eyesight 3 Flashcards

Question

Eccentricity

Answer 1

distance from the center of the visual field (the fovea)

Answer 2

Fovea (center of gaze) has: -Densely packed photoreceptors -One-to-one connections between cones and RGCs -A large cortical representation in V1 (cortical magnification) Result: High-resolution, detailed vision at the center Peripheral retina: -Fewer photoreceptors -More convergence (many photoreceptors → fewer RGCs) -Less cortical area devoted to processing Result: Lower visual acuity in peripheral vision 🧠 Behaviorally: To see peripheral objects clearly, we shift our gaze using eye or head movements, bringing them into the fovea for detailed processing.

Answer 3

Definition: Crowding = when objects in the periphery are surrounded by other objects (clutter), we can’t recognize them clearly, even if each object is visible on its own. 🔹 Effects: Items appear jumbled or merged Impairs tasks like: -Object recognition -Reading -Eye-hand coordination in cluttered environments 🔹 Example: You may easily recognize a letter in the periphery if it's alone, but fail to identify it when surrounded by other letters or shapes.

Answer 4

When auditory and visual stimuli are presented at the same time but from different locations, we perceive the sound as coming from the visual source. Classic example: A ventriloquist's dummy appears to speak, even though the real sound comes from the human performer. 🧠 Why Does This Happen? ✅ Multisensory Integration Principle: The brain combines information from multiple senses to create a coherent perception. Normally, it binds signals that are temporally and spatially aligned (from the same event). 🔁 But when there’s a mismatch… If the sound and visual cues don’t match in space, but do match in time → the brain resolves the conflict by favoring vision. Example: McGurk Effect (sound you hear depends on mouth movement and not the actual sound, sight overrides sound) example: The Rubber Hand Illusion A rubber hand is placed in front of a person while their real hand is hidden. Both the rubber hand and the real hand are stroked synchronously. Person starts to feel the rubber hand as their own. ✅ Why? Vision overrides somatosensory input → the brain trusts the visual match between the touch and what’s seen This alters body ownership and self-perception Why Vision Dominates (a.k.a. Visual Capture): Vision has higher spatial accuracy than audition Our visual system is much better at determining where things are located So, the brain "trusts" vision more when localizing the source of a sound

Answer 5

The "2 Beeps / 1 Flash" Illusion (a.k.a. Sound-Induced Flash Illusion) What happens: You see 1 flash but hear 2 beeps. What you perceive: You “see” 2 flashes — even though only 1 actually occurred. ✅ Why? The brain trusts the auditory system’s timing more than the visual system’s. Auditory system has better temporal resolution, so it dominates in timing-based tasks. 🧠 Key idea: Vision dominates for spatial tasks; audition dominates for temporal tasks.

Answer 6

Spatial (where?): 👁️ Vision : Ventriloquism effect Temporal (when?): 🔊 Audition: Sound-induced flash illusion Body ownership: 👁️ Vision over touch: Rubber hand illusion

Answer 7

Subcortical structures (e.g., superior colliculus) Cortical association areas (e.g., parietal and temporal lobes) Even primary sensory cortices (like V1 for vision or A1 for audition) show direct connections and can be influenced by other senses.

Answer 8

These neurons respond to two or more types of sensory input (e.g., both light and sound). They allow the brain to combine information from different senses to create a unified perception of space or events. 🎯 For example, one neuron might fire only when a sound and a flash come from the same location at the same time.

Answer 9

auditory and visual fields overlap a lot

Answer 10

Suggests that neurons coding different features of the same object fire in synchrony (i.e., at the same time). This synchronized firing acts as a temporal “tag” that links the features together in perception. 🔊👁️ Example: A neuron responding to the sound of a dog and one responding to its shape may fire together, helping the brain bind these into a single percept. ✅ Flexible & efficient, but hard to detect directly — still a theoretical model.

Answer 11

Proposes that one highly specific neuron responds only when all features of a known object are present. That neuron fires when it "recognizes" the exact combination (e.g., your grandmother’s face, voice, and smell). 🚫 Problem: Requires a huge number of specific neurons, one for every possible object/person we recognize → biologically inefficient

Answer 12

More widely supported. Each neuron responds to one feature (e.g., shape, color, sound frequency). Perception arises from the pattern of activity across many neurons — like a “neural barcode.” Synchronous firing across these neurons can signal co-occurrence of features → binding ✅ Efficient, flexible, and fits with known brain activity patterns.

Answer 13

A neurological condition where stimulation in one sensory modality triggers an involuntary experience in another. The brain blends sensory signals, creating multi-sensory perceptions from a single stimulus. ex: Grapheme-color: Letters or numbers evoke specific colors (e.g., “A is red”) Sound-color: Sounds (e.g., music, voices) trigger color experiences Auditory-tactile: Sounds create touch sensations (e.g., a bell causes a tingling feeling) Hearing-motion: Seeing movement causes the perception of sound (e.g., car "woosh") Caused by: Overactive perceptual binding machinery? * Abnormal strengthening of weak cross-modal connections, or, from the formation of intracortical pathways that never exist in people without synesthesia (artists are more likely to have synesthesia)