Lecture 1: Perception and Praxis

What is the difference between bottom up vs top down processing?

Bottom up: perception is built up from the sensory information that is interpreted in real time (data-driven)

• Eg., reading some unintelligible handwriting and not being able to decipher it (bottom-up)

• Perception drives cognition

• Action is driven by the environment

Top-down: Perception of the data is interpreted BASED ON CONTEXT - influenced by learned experience, background knowledge, and EXPECTATIONS (concept-driven)

• Eg., someone tells you what the unintelligible handwriting means (that knowledge would be top-down), you can suddenly recognize and read it

• cognition drives perception

• Action is driven by thought

Example: walking into a kitchen and seeing something on the counter

• Bottom-up processing: You notice the colour, shape, texture, and size first → round, red, smooth → you determine it’s an apple.

• Top-down processing: You glance quickly, and because you’re in a kitchen and expect food on the counter, you immediately think “apple” before really analyzing the details.

What is perception?

The dynamic process of receiving the environment through sensory impulses and translating those impulses into meaning based on a previously developed understanding of that environment

What is the pathway of perception?

Receive stimulus (internal or external) from sensory receptors

info is relayed to the cortex, which is made up of our primary sensory areas/association areas (organized, interpreted, conscious experience)

• influenced by learning, memory, emotions, and expectations

Finally, a motor response is exhibited, alongside a cognitive response and an emotional response

What is cognition?

Mental processes which include thinking, perceiving, feeling, recognizing, remembering, problem solving, knowing, sensing, learning, judging, and metacognition

How would your assessment/intervention differ between bottom up and top down processing?

Bottom up approach: addressing components or domains of function first

Top down approach: observing and engaging the person in function/occupation

What are the two different forms of intervention and explain the difference

1. Remedial (restorative) - bottom-up approach

   1. focused on decreasing severity of impairments

   2. Assumption: there is capacity for neuroplasticity to repair the function that is damaged, that improvements in domains of function will carry over into improvements in functional activities

   3. Retraining activities

2. Compensatory/Adaptive - top-down approach/occupation first

   1. Focused on increasing occupational performance in occupations that individuals need and want to do

   2. Often used when recovery is felt to be complete (remediation is no longer showing improvements)

   3. Occupation retraining, compensatory strategy training, environmental modifications

What are the 4 main impairments in perception?

1. Agnosias

2. Visual Spatial Deficits

3. Body Schema and Body Image Disorders

4. Awareness and Attention Disorders

What are the two extra-striatal pathways? Describe the difference

Ventral vs Dorsal Stream (visual, and potentially auditory, sensory input)

1. Ventral Stream - What Pathway

   1. Information regarding object recognition, identification, and meaning

   2. Travels to the temporal lobe from the occipital lobe (primary visual cortex or striate cortex)

   3. eg. Object and facial recognition

2. Dorsal Stream - Where/How Pathway

   1. Information regarding spatial location/relationships, and movement

   2. Travels to the parietal lobe from the occipital lobe (primary visual cortex or striate cortex)

   3. eg. body schema and visuo-spatial orientation

Define Agnosia

Impairment in stimulus recognition, despite a functioning sensory system

In other words, the peripheral sensory information is being gathered and sent to the brain correctly, but the brain is unable to recognize what it is

• There is no sensory deficit or language deficit

• It also cannot be explained by memory or attention deficits

• Various types of agnosia (auditory, olfactory, visual)…

What are the main types and subtypes of visual agnosia?

1. Object agnosia - inability to recognize or identify familiar objects

   1. Associative agnosia - inability to associate perception with meaning

   2. Apperceptive agnosia - inability to perceive the complete form of an object/pattern (can only perceive small local aspects) - perception is incomplete

2. Prosopagnosia - inability to recognize familiar faces

What kind of deficit is it if there is damage to the retina or in the pathways to the primary visual cortex?

Sensory deficit

• no sensory information is being transmitted to the primary visual cortex

What kind of deficit is it if there is damage to the primary visual cortex?

Apperceptive agnosia

• perception is incomplete

• Deficit in feature/pattern detection

What kind of deficit is it if there is damage to the visual association area?

Associative agnosia

• Cannot associate perception with meaning

• Deficit in object recognition

• Damage to occipito-temporal lobe

What is one way to assess object agnosia?

Show the client 5 common objects and ask for the name of each item

• if they are aphasic (communication disorder), have them select from 3 different options

What is a remedial intervention for object agnosia?

Practice verbalizing characteristics of objects prior to naming the objecting

Naming the objects as you use them

What is a compensatory/adaptive intervention for object agnosia?

Placing objects in a consistent location, relying on intact modalities (touch), labelling objects

Define prosopagnosia - where is the lesion in the brain?

Inability to recognize familiar faces

• retained ability to identify other features like hair or gender

• Can develop in stroke, Alzheimer’s, infection, brain injury, etc…

• But some people are born with developmental prosopagnosia

Result of lesion in the fusiform face area (inferior temporal lobe)

What is one way to assess prosopagnosia?

Have the client identify a series of familiar or famous faces

What is a remedial intervention for prosopagnosia?

Working on describing features of the face, hairstyle, and other characteristics to help learn and identify the identity

Practice looking at photos from different angles during identification

What is a adpative/compensatory intervention for prosopagnosia?

Helping them get used to using other features of the individual other than the face to help identify

Wearing name tags

Define visual spatial deficits - damage to what area of the brain leads to this?

An impairment in understanding the relation of objects to each other or to the self

Damage to the inferior parietal lobe areas, especially on the right hemisphere

• combination of parietal, occipital, and or temporal lobe info

What are the five types of visual spatial deficits? Briefly explain each impairment…

1. Astereopsis

   1. inability to perceive depth in relation to self or between various objects (deficit in stereoscopic vision/depth perception) - monocular vision

2. Topographical disorientation (4)

   1. difficulty navigating in a well-known environment

   2. Can be egocentric disorientation, anterograde disorientation, landmark agnosia, and heading disorientation

3. Visual closure impairment

   1. inabiltiy to identify objects based on the perception of only parts of the object (eg. cannot identify what an object is unless it is seen in its whole. Partial occlusion results in reduced perception/recognition)

4. Constructional disorder - debated whether this is a visuo-spatial deficit or a form of apraxia

   1. inability to assemble/organize parts into a whole

   2. eg. difficulty in 2D and 3D drawing, copying, and or construction

   3. lesion in left hemisphere = less detail in drawings

   4. lesion in right hemisphere = distortions in spatial relationships of drawings

5. Impairment in ground figure discrimination

   1. deficits in differentiating foreground from background when examining a complex visual array

What is an intervention for astereopsis?

Teach individuals how the following factors can indicate whether an object or person is closer or further away (monocular clues):

• Relative size (closer = bigger)

• Overlap of objects (overlap = closer)

• blurriness of distant objects (blurry = far)

• decrease in textures for objects far away

• Parallel lines come to a point (linear perspectives)

• Relative brightness (closer = brighter)

Describe the four types of topographical disorientation and which area of the brain is affected

1. Egocentric disorientation

   1. inability to learn or recall spatial directions and landmarks due to difficulties with representing the location of objects with respects to self

   2. Posterior parietal lobe

   3. Peri-personal/Extra personal

2. Anterograde disorientation

   1. ability to orient in known environments, but has problems in new environments

   2. Parahippocampal gyrus (think anterograde amnesia = memory)

3. Landmark agnosia

   1. inability to recognize landmarks but retaine ability to describe routes and draw maps

   2. Parahippocampal, fusiform and or lingual gyrus)

4. Heading disorientation

   1. Loss of sense of direction - problems learning new routes, giving directions, putting landmarks on a map, and describing where one is …

   2. Affected area of the brain not described

How can we assess for topographical disorientation?

Typically in clinical settings, we use real relevant routes that the client is either familiar with or needs to become familiar with and we ask clients to articulate landmarks along that route

Other measures:

• Walking Corsi Test

• Cognitive map test

• Wayfinding questionnaire

How can we assess for constructional disorder?

Have the client draw a complex image in 2D and 3D

How can we assess for figure ground discrimination impairment?

• Test of Visual Perceptual Skills

• Functional Based Tests related to their goals (measuring the time it takes to complete the task and number of objects located):

  • Locating the correct change in a change purse

  • Sorting laundry

  • Finding items on a shelf in a grocery store

  • Locating puzzle pieces

What are some remedial and compensatory intervention strategies for figure ground discrimination impairment?

Remedial:

• practicing picking up objects from a complex array

• Computer games

Compensatory/adaptive:

• Decluttering

• Using high contrast between the object to be found

• Strategy: locating objects by colour

• Putting tape at the edge of stairs to help with figure ground discrimination

Define body image and body schema

Body image: visual and mental picture of one’s body

Body schema: a representation of the position of body parts in space which is updated during body movements

What are the four types of body schema/body image disorders? Briefly describe each of these

1. Autotopagnosia/Somatotopagnosia

   1. inability to localize, recognize or identify specific parts of one’s body

   2. Deficits in left parietal lobe or posterior temporal lobe

2. Finger agnosia (form of autotopagnosia?)

   1. Inability to identify fingers, name fingers on caommand, located a finger that is touched, or recognize fingers of the hand (of self AND of others)

      1. MOST COMMON ON MIDDLE THREE FINGERS (RING, MIDDLE, INDEX)

   2. Impact on dexterity and hand function

3. Somatophrenia - very extreme, rare

   1. Belief that the affected limb post stroke belongs to someone/something else

4. Impaired L/R discrimination

   1. inability to accurately distinguish between R/L sides of one’s own body OR R/L directional terms

How can we assess for autotopagnosia/finger agnosia?

• Have them complete a body puzzle

• Ask them to point/localize a part of their body

  • finger agnosia: point to each part of the finger

• Ask them to draw a person’s body

How can we assess for R/L discrimination?

• Ask them to point to parts of their own body

• Ask them to follow directions when navigating a space

What are some remedial and compensatory intervention strategies for R/L discrimination?

Remedial: practice reciting R/L when carrying out functional activities or when mobilizing; laterality training; mirror box

Adaptive: visual markers to indicate R/L

What are the two main awareness and attention disorders? Briefly describe and list some ways we can assess hemineglect

1. Anosognosia

   1. Inability to perceive one’s own condition accurately (lack of insight) - patient is unaware of their own neurological impairment

   2. Often associated with somatophenia

   3. Can be assessed with the CBS, anosognosia questionnaire for stroke, patient competency rating scale (All of these are completed once by the client and once by the assessor. Any discrepancy between the scores may indicate anosognosia)

2. Hemineglect

   1. inability to respond to or report stimuli presented on the contralateral side of the lesion (UNRELATED TO SENSORY OR MOTOR DEFICITS)

   2. Occurs in three spatial domains (depending on size and location of stroke… larger the lesion, the more of the space is impacted)

      1. Personal/Body-Space

         1. Only dressing one side, only shaving one side of face

         2. Assess with fluff text (putting piece of cotton on the neglected side of the client and asking them to remove it)

      2. Peri-personal

         1. Only eating the right side of the food on the plate, only using right side of the desk

         2. Assess with bells test, line bisection, menu reading, letter cancellation, star cancellation

      3. Extra-personal

         1. Bumping into objects on their left side, inability to see people on their left, lecturing to only the right side of the audience

         2. Assess by asking client to describe articles in a room

We can also assess using the catherine bergego scale and by observing their ADLs

Why does hemi-neglect almost always present as left-side neglect?

Due to redundancies in the brain

• Specifically, the right parietal lobe has attention centres for both the left and right sides, while the left parietal lobe is responsible for attention only to the right side

• Lesion in the left parietal lobe means attention to the right is preserved due to the right parietal lobes dual-sided function, while a lesion in the right parietal lobe would lead to left neglect

What are some remedial interventions for hemineglect?

• visual scanning training - strong evidence to support this intervention

• neck vibration - lack of evidence

• mirror therapy

• music - placing music on the unattended side

• bilateral activities

  • volleying a balloon

• Partial occlusion of the unaffected side’s visual field using glasses (CIMT theory?)

What are some adaptive/compensatory interventions for hemineglect?

• anchor points

• vibratory or auditory cues attached to the arm or belt

• trunk rotation

• rearranging objects into visual field

• Prism glasses (shift items further to the right visual field)

  • over time it can shift their visual field slightly

  • improvements experienced are usually not sustained over time

Building awareness is more important than task completion

• the more awareness they have, the more likely they are to engage in these learning strategies

Define praxis. What are the three main components involved in praxis?

The ability to plan and perform purposeful movement

• it involves:

  • Ideation (conceptual) - realization that i need to tie my shoelaces

  • Planning (production) - planning how I am going to tie my shoelaces

  • Motor execution (execution) - actually tying my shoelaces with my hands

What is apraxia?

Apraxia is a motor planning disorder in which a person cannot carry out purposeful movements on command despite having the physical ability and understanding to do so.

Ideational apraxia
Inability to plan and sequence a multi-step action involving objects, leading to misuse of objects or steps in the wrong order.

Ideomotor apraxia
Inability to carry out a learned movement on command even though the person understands the task and can sometimes do it automatically.

Ideomotor apraxia = problem carrying out the movement

The person knows what the action is and what the object is for, but can’t translate the idea into the correct motor plan on command.

• Ask: “Show me how you would brush your teeth.” → awkward, incorrect movement

• Give them a toothbrush → they may do it much better

Key clue: performance improves with the real object or automatic context.

The idea is intact. The motor execution is the problem.

Ideational apraxia = problem with the idea of the action

The person has lost the concept of what to do and in what order. They don’t understand how the objects relate to the task.

• Given a toothbrush and toothpaste → they might try to brush before putting toothpaste on, or put toothpaste on their finger

• They misuse objects or do steps out of order

Key clue: they don’t understand the task concept.

The motor ability is intact. The action plan/idea is the problem.

One-line difference

• Ideomotor: “I know what to do, but my body won’t do it right.”

• Ideational: “I don’t know what to do with these objects.”

What are the three types of apraxia? Briefly describe them

1. Ideational

   1. Inability to plan and sequence a multi-step action involving objects, leading to misuse of objects or steps in the wrong order

   2. Uses the tool incorrectly, associates the wrong tool with the task, and has difficulty sequencing the task (eg. combing hair with a toothbrush)

2. Ideomotor - inability to mime the use of a tool

   1. Inability to carry out a learned movement on command even though the person understands the task and can sometimes do it automatically.

   2. Cannot carry out motor act on command without tool, cannot mine use of the tool, but they can carry out the task with the tool (still can complete these tasks everyday)

3. Dressing

   1. difficulty in dressing, usually related to inability to orient clothing spatially as well as body schema disorders

   2. sometimes categorized under visuo-spatial deficits

Transative vs non-transative tasks

Transative: “How would you use a pen, hammer, scissors, etc…” tool is required in the action you are asking them to mime

Non-transative: “Show me how you wave goodbye, give me two thumbs up” no tool is required

When assessing ideomotor apraxia, assess for both of these types of tasks

Why does a unilateral lesion have bilateral symptoms in apraxia?

Due to the neuronal processing pathway

Example:

• Motor plans are stored in the left inferior parietal lobe

• signal is sent to left pre-motor area, then to the left primary motor area

• but a separate signal is also sent to the right pre-motor area (and onward to the right primary motor area) via the corpus callosum

Thus, a lesion can happen in either hemisphere but will functionally impact both sides

How can we assess for apraxia?

• The sensory perceptual system

  • check for intact sensory systems (visual, auditory), and assess language comprehension as well as neglect

• Conceptual system

  • gestures and tool recognition

• Production system

  • Pantomime (ask them to mime with a verbal command: “show me how to do this”)

  • Imitation (ask them to mime by demonstration: “Copy what I am doing”)

  • Object use

Standardized assessments:

• Refer to slides

• Most likely you are going to be assessing them initially via simple observation of their ADLs and noting where they are experiencing challenges

How can you help people with apraxia? Stroke Best Practices (5)

1. Use short and simple instructions

2. Encourage repetition and practice using the same steps each time

3. Keep the environment as normal as possible

4. Encourage the patient to briefly close their eyes and visualize the movement and task

5. Instead of commands, state the task to be completed (here is your toothbrush and pass it to them

What are some interventions for apraxia? Briefly explain each

1. Strategy training

   1. graded instructions, assistance, and feedback

2. Forward/Backward Chaining

   1. Forward chaining: Client does the first step and is assisted for the rest - gradually building in success by having them focus on one step rather than the whole task

   2. Backward chaining: Therapist does the whole activity and has the client step in for the last step, then progressively have them do more and more of the last part of the activity

3. Errorless learning - no trial and error

   1. immediately intervene as soon as you see a breakdown in performance

   2. Could also guide hands, do the task alongside them, demonstrate first and have them mimic

4. Task-specific training

   1. break down the steps, followed by practice, chaining procedures, and verbal mediation

What are OTs expected to do for those with perceptual and praxis related deficits?

1. Basic understanding of impairments and be able to anticipate functional deficits in terms of activities

2. Be aware of available assessments (formal and informal)

3. Incorporate both remedial and adaptive interventions to improve functional outcomes

4. Analyze which impairments are impacting function, then creatively come up with safe, effective, and meaningful interventions to optimize performance