Fun

Principles of sensation & perception

Senses as (perception/action) systems

Source: Amazon

Source: Amazon

Source: Swanson

Source: Swanson

Source: Swanson, 2005

Source: Swanson, 2005

Smartphone as metaphor

  • Accelerometer
  • Gyroscope
  • Magnetometer
  • Proximity sensor
  • Ambient light sensor
  • Barometer
  • Thermometer
  • Mic
  • Camera
  • Radios (Bluetooth, wifi, cellular, GPS)

http://www.phonearena.com/news/Did-you-know-how-many-different-kinds-of-sensors-go-inside-a-smartphone_id57885

Perception/action system dimensions

  • Interoceptive
    • Body position, movement, posture
    • Internal status: hunger, thirst, arousal, discomfort/pain, etc.
  • Exteroceptive
    • Layout of environment, contents

Questions for interoception

  • Tired or rested?
  • Well or ill?
  • Hungry or thirsty or sated?
  • Stressed vs. coping?
  • Emotional state?

Questions for exteroception

  • Who/What is out there?
  • Animate/inanimate?
    • Conspecific (same species)/non?
    • Threat/non?
    • Familiar/un?
    • Mate/non? or Friend/not?
    • Food source/non
  • Where is it?
    • Distance
      • Proximal
      • Distal
    • Elevation, azimuth
    • Coordinate frames
      • Self/ego (left of me)
      • Object (top of object)
      • Allo/world (North of College)
  • Where moving?

Questions for action

  • What kind of response?
    • External
      • Move body
        • Approach/avoid/freeze
        • Signal/remain silent
        • Manipulate
    • Internal
      • Change physiological state
  • Speed, quality, direction of response

From world to brain

Realm Domain
\(W\) The world
\(B\) The body
\(N\) The nervous system
\(M\) The mind

Properties of the world

  • Behaviorally relevant conditions, events, and entities…
  • Generate patterns…
    • Chemical
    • Photic/electromagnetic
    • Mechanical/acoustic
  • That specialized sensors detect
  • Neural circuitry processes

More than 5 sensory channels

  • What is the energy/chemical channel?
  • Different energy/chemical channels carry different types of information
    • What is out there
    • Where it’s located
  • Different energy/chemical channels convey information at different rates
  • Information about behaviorally relevant dimensions often signaled by multiple sources

Vision

  • Source: Electromagnetic radiation
    • Reflected from surfaces
  • What is it?
    • Shape, size, surface properties (color, texture, reflectance, etc.)
    • Wavelength/frequency, intensity
  • Where is it?
    • Position: Left/right; up/down on retina
    • Near/far: retinal disparity, interposition, height above horizon…
    • Orientation, motion

Audition

  • Source: Mechanical vibrations in air or water
  • What is it?
    • Pattern of frequencies, amplitudes, durations
  • Where is it?
    • Left/right or up/down: Interaural time/phase, intensity differences, pinnae filtering
    • Motion: Frequency shifts via Doppler effect

Chemosensation

  • Source: Chemicals in mouth, nasal cavity
  • What is it?
    • Mixtures of chemicals
  • Where is it?
    • Left/right; up/down; near/far via intensity gradients

Somatosensation

  • Source: Thermal or mechanical stimulation (vibration/pressure) of skin
  • What is it?
    • Shape, size, smoothness, mass, temperature, deformability: Pattern of stimulation
  • Where it it?
    • Pattern of cutaneous receptors on skin

Interoception

  • Hunger/thirst
    • Receptors for nutrient, fluid levels
  • Energy levels
    • Receptors for hormones, NTs
    • ANS responses
  • Temperature
    • Receptors in skin, viscera
  • Mating interest
    • Receptors for hormones, NTs
    • ANS responses
  • Body position & movement (proprioception)
    • Receptors in muscles, joints, skin

Features of sensory signals

Change across time

  • Tonic (sustained) vs. phasic (transient) responses
  • Adaptation
    • Decline in sensitivity with sustained stimulation
    • Most sensory systems attuned to change

  • Information propagates at different speeds
    • Bigger diameter: Faster
    • Denser myelin: Faster

Detect repeating signals

  • In space (textures)
  • In time

Vision: Spatial frequency/contrast sensitivity

[[@Roark2019-fx]](http://dx.doi.org/10.1002/mnfr.201801053)

(Roark & Stringham, 2019)

Audition: Frequencies in sound

Compare (>1) sensors located in different parts of the body

  • Eyes
  • Ears
  • Skin surface
  • Nostrils
  • Tongue

Topographic maps

Auditory: Tonotopic maps

Visual: Retinotopic maps

[[@dougherty_visual_2003]](https://doi.org/10.1167/3.10.1)

(Dougherty et al., 2003)

Somatosensory: Somatotopic maps in S1 & M1

Sensivity non-uniform

Two-point touch thresholds

Somatosensory homunculus

Hearing thresholds non-uniform

http://auditoryneuroscience.com/

http://auditoryneuroscience.com/

Processing hierarchical/sequential AND parallel

Case study: Vision

Properties of Electromagnetic (EM) radiation

http://en.wikipedia.org/wiki/File:EM_Spectrum_Properties_edit.svg

http://en.wikipedia.org/wiki/File:EM_Spectrum_Properties_edit.svg

  • Wavelength/frequency
  • Intensity
  • Location/position of source
  • Reflects off some materials
  • Refracted (bent) moving through other materials
  • Information across space (and time)
http://apod.nasa.gov/apod/ap140605.html

http://apod.nasa.gov/apod/ap140605.html

  • Light provides fast (2.99 million m/s; 186 million mi/hr) information about surfaces at a distance
  • vs. sound (340 m/s; 767 mi/hr)
  • vs. chemical signals (min/mi)

Optic array specifies geometry of environment

Categories of wavelength specify perception of color

  • Eyes categorize wavelength into relative intensities within wavelength bands
  • RGB ~ Red, Green, Blue
    • Long, medium, short wavelengths
  • Color is a neural/psychological construct

The biological camera

part of a self-stabilizing system…

https://www.youtube.com/embed/JGArTWOJtXs

Parts of the eye

  • Cornea - refraction (2/3 of total)
  • Pupil - light intensity; diameter regulated by Iris.
  • Lens - refraction (remaining 1/3; focus)
  • Retina - light detection
    • ~ skin or organ of Corti in inner ear
  • Pigment epithelium - regenerate photopigment
  • Muscles - move eye, reshape lens, change pupil diameter

Geometry of retinal image

  • Image inverted (up/down)
  • Image reversed (left/right)
  • Point-to-point map (retinotopic)
  • Binocular and monocular zones

The fovea

http://www.brainhq.com/sites/default/files/fovea.jpg

http://www.brainhq.com/sites/default/files/fovea.jpg

  • Central 1-2 deg of visual field
  • Aligned with visual axis
  • Retinal ganglion cells pushed aside
  • Highest acuity vision == best for details
  • Acuity varies from center to periphery

http://michaeldmann.net/pix_7/blndspot.gif

http://michaeldmann.net/pix_7/blndspot.gif

What part of the skin is like the fovea?

Photoreceptors in retina detect light

  • Rods
    • ~120 M/eye
    • Mostly in periphery
    • Active in low light conditions
    • One wavelength range
  • Cones
    • ~5 M/eye
    • Mostly in center
    • 3 wavelength ranges
https://foundationsofvision.stanford.edu/

https://foundationsofvision.stanford.edu/

http://cnx.org/content/col11496/1.6/

http://cnx.org/content/col11496/1.6/

Photoreceptor physiology

  • Outer segment
    • Membrane disks
    • Photopigments
      • Sense light, trigger chemical cascade
  • Inner segment
    • Synaptic terminal
  • Light hyperpolarizes photoreceptor!
    • The dark current

Retina

  • Physiologically backwards
    • How?
  • Anatomically inside-out
    • How?

Retina

  • Physiologically backwards
    • Dark current
  • Anatomically inside-out
    • Photoreceptors at back of eye
http://www.retinareference.com/anatomy/

http://www.retinareference.com/anatomy/

  • Information flows…
    • From photoreceptors…
    • To Bipolar cells
      • <-> and Horizontal cells
    • To Retinal ganglion cells
      • <-> and Amacrine cells
    • To cerebral cortex

Center-surround receptive fields

  • Center region
    • Excites (or inhibits)
  • Surround region
    • Does the opposite
  • Bipolar cells & Retinal Ganglion cells ->
  • Most activated by “donuts” of light/dark
    • Local contrast (light/dark differences)

Opponent processing

http://www.visualexpert.com/sbfaqimages/RGBOpponent.gif

http://www.visualexpert.com/sbfaqimages/RGBOpponent.gif

  • Black vs. white (achromatic)
  • Long (red) vs. Medium (green) wavelength cones
  • (Long + Medium) vs. Short cones
  • Can’t really see reddish-green or bluish-yellow
    • “Oppose” one another at cellular/circuit level
    • DEMO

From eye to brain

  • Retinal ganglion cells
  • 2nd/II cranial (optic) nerve
    • Optic chiasm (\(\chi\) - asm): Partial crossing of fibers
    • Nasal hemiretina (lateral/peripheral visual field) cross
    • Left visual field (from L & R retinae) -> right hemisphere & vice versa
  • Lateral Geniculate Nucleus (LGN) of thalamus (receives 90% of retinal projections)
  • Hypothalamus
    • Suprachiasmatic nucleus (superior to the optic chiasm): Synchronizes day/night cycle with circadian rhythms
  • Superior colliculus & brainstem

LGN

  • 6 layers + intralaminar zone
    • Parvocellular (small cells): chromatic
    • Magnocellular (big cells): achromatic
    • Koniocellular (chromatic - short wavelength?)
  • Retinotopic map of opposite visual field

From LGN to V1

  • Via optic radiations
  • Primary visual cortex (V1) in occipital lobe
  • Create “stria of Gennari” (visible stripe in layer 4)
  • Calcarine fissure (medial occiptal lobe) divides lower/upper visual field

Human V1

[[@dougherty_visual_2003]](http://dx.doi.org/10.1167/3.10.1)

(Dougherty et al., 2003)

  • Fovea overrepresented
    • Analogous to somatosensation
    • High acuity in fovea vs. lower outside it
  • Upper visual field/lower (ventral) V1 and vice versa

Laminar, columnar organization

  • 6 laminae (layers)
    • Input: Layer 4 (remember stria of Gennari?)
    • Output: Layers 2-3 (to cortex), 5 (to brainstem), 6 (to LGN)
  • Columns
    • Orientation/angle
    • Spatial frequency
    • Color/wavelength
    • Eye of origin, ocular dominance
https://foundationsofvision.stanford.edu/wp-content/uploads/2012/02/dir.selective.png

https://foundationsofvision.stanford.edu/wp-content/uploads/2012/02/dir.selective.png

From center-surround receptive fields to line detection

[[@panichello_predictive_2013]](http://dx.doi.org/10.3389/fpsyg.2012.00620)

(Panichello, Cheung, & Bar, 2013)

Beyond V1

  • Larger, more complex receptive fields
  • Dorsal stream (where/how)
    • Toward parietal lobe
  • Ventral stream (what)

What is vision for?

  • What is it? (form perception)
  • Where is it? (space perception)
  • How do I get from here to there (action control)
  • What time (or time of year) is it?

References

Dougherty, R. F., Koch, V. M., Brewer, A. A., Fischer, B., Modersitzki, J., & Wandell, B. A. (2003). Visual field representations and locations of visual areas V1/2/3 in human visual cortex. Journal of Vision, 3(10), 1–1. https://doi.org/10.1167/3.10.1
Panichello, M. F., Cheung, O. S., & Bar, M. (2013). Predictive feedback and conscious visual experience. Perception Science, 3, 620. https://doi.org/10.3389/fpsyg.2012.00620
Roark, M. W., & Stringham, J. M. (2019). Visual performance in the “real world”: Contrast sensitivity, visual acuity, and effects of macular carotenoids. Molecular Nutrition & Food Research, 63(15), e1801053. https://doi.org/10.1002/mnfr.201801053
Smith, G. E., Chouinard, P. A., & Byosiere, S.-E. (2021). If I fits I sits: A citizen science investigation into illusory contour susceptibility in domestic cats (felis silvestris catus). Applied Animal Behaviour Science, 240, 105338. https://doi.org/10.1016/j.applanim.2021.105338