Sensation on Perception

Perceptual Reorganization

The reuse of brain regions after its original purpose is lost, like the occipital lobe being used for processing music in blind people

Senses

Physiological systems that translate information about the environment and the body into neuronal signals

Olfactory system

Processes smells

What is the olfaction process?

1. Odorants enter the nasal cavity and are likely received by odor receptors in the mucous membrane of the roof of the nasal cavity

2. Odor triggers the neuron, and a signal is sent to the olfactory bulbs, called the glomeruli

3. The signal travels using the olfactory nerve to the primary olfactory cortex

4. Signals are then sent to the secondary olfactory area of the orbitofrontal cortex, and other brain regions like the thalamus, hypothalamus, hippocampus, and amygdala

Bipolar neurons

Neurons with appendages that extend from opposite sides of its cell body

What is special about the olfactory nerve?

It does not pass through the thalamus before arriving to the primary olfactory cortex

How do olfactory receptors read odorants?

We don’t know, but it is either the odor receptors or vibrations of odor molecules

Synesthesia

The union of two sensations, like hearing words and music in colors

Explanations for synesthesia

Axon connections between different regions of the brain, anatomical differences, and failure of the brain regions to properly expand during brain development

First three steps of audition

1. Sound waves enter the ear through the ear canal, which amplifies the sound waves

2. The waves hit the tympanic membrane/eardrum, which vibrates

3. The vibration travels through the middle ear, and rattles the malleus, incus, and stapes

Steps four through seven of audition

1. These vibrations cause the oval window to vibrate

2. This opens the door to the cochlea, where tiny hair cells (stereocilia) produce vibrations in the fluid of the cochlea

3. This sends an action potential to the cochlear nerve, sending a signal to the cochlear nucleus in the medulla

4. Axons then travel to the pons, where the split to the left and right olivary nucleus, which allows both ears to process sound

Steps eight through eleven of audition

1. Then signals move to the inferior colliculus in the midbrain, activating motor neurons

2. Axons from the pons branch to the nucleus of the lateral luminiscus in the midbrain, where timing of sound is processed

3. From there, signals descend to the MGN in the thalamus

4. This sends signals to the primary auditory cortex in the temporal lobe

How is the auditory cortex organized?

Tonotopically, or by frequency

Steps of Gustation

1. Papillae and taste buds capture taste sensations

2. Then signals are sent up the chorda tympani nerve, where it eventually joins the facial nerve

3. Then the nerve sends signals to the gustatory nucleus in the rostral region of the nucleus of the solitary tract in the brain stem

4. Signals are then sent to the primary gustatory cortex in the VPM nucleus of the thalamus

5. Secondary signals are sent to the orbitofrontal cortex for the integration of taste and smell

How many types of taste buds are there?

five: salty, sour, bitter, sweet, and umami

Nociceptors

Pain receptors

Process of Somatosensation

1. Somatoreceptors lie under the skin and take in sensory information

2. Receptors enter the spinal cord via the dorsal root

3. Some axons travel up the spinal cord to the medulla

4. Information is sent to the VPM of the cortex and cerebral cortex

5. Primary somatosensory cortex (S1) processes basic information

6. Secondary somatosensory cortex (S2) process complex information like texture

Process of vision

1. Light passes through the cornea and lens, hitting the retina

2. Passes through ganglion and bipolar cells towards rods and cones (photoreceptors)

3. Photons of light break apart photopigments, depolarizing the photoreceptor (rods and pins)

4. Signals are sent from the photoreceptor through bipolar cells to ganglion cells and out from the optic nerve

5. Optic nerve splits into two parts

6. 90% of axons go to the lateral geniculate nucleus

7. 10% goes to the pulvinar nucleus and superior colliculus (Midbrain)

8. Signals then sent to the primary visual cortex

What do rods process?

Dim light

What do cones process?

Daylight and color

Three types of cones

Red, blue, and green

Largest sensory nerve

Optic nerve

Where are cones distributed in the retina?

The fovea

Where are rods distributed in the retina?

Across the retina, but not in the fovea

What is cone’s connection to ganglion cells?

1:1

What is rod’s connection to ganglion cells?

Many to one

What part of the visual cortex processes motion?

The medial temporal area

Sense Organ

Collects input of stimulus, filters, and amplifes

Sensory pathways

Processes basic information and transfers it

Sensory cortex

High level processing

Lateral geniculate nucleus of the thalamus

Relay station of visual input for the cortex

Akinetopsia

Impairments in the ability to process motion (Patient MT)

Achromatopsia

Inability to process color and decipher shapes (Patient PT)