CNS exam 2

Sensation

The effects of a stimulus on the sensory organs.

Perception

The elaboration and interpretation of a sensory stimulus based on, for example, knowledge of how objects are structured.

Retina

The internal surface of the eyes that consists of multiple layers. Some layers contain photoreceptors that convert light to neural signals, and others consist of neurons themselves.

Rod cells

A type of photoreceptor specialized for low levels of light intensity, such as those found at night.

Cone cells

A type of photoreceptor specialized for high levels of light intensity, such as those found during the day, and specialized for the detection of different wavelengths.

Receptive field

The region of space that elicits a response from a given neuron.

Fovea

The point in the retina with the highest concentration of cones, where visual acuity is greatest.

Bipolar cells

A type of neuron in the retina that behaves in one of two ways: detecting light areas on dark backgrounds (ON) or detecting dark areas on light backgrounds (OFF).

Retinal ganglion cells

Neurons that process visual information with a complex set of on and off properties.

Blind spot

The point at which the optic nerve leaves the eye; there are no rods and cones present there.

Primary visual cortex (or V1)

The first stage of visual processing in the cortex; the region retains the spatial relationships found on the retina and combines simple visual features into more complex ones.

Parvocellular cells

Cells that respond to detail and are concerned with color vision.

Simple cells

Cells that respond to light in a particular orientation (or points of light along that line).

Complex cells

Cells that respond to light in a particular orientation but do not respond to single points of light.

Hypercomplex cells

Cells that respond to particular orientations and particular lengths.

Geniculostriate pathway

The dominant visual pathway in the human brain that travels to the primary visual cortex via the lateral geniculate nucleus (LGN).

Lateral geniculate nucleus (LGN)

A processing station in the visual pathway that relays information to the primary visual cortex.

Center-surround cells

Cells that form the building blocks for more advanced processing by the brain, enabling detection of edges and orientations.

Visual acuity

The level of detail that can be perceived, greatest at the fovea.

Hemianopia

Cortical blindness restricted to one half of the visual field (associated with damage to the primary visual cortex in one hemisphere).

Quadrantanopia

Cortical blindness restricted to a quarter of the visual field.

Scotoma

A small region of cortical blindness.

Retinotopic organization

The receptive fields of a set of neurons are organized in such a way as to reflect the spatial organization present in the retina.

Blindsight

A symptom in which the patient reports not being able to consciously see stimuli in a particular region but can nevertheless perform visual discriminations (e.g., long, short) accurately.

Ventral stream

In vision, a pathway extending from the occipital lobes to the temporal lobes involved in object recognition, memory and semantics.

Dorsal stream

In vision, a pathway extending from the occipital lobes to the parietal lobes involved in visually guided action and attention.

V4

A region of the extrastriate cortex associated with color perception.

V5 (or MT)

A region of the extrastriate cortex associated with motion perception.

Achromatopsia

A failure to perceive color (the world appears in grayscale), not to be confused with color blindness (deficient or absent types of cone cell).

Akinetopsia

A failure to perceive visual motion.

Color constancy

The color of a surface is perceived as constant even when illuminated in different lighting conditions.

Biological motion

The ability to detect whether a stimulus is animate or not from movement cues alone.

Figure-ground segregation

The process of segmenting a visual display into objects versus background surfaces.

Lateral occipital complex (LOC)

A region of the brain that is specialized for processing object shapes.

Integrative agnosia

A failure to integrate parts into wholes in visual perception.

Object constancy

An understanding that objects remain the same, irrespective of differences in viewing condition.

Adaptation (or repetition suppression)

A reduced neural response to a stimulus, or stimulus feature, that is repeated.

Category specificity

The notion that the brain represents different categories in different ways (and/or different regions).

Face recognition units (FRUs)

Stored knowledge of the three-dimensional structure of familiar faces.

Person identity nodes (PINs)

An abstract description of people that links together perceptual knowledge (e.g., faces) with semantic knowledge.

Fusiform face area (FFA)

An area in the inferior temporal lobes that responds more to faces than other visual objects, and is implicated in processing facial identity.

Prosopagnosia

Impairments of face processing that do not reflect difficulties in early visual analysis (also used to refer to an inability to recognize previously familiar faces).

Categorical perception

The tendency to perceive ambiguous or hybrid stimuli as either one thing or the other (rather than as both simultaneously or as a blend).

Pure tones

Sounds with a sinusoid waveform (when pressure change is plotted against time).

Pitch

The perceived property of sounds that enables them to be ordered from low to high.

Loudness

The perceived intensity of the sound.

Fundamental frequency

The lowest frequency component of a complex sound that determines the perceived pitch.

Missing fundamental phenomenon

If the fundamental frequency of a complex sound is removed, then the pitch is not perceived to change (the brain reinstates it).

Timbre

The perceptual quality of a sound enables us to distinguish between different musical instruments.

Cochlea

Part of the inner ear that converts liquid-borne sound into neural impulses.

Basilar membrane

A membrane within the cochlea containing tiny hair cells linked to neural receptors.

Primary auditory cortex

The main cortical area to receive auditory-based thalamic input.

Belt region

Part of the secondary auditory cortex, with many projections from the primary auditory cortex.

Parabelt region

Part of the secondary auditory cortex, receiving projections from the adjacent belt region.

Tonotopic organization

The principle that sounds close to each other in frequency are represented by neurons that are spatially close to each other in the brain.

Inter-aural time difference

The difference in timing between a sound arriving in each ear (used to localize sounds).

Inter-aural intensity difference

The difference in loudness between a sound arriving in each ear (used to localize sounds).

Head-related transfer function

An internal model of sounds get distorted by the unique shape of one's own ears and head.

Planum temporale

A part of the auditory cortex (posterior to the primary auditory cortex) that integrates auditory information with non-auditory information, for example to enable sounds to be separated in space.

Auditory stream segregation

The division of a complex auditory signal into different sources or auditory objects.

Mismatch negativity (MMN)

An ERP component that occurs when an auditory stimulus deviates from previously presented auditory stimuli.

Cocktail party problem

The problem of attending to a single auditory stream in the presence of competing streams (with different acoustic and spatial properties)—for instance, attending to one person's voice in a noisy room of other voices.

Amusia

An auditory agnosia in which music perception is affected more than the perception of other sounds.

Tone-deafness (or congenital amusia)

A developmental difficulty in perceiving pitch relationships.

Prosody

Changes in the stress pattern of speech (e.g., to add emphasis), the rhythm of speech or the intonation (e.g., rising/falling pitch to indicate questioning or sarcasm).

Melody

Patterns of pitch over time.

Pure word deafness

Type of auditory agnosia in which patients are able to identify environmental sounds and music but not speech.

Spectrogram

Plots the frequency of sound (on the y-axis) over time (on the x-axis) with the intensity of the sound represented by how dark it is.

Allophones

Different spoken/acoustic renditions of the same phoneme.

Formants

Horizontal stripes on the spectrogram produced with a relative free flow of air (e.g., by vowels).

Voicing

Vibration of the vocal cords that characterizes the production of some consonants.

Co-articulation

The production of one phoneme is influenced by the preceding and proceeding phonemes.

Arcuate fasciculus

A white matter bundle that connects the temporoparietal region to the frontal lobes.

McGurk illusion

An auditory percept derived from a fusion of mismatching heard speech and seen speech.

Attention

The process by which certain information is selected for further processing and other information is discarded.

Inattentional blindness

A failure to be aware of a visual stimulus because attention is directed away from it.

Change blindness

A failure to notice the appearance/disappearance of objects between two alternating images.

Salient

Any aspect of a stimulus that, for whatever reason, stands out from the rest.

Orienting

The movement of attention from one location to another.

COVERT ORIENTING

The movement of attention from one location to another without moving the eyes/body.

Overt orienting

The movement of attention accompanied by movement of the eyes or body.

Inhibition of return

A slowing of reaction time associated with going back to a previously attended location.

Exogenous orienting

Attention that is externally guided by a stimulus.

Endogenous orienting

Attention is guided by the goals of the perceiver.

Visual search

A task of detecting the presence or absence of a specified target object in an array of other distracting objects.

Attentional blink

An inability to report a target stimulus if it appears soon after another target stimulus.

Lateral intraparietal area (LIP)

Contains neurons that respond to salient stimuli in the environment and are used to plan eye movements.

Saccade

A fast, ballistic movement of the eyes.

Salience map

A spatial layout that emphasizes the most behaviorally relevant stimuli in the environment.

Remapping

Adjusting one set of spatial coordinates to be aligned with a different coordinate system.

Frontal eye field (FEF)

Part of the frontal lobes responsible for voluntary movement of the eyes.

Hemispatial neglect

A failure to attend to stimuli on the opposite side of space to a brain lesion.

Pseudo-neglect

In a non-lesioned brain there is over-attention to the left side of space.

Phenomenal consciousness

The "raw" feeling of a sensation, the content of awareness.

Access consciousness

The ability to report on the content of awareness.

Pop-out

The ability to detect an object among distractor objects in situations in which the number of distractors presented is unimportant.

Illusory conjunctions

A situation in which visual features of two different objects are incorrectly perceived as being associated with a single object.

Early selection

A theory of attention in which information is selected according to perceptual attributes.

Late selection

A theory of attention in which all incoming information is processed up to the level of meaning (semantics) before being selected for further processing.

Negative priming

If an ignored object suddenly becomes the attended object, then participants are slower at processing it.