Introduction
-Neuropsychology = philosophy + psych + linguistics + AI + anthropology + neuroscience
-Patient = technology + cognitive models + therapeutic relation + trust/confidence + teamwork + science
-Current behaviour = SES + current functioning + personality + social context + brain damage
-Test Performance = psychological factors + genetic factors + methodological factors + other factors
(setting, mood, random variance) + past history
-Level of experiments =
- Behavioural: short, tunable, reproducible
- Pop-up: average all round
- Big data: scalable, universal, in vivo
-Hypothesis: theoretical framework literature review research question
-Experiments: reliable, valid, feasible, theoretically sound, data friendly, ethical
-Ethics: rules/regulations + values + research + moral principles + ethical practices + rules of conduct
-Healthcare system: bridge gap between research and care paradigm shift that aligns patient needs
with research goals cycles back to clinical decisions (continuous quality improvement)
-NeuroRights: mental privacy + personal identity + free will + fair access + protection from bias
(1) Article: Art of Reading Journal Articles
-IMRAD: Intro, Method, Results, Analysis, Discussion
-Randomized control trial, controlled clinical trial, experiment survey, case control, or cohort study
-TitleAbstractIntro Materials/Methods Results Discussion
Perception
-(1) Vision: guide action + perceive face/objects +
perceive danger + appreciate environment + recognition
+ navigating
-Visual System = main visual processing pathway from
eyes crossing optic chasm opposite primary visual
cortex Both eyes have L/R visual fields – only part of
the nervous system = exposed
-Visual perceptual deficits = damage between pathway
from eye to visual cortex location of damage =
different defects
Vision: higher cortical processing different features
(e.g. Form, color, motion, depth)
-Perceptual deficits co-occur if lesions are large, affect multiple functional areas
1. Akinetopsia = separate snapshots rather than fluid movement
Bilateral damage in V5/MT area Patient MP
2. Achromatopsia = processing color area V4 affect 1
hemisphere or both (half color, half b/w)
3. Visual Form Agnosia = perceiving shapes Associated with carbon
monoxide poisoning (no oxygen) Effron Shapes = differentiate
between different rectangles with same surface area Area LOC in occipital lobes is NB for
face perception Visual agnosia needs to be bilateral to cause problems in shapes because if
unilateral then patient can compensate
-Visual system pathways: 40% of brain area is involved in visual processing –beyond occipital lobes
- Ventral pathway = visual perception (e.g. what am I looking at?)
- Dorsal pathway = visual guidance (e.g. how am I doing it)
-Higher-order perceptual disorders:
- Visual Agnosia: selective deficit in object recognition (objects/faces) sensory processing
intact (touch & recognize) language processing intact (name it) object knowledge intact
(understand its use)
-Lissauer developed 2 types of visual perceptual agnosia
, - Apperceptive agnosia = putting all features of an object together to form coherent picture
(copying/drawing objects) sensory processing intact, perception deficit
- Associative visual agnosia = can copy/draw but cannot link with stored knowledge (identification
deficit ) impaired associating perceptual representation with semantic knowledge
o Unusual views (aerial view/shadows) Overlapping figures
-Theories of Object Recognition: from basic visual representations
to more complex representations to linking with existing knowledge
-Face Perception: separate system for faces
- Model Bruce & Young – Parallel Systems = different
aspects/components of face perceptions fairly independent
all happen in parallel
o Structural encoding: perceptual representation of face
o Face recognition units: link to existing knowledge
o Facial speech analysis: lip movements (decode)
o Expression analysis: read emotions on face
Matching unfamiliar faces: match pictures of faces only – lighting/viewpoint can be
changed for complexity Prosopagnosia: congenital/caused by lesions inability to
recognize faces Can be induce with electrical stimulation
- Separate Routes: for recognition & facial expression might be able to
recognize emotion but not who the person is (and vice versa).
-(2)Visuomotor Control: visual input guides actions = (1) reaching linked to location
(2) hand opening linked to size (3) hand orientation linked to object orientation
- Optic Ataxia = using visual information about position/orientation of objects to
guide actions Posterior parietal lobe visual perception can be intact
- Separate visuomotor channels: primary visual cortex to premotor areas reaching vs grasping
- Obstacle Avoidance in optic ataxia –also avoid dangerous objects or knocking things over
-(3)Body Perception:
Rubber Hand Illusion: how we perceive our body when stroking is synchronous, rubber hand = own
hand dissipates when movement becomes asynchronous, or participant moves out of position
- Requirements: (1) Multisensory synchronized information (2) temporal & spatial integration (3)
foreign body part should resemble own body part (4) placed in anatomically plausible orientation
o Multisensory = visuo-tactile, visuomotor, tactile-motor, or introceptive (heartbeat + visual)
o Measurement: ownership questionnaire (what it felt like)
o Dependent variables: (1) Proprioceptive Drift (where do they think their hand is) (2) skin
conductance when hand is threatened (hit with hammer)
o Other body parts: e.g. rubber foot, faces, whole body (mannequin or person)
- Enfacement illusion: take on characteristics of the other person (fear or compassion)
- Rubber tail illusion for rats and other animals
- Barbie Doll Illusion = scale the world around you based on body size perception
- MIRAGE Mediated Reality: disappearing hand trick
-Use in Practice: (1) lesions can cause body perception issues (e.g. phantom limbs) (2) body perception
disturbances occur in disorders (3) illusions may simulate disorders & provide insight into underlying
processes (4) gives additional info into disorders (5) provides treatment options
- Body Representations (Head & Holmes) – multiple body representations linked to different functions
- (1) Body Schema (unconscious) standard against which changes in posture are measured
- (2) Superficial Schema (unconscious) central mapping of body surface from tactile information
, - (3) Body Image (conscious) internal representation of experiencing self top-down
Double dissociation = 2 mental processes function separately (e.g. motor vs tactile)
Body matrix = network model of body perception = flexibility in different aspects of body.
- Body perception: tactile, postural, spatial localization, localization of touch, metric properties,
tactile object recognition
-Body perception disorders: (1) Structural (2) Metric (3) Bodily Awareness & Ownership
- (1) Structural Deficits:
o Finger Agnosia = finger identification (explicit = naming/pointing) vs (implicit btwn touches)
o Left-right orientation = deficit in identifying left/right half of body
o Gerstmann’s syndrome = finger agnosia + L/R orientation + dyscalculia + dysgraphia
- (2) Body Size (Metric) Deficits:
o Macrosomatognosia/Microsomatognosia = body is larger/smaller than reality medial
parietal cortex causes: peripheral anesthetic/ Migraines/complex regional pain syndrome
- (3) Body Awareness Deficits:
o Anosognosia = deny deficit exists
o Anosodiaphoria = admit deficit but minimize
o Asomatognosia = reject ownership of limb
o Somatoparaphrenia = attribute own arm to someone else Rubber hand illusion is Larger
for: somatoparaphrenia, hemiplegics (affected hand), schizophrenia, anorexia Rubber
hand illusion is smaller for: autism, hemiplegics (unaffected hand), and ADHD
- Body representation is not a unitary function but different aspects can be selectively impaired
ARTICLE: On Feeling and Reaching: Touch, Action, and Body Space (Dijkerman, 2017)
Chapter 3: Organisms move around & interact with objects spatial info is NB (where objects are):
externally + in relation to own body
-Proprioception (Kinesthesia) = sense that lets us perceive location, movement, action of body parts
-Spatial information of body = proprioception + touch + visual information
-Somatosensory input = used for guiding actions + provide spatial perceptual info + haptic exploration
(purposive action that encode properties of objects) + targets on our own body
-Normal Brain is prone to distortions in somatosensory experience underlying spatial representations
-Disturbed brain can result in perceptual somatosensory disturbance in clinical populations
-somatosensory input is NB for providing representations of body for haptic exploration of objects
-Somatosensory Processing for Perception & Action
- Dominant model for visual-cortical processing = 2 visual streams model visual info is processed
along 2 separate streams of cortical processing: ventral (perception & recognition) & dorsal
(guiding action) somatosensory processing is also divided by function but less anatomically clear.
- Somatosensory systems of brain: processes input from different sub
modalities (touch, proprioception, hot/cold, pain, itch) linked to
receptors on skin, muscles, joints, tendons info from receptors in all
parts (except face) are transmitted first to dorsal side of spinal cord
convey input to brain (1) dorsal column = tactile & proprioceptive info (2)
anterolateral system = temperature, pain & affective tactile info
project to thalamus primary somatosensory cortex (anterior parietal
lobe) PSC contains somatotopic map of the contralateral half of the
body parts with higher receptor density = more cortical surface
- Damage to primary somatosensory cortex = loss tactile and
proprioceptive perception for contralateral half of the body (hemianesthesia)
- Damage to insular cortex = loss of affective touch, pain & temperature contralaterally projected
- Secondary Somatosensory cortex =higher-order somatosensory processing (more distributed) =
parietal operculum, post parietal cortex + insular cortex e.g extracting features and recognizing
external stimuli, conscious bodily experience, spatial/structural aspects of body
, -numbsense = patients can correctly respond to somatosensory stimuli at a higher rate than expected by
chance, but cannot perceive the same stimuli consciously (dissociated) tactile info could not reach
perceptual detection centers but could access motor areas involving movements.
-Weber’s illusion: perceived distance between touches on a single skin surface is larger on regions of high
tactile sensitivity than those with lower sensitivity
-Bodily Illusions: way we experience body influenced by how sensory input is processed + stored
-Larger impact of rubber hand illusion = linked to reduced sense of ownership of body
-Multiple body representations exist: (1) Postural schema (2) superficial tactile schema (3) body image
-Body Space: multimodal process to detect tactile stimuli localize different body parts with each other
and in external space requires proprioceptive input (from joints/muscles) + tactile input (skin stretching)
- Efferent signals from motor system = estimate of extension of body part not sufficient to localize
in external space need info on distance between joints and length/size of body segments (from
postural schema)
- Localizing body part in external space requires afferent proprioceptive input + higher order stored
information
- To localize tactile stimuli NB visual input remapping external space
- Implicit representation of size of different body parts (stored metric representations) overall
overestimation of width and underestimation of length affects perceptual estimates
o Finger gnosis = bilateral parietal activation left anteromedial parietal lobe (finger
identification) Finger agnosia = tactile input to fingers cannot be used to guide
movements cluster of impairments in Gerstmann’s syndrome
-Active touch & haptic object recognition: microgeometrical properties (texture, density, thermal
properties) = input receptors of skin macrogeomectrical properties (size/shape) = input from tactile /
proprioceptive receptors of muscle, tendon, joint selective impairment in macro & micro properties
- Tactile apraxia: Deficits in exploratory hand movements (while basic sensorimotor function is
intact) difficulty adjusting hand movements to character of object (superior posterior parietal)
- Difficulties in haptic exploration can lead to recognition problems (can have different causes)
- Test of haptic perception: blindfolded with metal bars at different angles (make them match)
horizontal distance between two bars increased errors hand-centered egocentric reference
visual experience is NB for allocentric representations
-Haptic Object Recognition: exploratory hand movements, recognizing objects by touch requires
multiple somatosensory signals combined in a representation of an object (texture, shape, weight,
hardness) gathered & integrated semantic properties (use/function) are retrieved from memory
- Tactile agnosia: deficit in building the object representation or accessing semantic properties
- Tactile associate agnosia: representation of object is achieved (e.g. can draw) BUT access to
semantic knowledge is lost (blocking recognition)
Peripersonal Space: Area surrounding our body where objects are located = separately represented
multimodal Linked to safety zone around body & defensive action
- Posterior parietal regions + dorsal premotor areas receptive fields linked to head/hand/arm
- Lateral occipital complex (LOC) + intraparietal sulcus = approaching hand in near vs far space
- Cross-modal attentional cueing when visual cue is near, hand is followed by a tactile stimulus
- Patients = impaired in detecting tactile stimuli on contralesional side when accompanied by visual
stimulus on ipsilesional side.
- Extinction is pronounced when visual stimulus is near the similar body part on the ipsilesional side
NOT when visual stimulus on ipsilesional side is far away or near different part of body
- Different peripersonal space representations exist: (1) preparation for motor acts (e.g. goal-
directed sensorimotor) (2) visuotactile integration (e.g. grasping toward neutral objects)
- Peripersonal space = social function: visual attention, social context, interact, shared experience
-Visuomotor reaching/grasping: spatial info for goal-directed arm movements needs visual +
somatosensory systems Reaching = Dependent on location grasping = dependent on nonspatial size
separate visuomotor channels for reaching vs grasping
- Optic ataxia = selective visuomotor deficit for grasping while reaching is intact
