Chapter 14: Parietal lobes and networks

parietal lobe

processes and integrates sensory info to produce actions

anterior parietal region

postcenttral gyrus; PA, PB, PC, PD; processes somatosensory info

posterior parietal cortex

superior and inferior parietal lobules; PE, PF, PG; important for visuospatial behaviors; integrates somatosensory and visual info for the aim of controlling movement; spatial and mental imagery

superior parietal lobule

dorsal lateral regions of areea 7 and precuneus regioin

inferior parietal lobule

supramarginal gyrus and angular gyrus

anterior precuneus

sensorimotor functions

central precuneus

cognitive funcitons

posterior precuneus

visual funcitons

Somatosensory areas of the postcentral gyrus

project to secondary somatosensory areas in the parietal lobe as well as motor planning and motor control areas in the frontal lobe

are PE/ BA5

secondary somatosensory area that projects to motor areas 4, 6, and 8 to guide movements by providing info about limb position

area PF/ BA 7

receives input form somatosensory areas via PE and projects to motor areas; similar to PE

area PG

integrates info from visual, somatosensory, auditory, vestibular, and oculomotor systems with cognitive input from the cingulatet to control spatially guided behavior

dorsal visual strteam

contains info about how

premotor dorsal pathway

primary how pathway for motor control

prefrontal dorsal pathway

inveolved with working memory for visuospatial objects

medial temporal dorsal pathway

project to the hippocampus and parahippocampla region and is suggestted to be important for spatial recognition and navigation

ventral parietal regions

involved in perceptual functions

object recognition

• For movement guidance, the representation needs to be centered on the viewer

  • For object recognition, the focus needs to be object-centered, and much of the viewer-centered info is ignored 

• The brain extracts info about object size, shape, color, location relative to other objects

• Temporal lobe encodes info about how objects relate to each other 

movement guidance

• Viewer-centered movements likely have different control systems

  • Eye movements are based on the eye position

  • Limb control is based on joint position

• Posterior parietal cortex plays a significant role in guiding visuomotor behaviors

• Activity of neurons in posterior parietal cortex depends on the visual stimulation and the ongoing behaviors of the individual

  • Some neurons are only active when the individual makes an eye or arm movement toward an object

  • Other neurons are active when the individual interacts with or manipulates the object 

• Neurons in the posterior parietal cortex integrate sensory info, motivations, and motor control info and are more active when the individual shifts attention toward or makes a movement toward the object 

sensorimotor transformation

integration of movement intention with sensory feedback about how the intended movement compares with the actual movement to perform smooth movements towards the target

area PRR

involved in motor planning by encoding the desired outcome of the movement

medial parietal region

important for route knowledge; cells are active when a specific movement is made at a particular location; cells control body movements to specific locations

acalculia

parietal lobe dysfunction; unable to perform math calculations becausee it has a spatial component

parietal lobe dysfucnitons

acalculia, lagnuage difficulties, difficulty copying observed movements

damage to postcentral gyrus and adjacent posterior parietal cortex

somatosensory symptoms

Damage to postcentral gyrus

results in high sensory thresholds, impaired ability to sense position, and impaired stereognosis

sterognosis

ability to identify an object by touch

lesions to postcentrral gyrus

loss of feedback about the positions of the limbs, making clumsy movements; affeerent paresis

asterognossis

loss of the ability to id an object by touch 

simultaneous extinction

subject is presented with 2 objects at the same time, but patients with damage to the secondary somatosensory cortex notice and report only one of the objects

numb touch

somatosensory equivalent of blindsight; patient reports loss of sensation from a region but can accurately report where they were touched within that region

asomatognosia

condition where person loses knowledge of own body or condition

anosognosia

unawareness of illness

anosodiaphoria

indifference to illness

autopagnosia

inability to locate and name body parts

asymbolia for pain

lack of typical avoidance reaction to pain

autotopagnosia

finger agnosia; associated with dyscalculia; common in kids with spina bifida

balint syndrome

• Rare condition resulting from bilateral parietal lesions 

• Patients have normal vision and can recognize and use objects, pictures, and colors

• Patients can move eyes, but not fixate on a targe

• Has simultagnosia

• Had optic ataxia and was unable to reach a specific target with visual guidance

right parietal lesions

contralaterral neglect

contralateral neglect

• Associated with right parietal stroke

• Patients tend to neglect the left side of their own body and of the world

  • Only copy right side of pic, only dress right side of body

  • When asked to read compound words, only read right half

  • Ignore tactile stimulation to the left side of the body

• Patients generally don’t know that there’s anything wrong

• Patients can recover  by starting to respond to stimuli on the neglected side of the body as if they were on the intact side, and recovery can continue to simultaneous neglect 

• Can be induced in healthy individuals by applying TMS to the right intraparietal sulcus and angular gyrus

• Neglect can occur following damage to frontal lobes, cingulate cortex, or subcortical regions

• Neglect may be due to either impaired sensation and perception or impaired attention 

posterior parietal damage

patients have difficulty recognizing object in unfamiliar views or orientations; may have difficulty mentally rotating image

gestmann syndrome

• Damage to left parietal lobe around area PG

• Patient experience finger agnosia, left-right confusions, agraphia (inability to write), and acalculia

left parietal lesions associated with symptoms including

• Difficulties writing, reading, and grammar

• Apraxia

• Dyscalculia

• Decreased digit span in verbal working memory

• Difficulty with left-right discrimination 

apraxia

loss of skilled movement

ideomotor apraxia

unable to copy movements made by others; associated with left parietal lesions

construction apraxia

issues with spatial recognition; unable to assemble puzzles, draw pics, or copy facial movements; associated with posterior parietal damage to left or right hemispheres

right parietal damage and drawing

tend to neglect left side of image

left parietal damage and drawing

fewer recognizable drawings made and fewer lines used

left parietal damage and spatial cognition

impair the formation of the mental image

right parietal damage and spatial cognition

impair the manipulaiton of the image

symptom: disorders of tactile fucntion

lesion sight: areas 1,2,3

symptom: tactile agnosia

lesion sight: area PE

symtpom: defects in eye movement

lesion sight: areas PE, PF

symtpom: misreaching

lesion sight: area PE

symptom: manipulation of objects

lesion sight: areas PF, PG

symtpom: apraxia

lesion sight: areas PF, Pg, lect

symptom: constructional apraxia

lesion sight: area PG

symtpom: acalculia

lesion sight: areas PG, STS

symptom: impaired cross-modal matching

lesion sight: areas PG, STS

symptom: contralateral neglect

lesion sight: area PG right

symtpom: imapired object recognition

lesion sight: area PG right

symptom: disorders of body image

lesion sight: TPJ, PE

symtpom: right-left confusion

lesion sight: areas PF, PG

symtpom: disorders of spatial ability

lesion sight: areas PE, PG

symtpom: disorders of drawing

lesion sight: area PG

function: somatosensory threshold

test: 2-point discrimination

function: tactile form recognition

test: seguin-goddard form, board (patterns)

function:contralateral neglect

test: line bisection

function: visual perception

test: golin incomplete figures, mooney closure

function: spatial relations

test: right-left differentiation

function: speech and reading comprehension

test: token

function: apraxia

test: kimura box

TPJ

involved in attention (r), language (l), memory (l), social processing, and self-perception

parietal memory network

involved in learning and memory; includes precuneus, angular gyrus, and midcingulate cortex

dorsolateral parietal networks

connect prefrontal, temporal cortexes, and hippocampus regions to perform a variety of spatial functions