Visuospatial Disorders Tutorial PDF 2024

Visuospatial Disorders PSYU3344 NEUROPSYCHOLOGY IN CLINICAL PRACTICE Tutorial Outline Visual Attention and Visual Processing Agnosia Hemispatial Neglect Constructional Apraxia 2 PART 1 Visual Attention & Visual Processing Visual A...

Visuospatial Disorders PSYU3344 NEUROPSYCHOLOGY IN CLINICAL PRACTICE Tutorial Outline Visual Attention and Visual Processing Agnosia Hemispatial Neglect Constructional Apraxia 2 PART 1 Visual Attention & Visual Processing Visual Attention Attention supports conscious perception Attention is capacity-limited Attention is selective in nature Attention involves fronto-parietal networks 4 Visual Attention Bottom-up Processing Processing that is directly influenced by environmental stimuli and salience Involuntary Temporo-parietal junction, ventral frontal cortex (orange) Known as the ventral attention network Top-down Processing Processing that is influenced by sensory input as well as experiences and expectations Voluntary (goal directed) Inferior & superior parietal sulcus, frontal eye fields (blue) Known as the dorsal attention network Bottom-up & top-down processes interact 5 Visual Processing Damage to earliest visual brain areas cause blindness Damage to brain areas further along the visual information processing pathway do not cause blindness, but an inability to process specific features of a stimulus (e.g., colour [achromatopsia, V4], motion [akinetopsia, MT], etc.) Damage even further along causes specific object recognition deficits (visual agnosia; LOC, FFA, etc.) but intact processing of basic visual features Information in visual images is processed in a hierarchical fashion Early processing stages extract elementary features (lines, angles, edges, colour, curves, motion) (e.g., orientation-selective simple cells). Ventral (“what”) and dorsal (“where”) brain pathways process more complex aspects of visual information (e.g., object form, spatial representations). 6 Visual Processing 7 PART 2 Agnosia What is Agnosia? Inability to process sensory information Affects a single sensory modality Loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss 9  Types of Visual Agnosia Categories of visual agnosia Apperceptive visual agnosia Associative visual agnosia Subtypes of visual agnosia Simultanagnosia Prosopagnosia Achromatopsia Topographical agnosia Finger agnosia Agnostic alexia Akinetopsia 10 Apperceptive Visual Agnosia Difficulty assembling pieces/features together into common objects Failure of perception Not very common 11 Apperceptive Visual Agnosia Intact: Acuity Brightness discrimination Colour vision Recognition of lines, colours, angles Ability to attend, maintain fixation, reach for objects Object description when given names Impaired Object naming Object matching Object copying Shape identification Orientation judgment Affects words, objects, faces (all stimuli) 12 Apperceptive Visual Agnosia 13 Apperceptive Visual Agnosia Due to a defect in early stages of visual processing preventing the formation of a whole percept 14 Apperceptive Visual Agnosia Associated with diffuse posterior (parietal and/or occipital) damage or recovery from cortical blindness 15 Associative Visual Agnosia Can perceive a whole object but have difficulty naming it because they can’t link the visual percept to an identity/cannot assign meaning to it Perception occurs but recognition is impaired → “recognition without meaning” More common 16 Associative Visual Agnosia Intact: Acuity Brightness discrimination Colour vision Recognition of lines, colours, angles Object matching Object copying Object description when given names Object naming in non-visual modality (e.g., can’t name a key by looking at it but can name it based on touch) therefore not anomia Impaired Object naming based on visual information Better with verbal descriptions, drawings from memory, context Can be material specific: letters → pure alexia, faces → prosopagnosia, navigation → topographical agnosia Visual object agnosia can be category specific e.g., living things, tools, musical instruments 17 Associative Visual Agnosia 18 Associative Visual Agnosia 19 Associative Visual Agnosia Due to a defect in later stages of visual processing involving object representation 20 Associative Visual Agnosia Associated with bilateral damage to the inferior temporal-occipital junction 21 Subtypes of Visual Agnosia SIMULTANAGNOSIA Difficulty processing visual input as a whole Dorsal Able to recognise elements but not the whole scene One object at a time Ventral Multiple objects can be seen, manipulated, counted etc. Cannot grasp the meaning of the whole scene 22 Subtypes of Visual Agnosia PROSOPAGNOSIA Difficulty recognising faces Also known as face blindness and facial agnosia May recognise people based on extra-facial features, gait, voice etc Acquired prosopagnosia – inferior medial temporo-occipital damage (fusiform face area) due to TBI or stroke, usually on the right side Congenital prosopagnosia – no neurological condition or intellectual impairment but may have a genetic component, 2-3% prevalence rate 23 Subtypes of Visual Agnosia OTHER Achromatopia Inability to distinguish different colours Topographical agnosia Inability to navigate environment Finger agnosia Inability to name, move, or touch specific fingers identified by the examiner Agnostic alexia Pure word blindness Akinetopsia Motion blindness 24 Testing Visual Processing & Agnosia Object naming Object categorisation or figure matching Drawing and copying Unusual views Overlapping line drawings Partially degraded identification Fine line judgment Figure contour tracking Identification in other modalities Facial feature analysis Face recognition Visual Object & Space Perception Battery (VOSP) Birmingham Object Recognition Battery (BORB) Famous Faces Test, Benton Face Recognition Test, Cambridge Face Memory Test 25 Agnosia Case Studies https://www.youtube.com/watch?v=ze8VVtBgK7A Following a brain injury, CK developed agnosia and dyslexia but has normal face recognition https://www.youtube.com/watch?v=3-MzNPcEh6M 26 PART 3 Hemispatial Neglect Hemispatial Neglect Characterised by a failure to attend, respond, or orient to a stimulus or side opposite the lesion which is not due to a sensory or motor deficit May extend to all sensory modalities i.e., neglect of visual, auditory, and somatosensory stimuli on the side of the body and/or space opposite the lesion Patient is often unaware of the deficit Most commonly reported following a posterior parietal lesion of the right hemisphere May also be seen following right frontal lesions and lesions of the cingulate gyrus or of the thalamus and basal ganglia Often transient with the most conspicuous features in many cases lasting no more than a few weeks 28 Acute Stages of Hemispatial Neglect Patients attention systematically orients towards stimuli lying on the extreme part of the non-neglected side: May eat from only one side of the plate, neglect to lock the wheelchair on one side May be characterised by marked deviation of head, eyes and trunk away from the contralesional field When testing visual fields, the very placement of one’s hand to the patient’s right renders him unable to maintain central fixation. Known as ‘compulsive orientation’ to the right Scanning saccades restricted to the ipsilesional side although patient may have full ocular movement to command In severe cases patients may fail to recognise contralateral extremities as their own May experience difficulty in remembering left sided details of internally represented familiar scenes 29 Acute Stages of Hemispatial Neglect Asked to lift arms: will lift only one Asked to draw a clock face: reproduce only half or crowd all numbers into one side Asked to read a compound word such as ice-cream or football: read cream and ball Dressing: May fail to put on one side of clothes Grooming: Shave or apply makeup to only one side of the face Unaware that anything is wrong (anosognosia) 30 Later Stages of Hemispatial Neglect Extinction to Double Simultaneous Stimulation Patient asked to fix gaze. Test visual fields by presentation of a single stimulus on one side. Do the same on the other. Patients fields will be ‘Full to Confrontation’ i.e., detection appears normal in both the left and the right visual fields When two objects are presented at the same time, one in each field, only one of the stimuli is reported ‘Extinction to Double Simultaneous Stimulation’. 31 Acute & Later Stages of Hemispatial Neglect 32 Testing for Hemispatial Neglect Line cancellation Bells test Star cancellation 33 Testing for Hemispatial Neglect Line bisection Copying Drawing from memory 34 Hemispatial Neglect vs Visual Field Sensory Loss Hemispatial Neglect Not aware of deficit Do not compensate for deficit Attentional rather than sensory Visual Field Sensory Loss Aware of deficit Compensate for deficit 35 Hemispatial Neglect https://www.youtube.com/watch?v=d4FhZs-m7hA https://www.youtube.com/watch?v=ymKvS0XsM4w 36 PART 4 Constructional Apraxia Constructional Apraxia An impairment in combinatory or organising activity so that desired synthesis cannot be achieved Seen on tests where individual elements must be arranged in a given spatial relationship to form a unitary structure Inability to perceive how two or more parts form a whole Tests of constructional apraxia: Copying, Clock Drawing, Block Design 38 Constructional Apraxia 39 Constructional Apraxia 40 Constructional Apraxia 41 Constructional Apraxia 42 Thank you!