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Sensation and sensory processing PS 1003 Introduction to Biological Psychology.

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Presentation on theme: "Sensation and sensory processing PS 1003 Introduction to Biological Psychology."— Presentation transcript:

1 Sensation and sensory processing PS 1003 Introduction to Biological Psychology

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

3 PS 1003 The senses TouchSightHearingTasteSmellSense SkinEyeEarTongueNoseOrgan Spinal cord Optic IIVestibulo- cochlear VIII Facial VII Glossoph. IX Vagus X Olfactory I Nerve Somato- sensory VisualAuditory Somato- sensory OlfactoryCortex

4 PS 1003 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 PS 1003 Gustatory pathway Taste buds Taste receptor cellsTouch, pain receptors Brainstem Thalamus Taste centres of somatosensory cortexSomatosensory cortex Facial (VII), Glosso-pharangeal (IX), Vagus (X)

6 PS 1003 Gustatory pathway (2)

7 PS 1003 Olfactory perception Olfactory receptors in olfactory epithelium of nose Olfactory nerve (II) Olfactory bulb Olfactory cortex Hypothalamus

8 PS 1003 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 TEOInferior 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 Cortex Inferior Temporal Cortex Dorsal stream Ventral stream

9 PS 1003 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 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

10 PS 1003 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 PS 1003 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 PS 1003 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 PS 1003 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 PS 1003 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 PS 1003 V1 V2 V3 V4 V3A STS TEO V5 TE PPCx Summary of hierarchical processing Primary visual input Building object form Colour recognition Higher level processing of object form Ventral stream Movement recognition Spatial analysis of visual information Dorsal stream

16 PS 1003 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 PS 1003 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 PS 1003 Auditory processing (2)

19 PS 1003 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 PS 1003 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 o Dorsal stream (parietal lobe) – spatial analysis o Ventral stream (temporal lobe) – component analysis i.e. Where and What (similar to vision)

21 PS 1003 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 o Due to slightly different distance to reach each ear Duplex theory – sound location depends on a combination of intensity and latency

22 PS 1003 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 PS 1003 Vestibular pathways Vestibulocochlear nerve (CN VIII) Vestibular nuclei in the brainstemCerebellum Motor thalamus Cortex Vestibulo-ocular reflex Balance reflex

24 PS 1003 The vestibulo-ocular reflex (VOR) VOR Works with eyes closed Not dependent on visual input Dependent on vestibular input

25 PS 1003 The balance reflex Vestibular organ Vestibular nuclei MedialLateral Neck musclesPeripheral muscles Head orientationPostural muscles Balance Inner ear Brainstem

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