left index
finger.
The visual reaction time task and so¬matic reaction time task noticeably increased the rCBF in the MRF and the left intralaminar region, although there were no other significant increases of rCBF in the brain stem.
The authors found that the rCBF in the midbrain tegmentum and the intralaminar domain of the thalamus is greater during vigilance and attention than when the volunteers were awakened from resting or when they were awake performing self-generated activity. It can therefore be stated that these parts of the brain react without receiving a signal from any of the sensory modalities, and their activation was directly linked with an increase of blood flow in the cerebral cortex (Kinomura et al. 1996). The authors conclude that the MRF and thalamic intralaminal nuclei are responsible for not only the transition from sleep to alert but are also responsible for the transition from relaxed to high attention and the maintenance of high
attention. References
Kinomura, S., Larsson, J., Gulyás, B., & Roland, P. E. (1996). (Activation by attention of the human reticular formation and thalamic intralaminar nuclei). SCIENCE, 271, 512-514.
Morris, C. G., & Maisto, A. A. (2009). The biological basis of behavior. In Understanding Psychology (9th ed., p. 52).