The Reticular Activating System (RAS) is a network of neurons that extends from the brainstem to different parts of the brain and spinal cord. It functions to regulate arousal, alertness, and selective attention by increasing or decreasing activity and directing cortical areas to focus on relevant information. Destroying the RAS causes a coma similar to sleep, while stimulating it instantly awakens sleeping animals. The Thalamus filters and relays incoming sensory information, with the exception of smell, to cortical areas. It plays a role in attention by emphasizing certain information and regulates arousal through its connection to the RAS.

1. The Reticular Activating System
Friday, 11 January 2013

2. In topic 2 - Brain Structures and Processes we will
learn about many areas of the brain and their
functions.
We will learn how they communicate (neurons
and neurotansmitters) and control bodily
functions.
However to understand normal waking
consciousness in particular attention, we need to
jump ahead and look at the Reticular Activating
System and the role of the Thalamus.
Friday, 11 January 2013

3. The reticular activating system
Is a network of neurons extending in many directions from the reticular formation in
the brainstem to different parts of the brain and spinal cord
Functions include:
• Arousal, e.g. regulates by increasing or decreasing
• Alertness, e.g. regulates wakefulness and attention
• Selective attention, e.g. regulates what we choose to attend to,
directs specific cortical areas to focus on relevant information
Evidence for these functions includes:
• Destroying the RAS causes a coma resembling sleep
• Electrical stimulation of RAS instantly awakens sleeping animals
Friday, 11 January 2013

4. Thalamus
Is a small structure on the top of the brain stem that filters and relays incoming
sensory information (except smell) to relevant cortical areas. Information moves from
cortical areas to lower brain structures, the spinal cord and out to the peripheral
nervous system.
Function:
• Plays a role in attention by actively filtering incoming sensory information, giving
more weight to and emphasising certain information.
• Regulates arousal through connection with the RAs.
• Closes pathways of incoming information during sleep, preventing information from
reaching the brain as it rests
Friday, 11 January 2013