PSY290 - Sensory and Motor Function

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