Week 9 lectures biopsych

What is extracellular microelectrode recording?

A technique used to record electrical activity from single neurons using fine electrodes

What is another name for extracellular microelectrode recording?

Single-unit recording

Why are animals anaesthetised during extracellular recording surgery?

To allow insertion of electrodes into the brain

What is action potential depolarisation?

Influx of Na+ ions causing the neuron interior to become more positive

What happens during repolarisation?

K+ ions flow out and the neuron returns to a negative resting state

What is the function of an action potential?

To transmit electrical signals down the axon

What is audition?

The sense of hearing

Why is hearing important for survival?

It acts as an early warning system and supports spoken communication

What creates sound waves?

Vibrating objects causing compression and rarefaction of air molecules

What unit measures sound frequency?

Hertz (Hz)

What sound frequency range can humans hear?

Approximately 30–20,000 Hz

What physical property determines loudness?

Amplitude/intensity of the sound wave

What perceptual property corresponds to frequency?

Pitch

What determines timbre?

The complexity of the sound wave

What are the three parts of the ear?

Outer ear, middle ear, and inner ear

What structures make up the outer ear?

Pinna, auditory canal, and tympanic membrane

What is another name for the tympanic membrane?

Eardrum

What structures make up the middle ear?

Ossicles: malleus, incus, and stapes

What are the ossicles?

Three tiny bones in the middle ear

Which ossicle connects to the tympanic membrane?

Malleus

Which ossicle connects to the oval window?

Stapes

What structure is the receptor organ for hearing?

Cochlea

What is the function of the round window?

Allows fluid movement within the cochlea

What is the basilar membrane?

A membrane inside the cochlea containing auditory receptors

What is the Organ of Corti?

The sensory structure for hearing located on the basilar membrane

What cells act as auditory receptors?

Hair cells

What membrane lies above the hair cells?

Tectorial membrane

What happens when hair bundles bend?

Ion channels open causing receptor potentials

How is pitch encoded in the cochlea?

By place coding along the basilar membrane

Which region of the basilar membrane responds to high frequencies?

Base of the cochlea

Which region responds to low frequencies?

Apex of the cochlea

What is tonotopic organisation?

Systematic spatial representation of sound frequency

Where is tonotopic organisation found?

Cochlea and primary auditory cortex

What neurotransmitter system is associated with auditory signalling?

Glutamatergic transmission from hair cells to auditory nerve fibres

What are cochlear implants designed to do?

Restore hearing by stimulating auditory nerve fibres

Why do cochlear implants work?

Because of place coding organisation in the cochlea

What is the visible spectrum?

The range of electromagnetic wavelengths humans can see

What wavelength range is visible to humans?

Approximately 380–760 nm

What determines hue?

Wavelength of light

What determines brightness?

Intensity of light

What determines saturation?

Purity of light

What is the cornea?

The transparent outer layer of the eye

What is the function of the lens?

Focus light onto the retina

What is the retina?

The light-sensitive tissue lining the back of the eye

What is the optic disk?

The point where ganglion cell axons leave the eye

Why is the optic disk a blind spot?

It lacks photoreceptors

What are the two main photoreceptors?

Rods and cones

How many rods are in the human retina?

About 120 million

How many cones are in the human retina?

About 6 million

What are rods specialised for?

Dim light vision

What are cones specialised for?

Colour vision and fine detail

What retinal region contains the highest cone density?

Fovea

What is the fovea responsible for?

High-acuity central vision

What are the three retinal layers?

Photoreceptor layer, bipolar cell layer, and ganglion cell layer

What cells send axons through the optic nerve?

Ganglion cells

Do photoreceptors generate action potentials?

No

What do photoreceptors release instead of action potentials?

Neurotransmitters

What is rhodopsin?

The photopigment in rods

What are photopigments made of?

Opsin protein and retinal lipid

What are the three cone types?

S-cones, M-cones, and L-cones

What wavelength do S-cones respond best to?

~420 nm (blue)

What wavelength do M-cones respond best to?

~530 nm (green)

What wavelength do L-cones respond best to?

~560 nm (red)

What causes colour blindness?

Anomalies in cone photopigments

Which type of colour deficiency is most common?

Red-green deficiency

Why is red-green deficiency more common in males?

The responsible genes are X-linked

What are Ishihara plates used for?

Testing colour vision deficiencies

What is retinotopic organisation?

Spatial mapping of the visual field onto the visual cortex

What is the primary visual cortex also called?

V1 or striate cortex

Where does the majority of visual information travel before V1?

Lateral geniculate nucleus (LGN)

What is contralateral visual organisation?

Each hemisphere processes the opposite visual field

What is hemianopia?

Loss of vision in one side of the visual field

What causes hemianopia?

Damage to primary visual cortex

What is cortical magnification?

More cortical area devoted to processing foveal input

What are cortical columns?

Modules processing information from small regions of visual space

What are blob regions in V1 specialised for?

Colour processing

What are interblob regions specialised for?

Orientation, motion, and depth

What are simple cells in V1 sensitive to?

Specific orientations of bars and edges

Who discovered orientation-selective neurons?

Hubel and Wiesel

What Nobel Prize-winning discovery did Hubel and Wiesel make?

Orientation selectivity in visual cortex

What is the dorsal stream also called?

The “where” pathway

What does the dorsal stream process?

Location and motion

What is the ventral stream also called?

The “what” pathway

What does the ventral stream process?

Object identity and form

What visual area is associated with colour processing?

V4

What visual area is associated with motion processing?

MT/V5

What is the function of area MT/V5?

Processing visual motion

What is the function of area V4?

Processing colour and form

What is the LGN?

Lateral geniculate nucleus of the thalamus involved in vision