Psych 202 1st Edition Lecture 18 Introduction to Sensation and Perception-Overview of Today:-Discuss Basic Processes of Sensation and Perception-Review Visual Processes in Detail, with figures and video clips-Examine How Perception is “Constructed” and what features influence the construction process-Basic Processes of Sensation-1) Modification of stimuli via accessory structuresoe.g., lens of eye is accessory structure that changes light by focusing itoouter part of ear is accessory structure that collects sound-2) TransductionoDetectable Energy is Transduced oTransduction is process of converting energy into neural activityoTransduction Occurs at Sensory Receptors, which are cells that specialize in detecting certain forms of energy (light waves, sound waves, heat, etc)oSensory Receptors respond especially to CHANGES in stimulus intensityoAdaptation (decreased responsiveness in firing of cells and concomitant conscious experiencing) occurs to an unchanging stimulus over timeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-3) EncodingoTransduction results in encoding of energy that is detected/sensed: oCoding is the translation of physical stimulus properties into patterns of neural activity that specifically identify those physical propertiesoBegin with the action potentials sent by the ganglion cells-4) Representation in CortexoFinal output is action potentials firing down sensory neuronsoThe rates of firing of coalitions of action potentials “represent” the external stimulus in the final stage of sensation.oEncoded Information is “Represented” in CortexoThalamus is Relay Station for Sensory Information (except smell)-Cortical Representations are Topographically Contralateral to part of world sensed (left and right)-Topographical Representations exist in cortexoe.g., somatosensory cortex, visual cortex, auditory cortex, etc.-Example: Recall the split brain video and how visual information was presented and then cortically represented?-Next slides demonstrate the process-Visual Sensation begins with the modification structures in the eyeball:-Cornea, iris, pupil, lens-Retina: photo receptor area, has 2 different types of cells (rods and cones)oRods: respond to dark, lower levels of illumination, distributed to retina moreoCones: respond to light, more centrally located-The Main Pathway From the Distal Stimulus to the Proximal Stimulus: How Sensory Information Arrives in Visual Areas of Occipital Lobe -Distal stimulus: stimulus that is outside, what you're looking at when you watch someone do something, what you are looking at-Proximal stimulus: on the retina and brain, inside, in your body, we know this process-A closer look at the eyeball and some of its important structures:-Modification structures: cornea, iris, pupil, lens-A closer look at transduction and encoding structures-Transduction structures: the photoreceptive layer (note the distribution of rods and cones, relation to fovea)-Encoding structures: output from bipolar cells creates coding in ganglion cells which collectively form the optic nerve and relay ultimately to the occipital lobe-From Visual Sensation to Visual Perception: the role of feature detectors-Feature Detectors are neurons “specialized” to fire only in response to select dimensions of light stimulioThese are critical to the ultimate perception of visual objectsoWork with other processes to build a perception of what is actually happening-Video clip: Feature Detectors in Visual Sensation-Hubel and Weisel (1981) received Nobel Prize for their identification and specification of feature detectors in visual cortex of catsoSimple cells*-Make complex cellsoComplex cells-Make hypercomplex cellsoHypercomplex cells-Perceptual Processes: Beyond Sensation-Perception involves “construction” of the worldoConstruction involves: (top down process: what we expect to see alters what we are actually seeing), processes involved in of construction of perceptual world from sensory input-Selection of sensory input: your brain has to decide what to pay attention to, what to notice-Organization of sensory input-Interpretation of sensory input-Perceptual Construction is influenced by attitudes, preferences, and social-situational contexts of perception (i.e., expectations), bottom up-Simple Example: Context Effects-Gestalt principles of perceptionoClosure, continuity-Video clips of Context Effects and Role of Personal Factors-One image: see two different thingsoOld woman vs young woman-Discussion of Sack’s Cases-Hands: Madeline-Witty Ticcy Ray-Cupid's Disease: Natasha -The Man Who Mistook His Wife for a Hat: Dr. P-The Disembodied Lady: Christina-On the Level: Mr. McGregor-The Dog Beneath the Skin: