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Cortical Structure and Function

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1 Cortical Structure and Function



4 Connections of the Visual Cortex
Primary Visual Cortex (V1) Input from LGN Output to all other levels Secondary Visual Cortex (V2) After V2 Output to the parietal lobe - Dorsal Stream Output to the inferior temporal lobe - Ventral Stream Output to the superior temporal sulcus (STS) - STS Stream Dorsal Stream Visual Guidance of Movements Ventral Stream Object Perception STS Visuospatial functions (bio movement)



7 Disorders of Visual Pathways
2. Monocular Blindness Loss of sight in one eye Results from destruction of the retina or optic nerve 3. Bitemporal Hemianopia Loss of vision from both temporal fields Results from a lesion to the optic chiasm 4. Nasal Hemianopia Loss of vision of one nasal field Results from a lesion of the lateral chiasm 5. Homonymous Hemianopia Blindness of one entire visual field Results from a complete cut of the optic tract, LGN or V1 7. Macular sparing Sparing of the central or macular region of the visual field Results from a lesion to the occipital lobe 6. Quadrantoanopia or Hemianopia Complete loss of vision in one-quarter of the fovea or in one-half of the fovea

8 Disorders of Visual Pathways
Field Defects Scotomas - small blind spots Results from small lesions to the occipital lobe

9 Visual Agnosia Object Agnosia Apperceptive Agnosia Associative Agnosia
Deficit in the ability to develop a percept of the structure of an object or objects (still see color, motion, acuity) Simultagnosia Unable to perceive more than one object at a time Results from bilateral damage to the lateral parts of the occipital lobes Associative Agnosia Can perceive objects, but cannot identify them Results from lesions to the anterior temporal lobes

10 Visual Agnosia Other Agnosias Prosopagnosia Alexia
Cannot recognize faces Can recognize facial features, facial expressions, and tell human from nonhuman faces Alexia Inability to read Form of object agnosia - inability to construct perceptual wholes from parts or Form of associative agnosia - word memory is damaged or inaccessible Results from damage to the left fusiform and lingual areas

11 Neuropsychological Tasks seemingly linked to Occipital lobe
Benton task of Facial Recognition Fusiform gyrus (temporal lobe) Hooper Visual Organization Test (VOT) Dorsal stream (parietal lobe) Visual Motor Integration (VMI) Test of Visual-Perceptual Skills (TVPS) Not sure what region it tests and poor normative data Visual Neglect (Bells Test) Simultagnosia (occipital) or contralateral neglect (parietal)? Wide Range Assessment of Visual Motor Abilities (WRAVMA) No links to brain structures Embedded Figures Task (EFT)

12 Benton Face Recognition
History: “facial agnosia”/ prosopagnosia Purpose: Measures visualoperceptual discrimination of unfamiliar faces (not recognition/memory) Associated with right hemisphere: parietal, occipitoparietal and occipitotemporal 3 parts: Match identical front view Match front view with ¾ view Match front view with various lighting conditions History: Loss of ability to recognize familiar faces 1st seen as neuropsych sympton in 1867 by 2 opthalmologists with 54 aphasic patient with hemiperisis and blindess after stroke. Aphasia and hemiperises gone within few daysand visual symptoms apparently slowly lessened until left with inability to recognize familiy pepople, trouble with color vison and poor spatial orientation. Diagnosed hemorrage in right hemisphere. Over time, researchers realized that people with agnosia also had “facial agnosia”/prosopagnosia and usually accompanied some other deficit associated with right hemisphere damage e.g., (left visual field defect).. Also found that seemed to be 2 different groups: some patients able to recognize unfamiliar faces when assessed while others unable to recognize unfamiliar faces but not familiar. Benton Purpose: measure ability to ID and discriminate unfamiliar human faces in photos (without memory demands)/visuoperceptual functions typically associated with right hemisphere structures, especially parietal, occipitoparietal, and occipitotemporal structures. 3 parts: Matching identical front view photos by pointing or saying its number)- 6 items Matching fromt view with ¾ view photos- 12 items on short form, 24 on long form Matching of front view under various lighting conditions: shown face in full lighting view and then asked to find same face in different lighting conditions- 9 items on short form, 24 long Admin: Subjects can hold notebook. Present stimulus item and array at same time. 1-7:“you see this yong woman? Show me where she is on this picture” 7-13: you see this young woman? She is shown three times on this picture. Show me where she is. Find three pictures of her” Scoring: see scoring form Long form 54 scorable responses. 1 point per correct response. Effective range =25-54 Short form Short form effective range =11-27 Findinsg with Brain Disease There is consistent evidence that FRT performance, which is properly described as “visuoperceptual discrimination of unfamiliar faces” (and not facial “recognition”), is related to right hemisphere processing. Within the hemisphere, there is some indication that the posterior sector is more critical, but there is actually not much empirical evidence for this. There is an inkling that the left hemisphere makes a non-negligible contribution, and for the simpler aspects of the test (front-view and three-quarter view matching), may perhaps even be of comparable competence as the right hemisphere. Specific temporal lobe findings Patients undergoing left (n = 81) or right (n = 77) anterior temporal lobectomy were administered tests of object recognition (facial recognition) and spatial localization (line orientation) preoperatively and 6 mo postoperatively to determine the effects on the what and where visual systems. Postoperatively there was significant loss in facial recognition ability and concomitant improvement in line orientation performance. The pattern of performance was similar for both groups. The findings suggest that anterior temporal lobectomy had a specific effect on the occipitotemporal object recognition system while leaving the occipitoparietal spatial localization system unaffected. (PsycINFO Database Record (c) 2010 APA, all rights reserved)

13 Hooper Visual Organization Test (VOT)
Test of the ability to conceptually rearrange disarranged pictures Posterior parietal lobe (dorsal visual stream) 30 items, total # correct Answers at end of Occipital Lobe section

14 Visual Motor Integration (VMI)
3 parts: VMI, Visual Perception, Motor Coordination. VMI: Copy a developmental sequence of geometric forms Visual Perception: ID the exact match for as many of the 27 stimuli as possible in 3 minutes. Motor: Trace the stimulus forms with a pencil without going outside double-lined paths in 5 min. Two versions (short and long form)- ages 2-18) Short only ages 2-8 Long form for ages 9-18 takes minutes Long form is all about integration, that’s why you would want to add supplemental Visual perception and Motor coordination components- Allows you to see where the breakdown is occuring: motor, perception or the integration of the 2 Perceptual Motor Impairment and Academic Achievement/Learning VM measures originally designed for use with adults with brain injuries VM assessment now a part of evaluations due to correlations with specific learning problems Ex. Written expression Ex. Reading and math disorders- attention is usually associated; kids that skipping words when reading will often skip parts when reproducing figures in visual motor assessment.

15 Test of Visual-Perceptual Skills (TVPS)
Visual-spatial relationships Visual closure Visual memory (response page) Visual sequential memory (stimulus page) Using 7 subtests, in theory, assesses visual processing of form, but limited data Visual discrimination Visual form constancy Visual figure ground

16 Visual Neglect (Bells Test)

17 Visual Neglect (Bells Test)
Visual field defects and hemianopia impact performance minimally. This is about right parietal lesions not the occipital lobe.

18 Wide Range Assessment of Visual Motor Abilities (WRAVMA)
Measure of visual motor, visual spatial and fine motor skills 3 parts Drawing Test: Visual Motor Ability Matching Test: Visual Spatial ability Pegboard Test: Fine motor ability Designed for referrals in which kids with handwriting difficulties performed WNL on traditional visuomotor assessments. Measure of visual motor, visual spatial and fine motor skills with separate norms for each. Drawing test: measures integrated visual motor ability (which would lead to question if a visual issue, motor or both, so administered additional subtests) (5-10 min) Matching test: visual spatial ability (5-10 min) Pegboard test: measures fine motor ability (insert as many pegs as can in 90 seconds into a waffled pegboard. First with dominant hand (score is based on this), then with nondominant hand (may be useful in quantifiying impact of nerve damage, unilateral frontal brain injury or hemiplegia. (4 min) Administration:#1) We are going to do some drawing. This man has 2 balloons and they need some strings. I’ll make this one (model). Now you do this one” (acceptable versus unacceptable examples om page 13 of manual)

19 Embedded Figures Task (EFT)
Cognitive “style” measure Task= Find simple target shape within complex design Scoring: Average time in seconds Higher score= greater difficulty analyzing a parts separate from whole/tendency to perceive complete patterns instead of separate parts Sometiems referred to as a measure of cog styile rather than cog ability. Cognitive style or "thinking style" is a term used in cog psych to describe HOW people think, percieve and remember info. Different from cog ability/intelligence. There is some controversy over real meaning of cog style and it’s dimension in human personality. The EFT is a standardized measure of cognitive style and analytical ability. the subject is shown a complex design, and then is asked to find a target (simple) shape within the complex. The score is the average time in seconds to detect the simple forms. Thus, higher scores reflect greater difficulty in analyzing a part separately from a wider pattern. (Or, viewed more positively, a greater tendency to perceive complete patterns rather than their separate components.) The EFT is closely associated with other perceptual measures which require the participant to analyze part of an organized field independently of the These include tests of perception of orientation to the vertical (the rod-and-frame test and the body adjustment test); of certain illusions and reversible perspective; of similar auditory and tactile disembedding tasks; and of problem-solving which requires ``disembedding'' a part from its current environment. Previous work in 80’s suggests children with autism show superior performance (in relation to their general mental age) on the EFT. Frith interprets this as showing that they have “weak central coherence”. BUT Brian and Bryson and Ozonoff, Pennington and Rogers (1991) both attempted to replicate the Shah and Frith (1983) finding of autistic superiority on the EFT, but found no differences to matched controls. Baron cohen responded to this difference by attemptign to replicate and found that individuals with Aspergers and ASD were significantly faster on the EFT than age and IQ matched normal controls. This replicates the finding of superior performance reported by Shah and Frith (1983), and extends it by demonstrating this in terms of speed, on a more challenging adult-level test, and finding it in adults of normal intelligence who have either autism or Asperger Syndrome (AS). There were no significant group differences in terms of accuracy on the EFT, and this replicates the study by Ozonoff, Pennington and Rogers (1991). So- it is important to collecting response time (RT) data, rather than simply accuracy data. (Baron Cohen- 1997). There is continued discussion of WHY these differences exist. Sex differences- 1st grade boys performed better than 1st grade girls at pre test. However, after short period of instruction and exposure, gap disappeared. Boys and girls both benefited from instruction….calls into question causation of sex differences in visual-spatial type abilities. ane Marantz Connor, Maxine Schackman and Lisa A. Serbin Child DevelopmentVol. 49, No. 1 (Mar., 1978), pp

20 Answers to Hooper Visual Organization Test (VOT)


22 The Parietal Lobes Postcentral Gyrus Superior Parietal Lobule
Brodmann’s areas 1,2, and 3 Superior Parietal Lobule Brodmann’s areas 5 and 7 Parietal Operculum Brodmann’s area 43 Supramarginal Gyrus Brodmann’s area 40 Angular Gyrus Brodmann’s area 39 Process and integrate somatosensory and visual information Part of the Dorsal Stream Functional zones Anterior zone - 1,2,3, and 43 Somatosensory cortex Posterior zone - remaining areas Posterior parietal cortex Visual processing areas Intraparietal sulcus (cIPS) Control of saccadic eye movements Saccade - involuntary abrupt and rapid small movements made by the eyes when changing the fixation point Visual control of grasping Parietal reach regions (PRR) area 7 Visually guided grasping movements Anterior zones - process somatic sensations and perceptions Posterior zones - integrate information from vision with somatosensory information for movement Inferior Parietal Lobule

23 Use of Spatial Information
Spatial information can be used : Object recognition Viewer centered object identification Determines the location, location orientation and motion of an object Posterior parietal cortex Guidance of Movement Sensitive to eye movements Sensorimotor Transformation Neural calculations of the relative position of the body with respect to sensory feedback from movements being made and planned

24 Use of Spatial Information
Spatial Navigation Cognitive spatial map Route knowledge, unconscious knowledge of how to reach a destination Mental transformations are carried out by the posterior parietal cortex Other functions of parietal lobes: Aspects of math Aspects of language Movement sequencing Acalculia Inability to do arithmetic Noted in parietal lobe patients Might result from the spatial properties of addition and subtraction Two digit number occupy different spaces “Borrowing” during subtraction Language Words have spatial organization “tap” vs. “pat” Movement Sequencing Individual elements of the movement have a spatial organization

25 Somatosensory Symptoms of Parietal-Lobe Lesions
Lesions to the postcentral gyrus produce: Abnormally high sensory thresholds Impaired position sense Deficits in stereognosis, or tactile perception Afferent paresis Clumsy finger movements due to lack of feedback about finger position

26 Somatoperceptual Disorders
Astereognosis Inability to recognize an object by touch Simultaneous Extinction Two stimuli are applied simultaneously to opposite sides of the body A failure to report a stimulus on one side is referred to as extinction Blind Touch Cannot feel stimuli, but can report their location

27 Somatoperceptual Disorders
Agnosias Asomatognosia Loss of knowledge or sense of one’s own body Anosognosia Unawareness or denial of illness Anosodiaphoria Indifference to illness Asymbolia for pain Absence of normal reactions to pain Finger Agnosia Unable to point to the fingers or show them to the examiner Agnosia: partial or complete inability to recognize sensory stimuli, unexplained by a defect in elementary sensation or by reduced attention

28 Symptoms of Posterior Parietal Lobe Damage
Contralateral Neglect Neglect for visual, auditory, and somesthetic stimulation on one side of the body or space Lesion most often in the right inferior parietal lobe Right intraparietal sulcus and the right angular gyrus Defective sensation or perception Defective attention or orientation

29 Left Parietal Symptoms
Disturbed Language Function Apraxia Movement disorder in which the loss of movement is not caused by weakness, inability to move, abnormal muscle tone, intellectual deterioration, poor comprehension, or other disorders of movement Dyscalculia Difficulties with arithmetic Poor recall Inability to discriminate left from right Right hemianopia Dyscalculia has to do with complex mental manipulations (subtraction which requires borrowing) not a problem, but is.

30 Apraxia and the Parietal Lobe
Ideomotor Apraxia Cannot copy serial movements More likely to be associated with left parietal lesions Constructional Apraxia Cannot copy pictures, build puzzles, or copy a series of facial movements Associated with right and left parietal lesions

31 Symptoms of Posterior Parietal Lobe Damage
Deficits in drawing appear after damage to the right parietal lobe Spatial Attention Function of the parietal lobe to selectively attend to different stimuli Disengagement Shifting attention from one stimulus to the next

32 Disorders of Spatial Cognition
Mental rotation requires: Mental imaging of the stimulus Manipulation of the image Left hemisphere deficit associated with the inability to generate the image Right hemisphere deficit associated with the inability to manipulate the image Inability to use topographic information is associated with right hemisphere damage

33 Major Symptoms

34 Neuropsychological Tasks linked to Parietal lobe
Two Point Discrimination Seguin-Goddard Form Board/Tactual Performance Test Line bisection Incomplete Figures Mooney Closure Right-left differentiation

35 Two point discrimination
Sharp, two point calipers 2.85 cm, 2.7, 2.54…. At each distance, touch either 1 or 2 points , , etc Examinee indicates one or 2 touches. Linked to contralateral postcentral gyrus (BA1, 2, & 3).

36 Seguin-Goddard Form Board/Tactual Performance Test
Formboard, pieces, blindfold Repeat for left, right, and both hands Total time to place pieces in formboard for each trial. Remove formboard, provide paper Examinee draws formboard and places the shape in the outline of the formboard. Contralateral parietal lesions (PE, PF) for tactile and PG for drawing part

37 Line bisection Mark the middle of each line. Contralateral neglect
With right parietal lesion, the lines to the left side of the page would be left blank.

38 Incomplete Figures/ Mooney Closure
Label the object Right parietotemporal junction (ventral stream)

39 Right-left differentiation
Left parietal lesions

40 Answers to Incomplete Figures Test

41 Answers to Incomplete Figures Test

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