PS3019 Cognitive and Clinical Neuropsychology

Transcription

1 PS3019 Cognitive and Clinical Neuropsychology Lectures 3 & 4 The cognitive neuropsychology of spatial cognition and disorders of spatial processing Reading Essential Banich, chapter 7 Highly recommended Kolb and Wishaw, chapter 21

2 Conceptualisation and representation of space - body space - grasping space - distal space - egocentric space - allocentric space - cognitive maps - space can be used to represent time

3 Dorsal visual stream

4 Properties of cells in the dorsal stream Not suited for object recognition - not very sensitive to colour - not very sensitive to items in central vision where acuity is highest Suited for spatial processing - sensitive to large portions of space to detect position of objects rather than focused on detailed vision in small portions of space - ample visual field (controlateral visual field and large portion of ipsilateral) - sensitive to specific movement direction (from centre towards periphery of visual field or from periphery towards centre) Motter & Mountcastle, 1981; Anderson and Mountcastle, particularly sensitive to walking or running movement speed useful for updating positions of objects in space and landmarks - responsive to combined location of eye-retinal position or head-retinal position essential for effective movements towards objects (e.g. reaching) spatial equivalent of shape-size-lighting constancy of inferotemporal neurons

5 Lesion studies Bilateral parietal lesions impair landmark discrimination (Pohl, 1973) Bilateral temporal lesions impair Non-Matching-to-Sample (Mishkin et al. 1983)

6 Holmes (1918) Patients with bilateral damage to parietal lobe - spared ability to recognise objects placed directly in front - inability to judge relative position of two objects - inability to judge absolute position of objects - inability to reach for them as if blind gross mismatch in reaching (etc.) mismatched in all three space dimensions (depth, height, width) Cole et al. (1962); Warrington (1962); Ratcliff & Davies-Jones (1972) Patients with unilateral damage to superior regions parietal cortex - symptoms on controlateral side of body regardless of arm used

7 Assessment of ability to perceive locations in space Euclidean choice array Polar choice array Damage to posterior regions of right parietal lobe impairs tasks requiring to: - judge if dots presented successively are in the same location - indicate in array position of dot previously presented LVF advantage observed often with same tasks (e.g. Bryden, 1976)

8 Sound localisation also affected by parietal damage (Pinek et al., 1989; Ruff et al., 1981) - not clear lateralisation of this competence Behavioural studies support right hemisphere prominence for non-verbal sounds - Monaural sound localisation better with left ear (Butler 1994) - Sound localisation better for sounds located on left hand side of body (Burke et al. 1994) and hemispherectomy indicates more impaired sound discrimination on controlateral ear

9 Assessment of line orientation judgements Benton line orientation test identify lines presented in A in radial array B Visual and tactile versions - non-modality specific deficits - right hemisphere damage impairs performance in both (Benton et al., 1975) - deficits in visual and tactile versions of the task are correlated (Meerwaldt & Van Harskamp, 1982) General LVF advantage RVF advantage can be observed for vertical and horizontal lines - possible verbal strategies

10 Assessment of geometric relations judgements Recognition of non-sense shapes to avoid use of LTM templates Not easy to label verbally Easy to label verbally General LVF advantage but not always - possible role of verbal strategies - shapes easy to label verbally less likely to produce a LVF advantage

11 Processing of motion - Motion discrimination can be dissociated from other spatial skills - Supported by structures at the boundary between occipital, parietal and temporal lobes In monkeys MT (V5) cells active when animal tracking objects (Sakata et al., 1983) In humans - PET identified activity in posterior lateral temporal cortex (Zeki et al., 1991) - fmri and ERP studies produce similar results - case studies broad bilateral parietal damage (Hess et al., 1989) - intact object discrimination - intact spatial localization - unable to process motion in the threes spatial dimensions e.g. inability to predict overflow of liquids movement of cars bilateral posterior temporoparietal areas (Vaina et al., 1990) - similar problems in only two spatial dimensions

12 Processing of rotation Shepard (e.g. 1988) RT proportional to degree of rotation Matching following 80 degree rotation sideways Matching following 80 degree rotation in depth Non-matching mirror images Activation proportional to degree of rotation (Carpenter et al. 1999; Richter et al Ng et al. 2001)

13 Split brain patient L.B. shorter RT for LVF Controls L.B Corballis & McLaren (1984) Verbal stimuli (e.g. letters) RVF advantage Spatial stimuli LVF advantage Alivisatos & Petrides (1997) PET study with letters greater activation of left posterior-superior parietal cortex

14 Constructional abilities Constructional praxis ability to physically manipulate items to produce specific spatial relationships Copying Rey-Osterrieth Complex Figure Typically compromised by damage to right hemisphere but variability indicates involvement of a variety of skills and use of alternative strategies 3 patients with damage to right posterior cortex

15 Block Design Target Attempts by patient with right hemisphere damage -evidence of global (and local) deficit Attempts by patient with right hemisphere damage - evidence of local deficit Possible use of verbal and non-verbal strategies

16 Route finding skills Variety of skills compromised by right posterior lesions Stylus maze task find by trial and error unknown route through the maze negative feedback provided by clicks of counter Regions involved according to observed brain damage Newcombe, 1969 right posterior parietal cortex Milner 1965 right hippocampal region (learning component) frontal lobe (planning component)

17 Locomotor maze (Semmens et al., 1955) - dots marked on large floor surface - cardinal north given on one wall - participants given map and need to find route in the large scale environment - map to be kept in fixed orientation - damage following parietal damage unilateral-right (Semmens et al. 1955) bilateral (Ratcliff & Newcombe, 1973) - correlates with Stylus Maze task but dissociations have been observed reflecting differences in the two tasks Money Standardised Road-Map task - patient given route through fictional town - must determine left-right direction at each turning point - compromised by frontal rather than parietal damage

18 Body schema Disturbances of body schema inability to appreciate spatial relationships among own body parts typically dissociate from those mentioned so far e.g. Left-right confusion damage to left parietal region if rotation required to judge other person left-right then associated with functioning of right hemisphere Anosognosia stroke to right middle cerebral artery denial of paralysis of limb associated with neglect Somaparaphrenia denial of body parts possible involvement of right parietal regions lesions to parietal regions reduce phantom limb experience in amputees

19 Spatial memory Mainly function of right hemisphere Short-Term-Memory or Working Memory - information held temporarily while performing a task - frontal lobe Long-Term-Memory - permanent storage of information through learning - temporal lobe and hippocampus

20 Corsi tapping test (Milner 1971) Spatial span - forward or backward - damage to posterior areas of both hemispheres Visual span (Pigott & Milner, 1994) - patterns of white and black squares (50% of each) - identify missing white square on second presentation - typical span 22 cells (11 white 11 black) - span of 16 following frontal damage

21 PET Studies Jonides et al. (1993) Activation of frontal right frontal regions in Working-Memory condition Working-Memory condition Perception condition -Verbal working memory tasks activation of left frontal regions Smith et al. (1996) - Spatial working memory activated more dorsal regions of dorsolateral prefrontal cortex than memory for objects Smith et al. (1999)

22 Temporal cortex and Long-Term Spatial Memory LTM typically relies on temporal functions and dissociates from STM- WM Temporal lobe damage typically does not interfere with Corsi span Imposing delays of 8-16 sec between presentation and recall reduces Corsi span In patients with temporal damage Right hippocampus and Long-Term Spatial Memory

23 Hippocampus and Long-Term Spatial Memory Smith & Milner (1981) Removal of hippocampus as treatment for epilepsy 16 small toy-objects - Participants asked to price the items one by one - Following delays of different length were then asked to place the objects in their original locations -Measurement of distance between reproduced location and original location -Removal of right hippocampus produces the strongest effect -In immediate recall conditions left lesions do not impair performance -Objects remembered correctly indicating specific deficit of spatial memory

24 Topographical memory memory for routes and in new and familiar environments Topographical disorientation - caused by damage to right medial temporal cortex, right hippocampus and parahippocampal gyri surrounding occipital cortex - spared general log term memory and short term memory - spared recognition of landmarks - spared ability to find routes in stylus maze - impaired ability to remember routes in the environment problem can be confined to specific environments - possible disruption of link or inability to form links between visual information from environment and memory

25 Imaging the hippocampi of London taxi drivers Maguire et al. (1997; 2000) MRI studies to derive image of individual brain and PET to superimpose level of activity task 1 - spatial - describe shortest legal route between two locations in greater London task 1 - control - recall plot of a film task 2 - spatial - describe famous landmark from places never visited task 2 - control - describe individual frames of film Right hippocampus selective active during recall of routes MRI scans indicate increase in right posterior hippocampus as a function of years of experience

26 Balint s Syndrome Patients with bilateral damage to occipital and parietal cortex Optic ataxia inability to point to target Visual simultagnosia disturbance of spatial attention inability to perceive more than one part of a visual scene at the same time

27 Possible role of left hemisphere in spatial processing (Kosslyn, 1987) - Euclidean metric relations -Categorical spatial relations e.g. above-below; top-bottom; front-back; left-right -RVF advantage in the processing of categorical relations -LVF advantage for metric relations Task 1 Metric - judge distance of point from blob Categorical - judge if dot is on or off the blob Task 2 Metric -judge if dot is near (less than 2cm) or far (more than 2 cm) from bar Categorical - judge if dot above or below bar categorical

28 Summary General spatial concepts and partition of space Dorsal stream and spatial processing Assessment of spatial disorders Spatial memory