Lecture 6 - Sensory perception.pdf - Synapse Action Potential Sensory Perception motor perception somatory perception broader overview than just \u2014 mp

Lecture 6 - Sensory perception.pdf - Synapse Action...

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Unformatted text preview: Synapse - Action Potential - Sensory Perception - motor perception - somatory perception - broader overview than just — mp and sp - more of lecture than ch for this lecture Sensory Perception: The Variety of Eyes - (c) high degree of visual aquity Text - targets small prey - (a) multiple eyes ( visual receptors ) - some animals need to have quick motion to stay hidden - animals should be equipped with tools that maximize their survival All animals have sensory organs containing receptor cells that sense some stimuli but not others Sensory organs are very diverse but all senses use the same type of energy—action potentials bee assess the quality - If natural selection states that if evolution is true then it has provided each species with specailzed motor systems, requires for exploring in its unique ecological niche How do we see colour? - electromagnetic spectrum contains millions of electromagnetic waves / energy - we aren’t equipped with tools to detect most of these Text What colours do you see? What I see - alot of properties that we don’t see Text - bee’s a flower signaling they are ready to pollinating amist from ultraviolet light signaling its ready for collection What colours do you see? - perception of any stimuli via light or etc, ir more than a physical property, it is a psychological & is a experience, - sensory - experience may be different if we were equipped with sensory acessories What I see What I don’t see to humans the flower looks yellow - can be captured via ultraviolet cameras for enhanced visual capabilities, including color vision, may have played a role in the evolution of relatively large brains in primates (Chapter 12; Barton 2000). Behavioral tests of color matching are important in showing how photoreceptors are actually used: any wavelength can be matched with a mixture of the primary colors for that species (i.e., those at the peak sensitivities for the different photoreceptors). This principle is made use of in video screens that generate colors by activating red, green, and blue phosphors in different proportions for different colors. As a result, most animals do not see the colors on conventional TV the way we do because their peak sensitivities and/or distributions of different receptor types are different from ours (Box 6.1; Oliveira et al. 2000). What colours do you see? Relative sensitivity Mammal 1.0 Honey bee Pigeon - function in lower levels of light - have 2 types of cones 0.5 0 300 400 500 600 300 400 500 600 300 400 500 600 700 Wavelength (nm) - colour blindness is more common in men - same thing that makes men colour blind may make women more colour sensitive ( super colour percievers) - percieving up to a trillion diff. colours. - pigeons can see a trillion colours, have more photo receptors Figure B3.1. Relative wavelength sensitivities of photoreceptors in a representative - pigeons and honeybee can see lower down on the Electromagnetic Spectrum, see UV rays of light, - UV colours on pigeons influence mating ; Female mate choiceIn differs due toof anhuman UV rays perception, red is nonprimate mammal, honeybees, and pigeons. terms toward What do sensory receptors have in common? photo receptors in the retna Text What types of touch are there? pain is a element of touch perception - touch is not just 1 thing - represents a combination of multiple diff. receptors thats work together to form a rich description of the environmen t an individual is interacting with. - feel warms are cold, grip ( vibration as a feedback mec hanism) - variety of sensory receptors that work together to acc omplish the same goal What do sensory receptors have in common? Transduction - converting energy from the environment into an electrical signal Transduction of a skin receptor The Pacinian (or lamellated) corpuscle is a skin receptor that responds to vibration and pressure. A stimulus to the corpuscle opens sodium channels and produces a graded generator potential - takes physical energy, signals of touch causing channels inside to deform and stretch open - physical stimulis changes in order to open NA channels and pass through. - Before action potentials we work with graded potentials - amount of depolarization depends on the intensity of the energy that is being recieved Transduction of a skin receptor The Pacinian (or lamellated) corpuscle is a skin receptor that responds to vibration and pressure. A stimulus to the corpuscle opens sodium channels and produces a graded generator potential When the potential is big enough, the receptor reaches threshold and generates an action potential Transduction of… Photoreceptor: photopigment absorbs and changes shape in response to light. - Oxins - Transduction of… Hair cell: mechanical transduction open and closes ion channels - mechanical way indirectly - coclia is filled with fluid - ways cause ,potion within the ear and hairs will start moving back and forth - motion causes a mechanical change - hairs are interconnected via tep links,; pull on a channel door and Mechanically open and all for Na to pass through to start deploarization AP - depends on intensity of sound energy is, too much can tear the hair cell from the coclia - sound is frequency of channels opening and closing What do sensory receptors have in common? Do not ‘measure’ energy, but rather encode relative intensities. - no info in encoded in an absolute sense - visual,somtasensory system takes all the receptors and tries to put it together to make sense of the world around it - no encoding of info in absoulte environment - We Perceive in Context Diff of A & B - A is more intense - Not true, B is > than A intensity is precieved relative to everything around the stimuli - the brain takes in the context in which we are percieving in -- dress was taken in the skew ar as the pigment they express, cone formation. This is consist Same perception despite huge variation - individual vairation in receptors that we have - never will be able to deterimine if perception is relevant - fair amount of consistentcy in picking up the colour red - could tell what photoreceptors they were loking at - optimaly receptive to red, blue and green - a weak intensity laser shined into the eye and depending on the way it bounces back tells you what type of repector it is - a huge degree of variation in cone types in ppl - all 3 have normal colour perception - retina has reduced blue photoreceptors “The number of colour-sensitive cones in the human retina differ... by man retinae showing the distribution of S (blue), M (green) and L (red) cones in the c up to 40 times ... yet people appear to perceive colour in""the same centage of L cones (adapted with permission from Hofer et al. [19 ]). way.” Current Opinion in Genetics & D Hoefer, H., Carroll, J., Neitz J., et al. (2005) J. Neurosci., 25(42): 9669-9679. Sensory Adaptation: (or, …why relative perception is important) - if perception was an absolute process - 1000/s AP, more you press then it just maxes out, firing rate of neurons - limitation if it was an absolute process — intro a new stimuli then would not be able to percieve it, as you cant change your firing rate Action Potential Rate - after reaching a max rate then it gets to a point SR adapt, go down to a lower threshold, so then it can respond a again and increase firing rate back to max - not measuring any absoulte level “Maxed out” (500 AP/sec) Weak Stimulus Produces NO AP Strong Stimuli increases AP rate Adaptation! We can with adaptation A B Without adaptation, no way to distinguish A from B Sensory Adaptation: Sometimes, we need receptors to be quiet! Adaptation—the progressive loss of receptor sensitivity as stimulation is maintained. - generator potential; magnitude of response depends on the intensity of the stimuli - more spikes for a stronger stimuli in the beginning - less than 1 sec receptors adapt to it - see that based on lower rate of AP strikes Sensory Adaptation: Sometimes, we need receptors to be quiet! Benefits of Adaptation 1.Adaptation helps us to ignore constant, innocuous stimuli, reducing distraction 2.Adaptation helps to avoid saturation of neuronal firing rates, allowing us to detect change in stimulus intensity over a larger range of intensities. - What do sensory receptors have in common? Respond over a huge range of intensities Our visual sense can operate over a 10 billion– fold range from the dimmest detectable light. - detects signals that vibrate the eardrum to up to picometers, opening up to a range of 10 trillions Text Respond over a huge range of intensities… -sensory info needs to be coded in the AP - problem Ap are predictable — thus cant really code HOW!? Solution - uses diff types of receptors Range Fractionation - multiple sensory receptors each specalizing in a narrow range with the environment that we are working with that over the entire spectrum of range and intensities Text Text EMS 400 nm 700nm - rods and cones - range is limited to the diff. kind of cone types What do sensory receptors have in common? Different types Sensory Processing and Somatosensory System: the Somatosensory System Touch and Pain Our skin contains an amazying All animals have sensory organs containing receptor cells array of receptors thatthat sense somedifferent forms of energy transduce forms of energy to provide our sense of Sensory organs are very diverse touch. but all senses use the same type of - Tickles, smoothness, wetness Diff touch receptors that pick up slightly diff qualities of the stimuli - sent seperately to the brain and then info put back together to give us a sense of touch energy—action potentials The concept of labeled lines says that the brain recognizes distinct senses because action potentials travel along separate nerve tracts of labeled lines says that the brain recognizes The concept distinct senses because action potentials travel along separate nerve tracts Structure determines function Structure determines function Rats and cats , use wiskers “ called wiisker barrel, Labeled Line - each quality of astimuli is sent along a specific of the brain - for visual stimuli - dectects motion instead of detail of objects - two-point threshold tests An approximate measure of the density and receptive field properties of touch receptors - proritize centrain aspects that we are looking at - more receptors and brain devoted Range fractionation - is also proritizing the central visual field of vision - has more receptors in that area and much more of the brain is devoted to visual stimuli 2 - Point Touch Descrimination - ask if you can feel 1 or 2 points - two-point threshold tests An approximate measure of the density and receptive field properties of touch receptors - similar to our visual system - body priotizes the certain body - seperation of up to 40 mm so and ppl arent senstivie to it - Check in Sensory experience varies amongst animals - Should be a product of natural selection. Different qualities of a stimulus must be conveyed by different sensory receptors. Hierarchical organization of stimuli allows for complex representations to be formed. No single neuron can convey all sensory information - It simply can’t be coded by a single neuron. Text What do sensory receptors have in common? Text Information from sensory systems is conveyed by specific pathways. Two Major Somatosensory Pathways Each sensory system has a distinctive pathway from the periphery to the brain. The dorsal column system delivers touch 8. Primary afferents convey information from skin information to CNS - transmits info using a distinct pathway, - skin - enters in to the back portion ( dorsal colum) of the spinal colum - efferent - ventral side ( colum) Pain and Touch info seprates Pain and Temp, go immediately crossover and go to the spinothalamic Text Aβ axon Dorsal Column Spinothalamic (anterolateral) Two Major Somatosensory Pathways Each sensory system has a distinctive pathway from the periphery to the brain • The dorsal column medial Lemniscus system delivers touch information - dorsol colum nuclei is found in the barin and asends u and crosses over ( decussate) - PO desussation happens for all sensory stimuli - Somta sensory info then gets sent to the thalmus ( relay centre) - Thalmus prioritizes Intensity and location of a stimulus The organization of Labeled lines allow for the potential of ‘spatial’ organization of inputs. Primary Somtasensory Cortex All Sensory stimuli has a primary cortext - Epicenter where siezures were occuring - destroy it an reduce a - labeled lines create a repersentative map of our surroundings -Somtasensory map -Visual Map Somatosensory cortex - relay25. and Areas recieve info 3a,from 3b,thalmus 1 and - sends info to specific places to process info - has different area’s 2 Cortical Areas of Somatosensation - overemphazies the area of the places in our body that have the greatest detailed aquity in our brain - underrepesentation of calfs, arms etc. Somatotopic organization in different species 28. Somatotopic representations in different species rabbit cat monkey human Diff. animals have diff. neruological repersnetations of their body - Rats ( whiskers) - Use Staining Techniques Vibrissae (whiskers) on Vibaissae (whiskers) right side of face on right side of face Ratunculus “Barrels” in layer Ranunculus “Barrels’ in layer IV of left hemisphere IV of Left Hemisphere What do sensory receptors have in common? Decode and Reconstruct signals - From Stimulus to Perception: Principles of Sensory System Organization - Text Text Text Text From Stimulus to Perception: Principles of Sensory System Organization Hierarchal organization - to make sene of thing - 2nd sensory area’s, - temproal lobe ( IT) that specalizes in proccessing specific signals - first distingush what a hand is and orientation of the hand - cluster of cfells that specalize in faces eye photoreceptors - sensitive to certain quality of lights, - respond will to spots - LGN - info then sent to the thalmus - LGN ( thalamic relay ) - spot seems to be growning - V1 - visual cortex - get really sensitive to edges - respond well to lines - primary sensory areas are combning area’s from LGN relays and modifying the signal IT Deficits Reveal Hierarchal Organization - damage to the fusiform Check in Somatosensory system is a model to understand: How multiple lines of information are processed. How the brain organizes (or even re-organizes) sensory information. ...
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