Agnosias in other modalities

•      Auditory agnosia

–    verbal auditory agnosia

•    humming noise

–    nonverbal auditory agnosia

•    horn, bark, lawn mower

–    mixed auditory agnosia

•      Somatosensory agnosia

–    tactile agnosia

–    astereoagnosia

•      lesion: left inferior parietal

 

Category Specific Deficits

•      Fruits

•      Vegetables

•      Form percepts accurately

–    objects outside category recognized.

•      Percept can be linked to meaning.

•      Selective anomia.

–    Failure to recognize object

–    can’t provide adequate definition when provided with name of object.

 

 

Category-Specific Deficits

•      Living things versus nonliving things section

•      Function versus sensory attributes

Object recognition

•      Ventral stream

–    “what”

•      Dorsal stream

–    “where”

Area 7 (Monkeys)

•      Not sensitive to color

•      Not sensitive to items in central vision

•      Contralateral space

•      fire in response to movement in certain direction

•      Velocity

•      Retinal location and position of eyes/head

 

Monkeys

•       Landmark discrimination task

•       Nonmatch to sample paradigm

Spatial processing in humans

•       Posterior parietal areas

•       Six fundamental spatial skills

–    localizing points in space

–    depth

–    line orientation

–    understanding geometric relations

–    perceiving motion

–    rotation

Localization of points in space

•      Holmes (1918)

–    object recognition ok

–    acted as if blind (groping, misreaching)

•      The ability to direct movement toward an object is impaired

 

•      Perception of location of point in space.

•      Similar findings for auditory information

Localization

Depth Perception

•      Stereopsis

•      Binocular disparity

•      Local (stereoacuity)

–    point-by-point manner

•      Global stereopsis

–    whole visual scene

Orientation of lines

•      Location/orientation of string of points (line)

•      LVF advantage

•      Verbal/analytic strategy (stimuli can be described verbally)

Geometric Relations

•      LVF advantage

•      More likely for items that are difficult to label verbally

•      LH:  Euclidean geometry

•      RH:  Topology (curved spaces/forms)

Motion

•      Inferior parietal lobe

•      Case study

–    loss of ability to perceive motion

–    Pouring liquid appeared as a snapshot

–    Judging speed of cars

Mental Rotation

•      Some cells are sensitive to rotation (clockwise)

•      Time increases as degree or rotation required increases (Sheperd, 1988)

•      PET studies (Deutsch et al, 1988)

–    RH superiority

 

Mental rotation

•      Divided visual field

•      Equivocal (LVF, RVF)

•      Hemispheric superiority

–    function of direction of rotation (Burton et al, 1992; Corballis & Sergent, 1989)

–    RH:  clockwise rotation

–    LH:  counterclockwise rotation

Complex spatial skills

•      Constructional praxis

–    right hemisphere

Complex spatial skills

•      Constructional praxis

•      Note qualitative errors

–    RH brain damage

–    LH brain damage

Complex spatial skills

•      Route-finding and topographical skills

•      Buildings

•      Maze

•      Geography

Complex spatial skills

•      Disturbance of body schema (right versus left)

•      Left parietal damage

•      Gerstmanm syndrome (1957)

•      R-L disturbance

•      Finger agnosia

•      Dyscalculia

•      Dysgraphia

•      Left angular gyrus

Complex spatial skills

•      Anosognosia

–    “denial”

•      Macrosomatagnosia

•      Microsomatagnosia

 

Balint’s syndrome

•      Optic ataxia

–    inability to point to a target under visual guidance

•      Ocular apraxia

–    inability to voluntarily shift gaze toward a new visual stimulus

•      Simultanagnosia:  Inability to perceive different pieces of information (cannot direct attention to more than one small location)

Visual Field Cut

Optic ataxia

Simultanagnosia

 

Left versus Right Hemisphere
(Kosslyn, 1987)

•      Left

–    Categorical spatial relations (above vs below; front vs back)

•      Right

–    metric (coordinate) spatial relations

•    distance between two locations

Hemineglect

•      Typically observed on left side of space.

Attention

•      ADHD

•      Hemi-neglect

Attention - Basic Categories

•      Alertness and arousal

•      Vigilance - sustained attention

•      Selective attention

•      Resource

Selective Attention - filter

•      Early selection (Treisman & Gelade, 1980)

•      “T” example

•      attention directed to point in space

 

•      Late selection (Deutsch & Deutsch, 1963)

•      “A, C, R, T’ example

•      identification and categorization

Early Selection

•      Stimulus processing need not be complete before

–   1)  selected for further processing

–   2)  rejected as irrelevant

•      “X” example

–   is it a red “x”?

–   Directing attention to point in space precedes identification

 

Late Selection

•      Attended and irrelevant stimuli are fully analysed before selection between them takes place

•      Example:  dichotic listening

Selective Attention and ERPs

•      Early ERP components

•      Attend to one ear

•      N1 is early ~80ms

•      Nd

•      visual, somatosensory

•      P300

Selective attention

•      Space-based selective attention

•      Object-based selective attention

Spatial attention paradigm

•      Posner (1980)

Object-based attention

•      Negative priming paradigm (Neil, 1977)

Resource models of attention

•      Attentional abilities can be partitioned (Kahneman, 1973)

•      Multiple resource theory (Wickens, 1980)

•      Early vs late

•      Auditory vs visual

•      verbal vs spatial

Verbal vs spatial processing

•      Dual task method

•      interference if tasks compete for resources

•      divided visual field

•      LH

•      RH

•      CVC sequences (GEK)

•      CVCVCs (GOMIS)

Neuroanatomy of attention

 

Reticular activation system (RAS)

•      Alerting and arousal

•      sleep and wake cycles

•      coma….stupor…chronic vegetative state

•      alert, preparation to respond

 

Superior colliculus

•      Shifting attention to new locations

•      saccades

–   express saccades

–   regular saccades

•      supranuclear palsy

 

 

Pulvinar of thalamus

•      Important for selective attention

•      filter

•      brain damage case study

 

Cingulate cortex

•      Interface between subcortical and cortical

•      integration of information with emotion

•      selection of appropriate responses

•      PET scans reveal cingulate activation when

–   selection from array of possibilities

–   selection is complicated

 

Parietal Lobe

•      Spatial aspects of attention

•      Allocation of attentional resources

•      P300

–   largest over parietal regions

–   lesions over parietal regions diminishes P300 amplitude

 

Frontal Lobe

•      Selection of motor responses

•      recruiting attentional resources for goal

•      Lesion in dorsolateral frontal

–   hypokinesia contralateral to lesion

Frontal lobe - con’t

•      Voluntary control of eye movement

•      Inhibition of reflexive eye movement

•      P300

–   P3b (parietal regions)

–   P3a (frontal regions) novel/unexpected

–   P3a decreases after lesions to frontal lobes

Mesulam’s model of attention

•      RAS - maintain vigilance and arousal

•      Cingulate - impart emotional significance

•      Posterior parietal - sensory map of the world

•      Frontal - motor programs for exploring, scanning, reaching, and fixating

Posner’s model for visual selective attention
(posterior attentional network)

•      Parietal areas - disengage

•      Superior colliculi - move

•      Thalamus - engage

 

 

Hemineglect

•      Ignores space contralateral to lesion

•      not modality specific

•      no sensory explanation

•      double simultaneous stimulation technique

•      Neglect is moderated by attentional factors

•      motivational factors

•      anosognosia (unaware)

 

 

 

 

 

 

 

 

 

 

Treatment for hemineglect

•      Caloric stimulation

•      cold = opposite

•      warm = same

•      COWS

Object based attention

•      reading

Language

•      Aphasia:  loss of language processing ability after brain damage

•      Many different types of aphasia.

•      Poor naming is seen in ALL types.

Broca’s aphasia

•      Nonfluent

•      telegraphic speech

•      function words (but, and) missing

•      word endings missing (ing)

•      difficulty repeating

•      Lesion:  Broca’s area

 

Wernicke’s aphasia

•      Fluent

•      word salad

•      paraphasias

–   semantic paraphasia (“barn” for “house).

–   Phonemic paraphasia (“table” is “trable”)

•      neologisms (“galump”)

•      cannot comprehend language, can’t repeat

 

Wernicke’s aphasia

•      Lesion:  Wernicke’s area

 

Conduction aphasia

•      Inability to repeat

•      comprehension and production good

•      paraphasias

•      Lesion:  arcuate fasciculus

 

Lichtheim’s model

•      Concept center:    where meanings are stored

Transcortical motor aphasia

•      Similar to Broca’s

•      Little spontaneous speech

•      Retain the ability to repeat

•      Echolalia

•      Lesion:  outside Broca’s area

–   more anterior or superior

 

Transcortical sensory aphasia

•      Similar to Wernicke’s aphasia

•      But, the person can repeat

•      echolalia

•      Lesion:  more posterior than Wernicke’s area

 

Global aphasia

•      Cannot comprehend or produce speech

•      extensive left hemisphere damage

Table 8.1, page 287

Transcortical mixed aphasia

•      Elements of:

–   transcortical motor aphasia

–   transcortical sensory aphasia

 

Subcortical aphasia

•      Initially….mutism

•      slow recovery to slow, poorly articulated (mushy) output.

•      Paraphasias

•      paraphasias disappear when asked to repeat

•      strong tendency for subcortical aphasia to disappear