Chapter 14 – Cognitive Functions Flashcards
Bundle of axons that connects the two hemispheres of the cerebral cortex
Corpus callosum
Divisions of labour between the two brain hemispheres
Lateralization
Describe the visual, auditory, taste, and smell connections to the hemispheres of the brain
The left hemisphere is connected to skin receptors and muscles mainly on the right side of the body, and the right hemisphere to the left side. Both hemispheres control the trunk muscles and facial muscles.
Visual: the right hemisphere sees only the left half of the world, and the left hemisphere sees the right half of the world.
Auditory: each hemisphere gets auditory information from both ears but slightly stronger information from the contralateral ear.
Taste and smell: both are uncrossed. Each hemisphere gets taste information from its own side of the tongue and smell information from the nostril on its own side
Describe the areas of the cerebral cortex that exchange information between the left and right hemispheres
The corpus callosum, the anterior commissure, the hippocampal commissure, and a couple of other small commissures
Describe the division of labour between the left and right hemispheres
In most humans, the left hemisphere specialized for language. The functions of the right hemisphere are more difficult to summarize, but is better at perceiving emotions and at comprehending spatial relationships
Area of the world that an individual can see at any time
Visual field
Light from the right half of the visual field strikes the ____ half of each retina, and light from the left visual field strikes the _____ half of each retina.
The left half of each retina connects to the _____ hemisphere, which therefore sees the right visual field. Similarly, the right half of each retina connects to the _____ hemisphere, which sees the left visual field.
Left; right; left; right;
Area where the axons from each eye cross to the opposite side of the brain
Optic chiasm
Right visual field – left half of each retina – left hemisphere
Left visual field – right half of each retina – right hemisphere
The left hemisphere of the brain is connected to the right eye in rabbits. In humans, the left hemisphere is connected to the left half of each retina. Explain the reason for this species difference.
In rabbits, the right eye is far to the side of the head and sees only the right visual field. In humans, the eyes point straight ahead and half of each eye sees the right visual field
In humans, light from the right visual field strikes the ______ half of each retina, which sends its axons to the ______ hemisphere of the brain
Left; left
A condition characterized by repeated episodes of excessive synchronized neural activity
Epilepsy
People who have undergone surgery to the corpus callosum
Split-brain people
Point in the brain where an epileptic seizure begins
Focus
Describe various methods of treating epilepsy
Anti-epileptic drugs that block sodium flow across the membrane or enhance the effects of GABA.
Surgical removal of the focus, the point in the brain where the seizures begin.
Removing the focus is not an option if someone has several foci, and sometimes cutting the corpus callosum to prevent epileptic seizures from crossing from one hemisphere to the other is a possible treatment
Describe how having the corpus callosum cut has affected the daily lives of people who had this operation and their ability to do conflicting tasks with their two hands.
They maintain their intellect and motivation, and they still walk without difficulty and use the two hands together on familiar tasks such as tying shoes. However, they struggle with any task that is not familiar to them.
Split-brain people have no trouble planning two actions at once, such as simultaneously moving your left hand one way and your right hand a different way.
Describe the research by Roger Sperry where a split-brain person stared straight ahead as the experimenter flashed words or pictures on either side of the screen, too briefly for the person to move his or her eyes.
Information going to one hemisphere could not cross to the other, because of the damage to the corpus callosum. The person could. With the left-hand to what the right hemisphere saw and can point with the right-hand to what the left hemisphere saw. The person could talk about what the left hemisphere saw, but not what the right hemisphere saw, because in most people, the left hemisphere controls speech. The two halves of the brain had different information, and they could not communicate with each other
Can a split-brain person name an object after feeling it with the right hand? With left hand? Explain.
A split-brain person can describe something after feeling it with the right hand but not with the left. The right-hand sends its information to the left hemisphere, which is dominant for language in most people. The left-hand sends its information to the right hemisphere, which cannot speak.
Describe competition and cooperation between the split hemispheres of the brain
Conflicts are more common soon after surgery than later. The corpus callosum does not heal, but the brain learns to use the smaller connections between the left and right hemispheres. The left hemisphere somehow suppresses the right hemispheres interference and takes control in some situations.
Morphed pictures study: when he saw a picture in the right visual field (left hemisphere), he was more likely to say it was himself. When he saw it in the left visual field (right hemisphere), he usually thought it was the other person
Cooperation: when the left hemisphere guesses about what the right hemisphere saw, the right hemisphere, which knows the correct answer, makes the face frown, and the left hemisphere feeling the frown says that they meant the other answer
When a split brain person saw one group of words with the right visual field, and another group with a left visual field, the opposite hands could draw the different words but could not combine the words into one concept, such as hotdog or skyscraper
Describe the functions of the right hemisphere
People with left-hemisphere brain damage are better at guessing whether a person is lying or telling the truth because they are better at reading gestures and facial expressions – the right hemisphere is better than the left at perceiving the emotions in peoples gestures and tone of voice, and if the left hemisphere is damaged and prevented from interfering with the right hemisphere, the right hemisphere is free to make reliable judgments.
Dominant for recognizing emotions in others, including both pleasant and unpleasant emotions.
Better than the left at comprehending spatial relationships
What is a simple way to describe the difference in functions between the hemispheres?
As Robert Ornstein put it: the left hemisphere focuses more on details and the right hemisphere more on overall patterns
Which hemisphere is dominant for the following in most people: speech, emotional inflection of speech, interpreting other people’s emotional expressions, spatial relationships, perceiving overall patterns?
The left hemisphere is dominant for speech. The right hemisphere is dominant for all the other items listed.
Section of the temporal cortex that is larger in the left hemisphere
Plenum temporale
Describe the maturation of the corpus callosum
Gradually grows and thickens as myelin increases around certain axons during childhood and adolescence.
Also matures by discarding many axons. The reason is that any two neurons connected by the corpus callosum need to have corresponding functions and during early embryonic development, the genes cannot specify exactly where those two neurons will be. Therefore, many connections are made across the corpus callosum, but only those axons that happen to connect very similar cells survive.
Because the connections take years to develop their mature adult pattern, certain behaviours of young children resemble those of split-brain adults:
When feeling fabrics with either one hand add two times or both hands at the same time, five-year-olds did equally well with one hand or with two at describing whether the materials felt the same or different. Three-year-olds may 90% more errors with two hands than with one. Interpretation – the corpus callosum matures sufficiently between ages three and five to facilitate the comparison of stimuli between the two hands.
When using the Etch-a-Sketch, adults and older children are slower to respond with two hands than with one, presumably because the message to one hand interferes with the message to the other hand. Children younger than six years respond just as fast with two hands as with one, again suggesting that they do not yet have a mature corpus callosum
Describe what happens when a person develops without a corpus callosum
They are unlike people who have it cut in later life:
Whatever prevented formation of the corpus callosum undoubtedly affects brain development in other
The absence or near absence of the corpus callosum induces the remaining brain areas to develop differently
ways.
- perform more slowly or less accurately than average on tasks that require cooperation between the two hemispheres.
- perform reasonably well on many tasks were split brain people fail – verbally describe what they feel with either hand and what they see in either visual field, also feel objects with two hands and say whether they are the same or different.
How? Each hemisphere develops pathways connecting it to both sides of the body, enabling the left or speaking hemisphere to feel both the left and right hands. Also, the brains other commissures become larger than usual, including the anterior commissure. The extra development of these other commissures partly compensates for the lack of a corpus callosum