PRELIM 2

Sensation

The process of transforming physical energy (e.g., light) into neural signals that can be interpreted by the brain

Receptive field

The specific region of sensory space in which a stimulus will modify the firing of a neuron; in vision, the portion of the visual field a neuron responds to

Retinotopic map

A spatial mapping in V1 where neighboring neurons correspond to neighboring locations on the retina, preserving the layout of the visual field

Cortical magnification

The disproportionate representation of the fovea in V1, where central vision occupies more cortical space than peripheral vision

Phototransduction

The process by which photoreceptors (rods and cones) convert light into neural signals

Rods

Photoreceptors with high sensitivity to light, many inputs per cell, low spatial resolution, specialized for motion and low-light vision

Cones

Photoreceptors with low sensitivity but high acuity, few inputs per cell, specialized for color and fine detail

Magnocellular pathway

Visual pathway originating primarily from rods, integrating information across many inputs, sensitive to motion and luminance, fast but low spatial resolution

Parvocellular pathway

Visual pathway originating primarily from cones, with fewer inputs, sensitive to color and fine detail, slower but high spatial resolution

Optic chiasm

The structure where optic nerve fibers partially cross, resulting in contralateral organization of visual input

Lateral Geniculate Nucleus (LGN)

Thalamic relay structure that organizes visual input into layers and transmits it to V1

Primary Visual Cortex (V1)

The first cortical stage of visual processing, extracting basic features such as edges, orientation, and motion direction

Hierarchical processing (vision)

The progressive transformation of visual information from simple features (edges) in early areas to complex, abstract representations (objects) in higher areas

Feedforward processing

Bottom-up processing where information flows from lower-level sensory input (e.g., edges) to higher-level representations

Feedback processing

Top-down influence where higher-level expectations and prior knowledge shape perception of incoming sensory information

Invariance problem

The challenge of recognizing the same object despite variations in viewpoint, lighting, or size, solved via hierarchical abstraction

Ambiguity (vision)

The problem that a single visual input can correspond to multiple possible interpretations

Context effects (vision)

The use of surrounding information and prior knowledge to disambiguate visual input

Ventral stream (“what”)

Visual pathway projecting to the temporal lobe, specialized for object recognition, identity, and color

Dorsal stream (“where/how”)

Visual pathway projecting to the parietal lobe, specialized for spatial processing and guiding actions

Akinetopsia

A deficit caused by damage to area V5/MT resulting in impaired perception of motion

Prosopagnosia

A deficit associated with damage to fusiform face area leading to inability to recognize faces

Apperceptive agnosia

A deficit in early perceptual processing where individuals cannot form coherent visual representations of objects

Associative agnosia

A deficit where perception is intact but individuals cannot associate visual input with meaning

Double dissociation

Evidence for functional specialization where damage to area A impairs function X but not Y, and damage to area B impairs Y but not X

Body representation

Internal representation of the position and movement capabilities of one’s limbs required for action planning

Spatial representation

Encoding of object location, distance, and movement relative to a reference frame

Reference frame

The coordinate system used to encode spatial location, such as egocentric (self-based) or allocentric (world-based)

Egocentric reference frame

Representation of spatial information relative to the observer (e.g., eye-centered or head-centered coordinates)

Allocentric reference frame

Representation of spatial information independent of the observer, relative to other objects or the environment

Posterior Parietal Cortex (PPC)

Brain region that integrates sensory information and body representation to transform perception into action plans

Optic ataxia

A disorder resulting from parietal damage where individuals can perceive objects but cannot accurately reach toward them

Effector

A body part (e.g., eyes, arm, hand) used to execute an action, with specialized neural systems for each

Lateral Intraparietal area (LIP)

Region involved in planning eye movements (saccades) with neurons tuned to direction relative to eye or head

Parietal reach region

Area involved in planning reaching movements of the arm

Anterior Intraparietal area (AIP)

Region involved in shaping the hand for grasping based on object properties

Motor hierarchy

The organization of movement from abstract goals to concrete motor execution (goal → actions → movements → muscle activity)

Premotor cortex

Region that selects movements based on sensory input and external cues

Dorsal premotor cortex (PMd)

Area involved in planning and selecting movements toward spatial targets (reach direction)

Ventral premotor cortex (PMv)

Area involved in shaping the hand and adjusting grip based on object properties

Supplementary Motor Complex (SMC)

Region involved in planning and organizing sequences of movements and tracking position within a sequence

Primary Motor Cortex (M1)

Region responsible for executing voluntary movements by sending signals to muscles

Basal ganglia

Subcortical structures that select and initiate desired actions while inhibiting competing or unwanted movements based on goals and value

Parkinson’s disease

Movement disorder associated with excessive inhibition in basal ganglia circuits due to dopamine loss, resulting in difficulty initiating movement

Huntington’s disease

Movement disorder associated with reduced inhibition in basal ganglia circuits, leading to uncontrolled, excessive movements

Cerebellum

Brain structure responsible for coordination, timing, and error correction of movement through predictive modeling

Forward model

Internal prediction of the sensory consequences of a movement used by the cerebellum to compare expected vs actual outcomes

Prediction error

The difference between expected and actual sensory feedback used to update motor commands and learning

Central pattern generators

Spinal cord circuits that produce rhythmic movements such as walking without requiring continuous cortical input

Navigation

The process of moving through space using spatial representations and different strategies (cue-based, route-based, map-based)

Place cells

Neurons in the hippocampus that fire when an organism is in a specific location, forming an allocentric spatial map

Grid cells

Neurons in the entorhinal cortex that fire in a grid-like pattern to encode spatial distance and structure

Head direction cells

Neurons that fire based on the direction an organism is facing

Phonology

The rules governing the structure and organization of speech sounds (phonemes) that distinguish meaning

Morphology

The rules governing the structure of morphemes, the smallest meaningful units of language

Syntax

The rules governing how words are combined into grammatical sentences

Semantics

The representation of meaning in language at the level of words and sentences

Pragmatics

The influence of context, intention, and social cues on language interpretation

Auditory pathway

The neural pathway from ear to cortex (cochlea → brainstem → inferior colliculus → medial geniculate nucleus → A1)

Primary auditory cortex (A1)

Region that processes basic auditory features such as frequency and is organized tonotopically

Tonotopic organization

Spatial mapping of sound frequency across the auditory cortex

Speech segmentation

The process of dividing continuous speech into discrete units such as words despite lack of clear boundaries

Ambiguity (language)

The property that a single sound sequence can correspond to multiple meanings

Invariance problem (language)

The challenge that the same phoneme can sound different across speakers and contexts

Dual-stream model (language)

Model proposing two pathways: ventral stream for sound-to-meaning mapping and dorsal stream for sound-to-action mapping

Ventral stream (language)

Pathway involved in mapping auditory input to semantic meaning

Dorsal stream (language)

Pathway involved in mapping auditory input to motor representations for speech production

Hierarchical processing (language)

Organization of language processing from phonemes to morphemes to sentences to meaning

Temporal receptive window

The time span over which a brain region integrates information, increasing from early auditory areas to higher-level regions

Predictive processing (language)

The use of context and prior knowledge to anticipate upcoming linguistic input

Phonemic restoration

Phenomenon where the brain perceptually fills in missing speech sounds based on context