Chapter 16: Being Different From Others

Question 1

complex brains evolved at least ___ times among animals. outline the general outline of nervous system evolution

Answer 1

3 times. 1) no neurons 2) nerve nts: neurons distributed throguhout the body with no centralization 3) cerebral ganglia.CNS is inlarged in ganglia, some cephalization occured 3) brain and spinal cord.

Question 2

The smaller the animal, the _____ its brain:body ratio (other things being equal)

Answer 2

HIGHER.

Question 3

for their body size, ___ and ___ have the largest brains

Answer 3

birds and mammals

Question 4

T/F: brain:body radios remain constant as brains brains increase in size. What is this trend?

Answer 4

FALSE. there is NEGATIVE ALLOMETRY. brain body ratios decrease in larger animals. smaller animals have higher brain body ratios. ex/ mammals have relatively large brains for their body size compared to larger reptiles.

Question 5

Which animal has the highest encephalization quotient?

Answer 5

humans. we don’t have the largest brains, but we have the largest brains for our body size. eq= actual brain size/expected brain size

Question 6

as you get to larger and larger brain, which portion gets disproportionately large?

Answer 6

the neocortex

Question 7

T/F: humans have the highest brain to body ratio.

Answer 7

false. Brain-body ratios tend to decrease with increasing body size, which means that some animals with very small bodies tend to have very high brain-body ratios.

Question 8

the fossil record suggests that absolute brain size in our closest ancestors increased in two relatively brief growth spurts, separated by a long period of relative stability. when were they?

Answer 8

1) brain growth spur when early hominids tamed fire –> allowed homo erectus to cook its food and obtain more nutrients. 2) after the evolution of homo sapiens and is most likely linked to intraspecific competition for reousrces and mates (social maneuvering required more social intelligence and thus this was favored)

Question 9

in both primates and rodents, neuron numbers increases with increasing brain rate. What is the difference between these two groups?

Answer 9

the rate of neuron number increases significantly faster in primates than in rodents. therefore, large primate brains contain more neurons than equally large rodent brains.

Question 10

of the various neocortical areas, the ____ and ___ lobes are proportionally smaller in humans than in non human primates, but the prefrontal cortex is much larger.

Answer 10

of the various neocortical areas, the TEMPORAL and OCCIPITAL lobes are proportionally smaller in humans than in non human primates, but the prefrontal cortex is much larger.

Question 11

language is most affected by ____ sided brain lesions, espeically in the inferior ___ ____,

Answer 11

language is most affected by LEFT sided brain lesions, especially in the inferior prefrontal cortex. aka BROCAS AREA.

Question 12

where is wernickes area? What is it’s function?

Answer 12

posterior portion of the superior TEMPORAL LOBE. impairs language comprehension without impairing speech. people with damaging this area can speak fluently (unlike brocas aphasia)

Question 13

conduction aphasia

Answer 13

lesions in the inferior parietal lobe that resuls in word repetition and deficits in object naming

Question 14

transcortical aphasia

Answer 14

lesions in the prefrontal cortex that results in language deficits.

Question 15

even though the broca and wernickes area are on the lefts side, how does the right side of the brain affect langauge?

Answer 15

it involved in the prosodic aspects of language, including rhythym, stress, and intonation. people with damage to the right side of the brain tend to speak in a monotone fashion.

Question 16

T/F deaf people exhibit the same brain activity as people with spoken language

Answer 16

true. they show similar amounts of activation in Broca’s area and the auditory cortex, but in deaf people, the auditory cortex also lights up when they read sign language.

Question 17

language-related circuitry can be divided into ___ and ___ streams.

Answer 17

dorsal and ventral

Question 18

the dorsal langugage related circuit passes through the ___ ___ lobe and is involved in the ____ of speech. the ventral language related circuit passes toward the ___ ___ lobe and is involved in speech _____.

Answer 18

the dorsal langugage related circuit passes through the INFERIOR PARIETAL lobe and is involved in the PRODUCTION of speech. the ventral language related circuit passes toward the ANTERIOR TEMPORAL lobe and is involved in speech COMPREHENSION.

Question 19

in terms of the dorsal/ventral model of speech, when is speech processesing bilateral? When is it left hemisphere dominant?

Answer 19

only the late stages of speech processing are left hemishere dominant, the others are bilateral.

Question 20

what gene and its mutation MAY be correlated with language deficits

Answer 20

FOXP2 gene. FOXP2 portions were substituted in mammals that led up to humans. also, families with a mutated FOXP2 gene can’t talk and have smaller brocas areas. but they also have other problems too, so its tough to say if FOXP2 is alone responsible for language and language deficits.

Question 21

the Y chromosome contains the ___ gene, which causes gonadal precursor tissue to develop into testes rather than ovaries

Answer 21

SRY gene.

Question 22

how does testosterone promote brain masculization

Answer 22

during embryonic development and shortly after birth, a male’s testes produce a surge of testosterone.

• this testosterone binds to androgen receptors in the external genitalia, which in response, enlarge the embryonic phallus into a penis
• in the brain, all the testosterone produced is converted to estradiol via the enzyme aromatase.
• estradiol binds to estrogen receptors and causes the cell expressing those receptors to develop in the male-typical direction.

Question 23

during early postnatal development, females express very little estrogen, and whatever estrogen they do express is sequestered by ___ ____, which does not cross the BBB

Answer 23

alpha fetoprotein

Question 24

explain how the gynandromorph finch’s sex differences result from both genomic and circulating sex hormone effects

Answer 24

1) genomic effects: cells on right side of the gynandromorph finch contained the male mix of sex chromosomes, where as most of the cells on the left side contained the female sex chromosomes.
- left/right differences in the plumage of this finch were most likely caused by genes that are locted on only one of the sex chromosomes.
2) sex hormone effets: the song system HVC (telencephalic cell group) on the right side is larger on the left, because the “male” side is more likely to sing. but, the song system on the left side is also larger than most “full female” finches, indicating that the “female side” of this gynandromorph brain has been affected by the testosterone (and then converted estradiol) that was circulating from the birds single testis.

Question 25

onuf’s nucleus

Answer 25

the spinal motor neurons that innervate muscles at the base of the penis or nearby muscles.

Question 26

which sex has a larger onuf’s nucleus

Answer 26

males have larger onug’s nucleus. this structure is englarged in the presence of testosterone in newborns, which is higher in males

Question 28

female dogs exposed to high levels of testosterone in utero and shortly after birth end up with an increased number of Onuf’s motor neurons, implying that the ____ ____ results, at least in part, from sex differences in testosterone exposure during early development

Answer 28

that female dogs exposed to high levels of testosterone in utero and shortly after birth end up with an increased number of Onuf’s motor neurons, implying that the sexual dimorphism results, at least in part, from sex differences in testosterone exposure during early development

Question 29

in male rats, which nucleus in the hypothalamus is enlarged?

Answer 29

the sexually dimorphic nucleus, this nucleus is known to increase activity in male sexual behavior (SDN).

Question 30

human homolog of the sexually dimorphic nucleus (SDN) in rats.

Answer 30

the Third Interstitial Nucelsu of the Anterior Hypothalamus (INAH-3). this is larger in men and are involved in male sexual behavior, notably, ejaculation.

Question 31

hypothalamic differences in heterosexual and homosexual men

Answer 31

homosexual men have smaller third interstitial nuclei of the anterior hypothalamus regions than heterosexual men, but they have the same amount of neurons

women also have smaller INAH3’s then men. May correlate with sexual behavior differences.

Question 32

which hypothalamic nucleus is larger in females than males? What’s the purpose of this nucleus?

Answer 32

the anterocentral periventricular nucleus (AVPV) of the preoptic area is significantly larger in females. the AVPV helps to trigger ovulation by driving a surge of luteinizing hormone release from the pituitary gland.

Question 33

perinatal testosterone increases the rate of apoptosis in _____ and decreases it in ____ nuclei.

Answer 33

perinatal testosterone increases the rate of apoptosis in AVPV and decreases it in SDN/INAH3 nuclei.

this indicates that the sex difference in SDN and AVPV sizes are dependent on the action of sex hormones during the perinatal period.

Question 34

Dopaminergic neurons in the substantia nigra are _______ in femals compared to males

Answer 34

more numerous in females comapred to males.

Question 35

T/F: the sex difference in the DA neurons of the substantia nigra are influenced on prenatal hormons, like the hypothalamic nuclei.

Answer 35

false. this sex difference is sensitive to circulating sex hormones in ADULTs. castrating a male rat increases the number of dopaminergic SN neurons, relative to control rats, and this increse can be prevented by testosterone replacement therpay.

Question 36

explain why women are less likely to develop parkinson’s disease than men

Answer 36

testosterone is slightly toxic to the dopaminergic neurons in the substantia nigra in adultgood, whereas estrogen is protetive. this means that the SN in females is less liekly to “degenerate” and is less likely to demylinate.

Question 38

T/F: men have larger brains than women because they have a larger body size

Answer 38

false. it appears that the sex difference in the human brain size evolved independently of the sex difference in body size. This might actually have to do with the fact that over evolutionary history, men might have experiences natural selection for visuospatial processing because they had to hunt and stuff.

in contrast, the skillls in which women tend to outperform men (such as verbal ability) might have been boosted in women by mechanisms that do not involve neocortical enlargement.

Question 39

T/F: compared to men, women tend to have proporitionately more cortical gray matter and proportionally larger corpus callosum.

Answer 39

true. however, gray matter fraction and corpus callosum size decreases predictably with increasing brain size.

Question 40

what does allometrically predictable mean

Answer 40

a difference in proportional size of a structure that is consistent with how that structure sclares relative to other structures (such as absolute brain or body size)

Question 41

Discuess language lateralization between sexes

Answer 41

some studies show that left hemisphere dominance for language processing is less pronounced in women then in men. when subjects were asked to evaluate whether two sets of nonsense syllables rhyme, fmri studies have shown that women are less lateralized, with activation happening on both sides.

Question 42

describe the sex differences between the functional lateralization of the amygdala.

Answer 42

studies have shown that the degree of amygdala activation at the time of memory formation correlates positively with increased memory for the arousing images when subjects are tested several weeks later. there is a sex difference here though:

for women, this corrlation is more robust for the LEFT AMYGDALA. for men, this correaltion is more robust for the RIGHT AMYGDALA.

Question 43

if the left hemisphere is generally better at processesing detailed info, and the right is focused more on global info, what could be the predicted link about amygdala activation and memory in men and women

Answer 43

it could be predicted that emotional arousal should boost memory for detailes in women (b/c their left amygdala is more active), but increase memory for the overall gist of an event in men (b/c their right amygdala is more active).

Question 44

T/F meta-analysis of sex differences does not support language lateralization.

Answer 44

true. there really isn’t much language lateralization even though a few key studies showed this.

Question 45

which sex is more likely to be left handed?

Answer 45

men are consistently more likely than women to be left-handed or ambidextrous

Question 46

talairach space

Answer 46

an artifact in the location of averaged fMRI results that arises when researchers try and “standardize” all brains to tehe reference atlas-seized brain.

Question 47

explain the variability of broca’s area size and location across individuals.

Answer 47

Broca’s area (areas 44 & 45) varies in size between hemispheres and individuals.

significant variability exists both across brains and between hemispheres.

On average, area 44 was significantly larger in the left hemisphere. Area 45 was sometimes larger on the left and sometimes larger on the right.

Variation in the size of these two areas correlates only weakly with overall brain weight and is independent of sex.

Question 48

there is location variability in the human brain. even small sulci between individuals vary. how do we take these variabilities into account? (ie/ like during surgery or something)

Answer 48

Probabilistic brain atlases take variability between individuals into account.

Question 49

neocortical surface area triples between birth and young adult good. what accounts for this expansion?

Answer 49

due to increased myelination of the long axons that course through the neocortical white matter. gray matter also increases in volume somewhat, but mainly due tot he addition of more synapses. Neurogenesis usually happens before birth. therefore, brain size does not increase because you are making more neurons.

Question 50

in humans, neocortical expansion and maturation are delayed in the ___, ___, and ___ ___ lobes relative to other cortical areas

Answer 50

delayed in the PREFRONTAL, PARIETAL, and LATERAL TEMPORAL lobes.

the delayed prefrontal lobe development is linked to maturity differences in children and adults.

Question 51

T/F : boys lag behind girls in terms of brain growth and maturation. what may this cause in terms of differences in maturation

Answer 51

TRUE. boys don’t mature as fast as girls. there is a correlation between earlier cortical maturation and earlier language development. girls typically lead boys in language development, an advantage they retain through adulthood. this CANNOT be causally evaluated on an individual level. knowing the sex of a child does not allow you to make specific preductions about either their brain or their language abilities.

Question 52

brain volumes decrease ____ to ___ % per year

Answer 52

brain volumes decrease 0.5-1% per year.

Question 53

after 50, brain shrinkage tends to occur at a faster rate, many cortical regions shrink by 0.5% a year on average. what neocortical lobes are most affected? non-neocortical regions? what regions of the brain are englarged as you age?

Answer 53

most dramatic in the frontal, parietal, and temporal lobes. the same areas that mature late.

nonneocortical: hippocampus, amygdala.

ventricles take up the space of where neural tissue once was. ventricles expand.

Question 54

as aging brains shrink in volume, what portions of the tissue is primarily lost? is the overal neuron number really affected?

Answer 54

people lose a substantial amount of WHITE MATTER. (28% loss between 20 and 90).

However, you don’t lose this many neurons. neocortical neuron loss in healthy humans decreases about 10% between 20 and 90.

Question 55

what portion of the hippocampus is most severely affected by aging

Answer 55

the perforant path, which connects the entorhinal cortex to the CA3 and detate gyrus, loses a significant number o fsynpases as rats get old; but other hippocampal pathways are less affected by age.

Question 56

what is alzheimers disease and discuss the amyloid cascade hypothesis

Answer 56

a neurodegenerative disease caused by the presence of beta-amyloid deposis and neurofibrillary tangles. causes severe dementia and the terminal stage results in the loss of motor and autonomic coordination, which generally leads to infections and death.

amyloid casade hypothesis: these plaques and tangles result from the faulty processing of the amyloid precursor protein. build up and products of this faulty processing destroys synapses and eventually kills some neurons.

Question 57

which brain regions are more affected by alzheimers than others?

Answer 57

hippocampus

enterorhinal cortex

cholinergic neurons in basal forebrain

noradrenergic neuron in the locus coeruleus.

these play a huge role in attention and memory

Question 58

kroghs principle and an exemption

Answer 58

kroghs principle: there is a perfect animal to study any component of physiology ex/ squid axons were really good for studying action potential mechanisms

example: its really really hard to study alzheimers in any animal. as a result, we have to create triply-transgenic mice that house the genes linked to alzheimers.

Question 59

as measured with DTI, it was demonstrated that the ___ path of the hippocampus shrinks with agin

Answer 59

perforant path

Question 60

explain the genetic components of autism

Answer 60

autism is spectrum because it relies on a huge aggregation of mutations of multiple genes. the severity depends on the combination of genes a person is carrying

autism is also highly genetic. its 90% likely that a monozygotic twin has autism if their twin has autism. normal siblings and dizygotic twins are still 25x more likely than non related people to have autism.

there are also chromosomal rearrangements that occur that result in an increase in the copy number of several genes, and are linked not only to autism but also to other psychiatric disorders like schizophrenia.

Question 61

discuss brain differences in people with autism. How does their brain grow?

Answer 61

people with autism have larger brains and the overgrowth is primarily seen in the prefrontal cortex with MORE NEURONS.

there is an ACCELERATED BRAIN EXPANSION during the first 2-4 years of life, followed by a premature cessation of brain growth, and, more tentatively some neuronal shrinkage.

autism is also linked to reduced white matter. there are lesss connections between hemispheres and between PFCs. this nueonral tract connection may result in a decreased level of function integration across the brain.

Question 62

explain the swedish military study and the link between marjuana and schizophrenia

Answer 62

45000 swedish military recruits showed that individuals who had smoked pot at least ONCE before they entered military service were 2.6 times as likely to develop schizophrenia. Those who smoked more than 50 times increased their risk by 6 fold.

Question 63

which gene seems to be implicated in schizophrenia

Answer 63

people with specific allelic combination sof catecholomethyltransferase (COMT) are especially sensitve to the schizophrenia inducing effects of pot.

Question 64

explain the brain differences seen in people with schizophrenia

Answer 64

1) cerebral ventricles are excessively inlarged, while neural tissue shrinks
2) considerable shrinkage of the frontal lobe, mainly due to SYNAPSE LOSS. NOT CELL DEATH.
3) some thalamic and HC regions affected.
4) possibily linked to excessive dopamine in cortices. drugs used to treat schizophrenia tend to be dopamine antagonists.
5) there seems to be a link between schizophrenia and compromised glutaminergic and GABAergic transmission.

Question 65

explain monogamy and polygamy in voles

Answer 65

monogamous voles tend to have more vasopressin receptors in their pallidum

vasopressin is released IN the ventral pallidum by axons from parts of the amygdala.

To test whether this neural difference accounts for the behavioral species difference, researchers used a virus to overexpress the vasopressin receptor in the ventral pallidum of meadow voles, which are normally polygamous.

Sure enough, those genetically modified meadow voles preferentially huddled with their partner, just as prairie voles do (bottom).