Unit 3B:
Biological Bases of Behavior:
The Brain

Examining The Brain

There are many ways to examine a person's brain.  One way is to examine a lesion because it helps researchers learn about the function of that part of the brain.  Another way is through an Electroencephalogram, Computed Tomography Scan, Positron Emission Tomography Scan, Magnetic Resonance Imaging, and Functional MRI.  

Electroencephalogram

Electroencephalogram – an amplified recording of the brain’s waves of electrical activity

MRI
CT Scan
PET Scan
fMRI

Older Brain Structures

Our brain is composed of new systems built on top of old brain systems.  The older brain structures include the brainstem, which includes the medulla, pons, and the reticular formation.  Other older brain structures is the thalamus, cerebellum, and the limbic system which includes the hippocampus, pituitary gland, amygdala, and the hypothalamus.

Limbic System
Cerebellum
Cortex, brainstem, thalamus, and reticular formation

Reticular formation - a nerve network in the brainstem that plays an important role in controlling arousal.

Cerebral Cortex

The cerebrum is the newer part of the brain that contains two large hemispheres and enables thinking, speaking, and perceiving.  It is covered by the cerebral cortex, which is a thin surface layer of interconnected neural cells.  Each hemisphere is divided into four lobes called the frontal, parietal, occipital, and temporal lobes.  The functions of the cortex include motor functions, sensory functions, and association areas, and it is also responsible for language.  

Phineas Gage -  an example of how damage to the frontal lobe can affect one's personality

Cameron Mott - a six-year-old girl who had an entire hemisphere removed to eliminate seizures. This demonstrated brain plasticity which is the brain’s ability to change, especially during childhood.   

Phineas Gage's skull
The four lobes of the Cerebral Cortex
Motor areas, sensory areas, and association areas

Association areas - involved in higher mental functions such as learning, remembering, thinking, and speaking

Our Divided Brain

Splitting the brain reveals information about hemispheric specialization. Severing the corpus callosum, the large band of neural fibers that connects the two brain hemispheres and carries messages between them, is possible and creates a split-brain.  Information from the left half of your field of vision goes to your right hemisphere, and info from the right half of your visual field goes to your left hemisphere.

Vogel and Bogen - believed seizures resulted from brain activity bouncing back and forth between the two cerebral hemispheres.

Corpus Callosum
Diagram of our visual fields

The above experiment is from Gazziniga research which involves the participant looking at a dot.  The word heart was momentarily projected, separated by a dot (between he and art).  When asked what word they saw, they said art but when told to point at what word they saw, they pointed to he.  

Other experiments on split-brain patients have revealed a lot of info about each hemisphere’s special functions.

Right - Left Differences In the Intact Brain

Each hemisphere has special functions, called hemispheric specialization.  The right hemisphere is specialized in perceptual tasks and sense of self and the left hemisphere is specialized in language.  

The Brain and Conciousness

Consciousness is our awareness of ourselves and our environment.  Cognitive neuroscientists help us to understand how specific brain states relate to conscious experiences.  Perception, memory, thinking, language, and attitudes all operate on a conscious “high road” and an unconscious “low road, which is called dual processing.  

Cognitive neuroscience - the interdisciplinary study of how brain activity is linked to our mental processes

The above experiment involves a person in a vegetative state (top image) and a healthy person (bottom image).  When asked to imagine playing tennis or navigating her home, the patient’s brain exhibited activity similar to a healthy person’s brain.  

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