Chapter 11 Flashcards
Cerebral Asymmetry
MRI studies of living brains find consistent anatomical differences between left and right hemispheres
Planum temporale on the superior temporal gyrus is larger
in the left hemisphere than the right hemisphere in the majority of individuals
Right hemisphere is
larger and heavier than left hemisphere
Anatomical differences between the left and right temporal lobes may be related to their
relative differences in language and music abilities, respectively.
Anatomical differences in the thalamus are related to
anatomical differences in the temporal lobe, with the left thalamus specialized for language.
The slope of the lateral fissure
more angled on the right side
The frontal operculum (Broca’s area) is organized differently
in the left and right hemispheres
There are asymmetries in the
distribution of neurotransmitters
The right
hemisphere extends farther anteriorly, and the left hemisphere extends farther posteriorly
Neuronal Asymmetry
Neurons in different parts of the lobe have different patterns of dendritic branching
Genetic Asymmetry
Some genes are expressed differently in the two hemispheres, with such differences being observed as early as 5 weeks postconception
motor control, sensation
are symmetrical
language
asymmetrical
perceptual functioning is increased in areas of the
Right hemisphere
Stimulation of the left frontal or temporal lobes facilitated
speech production
Stimulation can
block functions when the subject is using that brain region to perform a task
The double dissociation is an
experimental technique used to show that a particular function is associated with a particular brain region
Left temporal lobectomy significant decrease in
Memory quotient and verbal recall
Right temporal lobectomy significant decrease in
Performance IQ, nonverbal recall, drawing: copy recall
Epilepsy results from
overexcitation of neurons, which can begin in one hemisphere and spread to the other over the corpus callosum
Commissurotomy
cuts the corpus callosum and the anterior commissure to prevent the spread of the seizure activity
Information presented in the left visual field goes to
to the right hemisphere
Information presented to the right visual field goes to the
left hemisphere
Brief presentation in just the left or right visual field presents the information to
a single hemisphere, and, because of the surgery, that information cannot be shared with the other hemisphere
when something is presented only in the left visual field what happens?
visual input is transferred from left visual field to the right visual cortex via corpus collosum, and then via corpus collosum to the left hemisphere
Split-Brain Patients
If information is presented to the left hemisphere (right visual field), the patient can name and describe it, If information is presented to the right hemisphere, they verbally report seeing nothing, but they can identify the object with their left hand
Split-Brain Phenomenon
when the left hemisphere which can speak sees the spoon in the right visual field the subject responds correctly. When the right hemisphere which cannot speak sees the spoon in the left visual field the subject does not respond
Facial recognition in split brain patients
faces that were chosen were presented in the left visual field
For most people who are right-handed, language is localized to
the left hemisphere
Before brain surgery, it is important to confirm which hemisphere
is the language hemisphere
Injecting sodium amobarbital into the carotid artery will briefly anesthetize the
the ipsilateral hemisphere, and clinicians can check for impairments of speech and language along with other cognitive functions
Language is processed better by the
left hemisphere
Faces and visuospatial information are processed better by the
right hemisphere
The predominant and fastest input to the auditory cortex comes from the
contralateral ear
Language stimuli presented to the
right ear are more memorable than those presented to the left ear
Melodies presented to the
left ear are more memorable than those presented to the right ear
right ear advantages
“working ear” Digits, words, nonsense syllables, format transitions, backward speech, Morse code, difficult rhythms, tone used in linguistics, decisions, tonal sequence with frequency transition, ordering temporal information, movement related tonal signals
left ear advantages
Artsy ear - melodies, musical chords, environmental sounds, emotional sounds and hummed melodies, tones processed independently of linguistic context, complex pitch perception
no ear advantages
vowels, isolated frictives, rhythms, nonmelodic hums
Somatosensory input is almost completely
crossed, so the left hand projects to the right hemisphere
Research has found a left-hand advantage to
reading Braille, supporting the specialization of the right hemisphere to recognize and process patterns
When recognizing objects that were previously touched while blindfolded, there was a
right-hand advantage for recognizing letters and a left-hand advantage for recognizing other shapes
Damage to left-hemisphere motor regions results in
apraxia, which is the loss of skilled fine movements
The different sensory inputs to the two hemispheres could confound the
interpretation of differences in the motor system
Emotions are displayed more strongly on the
left side of the face, relating the right-hemisphere specialization for emotions
Observations of mouth movements suggest that such movements start on the
right side, suggesting control by the left hemisphere
Studies that quantified movements while subjects manipulated blocks suggest that the two hemispheres play a
complementary role in controlling movements based on native hand preference
When pianists performed tasks that required them to play different pieces of music with each hand, other behaviors interfered with task performance
speaking and humming
Speaking disrupted playing with the right hand
Humming disrupted playing with the left hand
What Do Laterality Studies Tell Us
Many of these studies are indirect measures of brain function, Many researchers encourage skepticism when looking at the field of laterality research
PET and fMRI studies reveal a
left-hemisphere lateralization for language tasks
Changes in blood flow velocity also support the
the left-hemisphere lateralization of language
speaking activates the mouth tongue and larynx representations in the
motor and somatosensory cortices, the supplementary cortices, the supplementary motor area, the auditory cortex, and the left hemisphere language zones
during speech the mouth area and
auditory cortex in the right hemisphere are active but less active then the in the left hemisphere
left auditory cortex
Spoken words
Laterality
the idea that the two cerebral hemispheres have separate functions, leads to the notion that two different minds control our behavior
Five variables complicate research on laterality
Laterality is relative, not absolute, Cerebral site is at least as important in understanding brain function as cerebral side, Environmental and genetic factors affect laterality, A range of animals exhibit laterality, We act as though there is a single mind
Laterality is relative, not absolute
Both hemispheres participate in nearly every behavior
Cerebral site is at least
as important in understanding brain function as cerebral side
Environmental and genetic factors affect laterality
The cerebral organization of some left-handers and females appears to be less asymmetrical than that of right-handers and males.
A range of animals exhibit laterality.
we know that certain songbirds, rats, cats, monkeys, and apes also have functionally and anatomically asymmetrical brains
We act as though there is a single mind
Although the two hemispheres are specialized for different aspects of our mental life, we normally act as though there is a single cognitive processor
Applying an electrical current to the cortex of a conscious patient has four general effects — three excitatory and one inhibitory
The brain has symmetrical as well as asymmetrical functions, The right hemisphere has perceptual functions not shared by the left hemisphere, Stimulating the left frontal or temporal region may accelerate speech production, Stimulation blocks function
Stimulation blocks function
This sole inhibitory effect is apparent only when current is applied to left hemisphere temporofrontal areas while a patient is actively engaged in complex functions such as language and memory
The right hemisphere has perceptual functions not shared by the left hemisphere
Stimulation can produce what Penfield called “interpretive” and “experiential” responses. That is, patients report specific “memories” in response to specific stimulation
One of the most extreme specialization theories suggests that the
left hemisphere is specialized for fine motor control, and speech requires very detailed motor control, Therefore, speech is localized to the left hemisphere because of the need for motor control
Another theory suggests that the left hemisphere is organized with
many focal centers, while the right hemisphere is more diffusely organized
Other variants suggest the left hemisphere is very good at rapid
temporal processing, which is integral to language
Interaction theories suggest that
one hemisphere may be better at a task, but the two cooperate in performing the task
Two hemispheres both work on different parts of processing
at the same time
Both hemispheres may have the ability to perform the task, but
one inhibits or suppresses the activity of the other
One hemisphere receives information preferentially or pays attention to the information preferentially and therefore
therefore performs a specific type of analysis of that information
Preferred Cognitive Mode
Individual differences will cause people to use one type of thought process instead of another
Cognitive set, or the biases in how individuals approach problems, can influence
the results of tests of lateralization
Measuring Behavior in Neuropsychology
Measurements of one process often contain inferences about the underlying processes
in frogs and salamanders
Vocalization is left lateralized
Bees show lateralization in learning
odors associated with reward and in remembering the associations
Many birds have a left-hemisphere specialization for the production of their
songs, but this is not the case in all birds
Chimpanzees have asymmetries in the homologues of
Broca’s area and the planum temporale that mimic those observed in humans
In primates, some research suggests that the right hemisphere is specialized for ____ and the left hemisphere
rapid unimanual movements, the left hemisphere is specialized for whole-body movements
Visual system left hemisphere
Letters, words
Visual system right hemisphere
Complex geometric patterns
Faces
Auditory system LH
Language-related
sound
Auditory system RH
Nonlanguage environmental sounds
Music
Somatosensory LH
blank
Somatosensory RH
Tactile recognition of complex
system patterns
Braille
Movement LH
Complex voluntary
movement
Movement RH
Movements in spatial patterns
Memory LH
Verbal memory
Memory RH
Nonverbal memory
Language Left hemisphere
Speech
Reading
Writing
Arithmetic
Language RH
Prosody
Prosody
the patterns of rhythm and sound used in poetry.
Spatial processes LH
blank
Spatial processing RH
Geometry
Sense of direction
Mental rotation of shapes
Preferred cognitive model
the use of one type of thought process in preference to another
Destruction of the left frontoparietal region at birth produced this growth asymmetry in the
Right foot
