Sensory Perception and Processing

The lecture focuses on sensory perception, specifically moving beyond just vision.
The plan includes discussing various illusions, sensory modalities, and how the brain interprets them.

Initial Exercise: Students were shown a picture and asked how many spades were present.
The answer options led to a discussion about perceptual sets, biases based on prior experience.
- Correct Answer: Five spades.
- Common Misconception: Many reported four due to color misassociation where red and black spades were confused.
Explanation of perceptual sets: predispositions to perceive based on experience (i.e., card players vs. non-card players).

Vision is treated as the primary sense for humans, unlike other species like dogs, where smell is primary.
Significant brain cortex is dedicated to processing visual information.

Foveal vision orientation is crucial for detail recognition.
Comparison of foveal vision location and function in predatory birds such as eagles and owls.
Discussion of how predatory birds orient their heads to achieve optimal visual acuity during predation.

Left visual field signals are processed by the right hemisphere and vice versa.
Different brain areas specialize in processing various visual attributes:
- Motion, Form, Depth, Color: Areas do not process as a single entity but rather segregated functions.
- Issues like chromopsia (color blindness) and akinetopsia (motion blindness) arise from dysfunctional processing.

Color vision theory where complementary colors inhibit each other:
- E.g., red stimulation correlates with green inhibition; similar behavior with blue and yellow.
- Afterimages occur due to prolonged stimulation of specific ganglion cells, leading to a subsequent perception of opposite colors when stimulation ceases.

Understanding how we differentiate between foreground shapes and background.
Example of a chalice versus faces exercise demonstrating figure-ground perception shifts.
Humans have a natural inclination to focus on facial recognition, linked to dedicated neural areas in the brain (fusiform face area).

Depth perception enables three-dimensional understanding of spatial relationships, employing:
- Binocular Cues: Requires both eyes, sensing positional differences.
- Monocular Cues: Provides depth perception even with one eye closed, utilizing learned environmental patterns (e.g., size constancy).

Specialized neurons tuned to motion, primarily in the rod cells.
Distinctions between perceived motion while stationary and external movements in the visual field.
Importance of feedback from body movement in understanding perceived stability and motion outcomes.

Object recognition remains constant despite variable sensory inputs.
- Size Constancy: Recognition of size being consistent despite distance changes.
- Shape Constancy: Recognition of a shape despite changes in angle/views.
- Color Constancy: Recognition of color irrespective of lighting or background influences.

Various illusions demonstrated complexities in visual perception based on contrast differences and visual cues. Examples include:
- Rotational Illusion: Where lines appear to change dimensions based on perspective.
- Induction: Changes in color perception based on surroundings.

Frequency: Corresponds to pitch; measured in hertz (20 Hz - 20 kHz for humans).
Amplitude: Defines loudness levels of sound.
Timbre: Distinct quality of sound incorporating various frequency combinations.

Outer Ear: Includes the pinna; responsible for capturing sound.
Middle Ear: Contains the tympanic membrane (eardrum) that resonates with sound waves.
Inner Ear: Where sound transforms from air to liquid; contains cochlea and basilar membrane.
- Mechanism: Inner ear bones amplify sound waves transmitting them into cochlea; vibrational energy converts into neural signals via hair cells.

Place Theory: Pitch perception based on sound specific locations on the basilar membrane.
Frequency Theory: Sound frequency correlating with firing rate of neurons.
- Volley Principle: Clusters of neurons address higher frequencies beyond an individual neuron's firing capacity.

Determined by auditory signals received at different times and intensities in each ear.
Importance of neural pathways processing these discrepancies to determine sound direction (locating sounds).

Cutaneous Senses: Touch, pain, temperature as functional sensory information through skin.
Mechanoreceptors: Merkel receptors (continuous pressure) and Meissner corpuscles (on/off pressure).
Thermoreceptors: Distinction between warm (sustained temperature) and cold (change-sensitive).
- The human body strives to maintain a homeostatic temperature (98.6°F).

Classified into fast and slow pain pathways.
Pain thresholds vary based on individual physiology and neural connections.
Interaction of mechanical pain/allodynia (pain sensitivity) and touch information can alter pain experiences (gate control theory).

Taste and Smell: Limited detection abilities compared to higher species like dogs.
Taste Buds: Located between papillae, respond to five basic tastes (sweet, sour, salty, bitter, umami).
Olfaction: Direct pathways from nasal reception to brain, tied to memory/emotional responses (e.g. partner detection).

Kinesthetic Senses: Proprioceptors provide body position information.
Vestibular Senses: Balance determined by semicircular canals filled with fluid; responsible for spatial orientation and balance control.