5Parietal Lobe Function Somatosensory (anterior strip)Visual guidance of movements (superior)Spatial cognition and quasi-spatial processes like math and reading (inferior)Selective attention – shifting attention, disengagement, recruitment, and release (cingulate too)Polymodal integrationDisorders of visuospatial explorationAnosognosia (unawareness or denial of illness)
7Defects of visuospatial exploration Displace visual attentionInability to perceive more than one stimulus (simultagnosia = simultaneous agnosia)Defective visual control of movement (optic ataxia)Inability to follow moving targetInability to maintain fixationInability to voluntarily direct gaze to target (gaze apraxia)Abnormal visual search
8Posting performance Balint’s Normal Optic Ataxia Optic Ataxia
9Characteristics of Spatial Functions: modality-independentvisual, auditory, tactile, olfactory stimuli all have spatial location informationperception of location is an abstract concept located in a mental coordinate systemloss of spatial function affects all modalities
10Category Function Brain area 1) Spatial Attention Attention to left hemispace Right parietal Attention to right hemispace Left parietal2) Spatial Perception Object Localization R&L occipital and parietal lobes Line orientation Right parietal3) Spatial Construction Building with blocks; R&L parietal Drawing4) Spatial mental Mental Rotation Right parietal operations Mental Imagery “posterior”
11Visual Spatial Disorders Visual Spatial Constructiondifficulty with drawing and assembling 2D or 3D objects.AssessmentAsked to draw simple figures, such as a flower, square or the face of a clock.Pencil-and-paper mazesBlock designLine orientation testVisual Spatial Disordersrange from basic visual sensory deficits to more abstract visual spatial disability.Spatial Localizationgreat difficulty localizing objects in two and three dimensional space. Stereopsis (binocular depth perception) is often impaired.Topographical DisorientationErrors in forming spatial maps and using them to find places or solve topographical problems
12Body Schema Disturbance Finger Agnosiapatients cannot identify their own fingers or those of another person.Right-Left DisorientationLesions of the left parietal lobe commonly result in right-left disorientation.AssessmentAutopagnosia Have patient point to own body parts and those on othersFinger Agnosia Have patient close their eyes and indicate which of their fingers has just been touched.
13Newberg et al (2001)Used SPECT neuroimaging to scan eight experience Tibetan Buddhist meditators.IncreasedactivationDecreased activation
15Blanke 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.
16Neglect Syndrome (a.k.a Hemi-neglect) Fails to respond to meaningful stimuli presented to side opposite brain lesion (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 defectsOccurs in30-90% 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, 4 months, 6 months, 9 months
17Line Bisection Test(similar to item cancellation, every “e”)
25Pseudo-neglectWhich appears darker?Normals overattend to the LVF?
26Neglect according to Kinsbourne’s hypothesis Hemispheres normally compete for attentional control.With damage, intact hemisphere dominates.A release sign or positive symptom: left neglect involves “over attending” to the right.
27Two mechanisms for Visual Field processing problem
35Acalculia: Inability to perform mathematical computations.
36ApraxiaDifficulty in sequencing & executing movements
37Limb Apraxia Characterized by movement of the wrong part of the limb incorrect movement of the correct part, orcorrect movements but in the incorrect sequence.Often assessed by requesting patient to demonstrate the use of a tool or household implement (e.g., "Show me how to cut with scissors").
38Buccofacial ApraxiaDifficulty performing skilled movements with lips, face, tongue, larynx, and pharynx.E.g., when asked to blow out a match, suck on a straw or blow a kiss, s/he unable to make the movements or makes uncoordinated movements.S/he may substitute incorrect movements or perseverate, or substitute verbal expressions for the movement. (e.g., when asked to blow out a match, the patient might say "Blow“).
40Perimeter of a rectangle Gaze apraxiaBack and forthbetween two pointsnormalOutlining thePerimeter of a rectanglenormal
41Patient with constructional apraxia due to lesion of the right parietal lobe.
42not localized, often observed in dementia. Ideational ApraxiaCannot perform a series of acts although able to perform individual components of the series. May correctly perform each step (say, in making coffee but out of order, such as turning coffee maker on first).Loss of conceptual knowledge associated with objects and overall goal of the activity sequence.not localized, often observed in dementia.