Chapter 16 - Lateralization/split Brain/language Flashcards
Cerebral commissures
Tracts that connect the left and right cerebral hemispheres.
Name some cerebral commissures
Hippocampal commissures Corpus callosum Massa intermedia Anterior commissure Optic chiasm Posterior commissure
Lateralization of function
The differences between the major functions of the left and right hemisphere
Aphasia
A brain-damage-produced deficit in the ability to produce or comprehend language.
Broca’s area
The area of the inferior prefrontal cortex of the left hemisphere hypothesized by Broca to be the center of speech production.
Hugo-Karl Liepmann found that ______, like aphasia, is almost always associated with the left-hemisphere damage, despite the fact that its symptoms are bilateral.
apraxia
Apraxia
A disorder in which patients have great difficulty performing movements when asked to do so out of context but can readily perform them spontaneously in natural situations.
The combined impact of the evidence that the ______ hemisphere plays a special role in both language and voluntary movement led to the theory of _______.
Left,
Cerebral dominance
Theory of cerebral dominance.
Which is referred to as the dominant hemisphere and which is the minor?
One hemisphere, usually the left, assumes the dominant role in the control of all complex behavioral and cognitive processes, and the other plays a minor role.
The left is referred to as dominant, right is minor.
The sodium Amytal test of language lateralization
A test involving the anesthetization of first one cerebral hemisphere and then the other to determine which hemisphere plays the dominant role in language.
The dichotic listening test
A test of language lateralization in which two different sequences of three spoken digits are presented simultaneously, one to each ear, and the subject is asked to report all of the digits heard.
Dextrals
Right handers
Sinestrals
Left-handers
Corpus callosum
The largest cerebral commissure
There are two routes by which visual information can cross from one eye to the contralateral hemisphere:
Via the corpus callosum or via the optic chiasm
Scotoma
Area of blindness
Most efforts to identify interhemispheric differences in brain anatomy have focused on the size of three areas of cortex that are important for language:
The frontal operculum,
The planum temporale,
The Heschl’s gyrus.
The frontal operculum
The area of frontal lobe cortex that lies just in front of the face area of the primary motor cortex; in the left hemisphere, it is the location of Broca’s area.
The area of frontal lobe cortex that lies just in front of the face area of the primary motor cortex; in the left hemisphere, it is the location of Broca’s area.
The frontal operculum
The __________ lies in the posterior region of the lateral fissure; it is thought to play a role in the comprehension of language and is often referred to as Wernicke’s area.
Planum temporale
The planum temporale
The planum temporale lies in the posterior region of the lateral fissure; it is thought to play a role in the comprehension of language and is often referred to as Wernicke’s area.
Heschl’s gyrus
Located in the lateral fissure just anterior to the planum temporale in the temporal lobe; it is the location of primary auditory cortex.
Located in the lateral fissure just anterior to the planum temporale in the temporal lobe; it is the location of primary auditory cortex.
Heschl’s gyrus
There are two serious difficulties in studying anatomical asymmetry of the language areas:
- their boundaries are unclear, with no consensus on how best to define them.
- there are large difference among healthy people in the structure of these cortical language areas.
Analytic-Synthetic Theory
Holds that there are two basic modes of thinking– an analytic mode and a synthetic mode– which have become segregated during the course of evolution in the left and right hemispheres, respectively.
According to this theory, the left hemisphere operates in a logical, analytical, computerlike fashion; the right hemisphere is a synthesizer, which organizes and processes information in terms of gestalts, or wholes.
Motor theory
The motor theory of cerebral assymetry holds that the left hemisphere is specialized not for the control of speech specifically but for the control of fine movements, of which speech is only on category.
Support for motor theory of cerebral asymmetry:
Shortcomings of motor theory of cerebral asymmetry:
- support comes from reports that lesions that produce aphasia often produce other motor deficits.
- one shortcoming is that it does not suggest why motor function became lateralized in the first place.
Linguistic theory of cerebral asymmetry.
Says that the primary role of the left hemisphere is language; this is in contrast to the analytic-synthetic and motor theories, which view language as a secondary specialization residing in the left hemisphere because of that hemisphere’s primary specialization for analytical thought and skilled motor activity, respectively.
Is cerebral asymmetry exclusive to the hominin brain?
No.
There is evidence of lateralization of function in many vertebrates that evolved long before humans did.
The discovery of examples of cerebral lateralization in species from all five vertebrate classes suggests that cerebral lateralization must have _________.
Survival advantages.
Two fundamental advantages to cerebral lateralization:
1- In some cases it may be more efficient for the neurons performing a particular function to be concentrated in one hemisphere.
2- In some cases, two different kinds of cognitive processes may be more readily performed simultaneously if they are lateralized to different hemispheres.
Motor theory of speech perception
Proposes that the perception and comprehension of speech depends on the words activating the same neural circuits in the motor system that would be activated if the listener said the words.
(Wernicke-Geschwind model)
The ____ gyrus translates the visual form of a read word into an auditory code.
Angular
(Wernicke-Geschwind model)
The ________ cortex controls the muscles of articulation.
Primary motor
(Wernicke-Geschwind model)
The ________ cortex perceives the written word.
Primary visual
(Wernicke-Geschwind model)
________ area is the center for language comprehension.
Wernicke’s
(Wernicke-Geschwind model)
The _______ cortex perceived the spoken word.
Primary auditory
(Wernicke-Geschwind model)
_______ area contains the programs of articulation.
Broca’s
(Wernicke-Geschwind model)
The left _______ carries signals from Wernicke’s area to Broca’s area.
arcuate fasciculus
The cerebral _______ connect the two hemispheres.
commissures
Left-hemisphere damage plays a special role in both aphasia and _______.
apraxia
Cortex of the left inferior prefrontal lobe because known as _________.
Broca’s area
One common test of language lateralization is invasive; it involves injecting _________ into the carotid artery.
sodium amytal
Some evidence suggests that the brains of males are _______ lateralized than the brains of females.
more
The _______ is the largest cerebral commissure.
corpus callosum
cross-cuing
Nonneural communication between hemispheres that have been separated by commissurotomy.
