Brain And Perception 1 Flashcards
How Many Senses do we Have?
1.Vision
2.Audition (hearing)
3.Touch
4.Taste
5.Smell
6.Proprioception/ Vestibular perception
Features of All Sensory Systems
energy into electricity/ require neurons/ have receptive field/ Sensory neurons react to environmental stimuli by
firing action potential/ create a sensory relay
Principles of sensation
1.Hierarchical organisation
2.Functional segregation
3. Parallel processing
4.Multisensory integration
Hierarchical organisation - principles of sensation
processing becomes more complex & specific the further up the sensory pathways we go
Functional Segregation - principles of sensation
Primary, secondary, and association cortex take care of different functions across all senses
Parallel Processing - principles of sensation
Signals are processed in parallel across multiple pathways – some pathways are in consciousness, some are not
Multisensory Integration - principles of sensation
Our brain can integrate information across two or more sensory systems
Sensation
the process of detecting the presence of stimuli
Perception
the higher-order process of integrating, recognising and interpreting complete patters of sensations
Visual sensation
Humans are vision-dominant.
Vision involves converting light energy into electricity for the brain to comprehend.
Humans can process lightwaves with a wavelength of 380-760nm.
Association Cortex
The association cortex, distributed across many brain parts, has its largest single section situated in the parietal lobe.
Secondary Visual Cortex
The secondary visual cortex consists of two areas, one surrounding the primary visual cortex in the occipital lobe and another in the temporal lobe.
Primary Visual Cortex
The primary visual cortex, responsible for initial visual processing, is located in the occipital lobe.
Brain Areas and Vision
Areas of the brain associated with vision are the occipital lobe (primary role), as well as the temporal and parietal lobes.
Vision Dominance
Humans are vision-dominant.
Vision Process
Vision involves converting light energy into electricity for the brain to understand.
Light Processing Range
Humans can process lightwaves with a wavelength of 380-760nm.
Cortical Neurons and Visual Field
Each point in your visual field has a corresponding cortical neuron that fires only when something appears in its visual field.
Pupil Adjustment
The pupil adjusts to the amount of light in the environment. In bright conditions, it constricts, providing great acuity (detail). In dim conditions, it dilates, resulting in lower acuity
Accomadation
The lens, situated behind the pupil, focuses light onto the retina through a process called accommodation.
Depth Perception
Allows us to perceive depth through binocular disparity. Monocular cues provide information about size and shape in depth perception.
Binocular Vision
Binocular vision compares input from both eyes to create the perception of depth, known as stereopsis.
Shape Constancy
Shape constancy enables seeing an object with a constant shape from different angles. Both eyes contribute, recognizing a single shape and creating stereopsis—the impression of depth.
How is depth perceived
Depth is perceived when visual stimuli from each eye are compared binocularly, using both eyes to assess factors such as distance, size, or shape.
Retinal Pathway
- Light hits the back of the eye (retina).
- Retina contains visual receptors (receptor cells)
- Information from receptor cells is sent to bipolar cells.
- Bipolar cells transmit their messages to ganglion cells.
- Ganglion cells’ axons join together and travel back to the brain.
Foveal Fixation
When focusing, stimuli are fixated on the fovea, the central part of the retina.
Fovea Specialization
Fovea is specialized for focus and detail in vision.
Foveal Connection to Brain
Each foveal receptor connects directly to a bipolar cell, and each bipolar cell connects directly to a ganglion cell.
Peripheral vision - retina
Towards the periphery of the retina, multiple receptor cells converge onto bipolar and ganglion cells/ Peripheral vision is less detailed due to this convergence.
What are the visual receptor cells? – also referred to as photoreceptors
Visual receptor cells, also known as photoreceptors, include two types: rods and cones.
Rods (Photoreceptors)
■ Most numerous
■ Especially in the periphery of retina
■Operate in dim light
■Lack colour and detail processing – high sensitivity, low acuity
■Many rods converge onto a single retinal ganglion cell via a rod bipolar cell
Photoreceptors: Cones
■Less numerous – but more concentrated in and near the fovea.
■Operate in bright light
■Process colour information – high acuity
■Only a few cones converge onto a single retinal ganglion cell via a cone bipolar cell
rhodopsin
In rods, the pigment (chemical) is called rhodopsin
photopsin
In cones (which are responsible for colour information), the pigment is called photopsin
Missing Photopsin
If you are missing photopsin, the ability to process color information would likely be impaired, affecting color vision
The Retinal Ganglion Cells
M cells (magnocellular)
P cells (parvo cellular)
M cells (magnocellular) - The Retinal Ganglion Cells
–Specialised for motion detection
–Larger and more sparse than P cells
–Large receptive field
–Across retina
P cells (parvocellular) - The Retinal Ganglion Cells
–Specialised for object detection and colour sensitivity
–Smaller and more numerous than M cells
–Small receptive field
–Near fovea
Ganglion Connection
Ganglions connect to the brain through axons forming the optic nerve.
The Retinal Ganglion Cells function
The two kinds of ganglions carry parallel channels of information via the thalamus to the visual cortex
Cortical Visual Processing
Visual pathways bring information to the cortex
Primary Visual Cortex (V1)
Also known as Brodmann Area 17/ Receives majority of projections from the lateral geniculate nuclei/ Conducts simple processing before forwarding information to secondary visual areas.
Secondary Visual Cortex (V2-V5)
Comprises areas V2 through V5/ involved in further visual processing beyond the primary visual cortex.
Association Cortex
Found in regions of the parietal and temporal cortex/ Contributes to higher-order processing in visual perception.
Two Types of Cells Based on Receptive Fields
On-centre cells: Fire if the center of their receptive field is stimulated.
Off-centre cells: Fire if the peripheries of their receptive field are stimulated.
Receptive Fields
In the context of vision, it’s the area in the visual field that can excite or inhibit a neuron’s activity.
Receptive field of a rod or cone
The receptive field of a rod or cone is the point in space from which light strikes the cell.
Hubel & Wiesel (1959) experiment
Hubel & Wiesel (1959) implanted electrodes into single cells in the retinas, lateral geniculate nuclei, and visual cortex of cats
Three main types of cells in the interblobs
Simple cells
Complex cells
Hypercomplex or end-stopped cells
Simple Cells
■Respond to orientation
■They have fixed receptive fields of on and off regions in straight lines
■Tilting or moving light source = decreased response
Complex cells in V1, V2
■ Bar-shaped receptive fields
■No fixed field
■Strongest response to a moving stimulus
Cell response in one location only
Simple cell
Cell response across a large area
complex cell
End-stopped or Hypercomplex Cells
■Strong inhibitory/off area at one end of its bar-shaped receptive field
■Response to moving bars with particular orientations provided the bar does not extend past a certain point
■“End-stopped” - decrease firing in response to larger stimuli
What happens after V1?
■Information goes from V1 to secondary visual cortex (V2)
■V2: orientation, spatial frequency, and colour; also binocular disparity, and figure-ground distinction
■Gets transported to additional areas for specialised processing
Colour vision
■Starts in cones in retina – three types of cones
■Damage to V4: colour consistency is affected
■Processes apparent colour rather than actual colour
Colour consistency
Colour consistency refers to our ability to perceive colours as relatively constant over varying illuminations (i.e light sources)
Ventral stream
Responsible for conscious perception/ goes through temporal cortex
Two main pathways from V2
- Ventral stream
- Dorsal stream
dorsal stream
■ specialised for MOTION – it is the WHERE/HOW stream
■ allows us to visually control our actions and behaviour (Milner & Goodale, 1992)
Specialised Visual Perception
■ Inferior temporal cortex cells respond to meaningful objects
■Fusiform Gyrus cells: respond to faces
■Extrastriate body area: responds to bodies
Facial recognition
Particular regions of the visual cortex are specialised for processing special visual features.
What parts of brain is facial recognition dependent
occipital face area/ amygdala/ fusiform gyrus
Occipital face area - facial recognition
responds strongly to the eyes and mouth
Fusiform gyrus - facial recognition
Fusiform gyrus responds strongly to a face viewed from any angle, as well as drawings and other stimuli that look like faces.
damage to the fusiform facial area
Prosopagnosia – the inability to recognise faces
What is somatosensation?
sensations of touch/ also sensations of temperature and pain.
The Somatosensory Submodalities
- The exteroceptive system (external stimuli)
- The interoceptive system (internal stimuli)
- The proprioreceptive system (position of body)
The Exteroceptive System
■senses external stimuli applied to the skin
■three different divisions which sense touch, temperature and pain
The Interoceptive System
Provides information about physiological conditions inside the body/ Associated with the functioning of the autonomic nervous system (ANS)
The Proprioreceptive System
Monitors information about the position of the body that comes from receptors in the muscles, joints and organs of balance/ sent to the parietal cortex of the brain
four main kinds of receptors in the skin
- Free nerve endings – sensitive to temperature change and pain
- Pacinian corpuscles – respond rapidly to sudden movements on the skin
- Merkel’s disks
- Ruffini endings- both respond slowly, to pressure and skin stretching respectively
The Somatosensory Pathways(2)
- The dorsal-column medial-lemniscus (DCML) system carries information about fine touch and proprioception
- The anterolateral system carries information about pain and temperature
The dorsal-column medial-lemniscus (DCML) system
The dorsal-column medial-lemniscus (DCML) system tends to carry information about fine touch and proprioception
The anterolateral system
The anterolateral system tends to carry information about pain and temperature
Primary somatosensory cortex
Located in the postcentral gyrus of the parietal cortex/ behind the central fissure which divides the frontal lobes from the parietal lobes
Secondary Somatosensory Cortex
in the parietal cortex/ Somatotopically organised similar to the homunculus in S1
Somatosensory Association Cortex
In prefrontal and posterior parietal cortex/ integration of somatosensory and visual information
S1 and S2 somatosensory areas
The input to S1 is contralateral (from the opposite side of the body), S2 is from both sides of the body
Somatosensory Agnosias
result from brain damage to the parietal cortex
Astereognosia - Somatosensory Agnosias
Astereognosia is the inability to recognise objects by touch
Asomatognosia - Somatosensory Agnosias
Asomatognosia is the failure to recognise parts of your own body
Principles of Sensation
1.Hierarchical Organisation
2.Functional Segregation
3.Parallel Processing
4.Multisensory Integration
Principles of Sensation - Hierarchical Organisation
processing becomes more complex & specific the further up the sensory pathways we go
Principles of Sensation - Functional Segregation
Primary, secondary, and association cortex take care of different functions across all senses
Principles of sensation - Parallel Processing
Signals are processed in parallel across multiple pathways – some pathways are in consciousness, some are not
Principles of sensation - Multisensory Integration
Our brain can integrate information across two or more sensory systems
Sensory Receptors in the Auditory System (the ear)
■A specialised sensory receptor
■Turns soundwaves into electrical information
■Pinna (outer ear) reflect incoming sound waves to help identify source location
Auditory Sensation
Soundwaves enter the ear as long as they are carried by some medium (water, air)
