Exam 2 Study Guide: Methods, Vision, and Hearing

Vocabulary flashcards covering research methods, the visual system from retina to cortex, visual agnosia, object recognition pathways, and the auditory pathway based on the Exam 2 Study Guide.

Method of Converging Operations

A research approach that gathers information by combining findings from multiple sources, including clinical participant populations and neurologically intact reference populations.

Computational Model

An explicit and detailed model that tests complex theories and generates predictions while leaving little or no room for ambiguity.

Machine Learning Model

A type of computational model that discovers replicable patterns in data and generalizes them to new situations.

Symbolic Models

Computational models based on representations of complex symbol systems.

Neural Network Models

Computational models consisting of many simple units that send activation to other units.

Meta-Analyses

A method used to determine whether similar results are obtained across multiple studies, weighting individual studies by factors such as effect strength and sample size.

Retina

The layers of cells on the inside surface of the eye that register light and carry out complex computations before sending partly transformed information to the brain.

Photoreceptor Cells

Cells containing pigments that absorb light energy and transform it into electrochemical energy used by the nervous system, initiating parallel processing.

Rods

Photoreceptors numbering approximately $120\text{ million}$, located primarily in the periphery, containing rhodopsin, and sensitive to very small amounts of light; many feed into a single ganglion cell.

Cones

Photoreceptors numbering approximately $6\text{ million}$, packed most densely in the fovea, consisting of three types sensitive to different wavelengths in the visible light spectrum; comparatively few feed into a ganglion cell.

Rhodopsin

The single visual pigment found in rods that is sensitive to very small amounts of light.

Parvocellular Ganglion Cells (P Cells)

Small retinal ganglion cells whose axons project toward the brain and encode color information.

Magnocellular Ganglion Cells (M Cells)

Large retinal ganglion cells that are responsive to coarse patterns and detect rapid motion.

Receptive Field

The specific region of visual space to which a neuron responds; retinal ganglion cells feature a center-surround structure to enhance contrast.

Colorblindness

The inability to distinguish certain colors (commonly red and green) due to differences in cone types, occurring more frequently in males.

Tectopulvinar Pathway

A fast-acting visual pathway receiving input primarily from M ganglion cells, sensitive to motion and novel objects in the periphery, projecting to the superior colliculus, pulvinar nucleus, and motor regions.

Geniculostriate Pathway

The primary visual pathway containing about $90\%$ of optic nerve fibers, projecting from the retina to the lateral geniculate nucleus (LGN) and terminating in the striate cortex.

Superior Colliculus

A midbrain structure in the tectum that integrates auditory and visual sensory information.

Lateral Geniculate Nucleus (LGN)

A six-layered thalamic nucleus folded into a knee-like shape that receives input from the contralateral visual field, with magnocellular layers receiving M-cell input and parvocellular layers receiving P-cell input.

Koniocellular Layers

Small cell layers situated in between the six main layers of the lateral geniculate nucleus that receive input from small bistratified ganglion cells and the superior colliculus.

Retinotopic Mapping

The spatial organization of neural connections that preserves the spatial layout of visual information from the retina to the lateral geniculate nucleus and visual cortex.

Cortical Magnification Factor

The principle describing how the millimeters of cortical surface area dedicated to one degree of visual angle is much higher for the fovea than for the periphery.

Simple Cells

Striate cortex neurons that respond best to an edge of a specific orientation.

Complex Cells

Striate cortex neurons that respond best to certain line orientations while being less selective about the exact position of the line within the receptive field.

Hyper-complex Cells (End-Stopped Cells)

Striate cortex cells that respond best to lines of a specific orientation and a specific length.

Orientation Columns

Cortical columns in the striate cortex composed of neurons that share a preference for a particular line orientation.

Ocular Dominance Columns

Cortical columns in the striate cortex organized according to whether they receive input from the left eye or the right eye.

Hypercolumn

A cluster of cortex cells tuned to respond to all visual orientations and inputs from both eyes for a particular spatial location.

Binocular Disparity

Slight differences in the images projected onto the two retinas, used by specific cortical cells to determine depth.

Contextual Modulation

The modification of a visual neuron's response by stimuli outside its classical receptive field, which may aid in figure-ground segregation.

Blindsight

A condition resulting from extensive striate cortex damage where individuals have no conscious experience of seeing, yet retain the ability to make rudimentary visual discriminations.

Area V4

A retinotopically mapped extrastriate visual area that is especially sensitive to color, line orientation, depth, and motion.

Cerebral Achromatopsia

Altered color perception causing the world to appear in shades of gray, caused by damage to the posterior ventral cortex.

Ventral Pathway (What Pathway)

A cortical processing stream extending toward the temporal lobe involved in object identification; damage leads to visual agnosia.

Dorsal Pathway (Where Pathway)

A cortical processing stream extending toward the parietal lobe involved in representing spatial locations and guiding motion; damage leads to spatial neglect.

Visual Agnosia

A modality-specific inability to recognize objects through vision that cannot be accounted for by basic sensory loss or other general causes.

Apperceptive Agnosia

A type of visual agnosia caused by diffuse damage to the occipital lobe and surrounding areas, characterized by difficulty recognizing objects or letters from degraded stimuli or nonstandard viewpoints.

Associative Agnosia

A visual deficit caused by damage to occipitotemporal regions and white matter where visual forms can be perceived and drawn, but cannot be linked to stored knowledge, functional meaning, or object names.

Prosopagnosia

The inability to recognize or differentiate among faces, caused by damage to the ventral stream of the right hemisphere.

Thatcher Illusion (Inversion Effect)

The phenomenon where facial distortions become significantly harder to detect when a face is upside down, showing the importance of configural processing in expert face perception.

Sparse Coding

A visual coding hypothesis proposing that a small, highly specific group of neurons responds to the presence of a given object.

Grandmother Cell Theory

An extreme version of sparse coding stating that an individual neuron fires exclusively for a specific person or object.

Population Coding

A neural coding scheme where an individual object is represented by the coordinated pattern of activity across a large population of neurons.

Form-Cue Invariance

The brain's ability to maintain a constant categorization of an object regardless of the specific visual cue (e.g., motion, luminance) used to define it.

Perceptual Constancy

The ability to accurately recognize an object across changes in viewing angles, positions, sizes, and lighting conditions.

Lateral Occipital Complex (LOC)

A ventral stream area anterior to V2 and V4 that responds more to object shapes than to textures and is active in both visual and tactile object recognition.

Conjunctive Coding

A hierarchical processing model of ventral vision where lower-level regions represent simple features and pass activation to higher-level regions that combine them into whole shapes.

Non-Local Binding

A model of object representation wherein a whole object is recognized through the simultaneous co-activation of units representing parts in distinct locations.

Fusiform Face Area (FFA)

A region in the fusiform gyrus that is active in face recognition in the right hemisphere and active in both face and object recognition in the left hemisphere.

Visual Word-Form Area (VWFA)

A region in the fusiform gyrus, located dorsal to the FFA in the left hemisphere, that is active during word perception.

Parahippocampal Place Area (PPA)

A ventral cortical area located near the hippocampus that responds selectively to scenes, landscapes, and buildings.

Extrastriate Body Area (EBA)

An extrastriate visual region that responds selectively to visual images of human bodies and body parts.

Distributed Processing Model

An alternative to category localization proposing that object recognition is distributed across the ventral stream, with similar items producing similar neural activity patterns.

Encoding (Visual Neuroimaging)

The process of predicting or characterizing how sensory stimulus features are represented by neural activity, such as fMRI BOLD signals.

Decoding (Visual Neuroimaging)

The process of predicting or reconstructing the visual stimulus being viewed based on an observed brain state, such as BOLD activity.

Sound

Waves of compression and rarefaction in the air produced by vibrating objects, varying in amplitude (loudness) and frequency (pitch), with human hearing ranging between $20\text{--}20{,}000\,\text{Hz}$.

Cochlea

The spiral inner ear organ containing hair cells that performs auditory transduction and acts as a mechanical frequency analyzer.

Tonotopic Map

The orderly spatial arrangement of auditory structures where distinct sound frequencies stimulate specific subsets of hair cells or cortical neurons.

Tip Links

Filamentous structures connecting adjacent stereocilia that translate hair bundle movement into mechanical receptor potentials.

Superior Olivary Complex

The initial structure in the auditory pathway in the medulla that receives bilateral input from both ears to compute sound localization.

Medial Superior Olive (MSO)

A subregion of the superior olivary complex that computes horizontal sound localization by detecting interaural time differences via delay lines and coincidence detectors.

Inferior Colliculus

A midbrain auditory structure containing an auditory space map organized according to the spatial location of sound stimuli.

Medial Geniculate Nucleus (MGN)

A thalamic auditory nucleus that detects combinations of sound frequencies separated by specific time delays before relaying signals to the cortex.

Primary Auditory Cortex

Auditory cortex located below the Sylvian fissure in the temporal lobe consisting of Core, Belt, and Parabelt areas; Core possesses tonotopic mapping, with spatial features processed posteriorly and nonspatial features anteriorly.

Auditory Agnosia

An impairment characterized by the inability to recognize the meaning of sounds despite intact hearing, categorized into verbal, nonverbal, or mixed types.