Audition and Temperature, Touch and Pain

What is the geniculostriate pathway in vision?

Retinal ganglion cells → Lateral Geniculate Nucleus (thalamus) → Primary Visual Cortex (V1).

What is the main role of V1 (Primary Visual Cortex)?

Basic visual processing; also known as the striate cortex.

What is V2

and how is it connected to V1?

What are the two major visual streams beyond V1?

Ventral stream ("What") for object recognition and Dorsal stream ("Where/How") for spatial and motion processing.

What is the function and pathway of the ventral stream?

Function: Object recognition

Which cortical area processes color and what happens if it is damaged?

V4; damage causes cerebral achromatopsia (loss of color vision despite intact retinas).

What are the specialized areas in the Inferior Temporal Cortex?

FFA (Fusiform Face Area) for faces and PPA (Parahippocampal Place Area) for places.

What are the main types of visual agnosias and their differences?

Apperceptive: cannot integrate basic features; Associative: can copy but cannot name; Prosopagnosia: cannot recognize faces as wholes.

Describe Patient D.F.’s case and what it revealed.

D.F. had visual form agnosia (ventral damage) → impaired perception but intact action guidance

What is the function and pathway of the dorsal stream?

Function: Motion and spatial processing for action; Pathway: V1 → V2 → MT (V5) & MST → Parietal Cortex.

What do MT and MST process?

MT (V5): Direction

What disorders result from dorsal stream damage?

Optic Ataxia: cannot reach objects accurately; Akinetopsia: motion blindness (objects appear static).

Auditory System: Sound Waves to Neural Activity

What are the three main components of the auditory system?

Stimulus (sound waves)

What properties of sound waves correspond to auditory experiences?

Amplitude = loudness; Frequency = pitch; Complexity = timbre.

What are the main parts of the ear?

Outer: Pinna

What is the function of the Organ of Corti?

Houses hair cells on the basilar membrane for sound transduction.

Explain the role of inner and outer hair cells.

Inner: Primary sensory receptors; Outer: Amplify and modulate sensitivity.

How does auditory transduction occur?

Mechanical movement of cilia opens mechanically-gated ion channels → K⁺ & Ca²⁺ influx → depolarization → glutamate release → auditory nerve firing.

Primary Auditory Pathway & Sound Localization

Trace the auditory signal from cochlea to cortex.

Cochlea → Cochlear Nucleus → Superior Olive → Inferior Colliculus → Medial Geniculate Nucleus → Primary Auditory Cortex (A1).

What are the two main theories of pitch perception?

Place Theory: basilar membrane locations encode frequencies; Timing Theory: neurons fire in sync with wave phase.

What is tonotopy and where is it found?

Spatial frequency mapping in the cochlea and A1.

How is sound localized?

Binaural cues: ITD (time difference

Touch

Temperature

What are the three components of somatosensation?

Exteroception (touch

Name the four low-threshold mechanoreceptors (LTMRs) and their properties.

Merkel: sustained pressure; Ruffini: skin stretch; Meissner: low-frequency vibration; Pacinian: high-frequency vibration.

Which fibers transmit touch vs pain?

Touch: Aβ fibers; Pain/temperature: Aδ and C fibers.

What is the role of TRP channels in temperature sensing?

TRPV1: heat & capsaicin; TRPM8: cold & menthol.

What are the main somatosensory pathways?

Touch: Dorsal Column-Medial Lemniscus; Pain & Temp: Spinothalamic Tract.