Neuroscience unit 2

auditory

auditory

the cerebral commissures

language

brain damage produced defecit in the ability to produce or comprehend language - left hemisphere damage/Broca's area

inferior prefrontal cortex

associated with left hemisphere damage, but the symptoms are bilateral. difficulty performing movements when asked to perform them out of context

language, voluntary movement

the function of the corpus callossum is to transfer learned information between hemispheres. when it is cut, each hemisphere can function independently. one hemisphere working alone can learn simple tasks as rapidly as two. transferring the eye patch, however, tested the other hemisphere and performance immediately dropped

the means by which the two hemispheres communicate through indirect pathways through the brain stem/external route

• left: words, letters
• right: faces, geometric patterns, emotional expression

• left: language sounds
• right: nonlanguage sounds, music

a cognitive approach/hypothetical neuronal mechanism that asseses patterns of events and tries to make sense of them

temperature and pain

pinna, ear canal, tympanic membrane

• DCMLS: touch and proprioception
• Anterolateral system: temperature and pain

• pacinian corpuscles: rapid response, deeper pressure
• Ruffini corpuscles: slower response, shallow pressure
• Merkel's disks slower response, stretching

Broca's area

left

emotions

linguistic

• alexia: inability to read
• agraphia: inability to write

posterior to wernicke's area, comprehending language related visual input

damage to the pathway connection Broca's and Wernicke's area (arcuate fascilculus). difficulty repeating words that had just been heard, although comprehension and spontaneous speech would be intact

angular

primary motor

primary visual

angular

primary auditory

• lack of attention to the left half of things
• neglect usually dissipates over a few months
• right parietal lobe damage

complementary afterimages

reflectance

cytochrome oxidase

striate cortex

blind spot

fovea

photopic

optic chiasm

rhodopsin

convergence

association

• 1. hierarchical organization
• 2. functional segregation
• 3. parallel processing

ossicle

auditory vestibular

cochlear

localization

posterior parietal lobe

auditory

somatosensory system

somatosensory

olfactory

gustatory

rods: 120 million/abundant in PERIPHERAL retina/best for low light conditions/detect brightness and movement/low acuity

cones: 6 million/abundant in fovea/best for bright light conditions/detect color/high acuity

• magnocellular: lower two layers of LGN
• parvocellular: top 4 LGN layers
• koniocellur: ventral to each layer

• the area of sensory cortex that receives most of its input directly from
• the thalamic relay nuclei of that system. For instance, the primary visual
• cortex is the area of the cerebral cortex that receives most of its input from
• the lateral geniculate nucleus of the thalamus.

• comprises the areas of the sensory cortex that receive most
• of their input from the primary sensory cortex of that system or from other
• areas of the secondary sensory cortex of the same system.

• any area of cortex that receives input from more than one sensory
• system. Most input to areas of association cortex come from areas of secondary
• sensory cortex.

• ystems in which information flows through the components over multiple
• pathways. Parallel systems feature parallel processing, the simultaneous analysis
• of a signal in different ways by the mulitpl eparallel pathways of a neural
• network.

• the area of frontal lobe cortex that lies just in front of the face area of the primary motor cortex. in the left hemisphere it is the location of brocas area.
• anatomical assymetry b/w hemispheres

posterior region of lateral fissure; role in comprehension of language (wernicke's area)

lateral fissure anterior to planum temporale in temporal lobe- location of primary auditory cortexes

vibrations in stapes trigger vibration sof the oval window, which transfers vibration to the fluid of the cochlea. teh cochlea has an internal membrane called the organ of corti

auditory receptor organ

• basilar membrane: auditory receptors are mounted here
• tectorial membrane: rests on the hair cells

vibrations of cochlear fluid are dissipated by round window, as elastic membrane in cochlea wall

receptive orans of the vestibular system, which carries information about the direction and intensity of head movements, maintainting balance

axons of each auditory nerve synapse in the ipsilateral cochlear nuclei, from which many projections lead to the superior olives on both sides of the brain stem at the same level the axons of the olivary neurons project via the lateral lemniscus to the inferior colliculi, where they synapse on neurons that project to the medial geniculate nuclei, which project to the primary auditory cortex. signals are transmitted to both ipsilateral and contralateral cortices.

receives input from medial geniculate nucleus, located in temporal lobe, within lateral fissure. surround by "belt" of secondary cortex.

functional columns. all neurons encountered tend to respond optimally to same-frequency sounds; organized tonotopically, on the basis of frequency

association cortex: prefrontal cortex and posterior parietal cortex

• complicated because most auditory cortex is in the lateral fissure; few permanent hearing deficits following lesions. system is partially contralateral.
• -conductive deafness: ossicle damage
• -nerve deafness: cochlea/auditory nerve

simplest cutaneous receptors; neuron endings with no specialized structures. sensitive to temperature change and pain

• dorsal column medial lemniscus system: touch and prioception
• -enter via a dorsal root
• -ascend ipsilaterally in dorsal columns
• -synapse in dorsal column nuclei of medulla
• -decussate and ascend in medial lemniscus to contralateral ventral posterior nucleus of thalamus
• -also input from trigeminal nerve
• -most neurons project to primary somatosensory cortex

anterolateral: pain and temporature

posterior parietal cortex: respond to activation of 2 different sensory systems (somatosensory and visual)

a scotoma covers half the visual field

1. asterognosia: inability to recognize objects by touch

2. asomatognosia: inability to reconize parts of one's own body (unilateral-left side) damage to right posterior parietal

• 1) adaptiveness of pain: important for survival
• 2) lack of clear cortical representation of pain- areas of activation vary from person to person. removal of somatosensory cortex to not change the threshold for pain.
• 3) descending pain control: pain can be supressed by cognitive and emotional factors

ability of cognitive and emotional factors to block pain; signals coming from brain can activate neural gating circuits in spinal cord to block incoming pain signals

anterior cingular cortex (cortex of anterior cingulated gyrus) -EMOTIONAL reaction to pain rather than the perception of pain itself

olfaction and gustation; function is to mnitor the chemical content of the environment.

chemicals that influence the physicology and behavior of others in the same species

upper part of the nose, dendrites in nasal passages. axons pass through skull enter olfactory bulbs, synapse on neurons thea tproject via olfactory tracts to the brain

each olfactory receptor cell contains only one type of receptor protein molecule. receptors are scattered throughout olfactory mucosa,

• medial/temporal lobes
• AMYGDALA
• PIRIFORM CORTEX

Thalamus

• 1) projects diffusely to limbic system
• 2) projects via medial dorsal nuclei to orbitofrontal cortex

• taste receptors (clusters of 50) located around papillae
• do not have their own axons; each neuron that carries impulses away from ataste bud receives input from many receptors

• anosmia: inability to smell
• ageusia: inability to taste

we can only perceive a small amount of the many stimuli that excite our sensory organs at any time; ignore the rest

• wavelength: perception of color
• intensity: perception of brightness

difference in position of the same image on two retinas

• -receptors
• -horizontal cells
• -bipolar cells
• -amacrine cells
• -retinal ganglion cells

axons project across teh inside of th retina before gathering in a bundle and leaving eyeball (through blind spot)

lateral communication: communication across the major channels of sensory input

light reaches receptors after passing through the other four layers, then the message goes back through the layers to the retinal ganglion cells, then through those axons in a bundle out of the eyeball

• 1) incoming light is distorted by retinal tissue it has to first pass through
• -fovea helps: indentations specialized for high acuity, retinal ganglion layer in very thin here
• 2) for bundle of retinal ganglion axons to exit eyeball t here must be a blind spot
• -completion: filling in. visual system fills in gaps in retinal images

how we perceive surfaces; visual system extracts information about edges and fills it in

retinal ganglion cells may receive signals from hundreds of diff. rods, but signals from only a few cones. effect of dim lighting stimulating tons of rods can summate in the firing of a retinal ganglion cell when the same stimulation in cones does not summate to the same degree

• only cones in fovea, no rods
• more rods in nasal hemiretina than temporal hemiretina

lights of same intensity but different wavelengths differ in brightness due to visual system not being equally sensitive to all wavelengths in the visual spectrum

• a graph of the relative brightness of lights of the same intensity at different wavelengths
• -visual system is most sensitive to wavelengths (yellow, bright warm colors) - will look the brightest
• -in scotopic conditions, most sensitive to cool blue/violet colors

• before dusk, yellow and red flowers seem brighter than blue ones
• at night, blue flowers seem brighter than yellow

eyes continuously scan the visual field, and our visual perception at any instant is the summation of recent visual information (TEMPORAL INTEGRATION)

• tremor
• drifts
• saccades: small jerky movements
• visual neurons respond to change

• g protein receptor responding to light rather than neurotransmitters.
• rods are in darkness: sodium channels are partially open which keeps them slightly depolarized, allows a steady flow of excitatory glutamate to come from them
• light: series of events closes sodium channels and hyperpolarizes the rods, reducing release of glutamate

• conduct signals from each retina to primary visual cortex via lateral geniculate nuclei of the thalamus
• 90 percent of axons become part of RGS pathways; no other sensory system has such a predominant pair of pathways

6 layers, each layer receiving input ffrom all parts of the contralateral visual field (three from one eye, three from the other)

• RGS system
• each level of the system is organized like amap of the retina
• disproportionate representation of the fovea in the Primary visual cortex (25 %)

• two parallel channels of communication through each LGN
• parvocellular: small cell bodies
• -top 4 layers
• -fien pattern details
• -stationary, slow moving objects
• -CONES

• M layers
• bottom two
• movement
• RODS

• define extent and position of objects
• perception of contrast between two adjacent areas of visual field
• LATERAL INHIBITION
• mach bands

• -receptive fields in th efoveal area of the retina were smaller than the periphery, consistent with high-acuity in fovea
• -all neurons have circular receptive fields
• -all neurons were monocular (field in one eye)
• -excitatory and inhibitory area

respond to degree of brightness contrast between 2 areas in receptive field

• 1) characteristics of receptive fields can be attributed to flow of signals from neurons with simpler receptive fields to more complex. on center/off center in lower layer IV---simple cells---complex cells
• 2) primary visual cortex neurons are grouped in functional vertical columns

alternating areas of left eye and right eye dominance

• -research on reactions to simple stimuli cannot provide a complete explanation of how visual system works
• visual neurons are plastic, capable of changing structure/function
• -receptive field properties of each neuron change with the elements in the scene

• three different types of cones, each with a differetn spectral sensitivity
• color of stimulus is encoded byt he ratio of activity in three kinds of receptors
• three is the minimum number of different wavelengths needed to match every color

• two different classes of cells- BRIGHTNESS v COLOR
• each classes encoded two complementary color perceptions
• -red: hyperpolarization green:hypopolaraization
• complementary colors: produce white or gray when combined in equal measures

perceived color of an object is not a simple function of the wavelengths reflected; its the tendency for an object to stay the same color despite changes in the waelengths of light that it reflects

color of an object is determined by its reflectance; proportion of light of diff wavelenghts that a surface reflects. efficiency in ABSORBING each wavelength and reflecting unabsorbed does not change

• respond ON when center is illuminated with one wavelength and suround is stimulated with another wavelength
• respond OFF when pattern is reversed

not evenly distributed; concentrated in BLOBS

• cytochrome oxidase
• columsn
• dual opponent color cells

• larger receptive fields
• stimuli to which neurons respond are more specific/complex

• damage to the PVC
• ability to respond to visual stimuli in scotomas even though they have no conscious awareness
• Perception of MOTION most likely to survive damage

• dorsal: primary visual---- dorsal prestriate cortex----posterior parietal cortex
• SPATIAL STIMULI (location/direction of movement)
• ventral: primary visual----ventral prestriate cortex---inferotemporal cortex
• CHARACTERISTICS

• dorsal: behavioral interactions w/objects (visually guided behavior)
• ventral: mediate conscious perception of objects