parietal lobe and its functions

The Parietal Lobe

• ANATOMY

• FUNCTIONS

• CLINICAL EFFECTS

ANATOMY

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

Subdivisions of the Parietal Lobes Post central sulcus Interparietal sulcus 1. post central gyrus2. Somasthetic association area3. Superior parietal lobule4. Inferior parietal lobule – angular gyrus supra marginal gyrus

FUNCTIONS

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

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

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 )

• 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.

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.

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

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.)

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.

Cerebral laterality

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)

5. Short term memory Lt. – immediate recall for digits and words Rt. – immediate recall for geometric patterns

Left hemisphere6. Language – comprehension reading writing2. Calculations – verbal rote calculations and

recognition of signs.3. Non verbal symbolization (pantomime)

Right hemisphere

1. Constructional skills2. Dressing apraxia3. 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)

CLINICAL EFFECTS OF PARIETAL LOBE

LESIONS

• CORTICAL SENSORY SYNDROMES

• ASOMATAGNOSIAS

• APRAXIAS

• VISUAL DISORDERS

• AUDITORY NEGLECT

CORTICAL SENSORY SYNDROMESCortical 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.

• 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.

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).

Optic ataxia : clumsiness in reaching for and grasping an object.

Pseudocerebellar syndrome : incoordination and intention tremor of contralateral limbs.

Fixed dystonic postures

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

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.

D. Double simultaneous stimulation :

• Pin prick used (both must be equally sharp).

Eyes to be closedPt is told to expect sensation either one

side or both sides.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.

Sensory extinctionSensory inattentionSensory suppressionSensory eclipseTactile inattentionPerceptual rivalry

• CORTICAL SENSORY SYNDROMES

• ASOMATAGNOSIAS

• APRAXIAS

• VISUAL DISORDERS

• AUDITORY NEGLECT

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)

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 side).

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 presentFinds impossible to wear eye glasses.Sensory extinction - is subtle form of neglect.

• 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.

(ex : finger agnosia , right left confusion)

GERSTMANN SYNDROME

• An example of bilateral asomatognosia and is due to a left dominant parietal lesion.

1. Finger agnosia2. Right-left confusion3. Acalculia 4. Dysgraphia

• May be ass. with dyslexia or homonymous hemianopia / quadrantanopia.

Lesion – left inferior parietal lobule (angular gyrus).

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.

Tests for calculationsComponents – 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 ?

• Written complex examples :

• Pt with rt. hemisphere lesion & left neglect.

• Pt with rt. parietal hematoma – showing poor alignment and calculation errors.

• 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.

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.

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”

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?”

• CORTICAL SENSORY SYNDROMES

• ASOMATAGNOSIAS

• APRAXIAS

• VISUAL DISORDERS

• AUDITORY NEGLECT

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.

• 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.

1. Ideomotor apraxia *2. Ideational apraxia *3. Buccofacial apraxia *4. Constructional apraxia5. Dressing apraxia

• Constructional apraxia – visuospatial orientation• Dressing apraxia – form of sensory extinction and loss of

extra personal space.

* according to Liepmann

IDEOMOTOR APRAXIA (“how to do”)

• Most common type of apraxiai. 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

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

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)

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

• 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.

Tests of constructional ability

Reproduction drawings : given in order of complexity.

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 .

DRESSING APRAXIA

• Not a true apraxia.• Combination of spatial disorientation and

visuospatial inattention.

• CORTICAL SENSORY SYNDROMES

• ASOMATAGNOSIAS

• APRAXIAS

• VISUAL DISORDERS

• AUDITORY NEGLECT

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.

• 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)

Tests for visual disorders

• Visual field testing

• Visual neglect : - casual observation of pt’s behaviour. - drawings made by the pt.

• Visual inattention

• Topographagnosia : tests for geographic disorientation.

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?

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.

• CORTICAL SENSORY SYNDROMES

• ASOMATAGNOSIAS

• APRAXIAS

• VISUAL DISORDERS

• AUDITORY NEGLECT

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.

SUMMARY

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 ).

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.

NON DOMINANT PARIETAL LOBE

Additional phenomenon include,

1. Visuospatial disorders2. Topographic memory loss3. Anosagnosia 4. Dressing and constructional apraxias.5. Confusion6. Tendency to keep eyes closed, resist lid opening

and blepharospasm.

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