lecture 20 - parietal lobes

vestibular organ

mediates balance in the inner ear

• consists of two otolith organs and three semicircular canal

• balance is processed along with hearing, separate from the other somatosenses

otolith/otoconia

crystals/grains of sand shift around in the vestibular organ, and when the head shifts the grains move and press against the hair cells to trigger AP’s

utricle

senses horizontal motion (forward/backwards, left/right)

saccule

detects vertical movements (up/down)

semicircular canals

filled with jellylike substances that shift along hair cells when the head shifts, and triggers APs

when you spin for some time and then suddenly stop why do you feel that the world is still spinning?

when the semicircular canals detect that you are spinning because of the fluid in them moving, they send an AP to the brain telling it that you’re spinning; however, when you stop, the fluid remains moving for a while in a vortex-like manner, and so the brain still caches that as rotation.

CVIII/C8/Vestibulocochlear Nerve

which cranial nerve deals with the information from the vestibular system?

detecting motion, staying upright, eye movement

purpose of the vestibular system in general

VPL — primary somatosensory cortex

where in the thalamus does info from proprioception/hapsis go?

nuclei in pons/medulla connect at many points

thalamic relays for vestibular information; important for eye movements, how you move your body, audition, and catching yourself when tripping or falling

somatosensory mapping

somatopic (mapped onto the cortex based on body parts (homunculus diagram)

— based on order of nerves that bring in info (cranial nerves, then the rest of the body)

• more receptor density from lips and hands than other parts (more cortical real estate)

homunculus

means “little human” — discovered by stimulating different areas in the cortex

• size of body parts — how they are mapped cortically

• hands/lips huge — high receptor density

• shins have almost pain receptors

1. 3a — muscles

2. 3b — skin (slow touch)

3. 1 — skin (fast touch)

4. 2 — joints, pressure

in what sense are there multiple representations of the body on the body for the somatosensory cortex

be able to identify the parietal lobe on sketches

postcentral gyrus (brodmanns 1, 2, 3) $ parietal operculum (brodmann 43)

organization of connections in the anterior zone in the parietal lobe?

brodmanns 5, 7

organization of connections in the superior parietal lobule

supramarginal gyrus (brodmann 40) and angular gyrus (brodmann 39)

connections in the inferior parietal lobe

intraparietal sulcus

controls motor coordination — reaching, eye movement

pathway area 5

• handles input from primary sensory areas

• handles output to the primary motor cortex (4), supplementary motor area (SMA), and premotor areas (6 & 8)

• function: guides movement by giving information about limbs, their position, and movement

pathway: area 7a

• input from primary sensory areas (1, 2, 3) secondary sensory (5), motor and premotor cortex, and visual cortex

• output to primary motor cortex (4), supplementary motor area (SMA), and premotor areas (6&8)

• function: more elaborate movement guidance by giving information about limbs, their position, and movement

area 7b, 39, 40 (dorsal stream)

• input from visual, skin sensation, proprioception, auditory, vestibular, oculomotor, and cingulate areas

  • “parieto-temporal-occipital crossroads”

• outputs: many, but especially the prefrontal cortex

• function: intermodal integration, spatially guided actions based on visual and tactile information

bottom of angular gyrus, and supramarginal gyrus

which two areas comprise the inferior parietal lobe?

(They receive sensory information, skin sensation, and proprioception, does egocentric space)

route-based

the navigation strategy where you go based on landmarks (go straight and then turn left) — based on recognition

map based

navigation strategy where you have a map in your head (know in general relationships between various landmarks) — requires formation in head

landmark agnosia

not being able to recognize landmarks

What types of information are these areas processing?

MTL: maplike representations
RSC - bookstore at back -what building would you see here etc

Spatial navigation beyond personal space -combine your location with knowledge of landmarks and maps

parahippocampal place area

place in the brain where landmarks are processed

retrosplenial cortex

uses landmark info to figure out where a person is in an environment

medial temporal lobe

creates maplike representations of your environment

arithmetic

“vaguely spatial” because of two reasons:

• in arabic numeral system, numbers are read based on where they are spatially

• people learned to count mostly with their fingers

dyscalculia

damage to the inferior posterior parietal lobe can lead to _____ which is the inability to do math, and also problems in reading language, or finger agnosia.

alertness/arousal; ascending reticular activating system

one of the four attentional processes that is tasked with focusing attention on something

vigilance/sustained attention; basal forebrain/right hemisphere

one of the four attentional processes tasked with keeping your focus on a stimuli for an extended period of time

selective attention; superior colliculus

one of the four attentional processes tasked with discriminating where your focus goes in the face of many stimuli

attentional control/lateral PFC regions

one of the foura ttention processes tasked with controlling where you focus

selective attention

which attentional process is the parietal lobe very important for

Superior PL

part of the parietal lobe that controls where to attend, and how to shift attention

Inferior PL

part of the parietal lobe that tells you when to shift to important perceptual information

Intraparietal area

part of the PL tasked with weighing and prioritizing info

dizziness

light headed and vague

vertigo

• dizzy

• very specific way in which the world is spinning around you

• feeling occurs for no reason

• common with vestibular disorders

  • hard time staying upright

15/100,000

prevalence of meniere’s disease

vertigo attacks, hearing loss attacks, tinnitus

symptoms of meniere’s disease

antiemetics (for nausea), diuretic (for reduction of fluid), histamine antagonists (for sedative effects)

treatment for meniere’s disease