Quiz 6

Question 1

what are the non-neocortical areas of the brain and how many cell layers do they have?

Answer 1

olfactory cortex/bulb (paleocortex): 3-5 cell layers
hippocampus: archiocortex: 3-4 cell layers
neocortex has 6 cell layers

Question 2

what are the two types of cells in the cerebral cortex?

Answer 2

pyramidal: have different soma sizes and axon distributions depending on which layer they are in
non-pyramidal:
basket cells: highly branched, surround pyramidal cells
chandelier cells: vertical synapses that end on the initial segment of pyramidal axons
double bouquet cells: axons that ascend and descend

Question 3

what are the 6 cortical layers?

Answer 3

1: molecular layer
2: external granule layer
3: external pyramidal layer
4: internal granule layer
5: internal pyramidal layer
6: multiform layer

Question 4

how do agranular vs granular layers differ?

Answer 4

agranular (layer 1-3): large pyramidal cells, found in motor areas
granular (layer 4-5): mostly small cells, found in sensory areas

Question 5

what are the long association bundles that interconnect cortical areas?

Answer 5

uncinate fasciculus: connects lower fronal lobe to upper temporal lobe
inferior occipitofrontal fasciculus: connects frontal lobe to temporal lobe
arcuate fasciculus: connects frontal lobe to occipital lobe
superior occipitofrontal fasciculus: connects frontal/parietal lobe to temporal lobe

Question 6

which areas lack commissural connections?

Answer 6

primary visual cortex (lateral surface of occipital lobe) and the hand area of somatosensory cortex (postcentral gyrus)

Question 7

what is an example of disconnect syndrome?

Answer 7

destruction of left visual cortex prevents info from the right visual field from reaching language areas on the left hemisphere which causes alexia (unable to read)
destruction of splenium of CC prevents info from left visual fields from reaching language areas because the route from right to left is blocked, language areas are undamaged so production and comprehension of language are still intact

Question 8

what are the cortical connections in sensory and motor systems?

Answer 8

sensory: there is a combination of serial and parallel processing, sensory inflow from the thalamus is distributed to both primary and association areas
motor: outflow originates in both primary motor and motor association areas
(diagram on L21S25)

Question 9

what are the major cortical regions?

Answer 9

premotor: anterior to motor cortex
motor: precentral gyrus
somatosensory: postcentral sulcus
somatosensory association: posterior to postcentral sulcus and into
occipital and lower temporal lobe
secondary somatosensory: behind postcentral gyrus on lateral side of brain
visual: tip of occipital lobe
visual association: rest of occipital lobe
auditory: top of temporal
auditory association: below auditory, top to middle of temporal
vestibular: above auditory, midbrain
gustatory: anterior to auditory in frontal lobe

Question 10

what are the language areas of the brain?

Answer 10

Wernicke’s area: receptive speech area for word comprehension and formulation, lesions result in fluent aphasia (normal word production but inappropriate usage), superior posterior part of temporal lobe
Broca’s area: motor speech area for word production, lesions result in non-fluent aphasia (slow speech, poor articulation, short sentences), frontal lobe right above front of temporal lobe

Question 11

what is the general pathway for producing a spoken description of an object?

Answer 11

visual input to occipital lobe -> left angular gyrus (object recognition) -> Wernicke’s area (word formulation) -> Broca’s area (word production) -> motor cortex -> brainstem/cranial nerves (vocal cord activation)

Question 12

Leborgne vs Lelong?

Answer 12

Leborgne: could only say one word, couldn’t understand language but could speak, normal function otherwise, damage to Broca’s area
Lelong: could only say 5 words, couldn’t understand language but could speak, normal function otherwise, damage to Broca’s area and superior longitudinal fasciculus

Question 13

what is parietal lobe dysfunction/neglect syndrome?

Answer 13

results from damage to the right parietal lobe, causes patients to neglect the left half of the world

Question 14

what brain region makes up the minds eye?

Answer 14

right intraparietal sulcus, used to imagine if an object has been rotated

Question 15

what is the dominant hemisphere?

Answer 15

the side of the brain containing language centers, located in the left hemisphere in about 90% of right-handed people

Question 16

what is the result of parietal lobe lesions?

Answer 16

left parietal (and some frontal lobe): lead to apraxias: inability to perform certain actions even though
the muscles are perfectly normal (e.g. inability to touch one’s nose when asked, but able to touch nose in response to itch)
right posterior parietal (into visual association areas): lead to agnosias: inability to recognize the identity of an object using a particular sense even though the sense is intact (e.g.
vision – facial recognition; prosopagnosia)

Question 17

dorsolateral vs orbitofrontal prefrontal cortex?

Answer 17

dorsolateral: planning based on external criteria (sensory information informs motor plan)
orbitofrontal: planning based on internal criteria (subjective judgements based on personality, major connections with limbic system)

Question 18

how does epilepsy effect EEG results?

Answer 18

when neurons fire synchronously then the amplitude of the waves on EEG are higher, epilepsy results in an extreme form of synchronous activity (seizures)

Question 19

what does the brains electrical activity at different sleep stages look like?

Answer 19

awake, eyes open: higher frequency, low amplitude
awake, eyes closed: lower frequency, low amplitude
light sleep: high frequency, low amplitude
between light and deep sleep: brief spikes of high frequency occurs (sleep spindles)
deep sleep: high amplitude, low frequency
REM: high frequency, low amplitude

Question 20

what are the characteristics of slow wave/non-REM sleep?

Answer 20

high voltage, low frequency EEG activity, normal muscle tone, predominance of PNS activity, dull or absent sensation, several stages

Question 21

what are the characteristics of REM sleep?

Answer 21

tonic, low voltage, high frequency EEG signal, similar to waking pattern, loss of muscle tone (atonia) or
paralysis of all skeletal musculature, except the extraocular muscles and the muscles of respiration, phasic rapid eye movement, phasic tonic-clonic jerks of distal limbs, intense sympathetic nervous system activation, occurrence of dreams

Question 22

how do the sleep stages progress over the night?

Answer 22

wake -> stage 1-4 -> REM, stage 4 continues and then stage 4-1 and REM occurs after stage 1, this repeats and REM cycles get larger each time

Question 23

how does the ascending reticular activating system (ARAS) work?

Answer 23

awake: multiple inputs from the ARAS depolarize thalamic neurons, shifting them toward tonic mode
slow-wave sleep: ARAS activity is suppressed, and thalamic neurons switch into burst mode, blocking transmission of detailed information
REM: most ARAS activity is completely suppressed; however, cholinergic activity is as great as during wakefulness, allowing thalamic neurons to remain in tonic mode

Question 24

what are the structures important for the sleep-wake cycle?

Answer 24

ascending reticular activating system (ARAS): maintains wakefulness by acting on the cerebral cortex in a generalized manner, both directly and through effects on the thalamus, ARAS is periodically turned off
by projections from the medullary and pontine reticular formation, inducing sleep
diencephalic centers are also capable of inducing sleep and wakefulness via arousal-promoting projections from the posterior hypothalamus and basal nucleus and antagonistic projections from the preoptic area

Question 25

what are some sleep disorders?

Answer 25

sleep onset REM: no intervening SWS sleep attacks cataplexy: (a symptom of narcolepsy) results in a sudden loss of muscle tone while EEG arousal and wakefulness are maintained sleep paralysis: persists after arousal from sleep caused by orexin gene mutation in chromosome 6

Question 26

what brain regions are part of the limbic system?

Answer 26

septal nuclei, cingulate gyrus, hypothalamus, amygdala, hippocampal formation, corpus callosum, fornix, cerebral peduncle

Question 27

what are the functions of the hypothalamus?

Answer 27

1. affect autonomic motor neurons both directly and through visceral motor programs in the brainstem and spinal cord and can also influence visceral structures through its control over the pituitary gland 2. stimulate somatic responses through connections with limbic structures that interconnect the hypothalamus and neocortex, the latter are two-way connections, providing us a degree of voluntary control over responses that may be physiologically desirable but do not fit the current circumstances in some other way (e.g., “grin and bear it”) 3. cerebellum and basal ganglia also have connections with the hypothalamus, but their roles in the planning and coordination of drive-related activities are still poorly understood

Question 28

where are the precomissural fornix, mammillothalamuc tract, and dorsal longitudinal fasciculus?

Answer 28

precomissural fornix: in front of anterior commissure mammillothalamuc tract: under chin of seahorse above mammillary body dorsal longitudinal fasciculus: runs along backside of the brainstem (diagram on L23S16)

Question 29

how does the hypothalamus regulate the pituitary gland?

Answer 29

oxytocin and vasopressin are transported down the axons of magnocellular neurons of the supraoptic and paraventricular nuclei, reaching capillaries of the posterior lobe parvocellular neurons in the arcuate nucleus and nearby regions of the walls of the third ventricle secrete releasing and inhibiting hormones in the median eminence, where they gain access to the hypophyseal portal system and through it reach the anterior lobe

Question 30

how is body temperature regulated?

Answer 30

regulated by neurons within the anterior (heat loss) and posterior (heat gain) hypothalamic regions hyperthermia if lesion is restricted to the anterior hypothalamus, and hypothermia if limited to the posterior hypothalamus posterior hypothalamic lesions usually produce poikilothermy (dysregulated thermal control) because in addition to destroying the heat gain neurons, the fibers of heat loss neurons enroute to the brainstem are destroyed

Question 31

how is food intake regulated?

Answer 31

regulated by neurons in the ventromedial, paraventricular and lateral hypothalamic regions, destruction of ventromedial and paraventricular areas combined with continuous access to a food supply eventually lead to obesity, lesions of the lateral hypothalamus produced lowered food intake

Question 32

how are emotions regulated?

Answer 32

aggressive behavior can be elicited by destroying the ventromedial hypothalamus presumably by disrupting efferents from the amygdala (rage syndrome), hypothalamic outputs are also associated with emotional responses mediated by autonomic system (heart rate, respiration, pupillary dilation) these appear to be mediated by posterior hypothalamus

Question 33

how are endocrine imbalances regulated?

Answer 33

disrupted following a variety of hypothalamic lesions, most of these lesions affect function of the pituitary gland since this is the output or target of many hypothalamic peptides and releasing/inhibiting factors

Question 34

how does information flow through the hippocampus?

Answer 34

1. pyramidal cells in entorhinal cortex 2. granule cells in dentate gyrus (middle of swirl) 3. pyramidal cells in CA3 4. pyramidal cells in CA1 5. pyramidal cells in the subiculum (bend) that project to entorhinal cortex (end of hippocampus)

Question 35

what are the major inputs and outputs of the hippocampus?

Answer 35

inputs: entorhinal cortex which collects inputs from cingulate, temporal, amygdala, olfactory, and orbital corticies outputs: through the fornix to the mamillary bodies, ventral striatum, and septal nuclei

Question 36

what are the different types of memory and what brain regions are responsible for them?

Answer 36

working memory: prefrontal cortex explicit memory: events and facts in hippocampus and diencephalon implicit memory: skills (striatum, motor areas, cerebellum), emotional association (amygdala), reflexes (cerebellum)

Question 37

what are the projections of the amygdala?

Answer 37

amygdala through thalamus to cortex in ventral tract cortex to amygdala to septal area/hypothalamus to brainstem and vice versa through spintothalamic tract

Question 38

what are the outputs and inputs of the amygdala?

Answer 38

outputs: 1. the stria terminalis, which reaches the septal nuclei and hypothalamus 2. the ventral amygdalofugal pathway to the hypothalamus, thalamus, widespread areas of frontal and insular cortex, olfactory structures, and various brainstem sites 3. direct projections to the hippocampus, entorhinal cortex, and temporal and other neocortical areas inputs: 1. from the hypothalamus and septal nuclei through the stria terminalis 2. from the thalamus and hypothalamus, and from orbital and anterior cingulate cortex, through the ventral “amygdalofugal” pathway 3. from the olfactory bulb and olfactory cortex through the lateral olfactory tract 4. directly from temporal lobe structures such as neocortical areas and the hippocampus