Parietal LobeParietal Lobe

Superior and Inferior AspectsSuperior and Inferior Aspects

Superior BA 5 & 7

Inferior Inferior

BA 39 & 40BA 39 & 40

Dorsal and Ventral Streams Dorsal and Ventral Streams – Where and What– Where and What

Parietal Lobe FunctionParietal Lobe Function

1.1. Somatosensory (anterior strip)Somatosensory (anterior strip)2.2. Visual guidance of movements (superior)Visual guidance of movements (superior)3.3. Spatial cognition and quasi-spatial processes Spatial cognition and quasi-spatial processes

like math and reading (inferior)like math and reading (inferior)4.4. Selective attention – shifting attention, Selective attention – shifting attention,

disengagement, recruitment, and release disengagement, recruitment, and release (cingulate too)(cingulate too)

5.5. Polymodal integrationPolymodal integration6.6. Disorders of Disorders of visuospatial explorationvisuospatial exploration7.7. Anosognosia (unawareness or denial of illness)Anosognosia (unawareness or denial of illness)

Defects of visuospatial explorationDefects of visuospatial exploration

Displace visual attentionDisplace visual attention Inability to perceive more than one Inability to perceive more than one

stimulus (simultagnosia = simultaneous stimulus (simultagnosia = simultaneous agnosia)agnosia)

Defective visual control of movement Defective visual control of movement ((optic ataxiaoptic ataxia))

Inability to follow moving targetInability to follow moving target Inability to maintain fixationInability to maintain fixation Inability to voluntarily direct gaze to target Inability to voluntarily direct gaze to target

(gaze apraxia)(gaze apraxia) Abnormal visual searchAbnormal visual search

Normal Optic Ataxia Optic Ataxia

Posting performance Balint’sPosting performance Balint’s

Characteristics of Spatial Functions:

• modality-independent

•visual, auditory, tactile, olfactory stimuli all have spatial location information

• perception of location is an abstract concept located in a mental coordinate system

• loss of spatial function affects all modalities

Category Function Brain area

1) Spatial Attention Attention to left hemispace Right parietal

Attention to right hemispaceLeft parietal

2) Spatial Perception Object Localization R&L occipital and

parietal lobes Line orientation Right parietal

3) Spatial Construction Building with blocks; R&L parietal Drawing

4) Spatial mental Mental Rotation Right parietal operations Mental Imagery “posterior”

Visual Spatial DisordersVisual Spatial Disorders Visual Spatial DisordersVisual Spatial Disorders range from basic visual sensory range from basic visual sensory

deficits to more abstract visual deficits to more abstract visual spatial disability. spatial disability.

Spatial LocalizationSpatial Localization great difficulty localizing objects great difficulty localizing objects

in two and three dimensional in two and three dimensional space. Stereopsis (binocular depth space. Stereopsis (binocular depth perception) is often impaired. perception) is often impaired.

Topographical DisorientationTopographical Disorientation Errors in forming spatial maps and Errors in forming spatial maps and

using them to find places or solve using them to find places or solve topographical problemstopographical problems

Visual Spatial ConstructionVisual Spatial Construction difficulty with drawing and difficulty with drawing and

assembling 2D or 3D objects. assembling 2D or 3D objects.

AssessmentAssessment Asked to draw simple figures, Asked to draw simple figures,

such as a flower, square or the such as a flower, square or the face of a clock. face of a clock.

Pencil-and-paper mazes Pencil-and-paper mazes Block design Block design Line orientation testLine orientation test

Body Schema DisturbanceBody Schema Disturbance Finger AgnosiaFinger Agnosia patients cannot identify their patients cannot identify their

own fingers or those of own fingers or those of another person. another person.

Right-Left DisorientationRight-Left Disorientation Lesions of the left parietal lobe Lesions of the left parietal lobe

commonly result in right-left commonly result in right-left disorientation. disorientation.

AssessmentAssessment AutopagnosiaAutopagnosia

Have patient point to own Have patient point to own body parts and those on body parts and those on others others

Finger AgnosiaFinger Agnosia Have patient close their eyes Have patient close their eyes and indicate which of their and indicate which of their fingers has just been touched. fingers has just been touched.

Newberg et al (2001)

•Used SPECT neuroimaging to scan eight experience Tibetan Buddhist meditators.

Increasedactivation

Decreased activation

Body schema attenuated thru Body schema attenuated thru MeditationMeditation

Blanke et al (2002)

•Stimulation of the right angular gyrus caused reliable out of body experiences.

•Further evidence for the role of the parietal cortex in meditating self - other boundaries.

Neglect Syndrome (a.k.a Hemi-neglect)

Fails to respond to meaningful stimuli Fails to respond to meaningful stimuli presented to side opposite brain lesion presented to side opposite brain lesion (contralateral space)(contralateral space)Ignores people on one side of room; eats from only one side of plate; draws half of an object, grooms half their body.

But can adapt by learning to turn plate; to turn head; to move objects across visual field.

Not due to motor defectsNot due to motor defectsOccurs in

30-90% Right hemisphere damaged patients (RHD), depending on type of patient (tumor, injury, etc) and type of test2-15% Left hemisphere damage (LHD)

Right Parietal Stroke – recovery at 2 months, Right Parietal Stroke – recovery at 2 months, 4 months, 6 months, 9 months4 months, 6 months, 9 months

Line Bisection Test Line Bisection Test (similar to item cancellation, every “e”)(similar to item cancellation, every “e”)

Fellini’s Right Parietal StrokeFellini’s Right Parietal Stroke

Drawings by Neglect Drawings by Neglect PatientsPatients

Pseudo-neglectPseudo-neglect

Which appears darker?Which appears darker?

Pseudo-neglectPseudo-neglect

Which appears darker? Which appears darker? Normals overattend to the LVF?Normals overattend to the LVF?

Neglect according to Kinsbourne’s Neglect according to Kinsbourne’s hypothesishypothesis

Neglect according to Kinsbourne’s Neglect according to Kinsbourne’s hypothesishypothesis

Hemispheres normally Hemispheres normally competecompete for attentional control.for attentional control.

With damage, intact hemisphere With damage, intact hemisphere dominates. dominates.

A release sign or positive A release sign or positive symptom: left neglect involves symptom: left neglect involves “over attending” to the right.“over attending” to the right.

Two mechanisms for Visual Field Two mechanisms for Visual Field processing problemprocessing problem

HemianopiaHemianopia

Evidence of implicit recognitionEvidence of implicit recognition

House on fire example House on fire example • Which house do you prefer?Which house do you prefer?

• Unconscious perception of Unconscious perception of left side of spaceleft side of space

Maintainence of Syntactical SpaceMaintainence of Syntactical Space

Visuoconstructive – e.g., Block DesignVisuoconstructive – e.g., Block Design

Visuoconstructive – e.g., Picture AssemblyVisuoconstructive – e.g., Picture Assembly

Acalculia: Acalculia: Inability to Inability to perform perform mathematical mathematical computations. computations.

ApraxiaApraxia

Difficulty in sequencing & executing Difficulty in sequencing & executing movementsmovements

Limb ApraxiaLimb Apraxia Characterized byCharacterized by

• movement of the wrong movement of the wrong part of the limbpart of the limb

• incorrect movement of incorrect movement of the correct part, orthe correct part, or

• correct movements but correct movements but in the incorrect in the incorrect sequence. sequence.

Often assessed by Often assessed by requesting patient to requesting patient to demonstrate the use of a demonstrate the use of a tool or household tool or household implement (e.g., "Show me implement (e.g., "Show me how to cut with scissors"). how to cut with scissors").

Buccofacial ApraxiaBuccofacial Apraxia• Difficulty performing skilled movements with Difficulty performing skilled movements with

lips, face, tongue, larynx, and pharynx. lips, face, tongue, larynx, and pharynx. E.g., when asked to blow out a match, suck on a E.g., when asked to blow out a match, suck on a

straw or blow a kiss, s/he unable to make the straw or blow a kiss, s/he unable to make the movements or makes uncoordinated movements.movements or makes uncoordinated movements.

S/he may substitute incorrect movements or S/he may substitute incorrect movements or perseverate, or substitute verbal expressions for the perseverate, or substitute verbal expressions for the movement. (e.g., when asked to blow out a match, movement. (e.g., when asked to blow out a match, the patient might say "Blow“). the patient might say "Blow“).

Normal scan path

Gaze apraxic scan path

Back and forth between two points

Outlining the Perimeter of a rectangle

Patient with Patient with constructional constructional apraxiaapraxia due to due to lesion of the right lesion of the right parietal lobe. parietal lobe.

Ideational ApraxiaIdeational Apraxia• Cannot perform a Cannot perform a seriesseries of acts although able of acts although able

to perform individual components of the series. to perform individual components of the series. May correctly perform each step (say, in May correctly perform each step (say, in making coffee but out of order, such as turning making coffee but out of order, such as turning coffee maker on first). coffee maker on first).

Loss of conceptual knowledge associated Loss of conceptual knowledge associated with objects and overall goal of the activity with objects and overall goal of the activity sequence. sequence.

not localized, often observed in dementia.not localized, often observed in dementia.

Movement DisordersMovement Disorders

Movement Disorders (HD, PD)Movement Disorders (HD, PD)