Neural Pathways of Audition
Sound waves make the ear drum vibrate. Vibrations produce tiny waves in the inner ear fluid. Tiny hair cells are stimulated by these waves and generate action potentials. Output from Cochlea is projected to Cochlear nucleus and Inferior Colliculus. From there the infro is sent to the Medial Geniculate Nucleus.
Computational Goals of Audition
Frequency data are essential for deciphering sound. Sound producing objects have unique resonant properties that provide a characteristic signature. (Same note on different instruments will still sound different)
Processing Sound for Localization
Frequency data, essential for deciphering sound. Localizing sound sources in space is based upon two cues: Difference in time between when a sound reaches each ear & Difference in sound intensity at the two ears
Olfactory Perception (smell)
Odor molecules(odorants) enter the nasal cavity. They attach to the odor receptors in the olfactory epithelium. A signal is sent to the neurons in the olfactory bulb(glomeruli). Axons from the glomeruli exit the olfactory bulb forming the olfactory nerve
Smell and Memory
A specific smell can elicit a memory from a long time ago. The olfactory cortex is directly connected to the limbic system(memory/emotion). Odors appear to activate the limbic system more than a visual stimulus.
Begins when a food molecule(tastant) stimulates a receptor in a taste cell and causes the receptor to depolarize.
Located in the taste buds. Responds to one of the following: Salty, Sour Bitter, Sweet, and Umani(meat). Send a signal to the gustatory nucleus in the dorsal medulla.
Receptors lie under the skin and at musculoskelatal junctions.
Myelinated: quick, activation, produces immediate action
Unmyelinated: responsible for the duller, longer lasting pain that follows initial pain
Layer of neurons along the back surface of the eye. Contains protoreceptors.
Sensitive to lower light levels, most useful at night
Requires more light stimulation. More useful during the day. Essential for color vision
Eye to CNS
Signals from photoreceptors goes to bipolar cells then to ganglian cells. form a bundle called the optic nerve. Visual info is transmitted to the CNS via the optic nerve
A genetic abnormality in the photoreceptor system.
people having only two photopigments
See the world without color, shading reflects variations in brightness rather than hue. Depth and Perception remain intact
loss of motion perception
10% if optic nerve fibers go to sub cortical structures. It is possible that some visual info is still being processed from the area that is damaged in the primary visual cortex
characterized by an idiosynratic union between sensory modalities.