Studied by 45 people
sensation
receiving, collecting and amplifying information from the environment
initial phase
sensory organs
input
perception
interpreting/organizing information so that we can understand and react to it
later phase/output
what are the main characteristics of sensory pathways?
starts with receptors of specialized sensory organs
involves key nerves in peripheral nervous system
includes synapses with brain stem nuclei
routed/processed by thalamus
dedicated cortical areas
sensory organs
specialized receptors attached to neurons
neurons send signals into the brain
how do neurons encode information?
through firing rate
firing rate
related to nature of the stimulus and duration of its application
as it is prolonged there will be rate adaptation
rate adaptation
with prolonged stimulation rate will increase or decrease
common in sensory neurons
what is an example of adaptation in sensory systems?
fine touch is fast while pain is slow
what is the nerve associated with olfaction?
the olfactory nerve
what is the nerve associated with vision?
the optic nerve
what is the nerve associated with hearing?
vestibulocochlear nerve
what nerves are associated with taste
facial nerve
glossopharyngeal nerve
vagus nerve
what are the touch nerves
various cranial and spinal nerves
what is the primary olfactory area called?
pyriform cortex
what is the secondary olfactory area called?
orbitofrontal cortex
what is the primary cortex of taste called?
insula
where at the primary and secondary areas of hearing located?
in the temporal cortex
where are the primary and secondary areas of tactile perception located?
parietal cortex
where are the primary and secondary areas of vision located?
in the occipital cortex
topographic representation
high and low frequency on different cells
lateralization representation
left visual fields on right visual cortex
disproportionate representation
representation is linked to adaptive utility not size
what is an example of adaptive utility
more representation for hands than for legs
neuroplasticity
ability to form and reorganize synaptic pathways based on experiences like injury
what is the importance of olfaction?
survival (threat warning and social behavior)
response without awareness
emotional tears don’t have discernable odor but influence behavior
olfactory pathway
Bipolar Receptor > Glomerulus > Olfactory nerve > Primary Olfactory Cortex (Pyriform) > Secondary Olfactory Cortex (OFC)
olfactory receptors
detect volatile odorants
Shape/Docking Theory
odorants activate receptors that are responsive to their shape (in relation to chemical structure
odor compound may contain many chemicals and may then activate a compliment of receptors
what are the defining characteristics of the human olfactory system?
smaller olfactory bulb relative to brain volume
fewer coding proteins
no readily identifiable pheromones
non coding olfactory genes
learn some olfactory guided behaviors w/training
don’t use sense of smell to the fullest extent
anosmia
loss of sense of smell
taste buds
contain gustatory cells that have receptors responding to taste molecules
Umami
mediation of sweet and bitter tastes by activity of G-protein coupled receptors
what kind of channels are sour and salty tastes linked to?
ion channels
particularly for H+ and Na+ ions
is spice a taste?
argued to be more of a tactile sensation than a taste
what chemicals is spice linked to?
capsaicinoids
how do capsaicinoids signal spice?
they activate transient receptor potential cation channel subfamily V member1 (TRPV1) receptors
found on tongue and other parts of the body
what unit measures heat?
Scoville units
Taste Pathway
Taste cells > Bipolar neurons > Cranial nerves (7, 9, 10) > Brainstem Structures > VPM Thalamus > Primary Gustatory Cortex (Insula)
from insula, input might also be sent to the secondary olfactory cortex
what type of taste has the highest sensitivity?
bitterness
what is the range for the visible spectrum?
700 to 400 nm
photoreceptors
rods and cones that are responsive to the presence of light
rods
function well in low light + are used in scotopic conditions
night vision
cones
function well in phototropic conditions and are responsible for high acuity and color vision
what is the effect of cones dysfunction?
color blindness
what is the other name for Trichromatic Color Theory?
Young-Helmholtz Theory
Trichromatic Color Theory
every color is a combination of three colors (and maybe activity of three different cones)
Opponent Process Color Theory
contrasting color signals
explains after images
retinotopic mapping
different visual field region, different cortical region
spectral sensitivity curve
graph of the perceived brightness of the same wavelength under scotopic conditions and photopic conditions
what does the spectral sensitivity curve look like in the dark?
blue looks brighter than yellow
what does the spectral sensitivity curve look like in yellow light?
yellow looks brighter than blue
color constancy
subjective perception of a color remains constant under varying illumination conditions
visual system adjusts perception of color in a scene based on perceived illumination of that scene
what is an example of color constancy
dress illusion
light plays a role in perception of color
visual pathway
• Photoreceptors > Optic Nerve > Thalamus (Lateral Geniculate part) > Visual Cortex
frequency and pitch perception
rate at which sound wave vibrate measured as cycles per second (Hz)
amplitude and perception of loudness
intensity of sound is usually measured in dB
Complexity and timbre (perception of sound quality)
allows us to distinguish tones
Fundamental Frequency
perceive the pitch that is related to the greatest common divisor
sometimes its not even present in the combination of waves
applies to combos above 50 Hz
auditory pathway
auditory nerve > cochlear nuclei > superior olivary nucleus > inferior colliculus > medial geniculate nucleus of the thalamus > primary auditory cortex
tonotopic mapping
different frequencies , different regions of the cortex
pain
adaptive response to identify danger and withdraw
insensitivity is associated with high risk for injury + early mortality
what are the components of the pain network?
PFC
anterior cingulate cortex
insula
somatosensory cortex
associated with individual differences
why is rubbing the affected area an effective pain response?
transmission of touch information modulates transmission of nociceptive information
gate control theory
tactile stimuli will modify the pain stimuli form the activation of the pain pathway
occurs by unmyelinated fibers
touch activation inhibits pain processing
how is nociceptive information transmitted?
ascending spinothalamic tract and modulated by descending inputs
what are the vital parts of the pain pathway?
periaqueductal gray and rostroventral medulla
what is the motor sensory pathway?
primary motor cortex of the frontal lobe (upper motor neurons
motor neurons axons form motor tracts, (evident in midbrain and medulla
tracts synapse with lower motor neurons in the spinal cord which affects muscle activity
prefrontal cortex
planning
premotor cortex
sequence organization
coordinating motor actions
lesions would impair this ability
primary motor cortex
initiates voluntary movement (has the homunculus)
mental rehearsal/visualization
imaging movement produces similar pattern of brain activity in the frontal cortex as planning actual movement
M1: movement repertoire
part of the cortex for jumping or grasping (based on 1 brain region 1 movement involving many body parts in a particular way)
M1: Homunculus
1 brain region for 1 body part (popular theory)
efferent
motor and descending pathways
afferent
sensory and ascending pathways
what tracts are part of the sensory pathway?
dorsal column medial lemniscus system
spinocerebellar tracts
anterolateral system
what tracts are part of the efferent pathways?
pyramidal tracts
extrapyramidal tracts
what are the two division of the corticospinal tract?
lateral corticospinal tract
anterior corticospinal tract
lateral corticospinal tract
carries commands for movement of distal muscles (limbs + digits)
anterior corticospinal tract
carries commands for movement of the body’s midline (proximal muscles)
basal ganglia
movement coordinating network
striatum (caudate + putamen)
globus pallidus ( internal and external)
subthalamic nucleus
substantia nigra
what is the effect of basal ganglia dysfunction in disease?
parkinson’s disease
What happens in Parkinson’s disease?
loss of dopaminergic neurons in the substantia nigra
DA neurons
dopaminergic neurons
role in refining movement
cerebellum
role in posture, balance and coordination
has a representation of every body part (similar to motor homunculus
assist in adapting learned movements
Note 
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