Sensorimotor Functioning. Sensory and Motor Systems. Functional Anatomy of Brain- Behavioral Relationships

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William Ward
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Sensory System = Input Neural Processing Motor

1 Sensorimotor Functioning Sensory and Motor Systems Understanding brain-behavior relationships requires knowledge of sensory and motor systems. Sensory System = Input Neural Processing Motor System = Output Descartes, 1662 Functional Anatomy of Brain- Behavioral Relationships Blumenfeld,

based on modality specificity & complexity of functions Contralateral Processing

2 Properties of Cortical Organization Hierarchical ranking based on modality specificity & complexity of functions Contralateral Processing e.g. LH represents: Right Visual Field Right side of body Right Ear Input (sorta) Vice versa for RH Functional Segregation modules with specialized functions Generic (simplified) Pathway: SENSORY RECEPTOR THALAMIC NUCLEUS PRIMARY CORTEX SECONDARY CORTEX ASSOCIATION CORTEX Somatosensory Processing External processing: Touch, pain, heat Internal Processing: Body position, fever 5 types of receptors Mechanical Chemical Thermoreceptors Nocioceptors Proprioceptors Somatosensory System Info sent from body to Thalamus Contralateral primary somatosensory cortex Each body region is represented in a different cortex region Blumenfeld,

3 Motor System Info is sent TO the body through the Internal capsule (then decusates) Spinal cord Muscles via contralateral projections Each body region is represented in different cortical region Blumenfeld, 2002 The Homonculus Testing Somatosensory Functioning Stereognosis Bilateral Simultaneous Stimulation 3

Chemosensory Systems Olfaction system Information is sent from the

Gustatory (taste) sytem Information is sent from the tongue through the

from the cochlea through the thalamus (MGN) to primary auditory cortex

both ipsilateral and contralateral inputs to the cortex from each ear

(Medial geniculate nucleus) Inferior colliculus Superior Olivary nucleus

V1 Optic nerve Optic chiasm Left and right visual fields are processed

4 Chemosensory Systems Olfaction system Information is sent from the olfactory bulb to the limbic system, then back to the frontal cortex Gustatory (taste) sytem Information is sent from the tongue through the thalamus to multiple brain regions Auditory System Information is sent from the cochlea through the thalamus (MGN) to primary auditory cortex (Heschel s Gyrus) Left Auditory cortex Right Auditory cortex There are both ipsilateral and contralateral inputs to the cortex from each ear Cochlea Auditory nerve fiber Ipsilateral Cochlear nucleus Thalamus (Medial geniculate nucleus) Inferior colliculus Superior Olivary nucleus Visual System Info is sent from the retina through the thalamus (LGN) to V1 Optic nerve Optic chiasm Left and right visual fields are processed contralaterally Optic tract Thalamus (Lateral geniculate nucleus) Optic radiation Primary visual cortex 4

Visual System Deficits Cortical Blindness Visual Agnosia for

Achromotopsia Disconnection Syndromes Visual Field Deficits

Dorsal-Ventral Visual Streams Dorsal Where Stream Spatial

of movement Deficits Neglect Apraxia Left-right discrimination

5 Visual System Deficits Cortical Blindness Visual Agnosia for objects, faces, etc. Achromotopsia Disconnection Syndromes Visual Field Deficits Higher-order visuospatial deficits Visual Field Deficits Dorsal-Ventral Visual Streams Dorsal Where Stream Spatial location Topographical Orientation Planning and coordination of movement Deficits Neglect Apraxia Left-right discrimination problems Ventral What Stream Object recognition Matches visual shape to internal representation Deficits: Visual Agnosia 5

6 Ventral Stream Deficits FFA (face) V4 (color) Agnosia Failure to recognize previously familiar stimuli Modality-specific Not due to dementia, aphasia, or unfamiliarity with stimulus May be limited to particular classes of stimuli 6

Agnosia Examples Prosopagnosia: Familiar faces Auditory Sound Agnosia: Sounds of common objects Phonagnosia: Familiar people by their voices Tactile agnosia: What s placed in the hand Types of

7 Agnosia Examples Prosopagnosia: Familiar faces Auditory Sound Agnosia: Sounds of common objects Phonagnosia: Familiar people by their voices Tactile agnosia: What s placed in the hand Types of Agnosia (Lissauer s stage model) Apperceptive Agnosia inability to recognize or name objects Cannot copy unrecognized objects strong evidence for sensory-perceptual disturbance Associative Agnosia inability to recognize or name objects Generally can copy unrecognized objects Sensory-perceptual disturbance cannot explain defect Apperceptive Agnosia (Benson & Greenberg, 1969) 7

8 Associative Agnosia (Farah, Hammond, Levine, et al., 1988) Anatomy implied in Stage Model A-AP V-AP AS 8

Explanations Failure of perception to contact memory Failure of perception to contact language

impairment Prosopagnosia Inability to identify previously familiar people by facial features alone Intact

with object agnosia May take apperceptive and associative forms Frequent Co-existing Signs Object agnosia

9 Explanations Failure of perception to contact memory Failure of perception to contact language (visual-verbal disconnection) Impairment/degradation of stored representation Sensory-perceptual impairment Prosopagnosia Inability to identify previously familiar people by facial features alone Intact ability to identify people using nonfacial features (voice) May extend to nonfacial stimuli May co-exist with object agnosia May take apperceptive and associative forms Frequent Co-existing Signs Object agnosia Visual memory loss Superior visual field defects Altitudinal hemianopia Superior quadrantanopia Achromatopsia Topographical agnosia 9

presence of apperceptive defect Unilateral (right)

and Impaired Abilities in Prosopagnosia Can

emotions Recognize faces as such Match faces Cannot

(semantics) Feel familiarity when viewing faces Show

Deficits Poor angular judgments Poor coordination of

10 Lesion Profile in Prosopagnosia Bilateral occipitotemporal Extent of damage determines presence of apperceptive defect Unilateral (right) occipitotemporal Examples from recent cases Spared and Impaired Abilities in Prosopagnosia Can Discriminate age Discriminate gender Recognize emotions Recognize faces as such Match faces Cannot Identify individuals Describe the owner of the face (semantics) Feel familiarity when viewing faces Show indirect knowledge about faces Dorsal Stream Deficits Poor angular judgments Poor coordination of movement in space Visuoconstruction deficits Unilateral neglect Topographic disorientation 10

11 Dorsal Stream (Parietal) Deficits 11

Clinical and Experimental Neuropsychology. Lecture 3: Disorders of Perception

Clinical and Experimental Neuropsychology Lecture 3: Disorders of Perception Sensation vs Perception Senses capture physical energy from environment that are converted into neural signals and elaborated/interpreted