Understanding sensory-motor integration

ORGANIZATION OF SENSORY SYSTEMS: General perspectives

• Sensori-motor integration

• External senses

• Localize/Detect and monitor change

• Less sensitive to unchanging stimuli

• Tuned…sense modes

Organization of sensory systems

• Sense organs• Receptors-specificity and transduction

– Receptive fields- and limitations• coding- labeled lines vs pattern coding• Adaptation and suppression

• Neural relays and recoding• Intra-modality sensory Convergence• Cortical representation/ perception• Sensory subsystems

The Visual System

Tracing the ccts of vision

Organization of sensory systems

• Sense organs• Receptors-specificity and transduction

– Receptive fields- and limitations• Adaptation and suppression• coding- labeled lines vs pattern coding

• Neural relays and recoding• Intra-modality sensory Convergence• Cortical representation/ perception• Sensory subsystems

The organ of vision

The eye is like an SLR camera

Like a camera

• Lens-focus

• Iris-light control (aperture)

• Photoreceptors- transduction of light info (Light sensitive film)

The lens-a small point of interest

Like a camera-lens is curved

• Upside-down and inverted

Like a camera- Control of eye movement also critical

Eye movement- 3 major types of movement that can affect vision

Pursuit/tracking

Saccades

vergence

Organization of sensory systems

• Sense organs

• Receptors-specificity and transduction– Receptive fields- and limitations– Adaptation and suppression– coding- labeled lines vs pattern coding

• Intra-modality sensory Convergence• Neural relays and recoding• Cortical representation/ perception• Sensory subsystems

Sensitivity and Limitations of the visual system: visible light spectrum

Organization of sensory systems

• Sense organs• Receptors-specificity and transduction

– Receptive fields and limitations

– Adaptation and suppression– coding- labeled lines vs pattern coding

• Intra-modality sensory Convergence• Neural relays and recoding• Sensory subsystems• Cortical representation/ perception

The Iris

• Controls light exposure

Organization of sensory systems

• Sense organs• Receptors-specificity and transduction

– Receptive fields- and limitations

– Adaptation and suppression– coding- labeled lines vs pattern coding

• Intra-modality sensory Convergence• Neural relays and recoding• Sensory subsystems• Cortical representation/ perception

The retina-photoreceptive tissue

Visual field and retino-topic organization

More on the retina

Photoreceptors

Rods and Cones

Receptive fields and Coding

RODS- dark/low illuminationsensitive to movementperipheral vision

CONES- High illuminationsensitive to colorfoveal vision

ROD CONE DISTRIBUTION

FOVEA

FOVEA and optic disc/blind spot

Foveal acuity

Retinal circuitry

NOTE:

• Light passes through ganglion cell layer, and bipolar cell layer before striking photoreceptors ( light transparent).

• Activation of photoreceptor activats cct in reverse direction.

What accounts for Foveal acuity

Accounting for Foveal Accuity1. Cone properties2. Circuitry

Color Coding in cones

The Trichromatic Theory of color

Receptive fields of Ganglion cells

Set up for sensory evoked recording

Sensory convergence

Retinal photoreceptors corresponding to Ganglion cell

receptive fields

Purpose of ganglion cell receptive fields?

Lateral inhibition?

Lateral inhibition

Overlapping receptive fields contribute to lateral inhibition

The center of one field may be the surround of another

Retina ganglion cell axons coalesce

…and leave eye chamber to form the optic nerve

From retina to cortex

Decussation at optic chiasm

Decussation-crossing over..how does this work?

Partial decussation at optic chiasm

Decussation-crossing over

Not as simple as left and right eye

Decussation of visual field info

Temporal retina

Nasal Retina

-Nasal Retinal Fibers Cross-Temporal fibers do not

Retinotopic-Cortical representation

-Left and right visual field info-upside down-Foveal dominance

Cortical Organization- LGN input at layer 4

Vertical processing

Set up for sensory evoked recording

Remember sensory convergence

Receptive fields of neurons in the PVC-orientation specificity

Orientation specificity

Orientation modules:Sensory-evoked recording studies

Modules- orientation specific columns plus PVC “blobs”

Diagnosing/predicting visual deficits

What happens if the entire PVC is damaged?

Blind sight/ Superior Colliculi

• http://video.google.com/videosearch?hl=en&rls=GGIC,GGIC:2007-01,GGIC:en&ei=KD1bSsuNMJKKMe-c7EI&resnum=0&q=blindsight&um=1&ie=UTF-8&sa=N&tab=wv#

• Other visual subsystems

-SCN

-Pineal gland

Suprchiasmatic Nucleus-Circadian Rhythms

Pineal Gland-”the third eye” and Infradian rhythms

Secretor cells of the pineal gland

Produce melatonin

OK… so what happens next?

VENTRAL STREAM

• Object Recognition– Visual agnosias– Prosopagnosia– Anosagnosia

– http://video.google.com/videosearch?q=ramachandran+synesthesia&www_google_domain=www.google.com&hl=en&emb=0&aq=4&oq=ramachandran#q=ramachandran+imposter&hl=en&emb=0

prosopagnosia

• Dorsal Sream-

• WHERE/ CONTEXT/SPACE

– Balints– Movement agnosia– Visual Sensory neglect

Balint’s syndrome and Simultagnosia

• Balint's syndrome is a neuropsychological disorder that results from damage to both parietal lobes77. Clinically, it includes three main symptoms: simultanagnosia (the inability to see more than one object at a time); optic ataxia (the fixation of gaze with severe problems in voluntarily moving fixation); and optic apraxia (the inability to reach towards the correct location of perceived objects)78

• Spatial-visual agnosia

Visual hemilateral neglect

Putting the Visual World into perspective: The DLPFC

Synesthesia and the DLPFC?

• http://science.discovery.com/videos/when-senses-collide-origins.html

• Synesthesia

• Check it out Dawgs!

Sensori-Motor Integration