The parietal lobe is involved in somatosensory processing and integration. It has several subdivisions and connections to other brain regions. Lesions can cause various sensory deficits like impaired localization of touch. They can also result in asomatognosias like denial of illness in one side of the body. Parietal lesions are associated with different types of apraxia including limb apraxia and constructional apraxia. Visual disorders like neglect of one side of space can also occur due to parietal damage.

1. The Parietal Lobe

2. • ANATOMY
• FUNCTIONS
• CLINICAL EFFECTS

3. ANATOMY

4. BOUNDARIES OF PARIETAL LOBE
– Anterior border - Central Fissure
– Ventral border - Sylvan Fissure
– Posterior border - Parieto-occipital sulcus

6. Subdivisions of the Parietal Lobes
Post central sulcus
Interparietal sulcus
1. post central gyrus
2. Somasthetic association area
3. Superior parietal lobule
4. Inferior parietal lobule –
angular gyrus
supra marginal gyrus

7. FUNCTIONS

8. PRIMARY SOMASTHETIC AREA
Body image representation
• Afferents – VP nucleus of thalamus
• Efferents - to SPL (area 5)
- some to opp. Somatosensory cortex via
corpus callosum.
SOMASTHETIC ASSOCIATION AREA
Body in space
Tactile discrimination

10. PRIMARY SOMASTHETIC AREA
Body image representation
• Afferents – VP nucleus of thalamus
• Efferents - to SPL (area 5)
- some to opp. Somatosensory cortex via
corpus callosum.
SOMASTHETIC ASSOCIATION AREA
Body in space
Tactile discrimination

11. SUPERIOR PARIETAL LOBULE AND AREA 7
Information processed in primary and
association areas is transmitted to area 7, where
polymodel association takes place.
Area 7 is the highest level of somasthetic
integration. (also have connections with all lobes).
3 D analysis of body space interactions (body schema)
Visual spatial properties
Visual attention
Motivation and grasping functions.
(parietal lobe lesions - there is ‘self grasping’ of forearm opp. the
lesion )

12. • Areas 5 and 7
have connections with premotor and motor
cortex – so, lesions l/t disturbances in voluntary
movement.
also have connections with cingulate gyrus
and prefrontal cortex . Therefore they mediate
influence of emotion, attention and motivation
on behavior - produced by somatosensory &
visual stimuli.

14. INFERIOR PARIETAL LOBULE
Last to mature anatomically and functionally.
So, the functions are late, to develop b/w 5 and 8 yrs
age. ( reading , calculations )
Angular gyrus & Supra marginal gyrus -
they have interconnections with visual, auditory,
somasthetic, supr. colliculus, LGB and other lobes.

15. 1. Multimodal assimilation – capacity for
organizing , labelling and conceptualizing , using
all senses.
Ex : chair
2. Language capabilities
angular gyrus - anomia
supramarginal gyrus – conduction aphasia
visual cortex to IPL connections – word
blindness

16. 3. Agraphia – lt. lobe
Engrams for production and perception
of written language are stored in IPL .
So, misspellings, distorsions, and inversions occur.
4. Temporal sequential functions
IPL is the main track of input and output.
Therefore, information is organized appropriately
into a sequence here.
5. Caluculation (Lt.) and computation (Rt.)

17. IPL lesions l/t disruption of visual spatial
functioning and temporal sequencing ability
(apraxia).
i.e either spatial sequential tasks lost - OXOXOX
or sequential grammar relations are lost.

18. Cerebral laterality

19. Either hemisphere
1. Cortical sensations.
2. Integration of sensory , motor and attention signals
(i.e disengage attention - do other activity -immediately
reengage correctly)
3. Optic radiation passes through.
4. Constructional ability – capacity to construct or draw
3D/2D figures or shapes.
Lt. – programming of movements necessary for
constructional activity. (simplification of complex
diagrams)
Rt. – related to spatial relationships or imagery.
(rotation of diagrams)

20. 5. Short term memory
Lt. – immediate recall for digits and words
Rt. – immediate recall for geometric patterns
Left hemisphere
1. Language – comprehension
reading
writing
2. Calculations – verbal rote calculations and
recognition of signs.
3. Non verbal symbolization (pantomime)

21. Right hemisphere
1. Constructional skills
2. Dressing apraxia
3. Calculations –
arithmetic concepts of carrying and borrowing
spatial alignment of written calculations.
(computational difficulty – inability to manipulate
no.s in spatial relation, like using decimals,etc –
but he is able to do problems in his head )
4. Perceptual functions (inattention/neglect of lt.
hemispace)

23. CLINICAL EFFECTS OF
PARIETAL LOBE LESIONS

24. • CORTICAL SENSORY SYNDROMES
• ASOMATAGNOSIAS
• APRAXIAS
• VISUAL DISORDERS
• AUDITORY NEGLECT

25. CORTICAL SENSORY SYNDROMES
Cortical defect is essentially one of sensory
discrimination i.e impaired ability to integrate and
localize stimuli.
1. Loss of position sense and passive
movement.
2. Topagnosia – loss of localization of tactile,
thermal and noxious stimuli.
3. Astereognosis.
4. Agraphesthesia.
5. Loss of ‘two point’ discrimination.

26. • This type of sensory defect is sometimes referred
to as “cortical” , although it can be produced as
well by lesions of the subcortical connections.
• The perception of pain, touch, pressure, vibratory
stimuli, and thermal stimuli is relatively intact in
parietal lobe lesions.
Pseudothalamic pain syndrome : burning or
constrictive pain, identical to the thalamic pain
syndrome, resulted from vascular lesions restricted
to the cortex.

27. Other parietal sensory defects :
• easy fatigability of sensory perceptions
• inconsistency of responses to painful and tactile
stimuli
• Pain sensations outlast the stimuli & hyperpathia
• Tactile hallucinations
Motor deficits: mild hemiparesis +
hypotonia +
atrophy (unexplained by inactivity).

28. Optic ataxia : clumsiness in reaching for and
grasping an object.
Pseudocerebellar syndrome : incoordination and
intention tremor of contralateral limbs.
Fixed dystonic postures

29. Tests for cortical sensations
• Basic sensations must be intact.
A. Two point discrimination :
Calipers or compass used.
Sites – palms (8-15 mm) , dorsum (2-3cm)
, shins (3-4 cm).
 Ask pt. to close eyes – respond as ‘one’ or ‘two’.
 Single and double points to be varied
 Compare with other side

30. B. Graphesthesia :
done with pencil or swab stick.
sites – palms, fingers and face.
 Digits like 1-9 , or shapes/symbols used.
 Stand beside the pt and face the area to be
tested (so that he will be familiar).
C. Stereognosis :
• no preliminary visual demo given.
• ex: key, pen or coin
• abnormal side done first and then normal side.

32. D. Double simultaneous stimulation :
• Pin prick used (both must be equally Sensory extinction
sharp). Sensory inattention
Sensory suppression
 Eyes to be closed Sensory eclipse
 Pt is told to expect sensation either one Tactile inattention
side or both sides. Perceptual rivalry
 After stimuli, ask to indicate site of
stimulus and their nature.
POSITIVE test – stimuli on involved half is
ignored or sharp stimulus interpreted as
dull.

33. • CORTICAL SENSORY SYNDROMES
• ASOMATAGNOSIAS
• APRAXIAS
• VISUAL DISORDERS
• AUDITORY NEGLECT

34. ASOMATAGNOSIAS
• The term asomatognosia denotes the inability to
recognize part of one’s body.
• Visual and tactile sensory information is synthesized
during development into a body schema
(perception of one’s body and the relations of
bodily parts to one another)

35.  ANOSAGNOSIA : Unilateral asomatagnosia.
(Denial of illness) Anton–Babinski syndrome.
• Denial is more implict than explict, in many pts.
(i.e they may not actively deny that they are ill)
And some may act as if nothing were the matter.
• 7 times more frequent with Rt. sided lesions than
left.
• Ass. with blunted emotionality – pts look
dull, inattentive and apathetic. And also
confused.
• Ass. with hallucinations of movement and
allocheiria (one sided stimuli are felt on other

36. HEMI NEGLECT : neglect on one side of body in
dressing and grooming.
Shave only one side or use only one sleeve of shirt.
Deviation of head and eyes to side of lesion.
Torsion of body to the side of lesion.
Fail to use one side of body, even though paralysis
is not present
Finds impossible to wear eye glasses.
Sensory extinction - is subtle form of neglect.

37. • Basic disturbance in these cases is an inability to
summate a series of ‘spatial impressions’ -
tactile, kinesthetic, visual, or auditory — a defect
referred to as amorphosynthesis.
• Denial and neglect - non-dominant parietal lesions.
• These disorders of spatial summation are strictly
contralateral to the damaged parietal lobe (Rt > Lt)
It must be distinguished from a true
agnosia, which is a conceptual disorder and
involves both sides of the body and extrapersonal
space as a result of damage to the dominant
hemisphere.

38. GERSTMANN SYNDROME
• An example of bilateral asomatognosia and is due
to a left dominant parietal lesion.
1. Finger agnosia
2. Right-left confusion
3. Acalculia
4. Dysgraphia

39. • May be ass. with dyslexia or homonymous
hemianopia / quadrantanopia.
Lesion – left inferior parietal lobule (angular
gyrus).

40. Parietal lobe is – “ Lobe of hand ”.
 Hand is extensively represented
 Parietal lobe gathers information regarding
various objects through hand
 Parietal lobe lesions (Gerstmann syndrome) –
tetrad is related to
functions of hand.

41. Tests for calculations
Components – Rote tables (add, multiply, etc)
Recognition of signs (+ , - , * )
Basic arithmetic(carrying, borrowing)
Spatial alignment of written calculations
• Verbal rote examples : what is 4 plus 6 ?
• Verbal complex examples : what is 21 * 5 ?

42. • Written complex examples :
• Pt with rt. hemisphere
lesion & left neglect.
• Pt with rt. parietal
hematoma – showing
poor alignment and
calculation errors.

43. • Lt parietal lesions – inability to understand
and carry out numericals.
Severe acalculia = Anarithmetria.
• Rt parietal lesions – inability to align numbers
and to do complex computations (
borrowing, carrying, etc).
But, pt can do problems in his head.

44. Tests for right – left confusion
 Identification on self
ex : show your left foot.
 Crossed commands on self
ex : with your right hand touch your left ear
 Identification on examiner
ex : point my right elbow
 Crossed commands on examiner
ex : with your left hand point my right foot.

45. Tests for finger agnosia
• Inability to name , point or recognize fingers on
oneself or others.
1. Non verbal finger recognition :
with pt eyes closed, touch one of his fingers.
Ask him to touch the same finger of examiner, with
eyes open.
2. Identifying named fingers on examiner’s hand :
examiner places hand in some irregular
position and asks pt – “ point to my middle finger”

46. 3. Verbal identification (naming) of fingers :
either examiner’s or pt’s hand kept in an
irregular position. Examiner points to a finger and
asks him – “name this finger?”

47. • CORTICAL SENSORY SYNDROMES
• ASOMATAGNOSIAS
• APRAXIAS
• VISUAL DISORDERS
• AUDITORY NEGLECT

48. APRAXIA AND PARIETAL LOBE
• An inability to carry out a commanded task despite
the retention of motor and sensory function
• Sensory guidance of movement is lost
• Either spatial sequences lost (0VOOVOOOV)
or sequential grammar relations lost
(ex: father’s brother’s son).
• Defect - unable to show, but uses the object.
- unable to do whole task, but does
individual tasks.

49. • Failure to conceive or formulate an action , either
spontaneously or on command.
• Sensory areas 5 and 7 in dominant parietal
lobe, supplementary and premotor cortex of both
cerebral hemispheres and their integral
connections - are involved to accomplish these
actions.

52. 1. Ideomotor apraxia *
2. Ideational apraxia *
3. Buccofacial apraxia *
4. Constructional apraxia
5. Dressing apraxia
• Constructional apraxia – visuospatial orientation
• Dressing apraxia – form of sensory extinction and loss of
extra personal space.
* according to Liepmann

53. IDEOMOTOR APRAXIA (“how to do”)
• Most common type of apraxia
i. Buccofacial apraxia ( blowing a match )
ii. Limb apraxia ( flip a coin , comb hair )
iii. Whole body apraxia ( stand like boxer )
• Commands to be alternated b/w right and left
limbs

54. IDEATIONAL APRAXIA (“what to do”)
• Disturbance of complex motor planning of a higher
order .
• Pt able to do individual tasks, but cannot integrate
them as a whole.
• ‘Conceptual apraxia’ – there is apparent inability to
recognise the use of objects (object agnosia).
ex: pt attempts to light a candle by striking it on matchbox

56. Praxis testing (done in an order)
1. Observe the actions – shaving ,dressing,eating.
2. Carry out familiar acts – blow a kiss, wave gudbye.
3. Imitate the examiner (‘do this after me’)
4. How to use objects (pantomime)
simple acts – hammer nail, comb hair .
complex acts – light and smoke cigar; open soda
bottle, pour in glass and drink.
5. Demonstrate use of actual items
(both limbs and orofacial commands to be asked)

57. CONSTRUCTIONAL APRAXIA
• Constructional ability/praxis = visuoconstructive
ability - high level non verbal cognitive function.
• Perceptual motor ability involving integration of
occipito – parieto – frontal connections.
• Non dominant parietal lobe is imp. for this.
• Area 17 IPL (kinesthetic analysis of visual patterns
done here)
Premotor area

59. • Connections with frontal and occipital lobes provide
necessary proprioceptive and visual information –
for movement of body and manipulation of objects
or constructional activities.
Parietal lobes are principle areas of visual –
motor integration.

60. Tests of constructional ability
 Reproduction drawings :
given in order of complexity.

61. Drawings to command :
1. draw a clock with 10:20 time
2. draw a 2D figure - daisy in a pot
3. draw a house – in way you can see two sides
and the roof.
Block designs
 Lt. sided lesions – simplification of complex diagrams
 Rt. sided lesions – rotation of diagrams .

62. DRESSING APRAXIA
• Not a true apraxia.
• Combination of spatial disorientation and
visuospatial inattention.

64. • CORTICAL SENSORY SYNDROMES
• ASOMATAGNOSIAS
• APRAXIAS
• VISUAL DISORDERS
• AUDITORY NEGLECT

65. VISUAL DISORDERS
• Inferior part of the parietal lobe – incongruous
homonymous hemianopia or an inferior
quadrantanopia. (in practice, the defect is complete
or almost complete and congruous).
• Deep lesions - abolition of optokinetic nystagmus
with target moving toward side of the lesion.
• Rt. angular gyrus - Left sided visual neglect.
• Topographagnosia - visual disorientation and loss
of spatial (topographic) localization. Pts ar unable to
orient themselves in an abstract spatial setting.

66. • Others –
Deficits in localization of visual stimuli.
Inability to compare the sizes of objects.
Failure to avoid objects when walking.
Inability to count objects.
Disturbances in smooth-pursuit eye movement.s
Loss of stereoscopic vision.
• “Spasticity of conjugate gaze” : eyes may deviate
away from the lesion on forced lid closure.
• Optic ataxia : in reaching for a target, movement is
misdirected and dysmetric. (distance to target is misjudged)

67. Tests for visual disorders
• Visual field testing
• Visual neglect :
- casual observation of pt’s behaviour.
- drawings made by the pt.

68. • Visual inattention
• Topographagnosia : tests for geographic
disorientation.

69. Tests for geographic disorientation
• Geographic orientation is function of parietal lobe
and its multimodal association area.
• Combination of processes – spatial
orientation, right-left orientation ,visual perception
and its memory.
1. History from relatives :
Does he becomes lost in work?
Does he have difficulty in orienting to new
environment?

70. 2. Localizing places in maps :
Adequate literacy level and historical knowledge
is necessary.
ex : to locate cities or states on maps.
3. Ability to orient self in hospital :
By observing the pt’s capacity to find their bed,
ward and bathroom.

71. • CORTICAL SENSORY SYNDROMES
• ASOMATAGNOSIAS
• APRAXIAS
• VISUAL DISORDERS
• AUDITORY NEGLECT

72. AUDITORY NEGLECT
• This defect in appreciation of the left side of the
environment is less apparent than is visual
neglect.
• Many patients with acute right parietal lesions
are initially unresponsive to voices or noises on
the left side.
• Main lesion usually lies in the right superior
lobule.

73. SUMMARY

74. EITHER PARIETAL LOBES (Rt. or Lt.)
1. Loss of cortical sensations.
2. Mild hemiparesis, hypotonia and hemiatrophy.
3. Hemianopia / quadrantanopia .
4. Visual inattention.
5. Abolition of optokinetic nystagmus.
6. Hemineglect ( more with Rt. parietal lobe lesions ).

75. DOMINANT PARIETAL LOBE
Additional phenomenon include,
1. Disorders of language ( anomia, aphasia, alexia,
agraphia ).
2. Gerstmann syndrome
3. Tactile agnosia (bimanual astereognosis)
4. Bilateral ideomotor and ideational apraxia.

76. NON DOMINANT PARIETAL LOBE
Additional phenomenon include,
1. Visuospatial disorders
2. Topographic memory loss
3. Anosagnosia
4. Dressing and constructional apraxias.
5. Confusion
6. Tendency to keep eyes closed, resist lid opening
and blepharospasm.