MCAT Psychological Social Foundations Flashcards: 6a Visual System Processing

What this deck covers

This deck focuses on 6a Visual System Processing, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Psychological Social Foundations.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the functional difference between ON-center and OFF-center ganglion cells?

Answer: ON: fire to light in center; OFF: fire to darkness in center. Opposite responses create contrast detection mechanisms.

Flashcard 2: What is the function of amacrine cells in retinal processing?

Answer: Modulate bipolar-to-ganglion signaling; motion/temporal processing. They integrate signals laterally for complex processing.

Flashcard 3: What is binocular disparity, and what depth cue type does it represent?

Answer: Difference between the two retinal images; a binocular depth cue. Brain computes distance from horizontal image displacement between eyes.

Flashcard 4: Which retinal cells mediate lateral inhibition to enhance contrast?

Answer: Horizontal cells (and amacrine cells in inner retina). Horizontal and amacrine cells provide inhibitory feedback, sharpening edges and improving contrast detection in the retina.

Flashcard 5: What is rhodopsin, and in which photoreceptor is it found?

Answer: Light-sensitive pigment in rods (opsin + retinal). The visual pigment undergoes conformational change when light hits retinal.

Flashcard 6: Which visual field projects to the left cerebral hemisphere?

Answer: Right visual field. Contralateral processing: each hemisphere sees opposite field.

Flashcard 7: Which visual field projects to the right primary visual cortex after the optic chiasm?

Answer: Left visual field. The right visual cortex integrates signals from the left visual field via the optic pathways' decussation pattern.

Flashcard 8: What is the function of the ventral visual stream (the "what" pathway)?

Answer: Object identity processing (form, color); projects to temporal lobe. Processes visual features to recognize objects and faces.

Flashcard 9: What is rhodopsin, and in which photoreceptor is it found?

Answer: Light-sensitive pigment in rods. Rhodopsin absorbs photons in low light, initiating hyperpolarization in rods for scotopic vision.

Flashcard 10: What structure creates the retinal blind spot by lacking photoreceptors?

Answer: Optic disc (optic nerve head). Where ganglion cell axons converge to form the optic nerve, no photoreceptors exist.

Flashcard 11: What is the function of horizontal cells in retinal processing?

Answer: Lateral inhibition to enhance contrast and edge detection. They inhibit neighboring cells to sharpen visual boundaries.

Flashcard 12: What is the function of amacrine cells in the retina?

Answer: Modulate bipolar-to-ganglion signaling; important for motion/temporal processing. They integrate signals across multiple bipolar cells for complex processing.

Flashcard 13: Identify the visual pathway order from retina to primary visual cortex (V1).

Answer: Retina → optic nerve → optic chiasm → LGN → optic radiations → V1. Visual signals relay through thalamus before reaching cortex.

Flashcard 14: Identify the visual deficit from a lesion of the right optic nerve.

Answer: Right monocular blindness. Right optic nerve damage prevents signal transmission from the right retina, resulting in complete vision loss in that eye.

Flashcard 15: What is the ventral visual stream, and which function is it primarily associated with?

Answer: Occipital r temporal; object recognition (what). The ventral stream analyzes form and color for perceptual identification and categorization of visual stimuli.

Flashcard 16: What is the main function of cones in the retina?

Answer: Color (photopic) vision; lower sensitivity, high acuity. Cones contain opsins for detecting different wavelengths.

Flashcard 17: What is the correct sequence of retinal cell types in the vertical pathway?

Answer: Photoreceptors r bipolar cells r ganglion cells. Light activates photoreceptors, which synapse with bipolar cells that relay signals to ganglion cells for output via the optic nerve.

Flashcard 18: What is the difference between magnocellular and parvocellular pathways?

Answer: Magno: motion/low detail; Parvo: color/high detail. Magnocellular layers in LGN handle fast, low-resolution signals for motion, while parvocellular layers process detailed, color information.

Flashcard 19: What is the correct order of visual information flow from eye to cortex?

Answer: Retina r optic nerve r LGN r optic radiations r V1. Visual information flows from photoreceptors in the retina through neural pathways to the primary visual cortex for processing.

Flashcard 20: What are rods specialized for compared with cones?

Answer: Low-light, high sensitivity, low acuity, no color vision. Rods contain rhodopsin that detects dim light efficiently but provides poor resolution and lacks color discrimination.

Flashcard 21: Which structure in the thalamus relays visual information to primary visual cortex?

Answer: Lateral geniculate nucleus (LGN). The LGN organizes retinal inputs into layers, preserving retinotopy before projecting to the visual cortex.

Flashcard 22: What is the function of the cornea in vision?

Answer: Provides most light refraction to focus images on the retina. The cornea bends incoming light rays to converge them onto the retina, accounting for approximately 70% of the eye's refractive power.

Flashcard 23: Identify the lesion: A pituitary tumor compressing the optic chiasm causes what deficit?

Answer: Bitemporal hemianopia (loss of temporal visual fields). Crossing fibers are compressed, affecting peripheral vision from both eyes.

Flashcard 24: What do retinal ganglion cell axons form as they exit the eye?

Answer: The optic nerve (cranial nerve II). Ganglion cells are the output neurons whose axons carry visual signals to the brain.

Flashcard 25: What is the main function of rods in the retina?

Answer: Dim-light (scotopic) vision; high sensitivity, low acuity, no color. Rods contain rhodopsin for detecting low light levels.

Flashcard 26: What is the key retinal neurotransmitter released by photoreceptors in darkness?

Answer: Glutamate. Darkness depolarizes photoreceptors, triggering release.

Flashcard 27: What is the lateral geniculate nucleus (LGN) and where is it located?

Answer: Thalamic relay nucleus for visual input from retina to V1. Part of thalamus that processes visual signals before V1.

Flashcard 28: Which visual field information crosses at the optic chiasm: left or right visual field?

Answer: Both: nasal retinal fibers cross, carrying the contralateral visual field. Nasal fibers from each eye cross to process opposite visual fields.

Flashcard 29: What is the primary function of cones in the retina?

Answer: Color vision and high visual acuity in bright light (photopic) vision. Cones contain photopsins for detecting different wavelengths in bright conditions.

Flashcard 30: What is phototransduction in rods and cones?

Answer: Light converts signals in photoreceptors into neural activity. Photons trigger molecular cascades that hyperpolarize cells.

Flashcard 31: At the optic chiasm, which retinal fibers cross to the opposite hemisphere?

Answer: Nasal retinal fibers decussate; temporal fibers remain ipsilateral. This crossing allows each hemisphere to process both eyes.

Flashcard 32: Which visual field projects to the right cerebral hemisphere?

Answer: Left visual field. Visual fields project contralaterally after chiasm crossing.

Flashcard 33: What is the function of bipolar cells in the retina?

Answer: Relay signals from photoreceptors to ganglion cells. They form the middle layer of the retinal neural circuit.

Flashcard 34: Which pathway is the dorsal stream, and what is its main function?

Answer: Occipital-to-parietal "where/how" pathway for spatial location and motion. Guides actions and tracks movement through posterior parietal cortex.

Flashcard 35: What is the major thalamic relay nucleus for visual information before cortex?

Answer: Lateral geniculate nucleus (LGN) of the thalamus. LGN has 6 layers processing different visual features before cortical relay.

Flashcard 36: What is the accommodation reflex response when shifting gaze from far to near?

Answer: Lens thickens, pupils constrict, and eyes converge. Near triad response mediated by parasympathetic activation.

Flashcard 37: What is the primary function of the lens in the eye?

Answer: Fine-tunes focus by changing shape (accommodation). The lens adjusts its curvature via ciliary muscle contraction to focus on near or far objects, enabling clear vision at varying distances.

Flashcard 38: Identify the visual deficit from a lesion of the left optic tract.

Answer: Right homonymous hemianopia. Left optic tract lesion disrupts signals from the right visual field, causing loss in both eyes' temporal and nasal halves respectively.

Flashcard 39: What retinal change occurs when light activates photoreceptors in phototransduction?

Answer: Photoreceptors hyperpolarize and reduce glutamate release. Light closes cation channels, causing hyperpolarization and decreased neurotransmitter.

Flashcard 40: Identify the visual deficit from a lesion at the optic chiasm.

Answer: Bitemporal hemianopia. Optic chiasm compression severs crossing nasal fibers, leading to loss of temporal visual fields in both eyes.

Flashcard 41: What is the optic disc, and what key feature makes it a blind spot?

Answer: Exit of optic nerve; lacks photoreceptors (no rods or cones). The optic disc forms a physiological blind spot because ganglion cell axons bundle there, displacing photoreceptors.

Flashcard 42: What is the primary visual cortex (V1), and where is it located?

Answer: First cortical visual area in occipital lobe (calcarine cortex). Receives LGN input for initial cortical visual processing.

Flashcard 43: What are cones specialized for compared with rods?

Answer: Color vision and high acuity, best in bright light. Cones express photopsins sensitive to different wavelengths, enabling trichromatic vision and fine detail in photopic conditions.

Flashcard 44: Which retinal cells form the optic nerve by sending axons out of the eye?

Answer: Retinal ganglion cells. Their axons bundle together to carry visual signals to brain.

Flashcard 45: What is the pupil?

Answer: The opening in the iris that allows light into the eye. The pupil's size modulation by the iris controls light entry, protecting the retina and optimizing image clarity.

Flashcard 46: Identify the lesion: Damage to right optic tract causes loss of which visual field?

Answer: Left homonymous hemianopia (loss of left visual field in both eyes). Right tract carries left visual field from both eyes' nasal retinas.

Flashcard 47: What is the function of the dorsal visual stream (the "where/how" pathway)?

Answer: Spatial location and motion processing; projects to parietal lobe. Analyzes movement and guides visually-directed actions.

Flashcard 48: What is the optic chiasm, in terms of which fibers cross?

Answer: Nasal retinal fibers decussate; temporal retinal fibers remain ipsilateral. At the optic chiasm, nasal fibers cross to ensure contralateral representation of visual fields in the brain.

Flashcard 49: What is retinotopic mapping in visual cortex?

Answer: Spatial layout of retina is preserved in V1 cortical representation. Neighboring retinal points map to neighboring cortical areas.

Flashcard 50: What is the role of the iris in the visual system?

Answer: Controls pupil size to regulate light entering the eye. The iris adjusts pupil diameter via sphincter and dilator muscles to optimize retinal illumination under different lighting conditions.

Flashcard 51: What is the primary cortical area that first receives visual input from the LGN?

Answer: Primary visual cortex (V1, striate cortex) in the occipital lobe. V1 contains orientation-selective cells organized in columns.

Flashcard 52: What retinal region provides the highest visual acuity?

Answer: Fovea (within the macula). Dense cone concentration provides sharp central vision.

Flashcard 53: What do retinal ganglion cell axons form as they leave the eye?

Answer: The optic nerve. Ganglion cell axons converge at the optic disc to transmit integrated retinal signals to higher visual centers.

Flashcard 54: What structure is the optic disc, and what key feature does it create in vision?

Answer: Exit of optic nerve; creates the blind spot (no photoreceptors). Axons converge here, leaving no room for photoreceptors.

Flashcard 55: What is the dorsal visual stream, and which function is it primarily associated with?

Answer: Occipital r parietal; motion/spatial processing (where/how). The dorsal stream integrates visual input for guiding actions, processing location and movement in the environment.

Flashcard 56: Which visual field projects to the left primary visual cortex after the optic chiasm?

Answer: Right visual field. Post-chiasm, the left visual cortex processes input from the right visual field due to crossed nasal and uncrossed temporal fibers.

Flashcard 57: Which muscles change lens curvature during accommodation?

Answer: Ciliary muscles. Ciliary muscles contract to relax zonular fibers, allowing the lens to become more spherical for near vision during accommodation.

Flashcard 58: Which pathway is the ventral stream, and what is its main function?

Answer: Occipital-to-temporal "what" pathway for object identity and form. Processes visual features for recognition in inferior temporal cortex.

Flashcard 59: What are bipolar cells in the retina, in terms of information flow?

Answer: Intermediate neurons between photoreceptors and ganglion cells. They relay signals vertically through the retinal layers.

Flashcard 60: What is the name and location of the primary visual cortex?

Answer: V1 in the occipital lobe (calcarine cortex). V1 receives thalamic inputs and performs initial feature extraction like orientation and edge detection.

Flashcard 61: What is the primary function of rods in the retina?

Answer: High light sensitivity for dim-light (scotopic) vision; low acuity. Rods contain rhodopsin for detecting low light levels but lack color discrimination.

Flashcard 62: What is the fovea, and what visual function is it specialized for?

Answer: Central retina; highest visual acuity due to dense cones. The fovea contains a high concentration of cones with minimal convergence, enabling sharp central vision and detailed color perception.

Flashcard 63: What is the function of horizontal cells in retinal processing?

Answer: Lateral inhibition to enhance contrast via photoreceptor-bipolar modulation. They inhibit neighboring photoreceptors to sharpen edges and boundaries.

Flashcard 64: What retinal region has the highest density of cones and greatest acuity?

Answer: Fovea centralis (within the macula lutea). Dense cone packing with no rods creates the sharpest central vision.