Neuro 45 & 46: Cortex

Question 1

PET scan

Answer 1

-measures changes in cerebral blood flow or metabolism via short lived isotopes that are injected

Question 2

fMRI

Answer 2

-measures changes in cerebral blood flow based on how Hb/O2 affects protons

Question 3

2 types of cortical areas

Answer 3

1. primary areas:
   - sensory - have thalamic relays
   - motor
2. association areas- assist nearby primary areas
   - sensory association cortex
   - motor association cortex
   - also includes mutlimodal/integrative areas

Question 4

Post-central gyrus

Answer 4

-somatosensory homunculus

Question 5

Pre-central gyrus

Answer 5

-motor homunculus

Question 6

Which 3 deeps axons play a role in cortical communication?

Answer 6

1. association fibers
2. projection fibers
3. commissural fibers

Question 7

Association fibers

Answer 7

• interconnect cortical areas in one hemisphere
• there are short ones to interconnect adjacent gyri –> important for communication w/in an area
• there are long fibers to innerconnect more distant areas –> important for distance communication
• diseases that damage/interrupt these fibers will cause cognitive deficits

Question 8

Uncinate fasiculus

Answer 8

-association fibers that travel btwn the temporal and frontal lobes

Question 9

Cingulum

Answer 9

-association fibers that travel btwn the temporal and frontal lobes

Question 10

Superior longitudinal fasiculus

Answer 10

-association fibers that travel btwn the frontal, parietal, occipital, and temporal lobes

Question 11

Projection fibers: what are they? list the 4?

Answer 11

• input and output fibers of the cortex to other areas of the CNS
• damage to these cause major sensory or motor deficits
  1. corona radiata
  2. internal capsule
  3. thalamocortical fibers
  4. corticospinal fibers

Question 12

Commissural fibers

Answer 12

• interconect the cortex of the right and left hemispheres
  1. corpus callosum
  2. anterior commissure
  3. hippocampal commisure
• *damage or agenesis often do not result in obvious functional deficits!!

Question 13

Neocortex layers

Answer 13

• outer layer of the cerebral hemispheres
• has 6 lyrs
• organization of the layers is essential for information processing –> developmental problems can cause seizures, mental retardation, or cog deficits!
• involved in higher fctns such as sensory perception, generation of motor commands, spatial reasoning, conscious thought, and language

Question 14

Pyramidal neuron

Answer 14

• type of cortical neuron

- long axon projection neurons

Question 15

Golgi neuron

Answer 15

• type of cortical neuron

- short axon interneurons

Question 16

Asterognosis

Answer 16

• inability to identify an object by touch alone

- caused by lesions in the posterior parietal lobe

Question 17

Apraxia

Answer 17

• inability to produce familiar purposeful mvmnts
• NO sensory or motor impairment
• caused by a lesion in the posterior parietal lobe
• sometimes the pt can perform tasks on their own, but have trouble when they need to perform tasks on command

Question 18

Agraphesthesia

Answer 18

• inability to identify letters or numbers “drawn” on the skin –> disorientation of the skin’s sensation across its space
• caused by posterior parietal lesions

Question 19

Neglect

Answer 19

• denial of self-image of one side of the body or external world
• lesions usually in the RIGHT hemisphere in the posterior parietal lobe

Question 20

Aphasia

Answer 20

-disruption of language capacity, there are different forms

Question 21

Hemispheric dominance

Answer 21

• in some locations damage on the right may cause different deficits from damage in the same area on the left
• so each hemisphere has different capabilities
• dominance is clearly known for language, but is less clear for other functions
• plays a role in handedness too

Question 22

Delirium

Answer 22

• usually a temporary change & is reversible with tx
• acute/sudden onset/medical condition
• inattention, confusion, reduced comprehension, can have change in consciousness
• common in hopitalized older adults –> often drug induced
• *frequently mistaken for dementia or unrecognized!!!

Question 23

Dementia

Answer 23

• usually permanent & irreversible
• ongion medical condition
• slow onset
• no change in consciousness
• memory impairment

Question 24

Plasticity

Answer 24

• probably a general feature of the cortex
• reorganization of cortical maps
• experiences shape brain fctn
• can occur in developmental deficits –> ex. blindness/deaftness, stroke, hemispherectomy pts
• the cortex expects sensory input from the periphery, so when sensory info is elimintated it will create its own info! –> ex. phantom limb, tinnitus, chronic pain, etc.

Question 25

Control of consciousness

Answer 25

- ability to remain alert/awake is controlled by brainstem/system network that influences cortical function --> damage = coma - all sensory systems --> reticular activating system (RAS -midbrain) --> relay in thalmus --> cortical activation = alertness, awake status - need BOTH cerebral cortex and RAS to be conscious!

Question 26

Damage to primary areas v. damage to association areas

Answer 26

Primary: -cause loss of contralateral sensation or wkness -damage to single hemisphere is sufficient enough to cause deficit Association: -more complex deficits -often patient is not aware of deficit -usually bilateral damage is necessary to cause more complex deficits of association areas

Question 27

3 common ways to get bilateral cortex lesions?

Answer 27

1. trauma 2. infection - encephalitis, meningitis 3. vascular

Question 28

What 3 lobes does the visual system involve?

Answer 28

1. occipital lobe 2. parietal lobe 3. temporal lobe

Question 29

Dorsal visual pathway

Answer 29

- extends into the parietal lobe - analyzes the POSITION & MOTION of an object = "where" * *a bilateral lesion in this pathway causes motion agnosia = deficits in perceiving object motion

Question 30

Ventral visual pathway

Answer 30

- involves the occipitotemporal gyrus - analyzes an object's FORM & COLOR = "what" * *bilateral deficits cause color/form agnosia or prosopagnosia (inability to recognize faces of familiar people)

Question 31

Visual word form area

Answer 31

- unique to humans - specific area in the ventral pathway - involved in reading & face recognition - left-sided unilateral lesions will impair reading, but not auditory recognition of words

Question 32

Propagnosia

Answer 32

- inability to recognize faces of previously familiar people | - caused by a lesion in the occipitotemporal gyrus

Question 33

Anton's syndrome

Answer 33

- cortical blindness - pt lacks awareness of deficit = agnosia - caused by a lg bilateral lesion in the visual areas

Question 34

Posterior paritetal lobe

Answer 34

- integrates tactile and proprioceptive info and info from the 2 hands - mediates sterognosis and 2-pt discrimination - sends info to the motor cortex to provide sensory info to guide mvmnt * *lesions cause astereognosis, agraphesthesia, neglect, and apraxia

Question 35

Emotional component of pain: what 2 areas are involved and what do lesions cause?

Answer 35

- anterior cingular gyrus and the insula are involved | - lesions lessen the emotional component of pain

Question 36

Transverse temporal gyri

Answer 36

-primary auditory cortex

Question 37

Wernicke's area

Answer 37

- for language comprehension/understanding --> speech, written, or sign - found in posterior temporal lobe

Question 38

Broca's area

Answer 38

- inferior frontal gyrus, adjacent to motor cortex | - essential for motor aspects & vocalization of language --> speech, written, sign

Question 39

Multimodal auditory areas

Answer 39

- found superior to wernicke's area - receive visual, auditory, and somatosensory info important for language fctns of reading braille and sign lang * *lesions = affect reading and writing from visual cues = dyslexia & agraphestheisa

Question 40

Word memory

Answer 40

- anterior temporal lobe | * *lesions = deficits in naming and word finding

Question 41

Wernicke aphasia

Answer 41

- inability to understand the meaning of words - pt cannot comprehend speech, but they can verbalize well - spontaneous speech is fluent and word articulation is good, but content is meaning less - unaware of deficit

Question 42

Broca's aphasia

Answer 42

- inability to vocalize words - speech is sparse, slow, and words are mispronounced - writing can also be effected - aware of deficit

Question 43

Conduction aphasia

Answer 43

- damage to arcuate fasiculations disconnects wernicke's and broca's areas w/out directly damaging them - comprehension is good, speech is fluent, but contains errors - question-answer tasks are difficult

Question 44

Language localization and handedness

Answer 44

- in most adults language is localized on the left - rt handed ppl = most have lang localized to left - lft handed ppl = most have lang localized to left, and the rest are spilt btwn right and bilateral localization

Question 45

Bilingual localization

Answer 45

- both languages are localized to the same hemisphere | - lesions can preserve one lang but damage the other!

Question 46

Right hemisphere (nondominant) and language

Answer 46

- has simpler language capabilities | - can understand printed and spoken words, understand verbal descriptions of objects, write 3-4 words, and read braille

Question 47

Damage to the right hemisphere?

Answer 47

1. can cause loss of tonal/emotional content of language 2. neglect of tactile and space on left side 3. difficulty with visual discrimination --> face discrimination & recognition of expression of emotion 4. difficulty w/ spatial/geometric orientation 5. apraxia for left mvmnts 5. cheerful/elated mood if its a right pre-frontal lesion

Question 48

Split brain experiments

Answer 48

- hemisphere was surgically isolated - stimuli presented to the rt visual field only = pt names the object - simuli presented to the left feild only = pt says nothing --> but when a pencil is placed in the left hand the pt will draw the object but doesnt know why! --> pt is not conciously aware of info in the rt hemisphere * *so: speech is localized to the left hemisphere & info in the rt hemisphere must be transfere to the left tot speak about it!

Question 49

Damage to left hemisphere?

Answer 49

1. Broca's aphasia 2. Wernicke's apahsia 3. depressed mood if its is a left pre-frontal lesion

Question 50

Motor association cortex

Answer 50

- anterior to precentral gyrus: 1. ventrolateral premotor cortex 2. supplementary motor area (SMA) - mvmnts are learned and stored in motor areas --> lesions will impair access to the stored info!

Question 51

Premotor cortex

Answer 51

- important in mvmnts triggered by sensory events or requiring sensory GUIDANCE * *lesions = apraxia and deficits in visually guided mvmnts (hand-eye coordination)

Question 52

Supplementary motor area (SMA)

Answer 52

- involved in planning of mvmnts - active when mentally rehearsing - stimulation can cause bilaterally mvmnts * *lesions = apraxia & disrupt bimanual coordination

Question 53

Dorsolateral area of PRF

Answer 53

- important in long-term planning, problem solving, and working memory - deals with info thats logical in nature

Question 54

Ventromedial area of PFC

Answer 54

- for cortical control of emotional (limbic) centers | - deals with info that is emotional in nature

Question 55

What are the 5 areas involved in the limbic system?

Answer 55

Areas in the frontal, parietal, and temporal lobes: 1. subcallosal 2. cingulate gyrus 3. parahippocampal 4. amygdala** 5. hippocampus** * *most important areas

Question 56

Hippocampus

Answer 56

- in the temporal lobe - necessary to convert short-term memory into long-term memory - controls the process of memory conversion rather than storing the memory itself * *lesions = severe memory deficits --> cant remember anything past the lesion

Question 57

Amygdala

Answer 57

- in the temporal lobe - controls emotional responses involving fear, anxiety, & anger - influences our ability to associate stimuli w/ their negative consequences * *lesions = fearlessness

Question 58

Brainstem cause of coma & how to test brainstem fctns

Answer 58

- can be due to uncal herniation which causes damage to the brainstem - if important respiratory or cardiovascular control centers are damages = death! - brainstem fctn can be assessed in a comatose pt via testing brainstem reflexes