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Sensation and sensory processing

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.

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Sensation and sensory processing

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  1. PS1003 Introduction to Biological Psychology PS 1003 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

  4. Gustatory (taste) perception • 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.

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

  8. Dorsal stream Posterior parietal Cx V5 Ventral stream Superior colliculus V3A STS V3 Eye Dorsal LGN V1 V4 V2 TEO TE STS Superior temporal sulcus TEO Inferior temporal cortex TE Inferior temporal cortex Extrastriate Cortex Striate Cortex Inferior Temporal Cortex 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

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

  16. Primary Auditory Pathway Ear Pons Thalamus Cortex Cochlea Cochlear Nucleus Superior Olivary Nucleus Inferior Colliculus Medial Geniculate Nucleus Auditory 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. 20Hz 500Hz Apex Base 1kHz 5kHz 20kHz 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

  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 Balance reflex Vestibulo-ocular reflex

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

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

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