1. Introduction to Biological Psychology
Sensation and sensory processing

2. Organisation of sensory systems
PS 1003
Peripheral sensory receptors
[ Spinal cord ]
Sensory thalamus
Primary sensory cortex
Unimodal association cortex
Multimodal association cortex

3. The senses Touch Sight Hearing Taste Smell Sense Skin Eye Ear Tongue
Nose
Organ
Spinal cord
Optic II
Vestibulo-cochlear VIII
Facial VII Glossoph. IX Vagus X
Olfactory I
Nerve
Somato-sensory
Visual
Auditory
Olfactory
Cortex

4. Gustatory (taste) perception
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.

5. Gustatory pathway Taste buds
Taste receptor cells Touch, pain receptors
Brainstem
Thalamus
Taste centres of somatosensory cortex Somatosensory cortex
Facial (VII), Glosso-pharangeal (IX), Vagus (X)

6. Gustatory pathway (2)

7. Olfactory receptors in olfactory epithelium of nose
Olfactory perception
Olfactory receptors in olfactory epithelium of nose
Olfactory nerve (II)
Olfactory bulb
Olfactory cortex
Hypothalamus

8. Hierarchical processing
Sensory processing is organised in a hierarchical manner
Different areas for specific function
Similar in all sensory modalities
Visual system is a good example
STS Superior temporal sulcus
TEO Inferior temporal cortex
TE Inferior temporal cortex
Eye
Superior
colliculus
Dorsal
LGN V1 V2 V3 V4
V3A
STS
TEO V5 TE
Posterior
parietal Cx
Striate
Cortex
Extrastriate
Inferior Temporal
Dorsal stream
Ventral stream

9. Area V1 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
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

10. Area V3 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

11. Area V4 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

12. Temporal lobe (TEO, TE, STS)
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

13. Area V5
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

14. Posterior parietal cortex
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

15. Summary of hierarchical processing
Movement recognition
Spatial analysis of
visual information
Dorsal stream V1 V2 V3 V4
V3A
STS
TEO V5 TE
PPCx
Primary visual input
Building object form
Colour recognition
Higher level processing
of object form
Ventral stream

16. Primary Auditory Pathway
Cochlea
Cochlear Nucleus
Superior Olivary Nucleus
Inferior Colliculus
Medial Geniculate Nucleus
Auditory Cortex
Ear
Pons
Thalamus
Cortex
Vestibulo-cochlear nerve
(CN VIII)

17. Auditory processing Cochlea Cochlear Nucleus Superior Olivary Nucleus
Inferior Colliculus
Medial Geniculate Nucleus
Auditory Cortex
Cochlea
Cochlear Nucleus
Superior Olivary Nucleus
Inferior Colliculus
Medial Geniculate Nucleus
Auditory Cortex
Binaural

18. Auditory processing (2)

19. Cochlea 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
Information is transmitted along vestibulo-cochlear nerve
20kHz
5kHz
1kHz
500Hz
20Hz
Apex
Base

20. Auditory processing 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
Dorsal stream (parietal lobe) – spatial analysis
Ventral stream (temporal lobe) – component analysis
i.e. Where and What (similar to vision)

21. Localisation of sound
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
Due to slightly different distance to reach each ear
Duplex theory – sound location depends on a combination of intensity and latency

22. The vestibular organ 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

23. Vestibular pathways Vestibulocochlear nerve (CN VIII)
Vestibular nuclei in the brainstem Cerebellum
Motor thalamus
Cortex
Vestibulo-ocular
reflex
Balance
reflex

24. The vestibulo-ocular reflex (VOR)
Works with eyes closed
Not dependent on visual input
Dependent on vestibular input

25. The balance reflex Vestibular organ Inner ear Vestibular nuclei
Medial Lateral
Neck muscles Peripheral muscles
Head orientation Postural muscles
Balance
Inner ear
Brainstem