Module 5: Tools of Discovery and Older Brain Structures

Studying cases of brain damage When a stroke or injury damages part of the brain, we have a chance to see the impact on the mind.

3 Intentional brain damage:  performed on animals  has yielded some insights, especially about less complex brain structures  no longer necessary, as we now can chemically or magnetically deactivate brain areas to get similar information Lesions (surgical destruction of brain tissue)

Split-Brain Patients  “Split” = surgery in which the connection between the brain hemispheres is cut in order to end severe full-brain seizures  Study of split-brain patients has yielded insights discussed at the end of the chapter

We can stimulate parts of the brain to see what happens  Parts of the brain, and even neurons, can be stimulated electrically, chemically, or magnetically.  This can result in behaviors such as giggling, head turning, or simulated vivid recall.  Researchers can see which neurons or neural networks fire in conjunction with certain mental experiences, and even specific concepts.

Monitoring activity in the brain Tools to read electrical, metabolic, and magnetic activity in the brain: EEG: electroencephalogram MRI: magnetic resonance imaging fMRI: functional MRI PET: positron emission tomography

7 An EEG (electroencephalogram) is a recording of the electrical waves sweeping across the brain’s surface. An EEG is useful in studying seizures and sleep. EEG: electroencephalogram

The PET scan allows us to see what part of the brain is active by tracing where a radioactive form of glucose goes while the brain performs a given task. PET: positron emission tomography

9 MRI (magnetic resonance imaging) makes images from signals produced by brain tissue after magnets align the spin of atoms. The arrows below show ventricular enlargement in a schizophrenic patient (right). MRI: magnetic resonance imaging Functional MRI reveals brain activity and function rather than structures. Functional MRI compares successive MRI images taken a split second apart, and shows changes in the level of oxygen in bloodflow in the brain. fMRI: functional MRI

Areas of the brain and their functions The brainstem and cerebellum: coordinates the body The limbic (border) system: manages emotions, and connects thought to body The cortex (the outer covering): integrates information

The Brain: Less Complex Brain Structures Our tour of the brain begins with parts of the human brain found also in simpler animals; these parts generally deal with less complex functions: Brainstem (Pons and Medulla) Thalamus Reticular Formation Cerebellum Limbic System

The Brainstem: Pons and Medulla

The Base of the Brainstem: The Medulla  The medulla controls the most basic functions such as heartbeat and breathing.  Someone with total brain damage above the medulla could still breathe independently, but someone with damage in this area could not.

The Brainstem: The Pons The pons helps coordinate automatic and unconscious movements.

The Thalamus (“Inner Chamber”)  The thalamus is the “sensory switchboard” or “router.”  All sensory messages, except smell, are routed through the thalamus on the way to the cortex (higher, outer brain).  The thalamus also sends messages from the cortex to the medulla and cerebellum.

Reticular (“Netlike”) Formation  The reticular formation is a nerve network in the brainstem.  It enables alertness, (arousal) from coma to wide awake (as demonstrated in the cat experiments).  It also filters incoming sensory information.

The cerebellum helps coordinate voluntary movement such as playing a sport. Cerebellum (“little brain”) The cerebellum has many other functions, including enabling nonverbal learning and memory.

 emotions such as fear and aggression.  basic drives such as hunger and sex.  the formation of episodic memories. The hippocampus (“seahorse”)  processes conscious, episodic memories.  works with the amygdala to form emotionally charged memories. The Amygdala (“almond”)  consists of two lima bean- sized neural clusters.  helps process emotions, especially fear and aggression. The Limbic (“Border”) System The limbic system coordinates:

 lies below (“hypo”) the thalamus.  regulates body temperature and ensures adequate food and water intake (homeostasis), and is involved in sex drive.  directs the endocrine system via messages to the pituitary gland. The Hypothalamus: Thalamus Riddle: Why did the rat cross the grid? Why did the rat want to get to the other side? The Hypothalamus as a Reward Center Pushing the pedal that stimulated the electrode placed in the hypothalamus was much more rewarding than food pellets.

Review of Brain Structures