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134 Cards in this Set
- Front
- Back
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What are the two important properties of attention ? |
Capacity: amount of perceptualresources available for a task (varies)
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What structural damage impede the components of shifting attention? |
Disengagement: damage to parietal lobe Movement: superior colliculus (impedes movement) Engagement: Thalamus |
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Describe what happens in the olfactory bulb |
-Axons converge inthe outer layer of olfactory bulb and form glomeruli -then connect to mitralcells int he inner layer -synapse with axons from neurons with gromuleri -large convergence of axons synapsing with mitral -finally send odour info out to be synthesised |
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What does the olfactory epithelium do? |
One of two areas int he adult brain that is continually undergoing neurogensis (creating new stem cells CNS) |
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Olfactory receptors: Where are they and what processes underpin them ? |
- Receptors lovated in the nose -Underpinned by proceses that occur in the olfacory bulb (which is at the front of the brain behind the navalcavity) -Project to olfactory bulb in the limbic system via olfactory nerve (cranial nerve 1)by passing through perforations in the cribriform plate |
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What are the 9 senses? |
Propriocenption- bodily awareness Taste/Gustation Smell/olfaction Hearing/ audition Touch/somatosensation |
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What are the two components of selectivity? |
Overt attention- movement of eyes |
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Two working definitions of attention |
1. Processes that allow a person to recruit resources for processing selected aspects of the incoming snesory info more fully than non-selected 2. Allocating resources to relevent aspects of environment |
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What are parallel and serial tasks and how do they exemplify distributed attention concepts? |
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Difference between distributed and focused attention ? |
Distributed- parallel processing and visual pop out. Occurs at same time over whole visual field Focused- serialprocessing. bits of the environment at a time |
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Left sided visual extinction |
preserved detection of single contralesional left-sided stimuli better detect events when ingorning right field |
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Left-sided neglect |
Occurs after damage to one side of the brain (usually right hem) Patients act as is contralesional side ceased to exist Frequently co-occurs with hemiplegia and visual field defecits |
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Examples of attention failure |
Awareness test- gorilla or changing scenes Inattentional blindness- helps avoid sensory overload. Plane example Change blindness |
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Attentional control with left vs right field lesions |
Lesion in left hem- can still be both visual field Lesion in right- can only see right visual field |
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What does visual spatial attention in monkeys tell us about all information in the visual field? |
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What does distractor interference tell us about irrelevant information? |
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Describe Cherry's Early Selection theory |
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Describe Teisman's Late Selection theory |
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Describe voluntary and involuntary shifts in attention |
-Endogenous cues: voluntarily pushed attention. Top-down processing |
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What are the three components ofshifting attention? |
Disengagement- attention is normally focused on sometarget but must disengage Movement- free to move to new target Engagement - reengage with new target |
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What are the costs and benefits of moving attention? |
Posner cuing paradigm |
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What is the cocktailparty effect? |
Can redirect attention |
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Why is attention not alertness and arousal? |
- Coma -RAS: reticular activating system in the brain stem is the most basic attention function |
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What is a zoomlens of visual attention? |
- Continuation of spotlight theory -Wide field= coarser detail |
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What is the spotlighof visual attention? |
Illuminate object in target reigon |
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What pathways are present in the gustatory system? |
Central axons in cranial nerve ganglia project> to the solidarity nucleus in the medulla (gustatory nucleus) |
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What are the 3 different cranial nerves that taste receptors interface with? (gustation) |
-Primary axons in the facial nerve (CN VII) -Superior laryngeal branch of the vagus nerve (CN X) |
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List the 7 olfaction disorders |
-Ansomnia: inabilityto smell (damage to receptors) -Dysosmia:things smell different to memory (alzheimers) -Hyperosmia: acute sense of smell -Hyposmia: reduced ability (damage) -Olfactory reference: disorder where they think they smell bad (Body odour) -Parosmia: smell worse than they should (type of hyperosmia) -Phantosmia: hallucinated smell |
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Where are the taste receptors? |
Tongue, soft palate, pharynx and upper part of the oesophagus |
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Therapeutic implications of neurogenesis in the olfactory epithelium |
Neurogenesis subserved by olfactory ensheathing cells (OEC's) - type of schwann cell but always creating CNs cells |
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Primary and secondary auditory cortex |
2 principlesof organisation: -Columnar: frequency columns -Tonotopic organisation of cochlea is preserved all the way up |
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What is a disorder of gustation ? |
Ageusia- inability to taste |
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What does the outerear do for audition? |
Outerear collectes soundwaves and channels them into auditory canal Folds in pinnae (outerear) reflects sounds of various frequencies to localise sounds |
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What do the ossicles do? |
Lever action amplify vibrations by ~1.3x 22 fold increase in strength of vibrations hitting the tympanic memrane |
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In equilibrioception, what types of head movements are there (3)? |
Hair cells (cilia) in semicircular canals respond to head movement in three coordinate dimensions -Roll: rotation around x axis (nose to back of head) - Pitch: rotation around y axis (through ears) -Yaw: rotation around z axis (head side to side) |
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What are otholiths? |
Two primary sensory cells in cilia Utricle and saccule contain sensory epithelium (macula) - Utricle = horizontally aligned - Saccule = vertically aligned Cilia of hair cells embedded in otolithic membrane Calcium carbonate crystals (otoliths) embedded on surface. -Makes it top heavy Respond to linear acceleration and to gravity Otholiths have high density- shift when angle of the head changes Cilia of specific hair cells excites/ supresses neurotransmitter release relative to cilia orientation |
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What is the vestibular ocular reflex? |
A reflexive eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement |
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What is Oscillopsia? |
Bouncing vision Bilateral loss of VOR leaves patient with the sensation that the world is moving whenever the head moves. Information about head movements signalled by the vestibular organs is unavailable. -VSR vestiblulo-spinal reflex - VCR vestibulo-cervical reflex |
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How does alcohol effect oscillopsia? |
Alcohol causes temporary alterations in the vestibular system - vertigo and possibly nystagmus. Without alcohol – specific gravity of membrane and fluid in the semicircular canals Positional Alcohol Nystagmus (PAN): specific gravity of the membrane space of the semicircular canals differs from the specific gravity of the fluid in the canals because of the presence of alcohol- unbalanced. "Bed Spins". |
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What are three major skin-based senses- part of the exteroceptive system: senses external stimuli applied to the skin
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Touch, Thermoception, Nociception |
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Describe proproceptive processing |
Vestibular system senses: Orientation Conscious -Posterior column-medial lemnuscus pathway to the cerebrum Wanting to throw a ball Unconscious - The dorsal spinocerebellar tract and ventral spinocereballar tract to the cerebellum- critical for balance Everyday resting |
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What are the cutaneous receptors of somatosensation? (touch) |
Cutaneous receptors -Hair follice receptors: light touches,movement -Meissner corpuscle- one step up fromlight touches, feeling something slip from hand -Pacisian corpuscle:bivration, not pain -Merkle cells: pressure, diffuse, below dermis -Ruffini corpuscle: skin stretch -C-fibre LTM: light touch -Mechano-nociceptor: pain receptor |
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What do cutaneous receptors feed into? |
different spinal nerves: Dematomes V1 skin reigon feed into V1 spinal Afferent nerve fibres over a specific area of the body convergence on specific dorsal roots in the spinal cord Each area is called a dermatome Considerable overlap Damage or loss of one does not result in a large deficit in the sensation of the dermatome |
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What is nociception? |
pain receptors engage with sympathetic nervous system |
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What is thermoception? |
temperature perception |
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What are proprioceptor types? |
Muscle spindle - Muscle length -Limb position -Commands sent from CNS Golgi tendon organs - Feedback to CNs about the effort that is exerted - Muscle length - Limb position Joint afferents - Limb position - Movement - In each joint in the body Ruffini corpuscles - Limb position - Movement (skin stretch) |
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What are the two somatosensory pathways? |
Somatosensory information ascends from each side of the body to the somatosensory cortex via two pathways: Dorsal Column Medial-Lemniscus- carries information about touch and proprioception & Anterolateral system- carries information about pain and temperature |
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Describe the Dorsal Column Medial-Lemniscus |
Pathway mediates: Conscious proprioception, Tactile discrimination, Vibration sense, Form recognition Neurons in dorsal route ganglia >medulla Ipsilaterally travels Gracile and cuneate nuclei in the medulla > decussate to the medial lemniscus > VPL of the thalamus From VPL > somatosensory cortex |
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Describe the Anterolateral system |
From nociceptors and thermoceptors to the brain
Three seperate tracts - The spinothalamic tract: projects to the ventral posterior nucleus and carries information about crude touch and temperature - The spinoreticular tract: projects to the reticular formation- then to the parafasicular nuclei and instalaminar nuclei in the thalamus and info goes on to reigons of the brain that are responsible for arousal and emotion to change - The spinotectal tract: projects to the tectum, movement of head and eyes to the sight of pain |
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Describe cortical somatosensory processing |
Organised according to the map of the body- sensory homunculus Centre/surround receptive fields of the neurons in the somatosensory cortex - Touch outside centre, inhib response of neurons. Both centre and surround touched = diffuse firing of neither inhib or excit Damage to S1- not marked by major defecits in sensation - This is likely due tot he numerous parallel pathways in the two systems - Overlapping representations of the same regions of the body - Neuroplasticity- adaptation of receptive zones relative to changes in the body eg amputation |
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What systems are respnsible for pain reception? |
S1 and S2 respond to painful stimuli but are not necessary- removal of these structures does not reduce sensitivty to pain Full removal of entire hemisphere has little effect- we still dont know that much about this area though |
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What are types of nociceptors? |
Mechanical/ Polymodal: respond to excess pressure or mechanical deformation. Thermal: activated by noxious heat or cold at various temperatures. Chemical: TRP channels that respond to a wide variety of spice (e.g. pepper spray) Sleeping/ silent: response comes only on the onset of inflammation to the surrounding tissue (don’t respond directly to a particular type of pain input). |
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What roles do the lateral and medial thalamus play in effective pain perception? |
Lateral and medial thalamus have separate roles in pain processing: - lateral lemniscal regions transmitting discriminative information about location and intensity. - medial nonspecific regions are involved in emotional responses.
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What are some cortical regions involved in processing affective but not physiological pain. |
Nociception: anterior cingular gyrus -mediating the perception of pain. - PET studies showed increase in activity when participants touched very hot or very cold objects. -structure involved in the emotional response to pain. - Prefrontal lobotomy - reduced emotional response to pain no change in pain threshold. Heat perception: Thermoception - Responds to non-noxious temperature fluctuations. - Temperature inputs from thermoreceptors (free nerve endings) enters the spinal cord via the axons of Lissauer's tract. - Synapse on second order neurons in grey matter of the dorsal horn. - Second order axons decussate, joining the spinothalamic tract (part of the anterolateral system) as they ascend to neurons in the ventral posterolateral nucleus of the thalamus. |
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What is multisensory integration? |
Multisensory integration (MSI)- The processes by which information from the different sensory modalities are integrated by the nervous system.
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What multimodla neurons underpin multisensory integration |
Visual-tactile Auditory – visual Visual – gustatory Auditory-visual-tactile - Respond to three different types of stimuli, based on where they are in the cortex |
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What are mirror neurons? |
type of multisensory integration Now call them action observation neurons Visuotactile neurons in Premotor cortex: Fire in response to visual inputs presented on or near the hand & touch of the skin. |
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Give an example of multisensory integration distruptions |
The Ice cream stroop effect: Discontinuity between multisensory inputs can disrupt sensory perception. -- Example: eating a strawberry flavoured ice-cream that is yellow. Greater sensory concordance can enhance perceptual experience. -- Eating bacon whilst listening to the sound of sizzling bacon can enhance the bacony taste. |
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What effect does time have on maintenance and reorganisation of neural circuits? |
Time-dependance: window of opportunity within which experience can influence development Critical period – when it is absolutely essential that an experience occurs within a given time limit – and then other mechanisms follow on Sensitive period – when an experience can still have an influence outside the interval |
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What effect does usage have on maintenance and reorganisation of neural circuits? |
Hebb: neurones that fire together wire together If circuits are established, then not used, they do not survive ;they need to be maintained: USE IT OR LOSE IT Nature vs nurture |
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What is deprevation? |
e.g rearing animals in the dark: fewer synapses and dendritic spines poor depth and pattern perception |
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What did Hubel and Wiesel find? |
Cats have a critical period for developing sight ability. one week of monocular deprevation in criticalperiod= reduced axonal branching |
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what is enrichment? |
Antonni and Stryker found that rats who had an enriched environment had more dendritic spine and synapses |
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What role does exercise play in enrichment/deprivation? |
plays massive role and is found to be he most important influencing factor |
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Where can we find evidence for neurogenesis? |
Vision (re-wiring) -Ocular dominance columns (layer IV) in many species are developed at birth - Deprivation in one eye during sensitive period leads to reduced activation of layer IV of the corresponding visual cortex, but the activation of the other cortex by the intact eye is increased - Not just a single process Shifting and re-balancing Hippocampus (for enrichment) Effects of experience on hippocampus - In adult rats, increase in neurones in the dentate gyrus of the hippocampus, and in olfactory bulbs. - enriched environments: 60% more hippocampal neurones - associated with exercise <---> interaction with the enriched environment |
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What did Van Pragg do? (neurogenesis) |
-introduced virus to watch where it went throughout the hippocampus - the runner and enriched condition show neurogenesis the exercise is most important -Exercise and enrichment houses are far better than those in standard/sedentary housing -- Did a similar task in humans (word recall) --looked at their oxygen volume in hippocampus first trial of learning is where the greatest change is seen - remembner more words after first trial aerobic fitness positively correlated with whats going on in the dentate gyrus |
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What do we know about cortical maps and modification by experience? |
cutting nerves, sewing together fingers of one hand relevant part of the cortex no longer responds to the touch of that finger but that now defunct area soon starts to respond to stimulation of the ADJACENT finger, it fills in the silent area and takes over. So the adult cortex is a dynamic area, where changes can still happen |
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What can musicians tell us about brain plasticity? |
Elbert, Rockstroh et al used MEG to study somatosensory digit representations in musicians and non-musical volunteers. They stimulated thumbs and fingers, and showed that responses were higher in musicians – suggests that larger cortical area is dedicated to touch in musicians. The size of the effect correlated with the age at which they had began their musical training. |
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Can brain changes happen in adults? |
In normal brain, training can induce rapid changes in organisation that reflect plasticity, so there is a degree of functional plasticity in the cortex Lasted up to 8 weeks, even when no training ensued on the task in the interim |
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What did Knudsen and Brainard do? |
Prisms displace visual field X degrees to the left or right on barn owls Vision mapping shifted in the direction of the prism Auditory map also shifted in the tectum in the corresponding direction and by a corresponding extent This makes sense, because objects need to be heard in the location in space they occupy |
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What is thephantomlimb phenomena? |
After amputation, patients can still feel as though they have the limb and can feel pain and other sensations in or on it Ramachandran (1993) studied a patient with an amputated left arm. When parts of his cheek were stroked, the px reported sensations in his left hand – the missing left hand! |
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What are some causes of brain tissue damage? |
Neural degeneration after brain damage
Concussion ClosedHead Injury Penetrating Head Injury Skull fractures Post-traumatic epilepsy Cerebrovascular accidents and strokes |
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What are two typesof neural degeneration after brain damage? |
Anterograde - from the point of disruption forwards to the synaptic terminals (the distal segment); happens fast b/c of separation from metabolic centre Retrograde – from the point of disruption backwards to the cell body (the proximal segment); slow, over days; reduction in size, then death. There may be an increase in production of proteins, but the regeneration is not guaranteed Transneural degeneration Damage spreads to neurones that are linked synaptically |
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What is concussion? |
Blow to the head Extremely brief loss of consciousness, or may have no loss at all Temporary confusion Behavioural, affective and cognitive problems No evidence of structural (neuronal) damage |
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What are coup and contracoup injuries? |
coup injury occurs under the site of impact with an object, and a contrecoup injury occurs on the side opposite the area that was hit |
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What are the effects of concussion? |
Internal bleeds Linear and rotational forces can lead to cell death Punch-drunk syndrome in boxers: general cognitive deterioration, and eventual scarring after repeated concussions. Effects are summative Lavoie et al 2001: EEG recordings of university athletes (footballers) were altered even after two years of sustaining a concussion Shell shock |
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What can happen with a closed head injury? |
Contusions – bruises: when the brain slams against the skull. “coup” and “contra-coup” Haematomas – bleeds, due the shearing of blood vessels. Alcohol is anti-coagulant Oedema – swelling due to fluid – actually protective mechanims, but damages b/c of pressure Loss of consciousness – downward pressure on brain stem, but also when brain moves forward, it tends to ‘twist’ in the skull, disrupting brain stem functions including consciousness Epilepsy - disrupted tissue can start to produce impaired neural activity |
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What is a penetrating head injury? |
When the blow penetrates the skull As for Closed HI, plus: Infections Scarring, thus epilepsy Phineas |
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What are skull fractures |
Linear, or depressed. Depressed is more complicated b/c impacts drives fragments into dura and brain = > infection, and focus for epileptic activity. |
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Post-traumatic epilepsy |
Due to presence of scar tissue (changes in membrane structure and function). Patientstypically receive anticonvulsants prophylactically |
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Cerebrovascular accidents and strokes |
Sudden disruptions to brain’s blood circulation Any abnormality of the brain resulting from pathology of the blood vessels - lesion of vessel wall - occlusion of lumen due to thrombus/embolus - rupture, altered permeability - increased viscosity or other change of the blood (thinker/thinner) - The brain receives 15% of the resting cardiac output and accounts for 20% of the oxygen consumption. |
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Draw the circle of Willis, where it in in the brain and label the arteries |
. |
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Haemorrhage
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bleed into the brain, when blood vessel ruptures
May happen b/c of (congenital) weakness in blood vessel wall, or b/c of aneurysm |
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Ischaemia
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disruption in blood supply
- Thrombus - embolus - Arteriosclerosis (thickening of the vessel walls) The consequences of ischaemia typically take a few days to develop |
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What do strokes cause? |
Strokes cause INFARCTS: areas of dead tissue This is surrounded by the penumbra, which is ‘alive’ but dysfunctional, which may recover depending on treatment. |
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What are mitochondria and the cerebral hypoxia? |
Sitesof aerobic metabolism, converts food energy into useful form Kristian , 2000- Cerebral hypoxia leads to mitochondrial dysfunction Neurotransmitter dysfunction Neurone death |
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What is neural regeneration like in adults? |
The capacity is high in early development, but drops off with maturity
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What role does the PNS play in neural regeration |
morecapable, Schwann cells produce neurotrophic factors to stimulate growth andcell adhesion molecules on their membranes provide paths for growth Regeneration starts ~2 to 3 days after damage If the Schwann cells are not damaged, the axon can re-grow through and get to its original target If there is complete but small separation (incl Schwann cells), the axons may re-grow (attempt to re-wire) into the wrong sheaths = wrong destination = poor coordination If there is complete but large separation, there may be no regeneration, and the re-growing axons become a tangle, with no destination When an axon degenerates, axons from neighbouring intact neurones may grow to synapse at the vacated sites = collateral sprouting |
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What role does the CNs play in neural regeneration? |
Mechanismsof reorganisation - Establishment of new connections by collateral sprouting - Long-term re-organisation can be too great to be explained by changes to existing connections only Strengthening of existing connection due to release from inhibition (by original connections) Reorganisation can be so rapid but also restricted (<2 mm of cortical surface), it can’t be explained by normal growth, rather a change in the balance of maintenance We could use these to fix the penumbra |
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What else needs to be considered with strokes? |
Age - adults have less recovery - damage during neural migration= poor functional outcome - Injury during peak synaptogenesis = compensatorysynaptogenesis andcorrelated functional improvement Intelligence - higher premorbid intelligence = better recovery Sex - females have better functional recovery Hnadedness - left handers, lesslateralisation of function than right handers = advantage for recruitingundamaged regions after brain injury Personality -optimist = better recovery |
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Treatment of NSdamage- reducing brain damage |
Rehabilitative training - Reducing the extent of lesions - Strokes: e.g. Nudo et al (1996) – ischaemic lesions in the hand area of the motor cortex in monkeys.- Picking up pellets- Penumbra reduced Competition Strokes in humans: -Neurones compete for synaptic sites and neurotrophins. -This can be turned to advantage: increased training with affected limb or constraining intact limb and forcing use of affected one |
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What is Prosopagnosia? |
Prosopagnosics have difficulty recognising faces, including themselves Some patients show difficultiesspecific to faces and have no problems recognising common objects in theenvironment. Other patients show prosopagnosia as well as abnormalities inobject recognition. |
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What damage is usually associated with prosopagnosia ? |
Lesions to the occipitotemporal cortex are generally associatedwith impaired face recognition, but these areas are also associated withdeficits in object recognition. Is there an area specific to face processing? icuP6 |
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What did McArthy et al find with fMRIs and prosopagnosia? |
1st condition- Images of faces appeared intermittently among images of non-objects. Occipito-temporal regions, specifically the posterior fusiformgyrus, showed greater activity. 2nd condition- images shown to subjects consisted of common, knownobjects with faces appearing intermittently. Here, only the right fusiform gyrus showed greateractivation when the faces appeared |
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Why is the right fusiform gyrus important with Prosopagnosia? |
The right fusiform gyrus is often called the Fusiform Face Area, or FFA.E6 |
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Explain the famous faces method, task and result. |
-60 famous faces, for 5 seconds each -name the face, or report uniquely identifyinginformation -All family members were significantly impairedin identifying fewer faces compared with controls |
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Explain the Cambridge Face Memory Test justification, method, task and result.
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- not all individuals would be expected to‘know’ famous faces to the same extent -learn torecognise 6 novel target faces. Each of these ispresented from 3 viewpoints inprogressively difficult stages. -Thefamily members were significantly worse than the controls at identification ofthe target faces |
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Explain the Perception of Facial Similarity justification, method, task and result. |
-testearlier stages of face perception without requiring remembering the face. -Arrange sixfacial images according to their similarity to a target face. Six faces morphed with target face to differingdegrees. Each trial, Ps presented with ¾ profile viewof a target face, and 6 frontal views of faces to be sorteda - Familyperformed worse than controls in upright and inverted conditions -Facial identity perception impairment forprosopagnosic family. Not just memory impairment (maybe the earlyimpairment causes the memory problem??) |
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Explain the Facial emotion recognition justification, method, task and result. |
-evidence that identity processing and emotion processing are dissociable -Reading the Mind in the Eyes Test. 36 items – eye region and 4 emotion state words. -The family displays normal processing of facial emotions. - More evidence that perception of facial identity is dissociable from perception of facial emotion. |
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Explain the within-category object recognition justification, method, task and result.
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- Are these prosopagnosics specificallyimpaired at identifying faces, or are they impaired in within-categoryidentification in general?Are there separate mechanisms for face andobject processing? - Study phase, test phase - For each item, respond as quickly aspossible whether the object is ‘old’ or ‘new’. -Family has deficits inwithin-category identification of non-face objects, not just for faces,although it seems to a lesser extent. |
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Explain the global-local task justification, method, task and result. |
- test whether the family just have slowervisual processing, resulting in slower psychomotor performance (translationof stimulus into a response). Also want to test whether the familyhas a general global processing impairment. - Globaland local letters either match (consistent trials) or mismatch(inconsistent trials). -Verticalalignment of stimuli variedso that Ps could not just focus on asingle point in space - Family is notimpaired in all areas of visual cognition. Generalpsychomotor slowness does not account for poor performance in the other tasks. Family’s impairmenton faces (and other objects) not due to a general global visual processingdeficit. |
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What are the three types of space perception?
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Auditory - Visual - Multisensory
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What is auditory space perception?
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Auditory localisation On average, people can localise sounds directly in front of them mostaccurately and to the sides and behind their heads least accurately |
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What is ITD ? |
Interaural time difference (ITD) § Differencein the arrival time of a sound between two ears, which is important inlocalising sounds § Providesa cue to the direction or angle of the sound source from the head |
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What is ILD ? |
Interaural level difference (ILD) § Differencein sound pressure level reaching the two ears § Reductionin sound level occurs for high frequency sounds for the far ear- head casts anacoustic shadow § Strengthof the stimulation § Moresensitive to high frequency sounds |
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What are the major differences of ILD and ITD ? |
o ILD better attuned to high frequency/pitch sounds because it showsbetter where things are coming from o ITD better with low freq sounds o High freq sounds have higher wave length than head itself so casts lessacoustic shadow o Low frequency stimuli things less than 800hzrely more on ITD than for high frequency stimuli (higher than 1600hz),whichrely more on ILD |
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what is the cone of confusion ?
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§ Thresholdregion for sounds localisation § Anythingin the cone of confusion can't tell the difference between locations § Coneof confusion modulated by intensity of sounds. Low freq have a bigger cone ofconfusion § Betterlocalise higher freq sounds |
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How does sound localisation occur neurologically?
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§ Firstorder receptor cells in ears that receive the sounds and then the ITD arecalculated in the superior-olivary nucleus which is in the brain stem (Thisrelies on things called delay lines) § Neuronsreceive inputs from each ear § Differencein connecting axon length provide delay information § Somecells are more directly connected to one ear than the other § Specificfor one particular type of ITD § Similararchitecture underlies both ITD and ILD § ILDsensitive neurons rely on inhibition from one ear and activation from other ear. Inhibitory input from one ear and excitatory input from other ear § Dependson strength of input in terms of the response magnitude § Lowfreq rely on this |
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Describe the superior-olivary nucleus in ITD
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One on left and on right § (medialnucleus of the trapezoidal body has left and right side too) § Stimulationof one of those lateral olives, stimulates that one side, also stimulatescontralateral medial nucleus of the trapezoidal body (opposite side to superiorolive stimulation) § Soundat front of head, equal stimulation of both § Servesto shut down activation of the LSO. |
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Describe echolocation in ILD
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Up to 100000hz o Stimulation of tragus to see where things are |
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What did Tang et al find in the blind ?
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Far more sensitive than general population § Strongcorrelation of length of blindness and ability § Longer- better Length of blindness on ability study § Processingclick echos is recruiting what is a usual visual part of the brain § Thesereigons have been co-opted to allow the individual to be better at echolocation |
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What is visual depth perception?
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Ability to perceive the world in 3D in humans is underpinned bybinocular vision § Compositeof sensory inputs from the two eyes § Convergence:the two eyes as a range finders § Howeyes are crossed over each other |
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What is the near reflex?
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Convergence and accommodation are tied together o Although accommodation is a monocular depth cue andconvergence/divergence is a binocular depth cue, the two are closelylinked. When you converge your eyes, the lens in each of your eyes“fattens” to keep the image of the object you are looking at in focus on your retina. This is an automatic response and occurs even if there is no object insight--like when you cross your eyes to make a funny face. |
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What is stereopsis (binocular visual perception)?
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3D Depth perception derived from the visual input of two eyes (relieson binocular vision).
§ Humaneyes are located at different lateral positions on the head - binocular visionresults in two slightly different images projected to the retinas of the eyes § relativehorizontal position of objects in the two images (horizontal/ binoculardisparities). |
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What is Wheatsone's stereogram?
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One picture to one eye and one to the other § Canget participants to see 3d images § fundamental |
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What are corresponding retinal points?
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Theoretical corresponding points are defined as those points having thesame longitude and latitude in the two eyes. If you were to take theretina from your left eye and superimpose it upon retina of your right eye, apin pushed through both retinas would go through corresponding points in thetwo eyes. Points defined in this way have zero disparity. That isthere is no difference in the position of these points on the two retinas. |
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Describe the difference between crossed and uncrossed disparity
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Crossed: nearer than the fixation point and has a crosseddisparity because the visual lines (thin lines) intersect in front of thefixation point Uncrossed: farther than the fixation point and has an uncrosseddisparity because the visual lines (dashed lines) intersect beyond the fixationpoint |
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Describe binocular stimulation of receptive fields
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o From the LGN, we see that the mapping of the retinas bringscorresponding points into close register in the primary visual cortex. How isthis information combined and used? o Single unit recording is the traditional approach. 1) Find a cortical neuron’s receptive field: pattern oflight optimal for that neuron o 2) To find a BINOCULAR neuron, you need to find one that respondsdifferently to binocular stimulation than to monocular stimulation. o - A binocular cell will increase its firing from base level if itsreceptive field in one eye o -HOWEVER, its firing rate will dramatically increase when both receptivefields are stimulated. This is called binocular facilitation because the firingrate when both receptive fields are stimulated is more than twice the firingrates associated with monocular stimulation. This binocular facilitation isnecessary for stereopsis. |
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What is Panum's functional area?
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Points in space not lying on the horopter will stimulate disparatepositions on the two retinas. There is a small region around the horopterin which objects may be positioned and still be seen as single even though theyproject to disparate points in the two eyes. This is called Panum'sfusional area. § Thefusional limit is not absolute but corresponds to what has been called a disparitygradient *Hand check |
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Binocular vision in 3D space: summary
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§ 2eyes act as range finders to code for distance from the viewer to a fixatedobject. § Focusand convergence are hard wired together. § Binoculardisparity gives rise to precise relative depth perception and aids in breakingcamouflage. § Identicallocations on the two retinas are connected to binocular neurons in the cortexthat signal zero depth. § Similarlocations on the two retinas are connected to binocular neurons in the cortexthat signal depth. § Objectssituated such that their images fall on corresponding points - seen as single.Objects away from those locations - seen as double. |
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What are the different spatial coding systems?
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Allocentric: the location of one object is defined relative to thelocation of other objects and configural properties. o Egocentric: represents the location of objects in space relative to thebody axes of self (left-right, front-back, up-down). o underpinned by different neural processes. |
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What processes are allocentric and egocentric underpinned by in vision?
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Allocentric - Ventral stream involved primarily in theprocessing of complex object properties § Whatthings and how they are relationally organised. Egocentric- Dorsal involved in the processing of visual information as it pertains to thebody/ action. § Wherethings are in relation to the body and what their relative dimensions are. |
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Describe egocentric processing with peripersonal space
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Peripersonal space: The region of space immediately surrounding thebody in which objects can be grasped and manipulated.
§ Brainconstructs multiple, rapidly modifiable representations of space, centred ondifferent body parts (reference frames) § Referenceframes arise through extensive multisensory interactions within a set ofinterconnected parietal and frontal regions. |
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What role does the parietal lobe play coordinating in reference fames for specific body parts
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LIP – saccadic eye movements: activate to immediate (saccade to atarget) as well as delayed responses (saccade after a delay) § PRR– reaching: activate to immediate as well as delayed responses § AIP– grasp planning: grasp shaping to different shapes and sizes; depression ofarea with GABA = reaching but no grasp shaping is distorted |
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How are transformations completed by the LIP and PRR (ref frames)
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To do the transformations, the LIP and PRR take information frombody-related related signals: § Wherethe object is. § Wherethe body / head / arm / hand / fingers are (i.e., reference coordinatesystems). § Whatbody part to respond with. § Eyecentered § Firingpattern, optimal firing - some neurons attuned to fire at specific places § Limbcentered § Optimalfiring when hand moves § Headcentred § Onlyhead movement § Intermediate |
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What is peripersonal space?
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‘reachable/ actable’ space near the body § ~30cms of the hands |
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What do single cell recordings of macaques tell us about peripersonal space?
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Macaques: Periarcuate cortex (analogous to the premotor cortex inhumans).
§ F4subregion of inferior area 6 in ventral premotor cortex . § Neuronsfire in response to visual inputs presented on or near the hand & touch ofthe skin. § Multisensory– fire for both visual and tactile inputs. § Greatestfor the concurrent presentation of visual + tactile input (e. hand) § Activationprofiles remap with movement of the limb (limb-centred receptive fields). § Areindependent of gaze direction. |
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What are the features of peripersonal space
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Dynamic RFs - increase with increases in the velocity (20–80cm/s) of a visual stimulus approaching the cutaneous RF. § Crucialfor preparing and/or executing actions toward nearby object § Extendsto incorporate the effective space of tools (only when being actively used). § VisualRFs depend on specific motor action demands. |
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What are the different reference frames processed?
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At least four distinctive areas with similar visuo-tactile responses: § premotorinferior area 6 § parietalareas 7b and VIP § theputamen. § Sharecommon features: § Thevisual responses lie primarily within a head–face or arm–hand centredsomatosensory representation of the body. § Visualstimuli moving near the organism modulate the neurons' responses stronger thanfarther stimuli. |
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what behavioural evidence is found in humans? (peripersonal space)
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P responds to the location of the target (upper vs. lower) usingfootpedal. § FastestRTs for congruent V + T inputs on the same hand § SlowestRTs for incongruent V + T inputs on the same hand. § Integrationof V + T inputs = fast response if congruent, slow response if incongruent(disambiguation) cross modal congruency effect (CCE) |
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describe egocentric space and computing sensorimotor requirements of action
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§ Neuronsin PMC changed firing patterns based on whether the macaque retrieved the foodreward themself or food reward was provided by the experimenter. § Encodingnot only of objects location relative to the body but also relative to how themacaque planned to interact with it. o Tool use § Visualreceptive field accommodated for the tool. It extended the area of use for thetool |
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Peripersonal premotor neurons: summary
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Display VRFs that map onto the spatial location of a specific bodypart. o VRFs are adaptable – expand to incorporate the actable region of spacewhen using tools. o Have preferential activation relative to the action the organism plansto make. |
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What hz level is ILD and ITD more effective with? |
ILD - >1600hz ITD - <800hz |
