Midterm 2 Cognitive Neuroscience

Sensation and perception, development, Object recognition, attention, action

Sensation general pathway

Stimulus energy —> Sensory Receptor Transduction—> Neural Impulses—>Brain

Sound Characteristics —> Stim Char

Amplitude=loudness, Frequency = Pitch, Complex Sounds = Timbre

Equal Loudness Contours

Hearing sensitivity varies across

frequencies.

• Equal-loudness contours explain how

sounds at different frequencies can

seem equally loud.

• Human hearing is most sensitive

between 3-4kHz, crucial for speech

perception.

Hearing Outer Ear to Inner Ear parts

Sound waves travel through

the air. Waves enter the

outer ear, where they are

focused and amplified.

• The tympanic membrane

(eardrum) vibrates in

response to sound waves

• Vibrations are transferred to

the cochlea through the

ossicles (tiny bones in the

middle ear)

Cochlea Transduction

The cochlea is a snail-shaped

structure containing three

fluid-filled tubes.

• Sound vibrations are

transformed into neural

signals.

• The basilar membrane

responds to fluid waves

created by these vibrations. Tonotopic organization

• Inner hair cells (~16K)

convert the vibrations into

electrical activity.

Hearing Transduction Type (Hair Cells)

Mechanoreception converts

sound waves into neural signals.

• Inner hair cells’ unique structure

is crucial for hearing.

• Each cell has a hair bundle that

response to basilar membrane

movement.

• Tip links between hairs open ion

channels when stretched.

• This triggers cell depolarization

and release neurotransmitters

onto auditory fibers.

Auditory Pathway to Brain

Auditory Nerve Sound signals are transmitted to the

cochlear nuclei in the brainstem,

• Signals are relayed to the olivary nuclei

on both sides of the brainstem.

• They travel through the lateral lemnisci

nerve bundles to the inferior colliculi.

• Signals are passed to the medial

geniculate nucleus (MGN) in the

thalamus that relays signals to primary

auditory cortex.

Lateral Superior Olive

measures intensity

differences between ears for sound localization of high frequency sounds

Neurons respond strongly when

the sound is louder in the ear

closer to the source (ipsilateral

ear).

• These neurons compute loudness

differences between the two ears.

• The LSO’s output helps the brain

localize sound horizontally.

Medial superior olive

measures timing

differences between ears for sound localization of low frequency sounds

Neurons respond to specific

timing differences between the

ears

• Example: a neuron responds most

strongly when the sound in one

ear leads the other by ~50μs.

• Neurons tuned to different delays

work together to localize sounds

based on timing disparities.

Auditory Damage

Full deafness to outer or middle ear/cochlea

damage beyond inner ear usually affects processing and not full deafness bc auditory pathways project bilaterally to cortex

A1 damage affects sound localization

Higher-order auditory cortex can affect sound recognition

2 (need to know) layers of skin

Epidermis: pathogen/water barrier
Dermis: location of most receptor

Merkel’s Disk

Slow adapting, Small RF, pressure and texture

Meissner Corpuscle

Fast adapting, small RF, stroke, fluttering, light vibr

Ruffini Endings

Slow adapting, large RF, stretches across skin

Pacinian Corpuscle

Fast adapting, Large RF, general vibration

Thermoreceptors

relay temperature information:

• Different classes detect warm or cold sensations.

• Cells fire at slow, steady rate; temperature changes alter

firing rate.

• Can be activated by non-temperature stimuli, e.g., capsaicin

(activates warm receptors) or menthol (activates cold).

Nociceptors

relay pain information:

• Three types: (1) mechanical activated by physical damage,

(2) thermal responds to extreme hot / cold, (3) chemical

activated by toxins, poisonous gases, and several cooking

spices

• Signal speed depends on fiber diameter and myelination,

affecting pain perception.

Proprioception

Proprioception: awareness of body position and

movement.

• Receptors in muscles and joints provide information

about limb position and movement.

Muscle spindles:

(1) Detect muscle length and stretching speed.

(2) Found at higher density in muscles used for fine

motor tasks

Golgi tendon organs

measure muscle tension and

prevent damage by limiting overcontraction.

• Proprioceptive receptors enable precise object

manipulation and help maintain balance.

Somatosensory Topographic Map

Receptors send signals through

primary afferent fibers of dorsal

root ganglion neurons.

• The body is divided into skin

regions called dermatomes, each

connected to specific dorsal root

ganglia

Somatosensory Pathway to Brain

Most signals decussate (cross the midline) and are relayed to

the contralateral brain regions.
After decussation in the brainstem, signals travel to the

thalamus (ventral posterior nucleus) and then to S1

(primary somatosensory cortex).

Smell Pathway from OE to OB

Olfactory receptors bind to odorants and generate

electrical signals.

• Receptors recognize odorants based on molecular

features, not the overall odor.

• Each receptor responds to multiple odorants with

shared molecular characteristics (pattern encoding).

• Axons from similar receptor types converge on an

olfactory glomerulus in the olfactory bulb.

• Mitral and tufted cells receive these signals,

preserving odor specificity

Olfactory Pathway to the Brain

Olfactory pathway bypasses the

thalamus, connecting directly to the

cortex

• Primary olfactory cortex receives input

from the bulb.

• Signals are relayed to the hippocampus,

amygdala, and indirectly to the reticular

formation and hypothalamus.

Taste Receptor Locations

tongue,

palate, pharynx, epiglottis, and esophagus

5 tastants

Five categories of tastants: sweet (sucrose),

salty (sodium chloride), bitter (quinine), sour

(citric acid), and umami (MSG).

Gustatory Pathway

Primary gustatory afferent neurons relay taste signals

from taste cells to the brainstem.

• Signals proceed to the thalamus, then the primary

gustatory cortex (frontal operculum), and finally to the

insula (secondary taste areas).

• Damage to the primary gustatory cortex impairs taste

perception, whereas damage to the insula affects food

recognition and flavor intensity.

Stim Char—> Light Char

Hue = Wavelength
Brightness = Amplitude
Saturation = Light Complexity

Rod receptors

more numerous in humans and sensitive dim

light.

• Detect variations in light intensity.

• Many rods converge onto a single output cell,

reducing spatial precision.

Cone receptors:

10-100x less sensitive than rods and function

best in bright environments.

• Enable color vision via 3 types that respond to

different light frequencies.

• Each cone connects to an individual output cell,

precise and provide high acuity

Phototransduction

Light entering the eye triggers a

photochemical reaction in the rods

and cones.

• Light activates pigment molecules (e.g.,

rhodopsin) in the receptors, causing

them to break apart and alter the

membrane potential, initiating

neurotransmitter signaling.

• Bipolar cells are activated and, in turn,

stimulate ganglion cells.

• Ganglion cells transmit electrical

signals to the brain via the optic nerve.

Adaptation Mechanism (4)

Adaptation mechanisms help the retina adjust to ambient

illumination by:

(1) pupil size adjustment

(2) switching between rods and cones

(3) photopigment regeneration

(4) lateral inhibition

Sensory Adaptiation

Sensory adaptation reduces responsiveness to constant

stimulation, allowing focus on changes in input.

Visual Pathway (Optic Nerve to Brain)

Optic Nerve —> Cross at Optic Chaism (causing Contralateral projection of visual fields), then to LGN or Superior Colliculus. From LGN to V1

Receptive Fields + ON/Off Center Organization of RF

Visual receptive field: each retinal ganglion

cell responds to stimulation in a specific area

of visual space.

• Retinal ganglion cells maintain a center-

surround organization

• On-center cells: maximally active when light

stimulates the RF center.

• Off-center cells: respond to light in the

surround by not the RF center.

Mach Band Illusion

Mach bands: contrast between slightly differing shades

of gray is exaggerated.

• Lateral inhibition makes the darker area appear darker

and the lighter area appear lighter along the boundary.
Receptive field on a lighter band generates a stronger

response because part of its surround overlaps with the

darker areas.

Perception

the process of selecting, organizing, and interpreting sensory information to create

meaningful experiences.

the process of selecting, organizing, and interpreting sensory information to create

meaningful experiences.

Lightness constancy: perceived brightness or color

of an object remains constant under varying

illumination.

• Essential for recognizing objects as having consistent

properties regardless of lighting.

Color constancy

the tendency to perceive object

colors as stable despite changes in environmental

conditions (e.g., lighting).

• Even though all pixel data contains more green than

red, the strawberries appear red because our brain

uses context and prior knowledge of their natural

color.

Size constancy:

Perceptual mechanism where

objects are perceived as maintaining consistent

size, even when their distance changes.

• Changes in distance alter the size of the image

projected onto the retina, but not our perception

of the object’s size.

Shape constancy

Perceptual tendency to

maintain the perception of an object’s

shape, even as the viewing angle changes.

• Changes in viewing angle alter the shape of

the object’s retinal image but not our

perception.

Illusory motion

Contrast and spatial arrangement

of adjacent colored segments create

the illusion of motion in static

images.

Ponzo illusion:

Ponzo illusion: Two identical

horizontal lines appear to be different

in length due to their visual context.

• Often occurs with converging lines or

perspective cues that mimic a three-

dimensional scene (e.g., railway tracks). The line closer to the converging point

(or further away in the scene) appears

longer

Gestalt principles

Fundamental organizing

principles in perceptual psychology.

• Explain how we integrate sensory input into

meaningful wholes.

Illusory contours

Perceived edges and shapes

that aren’t physically present.

Multi-stable images:

Ambiguous stimuli that can

switch between alternative interpretations

Illusory contours Necker cube

Rubin’s vase Duck-rabbit

Cortical magnification:

certain sensory regions (e.g., fovea or fingertips)

are represented by disproportionately larger cortical areas.

Simple cells

V1 emerge

from this convergence and

respond selectively to specific

orientations (e.g., vertical or

horizontal lines) layer IV prefers bars of light or bars

of dark

V1 complex cells

integrate

inputs from multiple simple

cells.

• They respond to more

advanced visual features, such

as motion and texture

orientation

Hypercomplex cells

sensitive to length (short)

• aka end-stopping

hypercolumn

1mm block of cortex

containing a full set of orientation columns and

ocular dominance columns for a given retinotopic

location.

• This structure ensures all orientations and both

eyes’ inputs are represented within a single

visual field location.

Visual Heirarchy

V1<V2<V4<TEO<TE

Parvocellular Pathway

p-cell, small cells/RF, color sensitive, sustained response—> fine detail and color

Magnocellular Pathway

M-cells, larger RF/Cells, color insensitive, transient response —> motion and coarse detail

Dorsal Visual Pathway

Where; The dorsal pathway (occipital → parietal) processes

spatial location, movement, and relationships, aiding in

navigation and movement coordination

Ventral visual pathway

where;(occipital → temporal) specializes in

object identification, face recognition, and fine detail

perception, determining what we see

MT Processing

MT neurons are finely tuned to direction

and speed, enabling detection of object

trajectories and velocities.

• This tuning allows for precise motion

interpretation, supporting navigation

and understanding of dynamic

environments.

Specific MT Cells (3)

Pattern cells (~1/3 of MT neurons) detect

global motion in plaid patterns, exhibiting

single-lobed tuning centered on the overall

motion direction.

• Component cells respond to individual

grating movements, showing two tuning

peaks aligned with each component’s motion

direction.

• Some intermediate neurons exhibit broad

tuning without clear double peaks, suggesting

a role in bridging global and local motion

processing.

Achromatopsia

(loss of color vision) is linked to

ventral temporal damage (e.g., V4).

Akinetopsia

deficit in motion perception) is

associated with lateral occipito-temporal

damage (e.g., MT).

Regularity of Brain Function (2)

1) Consistent organization of brain areas

2) Consistent organization of brain function

Protomap theory

states that cortical

cells are preassigned

to specific functional

areas by genetic and

molecular markers

early in development.

This suggests a

blueprint-like

structure guiding

cortical organization.

Protocortex theory

argues

that the cortex starts as a

uniform structure, with

functional areas developing

postnatally through sensory

input and experience.

Ethology

examines animal behavior in natural

environments, historically emphasizing genetic

influences

General-Process Learning

General-process approach focused on

associative learning and conditioned

behavior (e.g., Pavlov & Skinner).

• Assumes learning follows universal

principles across species and contexts.

• Emphasizes conditioning and

reinforcement over innate behavioral

predispositions.

• Focuses on observable behavior rather

than internal cognitive processes

Experience-expectant:

Development is shaped by environmental input that is ubiquitous across

individuals and evolution.

• Intrinsic overproduction of connections, with survival determined by

experience.

Domain-relevant:

The brain begins with general biases and becomes specialized through

experience.

• Evolution has made brains more adaptable and less rigidly hard-wired.

Probabilistic epigenesis

The environment influences gene activation.

• Genes and environment interact to shape function.

Radial Migration

adial migration is the predominant

mechanism for excitatory pyramidal neurons,

which originate in the ventricular zone and

migrate outward to the cortical plate.

• Neural stem cells in the VZ divide to generate

new neurons, which then travel along radial

glial fibers that act as a scaffold for migration.

• This structured movement is crucial for

establishing the layered organization of the

cerebral cortex.

Tangential Migration

nhibitory

interneurons originate from

specific proliferative zones and

travel in diverse streams toward

the cerebral wall.

• Once in the cerebral cortex, they

refine their positions through both

radial and tangential adjustments.

Radial Unit Hypothesis

Radial scaffold fibers guide neuronal

migration from the ventricular surface to the

cortex.

• Neurons born in the same ventricular zone

region form vertical cortical columns.

• Cortex develops inside-out, with deep layers

forming first, followed by superficial layers.

• Neurons in a column may be clonally related,

originating from the same progenitor cells

Occlusion tolerance

allows recognition

even when objects are partially hidden.

Methods in Studying Visual Recognition

Theoretical and behavioral work provide insights into the processes and mechanisms of

object recognition.

• Lesion work reveals the specificity of visual deficits from brain damage, showing how

different areas contribute to various aspects of vision.

• Neuroimaging provides a macroscale view, identifying regions involved in visual processing

and their functions.

• Electrophysiology examines individual neuron responses to objects and stimuli, offering a

microscale perspective.

• Computational modeling helps uncover the underlying algorithms that simulate how the

brain processes visual information for object recognition.

Foveating

llows high-resolution

focus on specific regions while

peripheral vision captures less

detail. The brain directs the fovea to areas

most relevant for interpreting visual

information.

Double Dissociation Object recognition

Monkeys were first shown an object and

then, during a test phase, were given the

choice to select an object they had not seen

before (novel object) to receive a reward. (Temporal Lesion)

Double Dissociation Landmark Task

Monkeys were trained to recognize landmarks

and subsequently required to choose the food

well located nearest to a tall cylinder, serving

as the landmark, to obtain a reward (Parietal Lesion)

Patient DF

Patient DF could detect light and colors, with

normal acuity and visual memory.

• She had no difficulty naming objects (not anomia)

but showed severely impaired picture

recognition.

• She produced crude descriptions of displayed

objects and struggled with simple geometric

forms.

• Findings suggest a deficit in form perception,

linked to ventral stream damage.

Optic Ataxia

Deficit in coordinating visual

input and hand movements

Apperceptive Agnosia

Individuals can see elements

of objects but struggle to synthesize them into

recognizable shapes, affecting their ability to

recognize or copy designs

Typical Presentation:

• Individuals can see basic features (e.g., lines, edges) but

cannot combine these features into a meaningful whole

shape.

• They often cannot match or copy simple figures

accurately because the overall shape is not perceived in

an organized way

Patient F.R.A.

Normal visual acuity, speech, spatial

sensitivity, and memory, alongside an

ability to detect basic shapes.

• Has challenges in naming objects

presented visually and does not

recognize 'a' and 'A' as representing the

same letter.

• Cannot name objects he sees, but he

can color in parts of complex

drawings, demonstrating his ability to

dissect visual stimuli without

recognizing them.

Associative Agnosia

Individuals can perceive and

detail objects but fail to connect these perceptions

to known objects, leading to an inability to recognize

objects despite clear visual representation.

Typical Presentation:

• Individuals can typically copy or match objects quite

accurately, suggesting that “lower-level” perception is

intact.

• However, they cannot recognize the object or link it to

semantic knowledge (e.g., naming or stating its function).

Patient CK

Struggles to perceive objects as a unified whole

and tends to dissect objects into their

components.

• Capable of drawing objects even when he cannot

name them. e.g., when tasked with replicating a

figure, his drawing was accurate, with the two

diamonds and the circle being easily distinguishable.

However, the sequence in which he drew the

segments was unconventional.

Integrative Agnosia

Individuals can identify simple

shapes but cannot recognize the object as a whole,

especially in complex or jumbled presentations.

Typical Presentation:

• Individuals can identify separate components (e.g., color,

lines, corners) but cannot effectively “group” these

features when the presentation is complex.

• For simpler shapes, they might do better, but once the

object’s parts overlap or are jumbled, recognition falls

apart.

• They may produce highly fragmented copies or drawings,

indicating they struggle to see how pieces fit together.

Lateral Occipital Complex

The Lateral Occipital Complex (LOC) in the ventral temporal cortex is crucial for object

recognition, with particular sensitivity to object shapes.

• Its ability to process shape information is essential for identifying and differentiating

objects, reflecting the brain’s specialization in detailed visual processing.

prioritizes structural and

geometric configurations

rather than the semantic

meaning of visual stimuli. processes shape

independently of specific

visual cues,

Face Selective Regions (7)

1, occipital face area

2. posterior FFA

3. anterior FFA

4. posterior STS

5. middle STS

6. anterior STS

7. anterior temporal

Scene Selective Regions (3)

PPA
RSC
OPA

Localist (Clustered) Coding:

A selective response where a small subset

of neurons is activated by a specific

stimulus, creating an efficient and

specialized representation of visual

information.

Distributed Coding:

A broader array of neurons responds to

various stimuli, with each stimulus

represented by a unique pattern of neural

activity, allowing for a rich and nuanced

perception of the visual environment.

Univariate MRI

sees MR signal in a specific region

MVPA

sees multi voxel activity patterns across conditions across club

Prosopagnosia

A neurological disorder characterized by an

inability to recognize faces, including

familiar ones, while object recognition and

other visual processing typically remain

intact.

• Often results from damage to ventral

stream regions, particularly the fusiform

face area (FFA) in the temporal lobe,

which is specialized for facial recognition.

WJ

A 51-year-old professional developed

prosopagnosia following a series of strokes.

• Afterward, he took up sheep farming.

• Although human face recognition is typically

easier than recognizing sheep, WJ found it

easier to recognize sheep than human faces.

KC

Able to perceive individual parts

but not the whole (integrative

agnosia).

• Experiences alexia, an inability to

recognize written words,

• Retains the ability to recognize

faces.

Acquired Prosopagnosia

an individual's ability to recognize faces is impaired due to brain injury,

such as a stroke, affecting areas of the brain specialized in facial

recognition.

Developmental (Congenital) Prosopagnosia:

Face recognition impairment present from birth.

• Affecting approximately 2% of the population.

• Lacks a clear link to any specific neurological condition.

• This contrasts with "Super-Recognizers," individuals who possess an

extraordinary ability to recall and recognize faces - showcasing the wide

spectrum of facial recognition capabilities.

View-Dependent, Exemplar-Specific Model of Object Recognition

Suggests the brain stores multiple views of

an object, enabling recognition by

matching the current view with these

stored exemplars.

• This model explains why we recognize

objects more quickly and accurately when

viewed from familiar or typical

viewpoints, based on prior experience.

• It also accounts for the difficulty in

recognizing objects from uncommon or

unusual perspectives, as these may not

align with stored exemplars, leading to

slower or less accurate identification.