PS1003
Introduction to Biological Psychology
PS 1003
Sensation and sensory processing
Organisation of sensory systems
PS 1003
Peripheral sensory receptors
[ Spinal cord ]
Sensory thalamus
Primary sensory cortex
Unimodal association cortex
Multimodal association cortex
The senses
PS 1003
Touch
Sight
Hearing
Taste
Smell
Sense
Skin
Eye
Ear
Tongue
Nose
Organ
Spinal
cord
Optic II
Vestibulo- Facial VII Olfactory
cochlear Glossoph.
I
VIII
IX
Vagus X
Visual
Auditory
Somatosensory
Somatosensory
Olfactory
Nerve
Cortex
Gustatory (taste) perception
PS 1003
Taste
• Salty, sour, sweet, bitter, umani
Taste map? – different areas of the tongue sensitive to different tastes
• Myth!
All tastes are perceived over the full sensory area of the tongue.
Gustatory pathway
PS 1003
Taste buds
Taste receptor cells
Touch, pain receptors
Facial (VII), Glosso-pharangeal (IX), Vagus (X)
Brainstem
Thalamus
Taste centres of somatosensory cortex
Somatosensory cortex
Gustatory pathway (2)
PS 1003
Olfactory perception
PS 1003
Olfactory receptors in olfactory epithelium of nose
Olfactory nerve (II)
Olfactory bulb
Olfactory cortex
Hypothalamus
Hierarchical processing
PS 1003
Sensory processing is organised in a hierarchical manner
• Different areas for specific function
• Similar in all sensory modalities
STS
Superior temporal sulcus
TEO
Inferior temporal cortex
• Visual system is a good example
TE
Inferior temporal cortex
Dorsal stream
V5
Superior
colliculus
Eye
Dorsal
LGN
Ventral stream
V1
Striate
Cortex
Posterior
parietal Cx
V3
V3A
STS
V2
V4
TEO
Extrastriate
Cortex
TE
Inferior Temporal
Cortex
Area V1
PS 1003
Primary visual cortex (striate cortex)
• First level of input to the visual cortex
• Cells in V1 respond differently to different aspects of the visual
signal (e.g. orientation, size, colour)
• Involved in characterisation not analysis
o Sends independent outputs to several other areas
• Damage to V1 leads to total or partial blindness depending on
the extent of the damage
Blindsight
• Subjects are blind due to damage to area V1
• But can “guess” direction of travel of a moving object or colour
• Movement and colour not analysed in V1
• Information can bi-pass V1 to reach visual cortex
Area V3
PS 1003
First stage of building of object form
Code for component aspects of the object
• e.g. edges, orientation, spatial frequency (= size)
Feeds information to V4, V5, TEO, TE, STS and to parietal cortex
Area V4
PS 1003
Colour recognition
• Individual neurones in V4 respond to a variety of wavelengths
PET studies show
• Activation in V4 to coloured patterns, but not to greyscale
Achromatopsia
• damage to V4 causes an inability to perceive colour
• patients “see the world in black and white”
• also an inability to imagine or remember colour
Temporal lobe (TEO, TE, STS)
PS 1003
Highest level of processing of visual information
Recognition of objects dependent on their form
• Independent of scale (distance), orientation, illumination.
Visual memory
Face recognition
• Features of a face (subject specific)
• Expressions on a face (independent of subject)
• Gaze direction
Associative visual agnosia
• Normal visual acuity, but cannot name what they see
Aperceptive visual agnosia
Normal visual acuity, but cannot recognise objects visually by shape
Area V5
PS 1003
Movement perception
• Movement is perceived in area V5
PET studies show
• Activation in V5 to moving patterns, but not to stationary ones
Middle aged woman, who suffered a stroke causing bilateral
damage to the area V5
• became unable to perceive continuous motion
• rather saw only separate successive positions
• unaffected in colour, perception, object recognition, etc
• able to judge movement of tactile or auditory stimuli
Posterior parietal cortex
PS 1003
Analysis of spatial location of visual cues
• Building of an image of multiple objects within space
• Coordinates visually directed movement (reaching)
• Receives information from all areas of the visual cortex
Balint’s syndrome (damage to PPCx)
• Optic ataxia
• deficit in reaching for objects (misdirected movement)
• Ocular apraxia
• deficit in visual scanning
• difficulty in fixating on an object
• unable to perceive the location of an object in space
• No difficulty in overall perception or object recognition
Summary of hierarchical processing
PS 1003
Spatial analysis of
visual information
Movement recognition
Dorsal stream
Primary visual input
V1
V5
PPCx
V3
V3A
STS
V2
V4
TEO
TE
Building object form
Ventral stream
Colour recognition
Higher level processing
of object form
Primary Auditory Pathway
PS 1003
Cochlea
Ear
Vestibulo-cochlear nerve
(CN VIII)
Cochlear Nucleus
Pons
Superior Olivary Nucleus
Inferior Colliculus
Thalamus
Medial Geniculate Nucleus
Auditory Cortex
Cortex
Auditory processing
PS 1003
Cochlea
Cochlear Nucleus
Cochlear Nucleus
Superior Olivary Nucleus
Superior Olivary Nucleus
Inferior Colliculus
Inferior Colliculus
Medial Geniculate Nucleus
Auditory Cortex
Binaural
Cochlea
Medial Geniculate Nucleus
Auditory Cortex
Auditory processing (2)
PS 1003
Cochlea
PS 1003
Sound waves converted into vibration in basilar membrane
Hair cells in organ of Corti transduce movement of basilar membrane
into electrical signal
• High frequency sound transduced at base
• Low frequency sound transduced at apex
20Hz
500Hz
Apex
1kHz
Base
20kHz
5kHz
Information is transmitted along vestibulo-cochlear nerve
Auditory processing
PS 1003
Originally thought to be in auditory cortex
• Intermediate stages only ‘stepping stones’
BUT
• Auditory discrimination possible in the absence of auditory
cortex (e.g. direction, pitch, tunes)
THEREFORE
• Initial processing occurs in pons and thalamus
• Auditory cortex analyses complex aspects of sound
o Dorsal stream (parietal lobe) – spatial analysis
o Ventral stream (temporal lobe) – component analysis
i.e. Where and What (similar to vision)
Localisation of sound
PS 1003
Dependent on different characteristics of a
sound arriving at each ear
Intensity difference
• Difference in intensity of the sound
between the two ears
Latency
• Phase shift between the two ears
o Due to slightly different distance to
reach each ear
Duplex theory – sound location
depends on a combination of intensity
and latency
The vestibular organ
PS 1003
Semicircular canals:
• Detect head rotation and tilt around three axes
Head movement
Movement of endolymph
Displacement of capula
Stimulation of hair cells
Activation of CN VIII
Information
transmitted to brain
Vestibular pathways
PS 1003
Vestibulocochlear nerve (CN VIII)
Vestibular nuclei in the brainstem
Cerebellum
Motor thalamus
Cortex
Vestibulo-ocular
reflex
Balance
reflex
The vestibulo-ocular reflex (VOR)
PS 1003
VOR
• Works with eyes closed
• Not dependent on visual input
• Dependent on vestibular input
The balance reflex
PS 1003
Vestibular organ
Inner ear
Vestibular nuclei
Brainstem
Medial
Lateral
Neck muscles
Peripheral muscles
Head orientation
Postural muscles
Balance