PSC 135 Unit 2 Double-Sided Study Guide PDF

Perception as construction: bits of energy are taken through receptors and actively constructs an image of the object percepted. energy sources- visible light waves with different wavelengths, spectrum determines color. object/environment- orange(fruit eg) absorbs lower wavelengths and reflects colo...

Perception as construction: bits of energy are taken through receptors and actively constructs an image of the object percepted. energy sources- visible light waves with different wavelengths, spectrum determines color. object/environment- orange(fruit eg) absorbs lower wavelengths and reflects color orange. some with other objects. some things like color are stable/diagnostic some can be temporary like size. environment: includes things that get in the way(occlude) like other objects or walls. anatomy: optical components focus light onto neural components cornea transparent front layer protects eye and refracts little light lens focusing structure, focuses photons to make each point on visual field and makes it all go into retina if focused correctly pupil regulates how much light goes into eye, more light=smaller less light=larger iris colored light controlling diaphragm that makes pupil get larger or bigger light travels through multiple structures to start visual perception Neural components- retina light sensitive area in the back of the eye contains photoreceptors(rods/cones, light detecting cells), fovea high acuity(sharpness) center dense with cones very few rods bipolar cells integrate signals from rods and cones horizontal cells lateral inhibitors ganglion cells output neurons, generate action potential optic nerve information conduit to brain Receptor properties- rods highly sensitive, better in dim light, more rods then cones, peripheral vision, no color only light or no light, multiple rods to one bipolar cell more sensitive but less spatial resolution, low sharpness, cant see color in peripheral vision cones best in bright light, less then rods, found in fovea, color vision, one cone to one bipolar cell high spatial resolution,3 types red green and blue cones, only respond to light that falls in their wavelength, cones create every color, high sharpness. Phototransduction steps- light to vision, Light enters the eye, Photons reach photoreceptors(rods/cones), Photons absorbed by photopigments in rods/cones, Absorbed photons turn into an electrical signal(through complex molecular pathways), Electrical signal gets send through intermediate cell layers(bipolar, horizontal), Transmitted to optic nerve by ganglion cells, Sent to brain. Optic nerve leaves hole in retina, blind spot lateral inhibition(see back)- less firing of a neuron due to excess firing of neighboring neuron. causes contrast, edges and boundaries. contrast illusion(see back)- the same color looks different due to lateral inhibition(two dots on the image shown in class) receptive field- region of space in which presence of a stimulus can elicit a response from a neuron. photoreceptors fire when looking at a location in their determined region(zone coverage) eye to visual cortex: optic chiasm where optic nerve carries signal, maintains contraletalism LGN bundle of axons named optic tract transmit to thalamus to relays info, pit stop brings information to visual cortex. LGN connects only inputs info from optic tract and only outputs to optic radiation Distinct architecture Primary Visual Cortex(V1)- occipital lobe, topographically organized with cort. magnification, each area processing one topic(edges, etc) every region in visual field has one area in the retina and each area of visual field represented by one area in the PVC. Left translates to right and right translates to left. Cort. mag=fovea, fovea has most connections although very small. V1 responds to all stimuli well regardless of shape being familiar or not, unlike LOC. There are roughly two hierarchies- V1->V2.>V4.>MT->(up to parietal/frontal) V1->V2->V4->IT-> down through temporal How do we define a visual area? Function: do they process one specific type of information(e.g. MT only processes motion) V1(exclusively edge detection) Huber did glowstick experiment with cat proving edges. Dorsal path- “where” pathway, visually guided action. Monkeys with inferior temporal cortex cannot do “what” tasks, but can do “where” tasks. 2x dissociation study. Patient RV(parietal lobe damage) cannot pick up objects in any logical way(such as water bottle from corner) can do all the perceptual matching DF cant. Has object ataxia. Ventral path- “what” pathway, category selective, object recognition. Monkeys with parietal lobe cut off can do “what” task, but cannot do “where” task. 2x dissociation. Patient DF(Ventral, IT damage) had object agnosia, cannot identify objects from drawing, sometimes(10%) can detect what it is(3d). cannot copy drawings. can draw from memory. cannot do perceptual matching where they have to match a line with paper(no shape recognition, not even lines). can put paper in mailbox slit because her dorsal pathway is good. can pick up rocks and know their location, and can also hold things like water bottles logically. Hierarchy of visual feature detectors Retinal Ganglion Cells and LGN: small dots V1: orientation, disparity, some color LOC(lateral occipital complex): basic shapes V1(edge detection) projects to LOC(shape detection) on ventral pathway lateral occipital complex(loc)- selective to objects/shapes and connects to multiple gyri and sulci, which is why its called complex. Inferior temporal cortex. Both familiar and abstract shapes responded well. fusiform face area(FFA)- part of the brain that responds to faces. house/face experiment made to see if FFA responds to instances of the same category being represented over time. found that FFA does respond to faces. part of ventral pathway. houses were remembered equally but FFA remembered whole faces better than isolated factors(just noses). FFA is also part of inferior temporal cortex. Parahippocampal place area(PPA)- looks at whole images/scenes/spatial layout. processes scenes. Waterfall illusion/ motion after effect- up the dorsal pathway, neurons in middle temporal cortex sensitive to motion direction. some MT neurons like particular areas of motion and only responds to movement. Firing rate of MT neurons elevated when motion then goes back to baseline when done. Neuron slowly decreases firing rate over time if same motion goes on for too long. Sensory adaptation- neurons become less sensitive to repetitive motion over time. if motion is in left area for long time, neurons in left will go below baseline when it stops but neurons in right area will stay normal, causing illusion that there is movement in the right. Prosopagnosia- loss of recognition of faces but not other objects. Can detect faces and acknowledge there is one but cant recognize whos face it. Can recognize through voice and description. Caused by loss of function in FFA. Can identify from non facial distinguishing features such as birthmarks. Akinetopsia- motion blindness. patients have trouble pouring liquids because they look frozen in place, cannot see people walk because it looks like they teleport, and can recognize there is a car but cannot understand the speed of the car when crossing the street. Can detect some motion if moving VERY slowly, but any reasonable pace makes it stop. Caused by loss of function in MT. Physics of sound: Sound waves are mechanical waves that require a medium to travel through, light does not need a medium to travel and can travel through space. Sound needs a medium like air. Waves differ in sound with frequency(closely related to pitch, high or low) and amplitude(loudness) Frequency: Number of oscillations per second measured in Hertz. The audible range for humans is approximately 20 Hz to 20,000 Hz.Low frequency passes through space slower than high frequency Spectrogram: shows distribution of frequencies in a sound wave over time. Talking produces waves with many different frequencies Amplitude: Level of intensity or strength of sound wave measured in decibels. Distance with which particles are disturbed is amplitude. More distance=distance sound is carried is longer and more hearable/less hearable Waveform: time-domain representation of sound wave that shows how the amplitude of the sound varies over time Outer ear: receivers sound Middle ear: amplifies and transmits sound waves from outer ear into inner ear Inner ear: contains the cochlea converts mechanical vibrations into neural signals that can be interpreted by brain Almost one to one process with eyesight, very similar in the brain. Vision->photoreceptors turn light into electrical signals. Audition-> hair cells in cochlea(inner ear) convert sound vibrations into electrical signals Primary auditory cortex processes incoming sound; it includes areas like primary auditory cortex(A1) which has a topographic representation of the auditory input, and higher level areas(like the so-called belt areas) that process more complex features(such as auditory object recognition). Frequencies in higher areas can fire to the internal thoughts so people with schizophrenia can cause the auditory cortex to start firing, which can lead people to hear voices. Different frequencies are represented in an orderly manner along the surface of the auditory cortex, with low frequencies at the anterior end and high frequencies at the posterior end.