GRISTO Module 4 Anatomy: Visual and Auditory Pathways

VISUAL PATHWAY

VISUAL PATHWAY

primary visual cortex in the occipital lobe

Vision is initially processed in the

retina

Light passes through the cornea, aqueous humor, pupil, lens, and vitreous humor to reach the

pass through all cell layers in the retina

To reach photoreceptor cells, light must

optic nerve

Photoreceptors send signals back through layers of the retina to reach the

2nd order ganglion cells that run the length of the retina and send central axons into the optic n.

Instead of one large ganglion, bipolar cells relay to

initial receptors that detect the light

Photoreceptor cells are the

area in which objects are visible at the same moment during steady fixation of gase

The visual field is the

right-left reversed and inverted

Images in the visual field are what on the retina

A. Optic nerve

B. Optic chiasm

C. Optic tract

D. Lateral geniculate nucleus (LGN) of thalamus

E. Optic radiation

F. Primary visual cortex

posterior part of the thalamus: the pulvinar

Lateral Geniculate Nucleus (LGN) hangs off the

optic radiation, which relay to the primary visual cortex

The LGN give off the

predictable locales

Just like the nasal and temporal regions of vision the superiro and inferior regions run in

the temporal lobe a

Fibers from the superior visual field run through

parietal lobe

Fibers from the inferior field run through the

calcarine sulcus (CS)

The primary visual cortex is above and below the

Reversed: Left visual field maps to the right cortex (and vice versa)

Upside down: The inferior visual field is on the superior half of visual cortex- meaning in the brain the image is inverted (and vice versa)

Inside-out: The center of visual field is posterior (outer) and peripheral vision is anterior (inner)

Relative to the visual field the visual cortex is

one sided blindness

Visual field Dysfunction:

Optic nerve

loss of peripheral fields (temporal fields cross)

Visual field Dysfunction:

Optic chiasm

Loss of an entire visual field (right or left)

Visual field Dysfunction:

Optic tract

suggests temporal lobe damage

Visual field Dysfunction:

Homonymous superior quadrantanopia (pie in the sky)

suggests parietal lobe damage

Visual field Dysfunction:

Homonymous inferior quadrantanopia (pie on the floor)

Optic nerve damaged

Optic chiasm damaged

Optic tract damaged

Homonymous superior quadrantanopia

Homonymous inferior quadrantanopia

YES it does

The primary visual cortex relays to other regions of the brain to further process what the visual cortex sees

the where and how stream

Occipital --> parietal

- For processing of spatial and contextual relationships, movement

Dorsal stream

The what stream

Occipital --> temporal

- for processing of face and scene recognition

Ventral stream

AUDITORY PATHWAYS

AUDITORY PATHWAYS

Is the big important guy for this stuff

Vestibulocochlear nerve

Primary auditory cortex

The MGN projects to the

inferior quadrigeminal brachium from the inferior colliculus to the MGN

Auditory sensations then follow the

auditory reflexes

The inferior colliculus also relays to regions that participate in

ipsilaterally and contralaterally to the inferior colliculus in the midbrain

CN VIII synapses on neurons in the CN VIII nucleus. From there fibers ascend

not all of those bitches

Most fibers emanating from the CN VIII nucleus decussate but

unilateral central lesions rarely produce more than subtle changes in hearing, generally contralateral to the lesion

Functionally, this means

pathology in peripheral auditory structures (middle and inner ear, cochlear nerve)

Most disturbances in auditory functions are associated with

bottom of the pulvinar on the posterior thalamus

The medial geniculate nucleus (MGN; auditory pathway) and the Lateral geniculate nucleus (LGN; vision pathway) hang off the

transverse temporal gyrus (Heschl's gyrus)

Primary Auditory cortex is located in the

may lead to loss of awareness of sound, but reflexes involving sound remain intact

Lesions to the primary auditory cortex

1. Primary auditory cortex --> Wernicke's area (language comprehension)

2. Wernicke's area --> Broca's area (motor speech)

3. Broca's area --> Pre-central gyrus (primary motor cortex)

When a spoken word is heard by the primary auditory cortex:

- CN V: Motor nucleus of V (pons)

- CN VII: Motor nucleus of VII (pons)

- CN IX, X: Nucleus ambiguus (medulla)

- CN XII: Motor nucleus of XII (medulla)

Corticobulbar tract to cranial nerve nuclei involved in speech:

QUIZ

QUIZ

right, left

Images in the left visual field are sseen by the _____ retina and images in the right visual field are seen by the _____ retina

BDAEC

Put in order the pathway of vision from the retina to the primary visual cortex.

Retina

A. Optic tract

B. Optic nerve

C. Optic radiation

D. Optic chiasm

E. Lateral geniculate ganglion

Primary visual cortex

The nasal visual field of the left eye

The temporal visual field of the left eye

The left optic nerve contain fibers from

the temporal visual field of the right eye

the nasal visual field of the right eye

the nasal visual field of the left eye

the temporal visual field of the left eye

The left-sided nasal and temporal visual fields

The right optic tract contains

The inferior nasal and temporal visual fields from the right eye

The left optic radiation in the parietal lobe carries

Parietal, Where and how, Spatial and contextual relationships, movement

The dorsal visual association stream enters the _____ lobe and relays _____ visual information for processing ______

Temporal, What, Face and scene recognition

The ventral visual association stream enters the _____ lobe and relays ______ visual information for processing ______

Wernicke's area

From the primary auditory cortex, the first place a spoken word is relayed is