Perception Exam 1

Bottom up processin

processing of sensory info as it comes into the sensory system. Raw info, data driven.

Top down processing

interpretation of sensory info depends on prior info, expectations, context, understanding. Behavior is influenced by perceptual data. ex. walking around in the dark

perception

cognitive processes by which the brain organizes and interprets sensationto give meaning and context to sensory input, influencing our understanding of the environment.

sensation

energy from environmental stimulus activates specialized receptor cells in the sense organ

capsaicin

chemical that stimulates the somatosensory system, especially heat and pain receptors in our mouths and eyes

method of limits

stimuli are presented on a graduated scale and participants must judge the stimuli along a certain property that goes up or down. y= they detect stimulus. n=they dont detect stimulus.

psychophysical scale

one way in which people rate their physiological experiences as a function of the level of a physical stimulus.

absolute threshold

smallest amount of stimulus necessary to allow an observer to detect its presence

difference threshold

smallest difference between two stimuli that can be detected

ascending series

stimulus gets increasingly larger

descending series

stimulus gets increasingly smaller

cross over point

point in which people begin to detect a stimulus/not detect

2 point touch threshold

minimum distance along the skin at which two touches are perceived as two not one

method of adjustment

observer controls the level of stimulus and adjusts to be at perceptual threshold

point of subjective equality (PSE)

designates the setting of two stimuli at which the observer experiences them as identical

sensitivity

ability to perceive a particular stimulus, inversely related to threshold

magnitude estimation

psychophysical method where participants judge and assign numerical estimates to the perceived strength of a stimulus

response compression

as the strength of a stimulus increases so does the perceptual response but the response increases less that stimulus

response expansion

as the strength of the stimulus increases, the perceptual response increases even more

catch trial

trial where the stimulus is not present to check for honesty and accuracy

force choice method

subject reports either when the stimulus occurred or where it occurred

signal detection theory

in every sensory detection or discrimination there is both sensory sensitivity to the stimulus and a criteria used to make a cognitive decision

false alarm

mistakes a nonsignal for active signal

miss

incoming signal is not detected

psychophysics

study of relationship between physical stimuli and resulting sensations and perception (oldest problem of philosphy and psychology)

3 primary issues with perception

1. detection (sensitivity): how much energy is needed to result in a sensory experience

2. discrimination: how much energy is needed to detect change?

3. intensity: what is the relationship between physical magnitude and perceived intensity?

optic apraxia

inability to use vision to guide hand to object

ocular motor apraxia

difficulty in controlling eye movement, greatly rediced spatial localization

simultagosnia

inability to percieve more than one object at a time

balint syndrome

disorder of spatial and visual abilities due to bilateral parietal lobe lesions

volatile

stimulus that gives off vapors. must be water and fat (lipid) soluble

nasal cycle

rythmic, alternating side to side fluctuation in nasal airflow. Changes periodically (45 mins to couple hours). Helps prevent adaptation (reduced reaction to stimulus). Parallels ultraradian rythms of hemisphere activity

Olfactory epithelium

postage stamp size region at top of nasal cavity surrounded by respitory epithelium. Contains olfactory receptors: neurons specialized to repsond to odor molecules. About 10 mil receptors embedded in supporting cells.Only brain nuerons that regenerate on a consistent basis (6-8 weeks).

olfactory cilia

olfactory receptors terminate in cilia which are actual receptor sites, microscopic hair cells

olfactory transduction process

Odor molecules bind to specific proteins which form outer membrane of cilia (lock and key). Activates second messenger system which generates action potentials.

1. Receptor activates G protein

2. G protein activates adenylate cyclase

3. Adenylate cyclase converts ATP to cAMP

4. cAMP opens a gated channel causing depolarization

Olfactory axons

Olfactory receptors perform both transduction and and reception. Form olfactory nerve (1st cranial nerve). Axons from receptors synapse onto glomeruli of olfactory bulb (1000:1 reduction)

lateral olfactory tract

a bundle of nerve fibers that carries smell signals directly from the olfactory bulb to the primary olfactory cortex in the brain. Has many diffuse connections to other parts of the brain.

Secondary Olfactory Cortex/ Orbitofrontal Cortex

integrates smell with taste

Primary olfactory cortext

Includes piriform cortex and entorhinal cortex. Smell perception.

limbic system

emotion

hippocampus

memory

medial dorsal nucleus of thalamus

slight connection to olfaction. Medial dorsal nucleus of the thalamus that acts as a major relay and integration hub for the prefrontal cortex

anosmia

complete loss of smell. More common than loss of taste because the transmission to the brain only happens in one cranial nerve (olfactory nerve). Can also be caused by head trauma, nasal sinus diseases, upper respritory infections

Coding in Olfactory system

Duration: limited because of adaptation, periodic nature of odors

intensity: number and rate of neurons firing

location: poorly identified because no internasal comparison

type: can identify over 10,000 odors

Stereochemical theory of olfaction

Structure of odorant determines activity (like neurotransmitters). We should be able to predict odor on basis of shape of odor molecule, except enantiomers prevent this from being true.

Specific anosmias

Inability to smell a particular odor with otherwise normal sense of smell. Most are odors with biological relvance

Linda Buck: Coding for type

Cloned olfactory receptors in rats. Found that only 350-400 are operational and each receptor is activated by many similar odorant structures. Each olfactory neuron expresses only one olfactory receptor protein and makes single connection to a single glomerulus bulb. Combinations of receptor activation determines odor perception (cross-fiber patterning).

Vomeronasal system

second (accessory) olfaction system in many species. Vomeronasal Organ (VNO). Energy is non volatile chemical stimuli. Receptor site at base of nasal cavity and connects to accessory olfactory bulb. Detects pheremones and can trigger flehmen response.

Human pheremones

Human VNO is jacobsons organ. Limited evidence supporting it’s existence, no evidence supporting its fuction

Primary tastes

Sweet: organic (carbon based) molecules= energy

salty: compounds that break into 2 ions (Na Cl), CRITICAL for fuctioning

bitter: typically nitrogen, closely related to sweet

sour: acids that break into ions

umami: monosodium glutamate (MSG)

Gustatory Transduction

taste buds contain specialized gustatory receptor cells for transduction of taste stimuli (on papillae)

-9000 to 10000 buds

• found on papillae (small elevations on tongue)

• average life is around 10 days

• terminate on microvilli for chemical contact (hair cells)

• found throughout oral cavity: tongue, soft palate, esophagus, cheeks, epiglottis.

Circumvallate papillae

large circular structure, back of tongue

foliate papillae

series of folds, sides on tongue

fungiform

looks like tiny mushrooms, anterior part of tongue, visible

filiform

anterior portion of tongue, NO TASTE FUCTION

Gustatory transition to brain

Multiple nerve innervation is why ageusia is rare.

3 major cranial nerves:

• chorda tympani=anterior 2/3 of tongue

• glossopharyngeal= posterior 1/3 of tongue

• vagus= back of throat and epiglottis

Nucleus of solitary tract in Medulla

Part of gustatory transmission to brain. Regulates homeostatic mechanisms, including breathing and heart rate. Hunger/satiety from GI tract synapse here (glutamate). controls gag relex.

Insula

contains gustatory cortex in the lateral sulcus. Integrates taste with oral signals (texture, temperature, trigeminal). Processes taste and codes for intensity. Works with the orbitofrontal cortex and olfactory system to turn simple tastes into perceived flavors.

cingulate cortex

Collar shaped region in cerebral cortex (emotion and motivation, cognitive control, memory and self). This controls how we emotionally react to sensations and is a warning sign with trigeminal sense.

somatosensory cortex in parietal lobe

body sensation, where body is, sensory integration

epithelial cells

50-100 per taste bud, registers and responds to different molecules in food. Must synapse to sensory neurons that carry info to brain.