Chapter 12 Flashcards
trends in handedness
- left handers display more variation speech lateralization
- in 80% of rt handers, the pyramidal tract descending to the right hand contains more fiber than does the same tract going to left hand
- more fibers descend
- some left and rt handers show marked dissociation between morphological and functional asymmetry
environmental theories of handedness
-
utility of handedness
- ex: adaptive for mother to hold infant in left hand to be soothed by rhythm of her health and leaving rt hand to do things
-
reinforcement for hand use
- established by bias in environment or genetics
anatomical theories of handedness
- rt handedness attributed to enhanced maturation and ultimately greater development of left hemisphere
- non familial left handers will show an asymmetry mirroring that of right handers, whereas familial left handers will show no anatomical asymmetry
hormonal theories of handedness
inhibitory
- early in life, brain plasticity can modify cerebral asymmetry significantly leading to anomalous patterns of hemispheric organization
- action of sex linked male hormone testosterone in altering cerebral organization during course of development
- testosterone’s inhibitory action takes place largely in lt hemi, allowing rt hemi to grow more rapidly → leads to altered cerebral organization and in some ppl to lt handedness
genetic theories of handedness
- dominant gene for rt handedness and recessive gene for left handedness
- the processes necessary for left hemi speech also confer advantage on motor control in rt hand
sexual differences
children’s play
- toy preferences, as well as other sex-typed aspects of play, are influenced by prenatal testosterone
- production of testosterone begins at about seven weeks of gestation and leads to a vast difference in concentrations between males and females prenatally
sexual differences
prenatal exposure to testosterone
androgen receptors in the brains of laboratory animals have shown that prenatal exposure to testosterone produces sex differences in brain structure and function
influence of sex hormones
difference in estrogen and androgen receptors
sexually dimorphic regions
- purple - high estrogen receptors; pink - androgen
- male brains are larger
- sexually dimorphic regions in PFC, paralimbic cortex, posterior parietal cortex
- womens brain volume in PFC and medial paralimbic regions is significantly higher than men
- men have larger volumes in medial and orbitofrontal cortex and angular gyrus
asymmetry in planum temporale
planum temporale (Wernicke’s area)
- asymmetry (left larger than right) is seen more often in men than women - sex difference in organization of language related functions
- large asymmetry in males than no asymmetry in females
sex differences
callosal studies
- posterior part of callosum (splenium) is significantly larger in women than men
- women have more interhemisphereic connections in both the corpus callosum and anterior commissure than men
sex differences from resting state fMRI studies
- extensive sex differences in neural connectivity
- men show greater connectivity within the rt hemi, women greater in left
sex differences from diffusion tensor imaging
diffusion tensor imaging (tracks white matter fibers in brain)
- females have greater interhemispheric connectivity
- males have greater intrahemispheric connectivity
- If female and male brains differ in anatomical organization and connectivity as well as in metabolic activity as shown by the results of blood flow,fMRI and DTI studies → effects of injury also might differ between the sexes
sex differences
effects of lateralized lesions
- equivalent effect of lt hemisphere lesions on verbal IQ scores in both sexes
- men with right hemisphere lesions were more disrupted than women on the performance IQ test → could imply that rt hemi organization differs in men and women (or women more likely than men to use verbal strategies)
sex differences explanations
types
- hormonal effects
- genetic sex linkage
- maturation rate
- environment
- preferred cognitive mode
sex differences
hormonal effects
inductive or organizing effect: influence of gonadal hormones on brain and behavioral development → could lead to sexual differentiation
sex differences
genetic sex linkage
- if a gene for a particular trait such as spatial analysis is recessive, the trait will not be expressed in a girl unless the recessive gene is present on both X chromosomes
- if the child is a boy, the recessive gene need be present only on one chromosome
- if a mother carries the gene on both X chromosomes, all of her sons will have the trait, but her daughters will possess it only if their father also carries the recessive gene on his X chromosome
sex differences
maturation rate
- regardless of sex, early maturing adolescents perform better on tests of verbal abilities than on tests of spatial ones, while late maturing adolescents do the opposite → maturation rate may affect the organization of cortical function
- bc on average, girls mature faster than boys, superior spatial abilities in boys may relate directly to their relatively slow development
sex differences
environment
- exposure to gonadal hormones perinatally, near birth, determines the later ability of environmental stimulation to alter the synaptic organization of the cerebrum of rats
- environmentally induced changes in hippocampus and neocortex are affected differentially by gonadal hormones
- ex: female hippocampus is far more plastic new environments than the male hippocampus and this plasticity depends on estrogen
sex differences
preferred cognitive mode
genetic, maturational, and environmental factors may predispose men and women to prefer different modes of cognitive analysis
cerebral asymmetries development
- adult-like cerebral asymmetries are present before birth
- parallel development theory: initally permits some flexibility or equipotentiality
- the hemispheres themselves are not becoming more lateralized wrt a given function, instead they are developing more highly specialized functions
development of simple cognitive functions (birth)
- functions in the primary somatosensory, motor, language or visual spatial areas
- two hemispheres overlap functionally because each is processing low level behavior
development of intermediate cognitive functions (5yo)
high order cognitive processes have very little overlap, and each hemisphere, thus becomes increasingly specialized
development of complex cognitive functions (puberty 13yo)
- most lateralized
- each hemi has developed its own unique function
moscovitch 1977
- possibility that one hemi actively inhibits the other → preventing the contralateral hemi from developing similar functions
- active inhibitation develops at age 5, as the corpus callosum becomes functional
- inhibitory process not only prevents subsequent development of language process in rt hemi, but also inhibits expression of language processes already in rt hemi
__ handers display more variation speech lateralization
left
-
utility of handedness
- ex?
-
reinforcement for hand use
- established by bias in environment or genetics
environmental theories of handedness
adaptive for mother to hold infant in left hand to be soothed by rhythm of her health and leaving rt hand to do things
- __ handedness attributed to enhanced maturation and ultimately greater development of __ hemisphere
anatomical theories of handedness
right; left
- early in life, brain plasticity can modify cerebral asymmetry significantly leading to anomalous patterns of hemispheric organization
- action of sex linked hormone ____ in altering cerebral organization during course of development
- __ inhibitory action takes place largely in __ hemi, allowing __ hemi to grow more rapidly → leads to altered cerebral organization and in some ppl to __ handedness
hormonal theories of handedness
testosterone; testosterone; left; right; left
- dominant gene for rt handedness and recessive gene for left handedness
- the processes necessary for __ hemi speech also confer advantage on motor control in __ hand
genetic theories of handedness
left; right
- toy preferences, as well as other sex-typed aspects of play, are influenced by prenatal ____
- production of testosterone begins at about seven weeks of gestation and leads to a vast difference in concentrations between males and females prenatally
sexual differences
children’s play
testosterone
___ receptors in the brains of laboratory animals have shown that prenatal exposure to ___ produces sex differences in brain structure and function
sexual differences
prenatal exposure to testosterone
androgen; testosterone
- ___ brains are larger
- sexually dimorphic regions in PFC, paralimbic cortex, posterior parietal cortex
- ____ brain volume in PFC and medial paralimbic regions is significantly higher
- ___ have larger volumes in medial and orbitofrontal cortex and angular gyrus
influence of sex hormones
difference in estrogen and androgen receptors
male; women’s; men’s
planum temporale (Wernicke’s area)
- asymmetry (left larger than right) is seen more often in ___
- large asymmetry in __ than no asymmetry in __
asymmetry in planum temporale
men
men; women
- posterior part of callosum (splenium) is significantly larger in __
- __ have more interhemisphereic connections in both the corpus callosum and anterior commissure
sex differences
callosal studies
women
men show greater connectivity within the ___ hemi, women greater in ___
sex differences from resting state fMRI studies
right; left
- ___ have greater interhemispheric connectivity
- ___ have greater intrahemispheric connectivity
sex differences from diffusion tensor imaging
females; mles
- equivalent effect of __ hemisphere lesions on verbal IQ scores in both sexes
- men with __ hemisphere lesions were more disrupted than women on the performance IQ test
sex differences
effects of lateralized lesions
left; right
- hormonal effects
- genetic sex linkage
- maturation rate
- environment
- preferred cognitive mode
sex differences explanations
types
influence of gonadal hormones on brain and behavioral development → could lead to sexual differentiation
sex differences
hormonal effects
inductive or organizing effect
- if a gene for a particular trait such as spatial analysis is recessive, the trait will not be expressed in a girl unless the recessive gene is present on both X chromosomes
- if the child is a boy, the recessive gene need be present only on one chromosome
- if a mother carries the gene on both X chromosomes, all of her sons will have the trait, but her daughters will possess it only if their father also carries the recessive gene on his X chromosome
sex differences
genetic sex linkage
- regardless of sex, early maturing adolescents perform better on tests of ___ than on tests of __ ones, while late-maturing adolescents do the opposite → maturation rate may affect the organization of cortical function
- bc on average, girls mature faster than boys, superior __ abilities in boys may relate directly to their relatively slow development
sex differences
maturation rate
verbal ability; spatial;
spatial
- exposure to gonadal hormones perinatally, near birth, determines the later ability of environmental stimulation to alter the __ of the __ of rats
- environmentally induced changes in __ and __ are affected differentially by gonadal hormones
- ex: female __ is far more plastic new environments and this plasticity depends on __
sex differences
environment
synaptic organization; cerebrum
hippocampus; neocortex
hippocampus; estrogen
genetic, maturational, and environmental factors may predispose men and women to prefer different modes of cognitive analysis
sex differences
preferred cognitive mode
- functions in the primary somatosensory, motor, language or visual spatial areas
- two hemispheres overlap functionally because each is processing low level behavior
development of simple cognitive functions (birth)
high order cognitive processes have very little overlap, and each hemisphere, thus becomes increasingly specialized
development of intermediate cognitive functions (5yo)
- most lateralized
- each hemi has developed its own unique function
development of complex cognitive functions (puberty 13yo)
- possibility that one hemi actively inhibits the other → preventing the contralateral hemi from developing similar functions
- active inhibitation develops at age 5, as the corpus callosum becomes functional
- inhibitory process not only prevents subsequent development of language process in rt hemi, but also inhibits expression of language processes already in rt hemi
moscovitch 1977
when neuropsychologists refer to a function as being lateralized, they mean that the function
a. is performed most efficiently by a lateral region of the brain
b. can be performed equally well by either hemisphere of the brain
c. is performed most efficiently by one hemisphere of the brain
d. is performed most efficiently in a lateral motion
c. is performed most efficiently by one hemisphere of the brain
the most convincing experiemental design for demonstrating the localization of a particular function to a brain region is the
double dissociation
following damage to the left hemisphere, the most likely outcome would be a decline in
verbal ability
which is an example of double dissociation for two areas of the cortex?
a. patient A can neither read nor write after injuries to both regions, while patient B can write but not read after injuries to both regions
b. patient A can read but not write after an injury to one region, while patient B can write but not read after an injury to the other region
c. patient A can read but not write after an injury to one region, while patient B can ready but not write after an injury to the other region
d. patient A can read but not write after an injury to one region, but he can neither read nor write after an injury to the other region
b. patient A can read but not write after an injury to one region, while patient B can write but not read after an injury to the other region
surgical deconnection of the two cerebral hemispheres by cutting the corpus callosum (and other commissures) is a “last resort” treatment for ___.
epilepsy
visual images can be presented individually to each hemisphere using a device known as:
tachistoscope
the right carotid artery is injected with an anesthetic drug, within a few seconds ___.
a. speech will always be interrupted
b. speech will probably be interrupted
c. the contralateral arm will exhibit flaccid paralysis
d. the ipsilateral arm will exhibit flaccid paralysis
c. the contralateral arm will exhibit flaccid paralysi
specialization models of hemispheric function posit:
a. identical information processing roles for each hemisphere
b. nonoverlapping information processing roles for each hemisphere
c. shifting information processing roles for the two hemispheres
d. overlapping information processing roles for each hemisphere
b. nonoverlapping information processing roles for each hemisphere
the most pronounced anatomical asymmetries are found in the areas associated with
language
the ability of the right hemi to support language abilities after damage to the left hemisphere supports:
a. supermodels
b. interaction models
c. isolationist models
d. specialization models
b. interaction models
which of the following is true for right handed persons?
a. they have more pyramidal tract fibers descending to the right side of the body
b. they have larger blood volume in the left hemisphere
c. they have less asymmetry
d. the corpus callosum is larger in the cross sectional area
a. they have more pyramidal tract fibers descending to the right side of the body
which of the following is generally true of the left hemisphere, relative to the right hemisphere in humans?
a. it has a smaller visible frontal operculum
b. it has larger size and weight overall
c. it has a larger Heschl’s gyrus
d. it has a larger planum temporale
d. it has a larger planum temporale
in 80% of __ handers, the pyramidal tract descending to the __ hand contains more fiber
right
some left and rt handers show marked dissociation between __ and __ asymmetry
morphological and functional asymmetry
difference in receptors
womens brain volume in __ and __ regions is significantly higher
PFC; medial paralimbic
sexually dimorphic regions in _, _, and _
sexually dimorphic regions in PFC, paralimbic cortex, posterior parietal cortex
men have larger volumes in __ and __ cortex and __
men have larger volumes in medial and orbitofrontal cortex and angular gyrus
women have more interhemisphereic connections in…
women have more interhemisphereic connections in both the corpus callosum and anterior commissure than men
environmentally induced changes in __ and __ are affected differentially by __
environmentally induced changes in hippocampus and neocortex are affected differentially by gonadal hormones
female __ is far more __ in new __ than the male and this plasticity depends on __
ex: female hippocampus is far more plastic in new environments than the male hippocampus and this plasticity depends on estrogen
